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2.1 History and General Introduction of Plastic
2.2 Plastic Statistics of the World
2.3 Plastic Statistics of India
2.4 Issues Related with Plastic Bags
2.5 Plastic Footprints in Oceans and Impact on Marine Life
2.6 Issues Related to Plastic Products Manufacturing
2.7 Plastic Waste Scenario (Quantity and Composition)
2.8 Facts Related to Degradation of Plastic
2.9 Problems in Recycling and Incineration of Plastic Garbage
2.10 Biodegradable Polymers and Bio-plastic (Issues and Scope)
2.10.1 Types of biodegradable plastics
2.10.2 Economical aspects of biodegradable plastic/polymers
2.10.3 Decomposition of biodegradable plastic/polymers
2.10.4 Problems and challenges
2.11 Citation of Related Patents
2.12 Commercially Available Biodegradable Products
2.13 Nursery Bags & Containers Related Research (Type/Shape/Size/ Design)
2.14. Air Induced Root Pruning
2.15 Role of Copper in Root Pruning
2.16 Copper as Biocide
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 8
2.1 HISTORY AND GENERAL INTRODUCTION OF PLASTIC
According to the „Oxford Dictionary‟ word „Plastic‟ was coined in the mid of 17th
century and derived from French „plastique’, Latin „plasticus’ or from Greek „plastikos’/
„plassein’. Meaning of all these cognates is „able to be molded into different shapes‟ (Joel,
1995). The first man-made plastic, a modification of cellulose, was created by Alexander
Parkes in 1862 and called „Parkesine‟. In 1868 John Wesley Hyatt invented Celluloid,
derived from cellulose and alcoholized camphor that could be molded with heat and pressure
into a durable shape. By 1900, movie film was an exploding market for celluloid (Harris,
1981).
Plastic, from the time of their origin have become an indispensable part of our life and
in modern society. Synthetic plastics are extensively used in packaging of products like food,
pharmaceuticals, cosmetics, detergents and many products manufactured from plastics are a
boon to public health, e g. disposable syringes and intravenous bags (Halden, 2010). This
utilization is still expanding at a high rate of 12% per annum (Sabir, 2004) and has replaced
paper and other cellulose-based products for packaging because of their better physical and
chemical properties viz. strength, lightness, resistance to microorganisms (Shah et al., 2008)
and favorable mechanical/thermal properties, stability and durability (Rivard et al., 1995).
With time, stability and durability of plastics have been improved continuously, hence this
group of materials is now considered as a synonym for the materials being resistant to many
environmental influences (Joel, 1995). Plastic is inert i.e. resistant to biodegradation, durable,
hygienic, lightweight, cheap, and malleable (Mohee and Unmar, 2007). It has been proven
that polyolefins especially low density polyethylene (LDPE), are resistant against degradation
and microorganism attacks (Mahmood and Reza, 2004).
These are manmade long chain polymeric molecules (Scott, 1999). The basic materials
used for making plastics are extracted from oil, coal and natural gas that comprise inorganic
and organic raw materials, such as carbon, silicon, hydrogen, nitrogen, oxygen and chloride
(Seymour, 1989). Petroleum-based synthetic polymers are introduced in the ecosystem as
industrial waste products that generate several problems e.g. visual pollution, blockage of
gutters and drains, livestock deaths and threat to aquatic life (Shimao, 2001).
2.2 PLASTIC STATISTICS OF THE WORLD
Production of plastic has increased from 0.5 million tonnes in 1950 to 260 million
tonnes in 2007. This increase in usage, especially disposable items of packaging, makes up
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 9
37% of all the plastic produced (Plastic Europe, 2008). Packaging utility is the biggest field
where polythene and its kind material are used. It is estimated that 41% of plastics are used in
packaging, and that almost half of that volume is used to pack food products (O'Brine and
Thompson, 2010). Low density polyethylene is the most applied polyolefin in packaging,
horticulture and agricultural utilizations (Bastioli et al., 1991).
As population is increasing so the consumption of synthetic plastic is increasing, only
in a span of one year (1996-95) shipments from the Canadian Plastic Industry increased by
10.6% (Charron, 2001). In Australia about 1 million tones of plastic materials are produced
each year and a further 587,000 tonnes are imported (Australian Academy of Science, 2002). In European countries on an average 100kg of plastic is used per person each year (Mulder,
1998.) The bags, with a typical thickness of 16 microns and weight of 7-8 gm are provided
free of charge in Israeli stores and supermarkets (Ayalon et al., 2009). In Mauritius, plastic
wastes constitute around 8% by weight (or 100 tonnes) of the total solid waste generated
daily. The amount of plastic carry-bags disposed at the landfill is approximately 1000 tonnes
annually, while the local plastic industries generate around 250–300 million plastic carry
bags per annum (Mohee and Unmar, 2007). In Israel, 2 billion HDPE carrier bags are
manufactured every year. The total amount of these bags is 30,000 tons/year. At the end of
2007, there were 2,007,300 households in Israel. It means that the consumption in Israel per
household is 1000 bags /yr, 2.7 bags per day. Every person in Israel uses an average of 300
bags /yr, similar to other countries such as Ireland, where before introduction of the levy, a
yearly average was of 330 bags per person (Ayalon et al., 2009). The estimated figure of
plastic waste generation across the Pakistan was 1.32 million tons per annum (Sabir, 2004).
The plastic industry in Pakistan was reported to be growing at an average annual growth rate
of 15% (Shah et al., 2008).
2.3 PLASTIC STATISTICS OF INDIA
In India, plastic consumption grew exponentially in the 1990s. In the decade 1990 -
2000, total consumption of plastics grew twice (12% /yr) as fast as the gross domestic
product growth rate based on purchasing power parities (6% /yr). The current growth rate in
Indian polymer consumption is higher than that in China and many other key Asian countries.
The average Indian consumption of virgin plastics per capita reached 3.2 kg in 2000/2001 (5
kg if recycled material is included) from a mere 0.8 kg in 1990/1991 that is only one-fourth
of the consumption in China (12 kg/capita, 1998) and one sixth of the world average i.e.18
kg/capita (Muthaa et al., 2006). This consumption led to more than 5400 tones of plastics
waste being generated per day in 2000/2001 and the percentage of plastics in municipal solid
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 10
waste (MSW) has also increased significantly from 0.7% in 1971 to 4% in 1995
(TERI,1998). Polyolefin account for about 60% of the total plastics consumption, followed
by PVC and polystyrene. Together, the commodity plastics (PE, PP, PVC and PS) accounted
for 83% of the total plastics consumption in India in 2000/2001. Between 1990 and 2000,
LLDPE was the material with the strongest growth rate of (20% /yr), followed by PP (16%
/yr), HDPE (14% /yr), PVC (12% /yr), PS (10% /yr) and LDPE (Muthaa et al., 2006).
Polyolefin account for the major share of 60% in the total plastics consumption in
India. Packaging is the major plastics consuming sector, with 42% of the total consumption,
followed by consumer products and the construction industry. This is similar to the situation
in Western Europe where packaging accounts for 37- 40% of the total plastics consumption
(APME, 2002; SGCCI, 2000; VKE, 2002). In the year 2000-01, the share of recycling
accounted for 47% of the total volume of waste generated including primary, secondary and
tertiary recycling (Muthaa et al., 2006). According to ICPE (2005) the per capita
consumption of the plastic is 4 kg in India whereas in china it accounts 18 kg while 20 kg in
the other developed nations. Recycling is highest in India that is 60 % while it comes only 20
% for the rest of the world.
Further, according to Muthaa et al. (2006) the consumption of plastics will increase
about six-fold between 2000 and 2030 and LLDPE, HDPE, PP will dominate in India due to
their versatility and cost benefits. PVC will grow very slowly because it will be replaced by
PP and HDPE. Due to the increasing share of long-life products in the economy, and
consequently in the volume of waste generated, the share of recycling will decrease to 35%
over the next three decades. The total waste available for disposal will increase at least 10-
fold up to the year 2030 from its current level of 1.3 million tones. This model result assumes
that the plastics recycling rates will remain at the current level for the next three decades.
However higher recycling rate improved waste management system still a strong
regulatory discipline is required in India because volumes of plastic waste will clearly rise in
the future as the per capita consumption of plastic products increases. Plastics waste
management, therefore, needs continued policy attention from both stakeholders:
Government and Industry. Some initiative examples are; Plastics Waste Management Task
Force established the Ministry of Environment and Forests in 1997 and the Indian Center for
Plastics and Environment (ICPE) that was established by the Indian plastics industry in 1999
(Muthaa et al., 2006).
Recently, Ministry of Environment and Forests issued a new gazette of rules (4th
Feb,
2011) known as Plastic Waste (Management and Handling) Rules, 2011. Some salient
features of these rules are; (a) No person shall use carry bags made of recycled plastics or
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 11
compostable plastics for storing, carrying, dispensing or packaging food stuffs. (b) No person
shall manufacture, stock, distribute or sell any carry bag made of virgin or recycled or
compostable plastic, which is less than 40 microns in thickness. (c) Sachets using plastic
material shall not be used for storing, packing or selling gutkha, tobacco and pan masala.
2.4 ISSUES RELATED WITH PLASTIC BAGS
Plastic grocery bags have been a part of daily life in developed countries since their
introduction in 1977 and in more recent years, their use has spread to many developing
countries as well (Williamson, 2003). Countless numbers of bags filling landfills and spilling
over every surface of the Earth (Chauhan, 2003; Thiel et al., 2003). This prevalence results in
several critical environmental and social impacts associated with their use and immediate
disposal. Plastic bags are also problematic in terms of the loss of agricultural potential and
impacts on tourism, in addition to the high cost of cleanup that falls to local and national
governments. In these regions, plastic bags are found everywhere, from remote tourist
destinations to city streets where they can clog drain pipes, contributing to massive flooding
that has already cost thousands of lives. In 2005, city Mumbai, India experienced massive
monsoon flooding, resulting in at least 1,000 deaths, with additional people suffering injuries
(The Asian News, 2005). City officials blamed the destructive floods on plastic bags that
clogged gutters and drains, preventing the rainwater from leaving the city through
underground systems. Similar flooding happened in 1988 and 1998 in Bangladesh that led to
the banning of plastic bags in 2002 (World Watch, 2004). By clogging sewer pipes, plastic
grocery bags also create stagnant water that produces the ideal habitat for mosquitoes and
other parasites that have the potential to spread a large number of diseases, such as
encephalitis and dengue fever, but most notably malaria (Edwards, 2000; World Watch,
2004).
Plastic also have the potential to leach their chemical components and toxins into soil
and water sources that can be passed on to humans, resulting in health dangers such as
neurological problems and cancers (Butte Environmental Council, 2001; Lane, 2003). Plastic
bags are mistakenly eaten by animals, leading to suffocation or blockage of digestive tracts,
and eventually death. South Africa, Kenya, Somaliland, and India are four nations that report
high levels of these problems, with as many as 100 cows dying per day in India (World
Watch, 2004; Edwards, 2000). Due to their propensity to be carried away on a breeze and
become attached to tree branches, fill roadside ditches or end up in public waterways, rivers
or oceans. In one instance, Cape Town, South Africa, had more than 3000 plastic grocery
bags that covered each kilometre of road (Ryan and Rice, 1996). In this century, an estimated
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 12
46,000 pieces of plastic are floating in every square kilometre of ocean worldwide (Baker,
2002). According to Williamson (2003) about 96 % of all grocery bags are thrown into
landfills. A bag can last up to 1000 years, inhibiting the breakdown of biodegradable
materials around or in it (Stevens, 2001). According to Matlack (2001) problems of air and
water pollution become more intensive in several countries with few environmental
regulations over plastic shopping bags that results in even greater impacts on the environment
and human health.
The ecological footprint of the plastic bag grows with each increasing statistic.
Australia alone imports 4 billion bags annually (Australian Bureau of Statistics, 2004).
Container ships used to transport these bags to each consumer country use fuels that produce
high levels of pollutants, such as sulphur (Long and Wagner, 2000). To illustrate, of the
estimated 4 to 5 trillion plastic bags produced per year, North America and Western Europe
account for nearly 80 %, with the U. S. that throwing away 100 billion plastic grocery bags
annually (Geographical, 2005; Murphy, 2005). Australia uses 7 billion plastic bags annually,
of that 53 per cent come from supermarkets (Australian Bureau of Statistics, 2004; Brown,
2003). The United Kingdom consumes between eight and 10 billion bags annually and in
Taiwan this number rises to 20 billion (Geographical, 2005).
2.5 PLASTIC FOOTPRINTS IN OCEANS AND IMPACT ON MARINE LIFE
Human activities are responsible for a major decline of the world‟s biological
diversity, and the problem is so critical that combined human impacts could have accelerated
present extinction rates to 1000–10,000 times the natural rate (Lovejoy, 1997). One particular
form of human impact constitutes a major threat to marine life: the pollution by plastic debris.
Plastics are synthetic organic polymers, and though they have only existed for just over a
century (Gorman, 1993). These threats to marine life are primarily mechanical due to
ingestion of plastic debris and entanglement in packaging bands viz. synthetic ropes and lines,
or drift nets Broken or discarded fishing gear, pellets, scrubbers, microplastics, films and
flakes (Gregory, 2009; Mallory et al., 2006; Thompson et al., 2004; Derraik, 2002; Moore et
al., 2001; Baird and Hooker, 2000; Blight and Burger, 1997; Laist, 1987, 1997; Quayle,
1992; Colton et al., 1974; Rothstein, 1973; Carpenter and Smith, 1972).
Plastic fragments on beaches are derived either (1) from inland sources and are
transported to coasts by rivers, wind, man-made drainage systems or human activity, or (2)
directly from the oceans where low density floating varieties accumulate and are transported
across great distances. (Corcoran et al., 2009) Floating plastic fragments in the world‟s
oceans have been reported since the early 1970‟s (e.g. Carpenter and Smith, 1972; Colton et
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 13
al., 1974), with the amount of debris showing a documented exponential increase (Ryan and
Moloney, 1993).
The majority of these items are non-biodegradable and can attract encrusting
organisms as drift plastics (Minchin, 1996; Gregory, 1983; Winston, 1982).Types and
amounts of plastic debris on beaches are controlled mainly by topography, current and storm
activity, proximity to litter sources and extent of beach use (Storrier et al., 2007). Surveys
carried out in South African beaches, showed that the densities of all plastic debris have
increased substantially (Ryan and Moloney, 1990). In Panama, experimentally cleared
beaches regained about 50% of their original debris load after just 3 months (Garrity and
Levings, 1993). Plastic pellets can be found across the Southwest Pacific in surprisingly high
quantities for remote and non-industrialised places such as Tonga, Rarotonga and Fiji
(Gregory, 1999). In New Zealand beaches they are found in quite considerable amounts, in
counts of over 100,000 raw plastic granules per meter of coast (Gregory, 1989), with greatest
concentration near important industrial centers (Gregory, 1977). Their durability in the
marine environment is still uncertain but they seem to last from 3 to 10 years, and additives
can probably extend this period to 30–50 years (Gregory, 1978). Since they are also buoyant,
an increasing load of plastic debris is being dispersed over long distances in marine
environments and beaches across the globe are littered with plastic debris. Items of plastic
have been reported from the poles to the equator (60–80 percent of marine litter being plastic)
(Oigman-Pszczol and Creed, 2007; Storrier et al., 2007; Thompson et al., 2004; Derraik,
2002, Gregory and Ryan, 1997). Even far and remote beaches (Subantarctic islands and
South Pacific) are becoming increasingly affected by plastic debris, especially fishinglines
(Walker et al., 1997; Benton, 1995)
In 1975 the world‟s fishing fleet alone dumped into the sea approximately 135,400
tons of plastic fishing gear and 23,600 tons of synthetic packaging material (DOC, 1990;
Cawthorn, 1989). Horsman (1982) estimated that merchant ships dump 639,000 plastic
containers each day around the world and ships are therefore, a major source of plastic debris
(Shaw, 1977; Shaw and Mapes, 1979). Recreational fishing and boats are also responsible for
dumping a considerable amount of marine debris, and according to the US Coast Guard they
dispose approximately 52% of all rubbish dumped in US waters (UNESCO, 1994).
Unfortunately, plastics do not degrade rapidly through mineralization, and may remain
in microscopic form indefinitely (Corcoran et al., 2009). Conventional plastics show high
resistance to aging and minimal biological degradation (O'Brine and Thompson, 2010) and
when they finally settle in sediments they may persist for centuries (Goldberg, 1995, 1997;
Hansen, 1990; Ryan, 1987). According to Kanehiro et al., (1995) plastics made up 80–85%
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 14
of the seabed debris in Tokyo Bay. The accumulation of such debris can inhibit the gas
exchange resulting hypoxia or anoxia in the benthos that can interfere with the normal
ecosystem functioning (Goldberg, 1994). In addition, chemicals including phthalates, PCB‟s
and organochlorine pesticides, reported in plastic fragments may present a toxicological
hazard (Teuten et al., 2009, 2007; Mato et al., 2001; Andrady et al., 1993). Dispersal of
aggressive alien and invasive species by these mechanisms leads one to reflect on the
possibilities that ensuing invasions could endanger sensitive or at-risk coastal environments
(both marine and terrestrial) far from their native habitats (Tourinho et al., 2010).
This plastic can affect marine wildlife in two important ways: by entangling creatures,
and by being eaten. However, the impact of plastic bags does not end with the death of one
animal; when a bird or mammal dies in such a manner and subsequently decomposes, the
plastic bag will be released into the environment to be ingested again by another animal
(Derraik, 2002). The problem may be highly underestimated as most victims are likely to go
undiscovered over vast ocean areas, as they either sink or are eaten by predators (Wolfe,
1987). Marine debris are affecting at least 267 species worldwide, including 86% of all sea
turtle species, 44% of all seabird species, and 43% of all marine mammal species (Laist,
1997). Some representative examples typifying the global spread of plastic ingestion
behaviour are red phalaropes (Connors and Smith 1982); 15 species of sea birds, Gough
Island, South Atlantic Ocean (Furness ,1985); Wilsons storm-petrels, Antarctica (Van
Franeker and Bell 1988); storm-petrels (Blight and Burger 1997); short-tailed shearwaters,
Bering Sea (Vlietstra and Parga 2002); southern giant petrels, Southern Atlantic Ocean
(Copello and Quintana, 2003); northern fulmars, Nunavut, Davis Strait (Mallory et al.,2006).
Most distressing, over a billion seabirds and mammals die annually from ingestion of plastics
(Baker, 2002). Brown (2003) mentioned that in Newfoundland 100,000 marine mammals are
killed each year by ingesting plastic.
2.6 ISSUES RELATED TO PLASTIC PRODUCTS MANUFACTURING
The manufacturing of plastic bags accounts for 4 per cent of the world‟s total oil
production (Greenfeet, 2004). The energy used to make one high-density polyethylene
(HDPE) plastic bag is 0.48 mega-joules. To give this figure perspective, a car driving one
kilometre is the equivalent of manufacturing 8.7 plastic bags (Australian Bureau of Statistics,
2004). If a country such as Ireland, with approximately 1.23 million shoppers, switched 50
per cent of plastic bag users to cotton, 15,100 tones of CO2 emissions would be saved per
annum. This is equivalent to one person driving around the world 1,800 times (Simmons,
2005). Two plastic bags require 990 kJ (kilojoules) of natural gas, 240 kJ of petroleum, and
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 15
160 kJ of coal (ILEA, 1990). Additionally, there are large amounts of energy used to acquire
oil, such as the large, fuel-burning heavy machinery, and most of the electricity used in the
process of manufacturing the actual bags comes from coal-fired power plants (Greenfeet,
2004).
Manufacturing process of plastic bags contribute to air pollution i.e. acid rain, smog
etc. Other harmful effects associated with the use of petroleum, coal, and natural gas, such as
health conditions of coal miners and environmental impacts associated with natural gas and
petroleum retrieval is a significant environmental impact. Additionally, the manufacturing of
plastic grocery bags produces waterborne waste, that has the capability of disrupting
associated ecosystems, such as waterways and the life that they support (Environmental
Literacy Council, 2005; ILEA, 1990; NPBWG, 2002).
Toxic chemicals that are most frequently released during the production of plastics
include trichloroethane, acetone, methylene chloride, methyl ethyl ketone, styrene, 3 toluene,
and benzene (IFC, 2009). Other major emissions are sulfur oxides, nitrous oxides, methanol,
ethylene oxide and volatile organic compounds (NSEPB, 1987). Benzene is believed to be
extremely toxic while a cause of cancer. Sulfur oxides are known to harm the respiratory
system, nitrous oxides adversely affect the nervous system and child behavioral development
and ethylene oxides harm the male and female reproductive capacity (Xiao and Levin, 2000;
IARC. 1998; Schaumburg, and Spencer, 1978; Seppäläinen and Tolonen 1974).
2.7 PLASTIC WASTE SCENARIO (QUANTITY AND COMPOSITION)
The dramatic increase in production and lack of biodegradability of commercial
polymers, particularly commodity plastics used in packaging (e.g. fast food), industry and
agriculture, focused public attention on a potentially huge environmental accumulation and
pollution problem that could persist for centuries (Albertsson et al., 1987). Moreover, the
problem of wastes cannot be solved by landfilling and incineration, because suitable and safe
depots are expensive, and incineration stimulates the growing emission of harmful,
greenhouse gases, e.g. NOx, SOx, COx, etc. (Miskolczia et al., 2004). The same as in
wealthy countries, light-weight and dirty plastics products (e.g. packaging films) are disposed
of in India together with the normal household waste (without reimbursement). The major
part of this waste stream is either dumped on landfill sites or remains in the environment
where it is the main contributor to littering. A minor part of this light-weight and dirty
plastics waste is suitable for recycling and is collected in various stages via various
middlemen; it ultimately finds its way to the preprocessors (Muthaa et al., 2006)
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 16
Since they are also buoyant, an increasing load of plastic debris is being dispersed over
long distances, and when they finally settle in sediments they may persist for centuries
(Goldberg, 1995, 1997; Hansen, 1990; Ryan, 1987). Clearly indicates the predominance of
plastics amongst the marine litter, and its proportion consistently varies between 60% and
80% of the total marine debris (Gregory and Ryan, 1997). Kikuchi et al. (2006) reported
following statistic data of composition of post-user plastic wastes (municipal waste and
industrial waste) in Europe; 32.9% low density polyethylene (LDPE), 14.1% high density
polyethylene (HDPE), 11.6% polypropylene (PP), 11.0% polyvinyl chloride (PVC), 8.7%
polystyrene (PS), 5.7% polyurethane (PU), 3.6% polyethylene terephtalate (PET), 2.5%
acrylonitrile butadiene styrene (ABS) and others.
Environmental health costs associated with a plastic product life cycle could reveal the
true costs of plastic bag consumption. Western nations have infrastructures that are able to
deal well with waste and recycling; generally do not feel the same effects of plastic bags in
the environment like underdeveloped countries (Spivey, 2003). However, this is far from the
case in developing nations where waste management is not well established or is non-existent
(Environmental Literacy Council, 2005). The effects of plastic bags are most severely felt in
poor and rural areas, where shopping bags are dispensed and used widely but not disposed off
properly (Reynolds, 2002). The footprint of plastic grocery bags also includes high civic
costs to governments, most of that are incurred through clean-up efforts. Plastic bags can
litter roads, sewers and waterways, making litter collection and disposal difficult and costly
(NPBWG, 2002; Reynolds, 2002; Ryan and Rice, 1996; World Watch, 2004). High costs are
being shouldered by governments and taxpayers that result in the loss of funds from other
services offered by the government. Because of this myriad of problems, many governments
have banned plastic grocery bags entirely or imposed levies on their use (The Asian News,
2005; Environmental Literacy Council, 2005; World Watch, 2004).
2.8 FACTS RELATED TO DEGRADATION OF PLASTIC
As a known fact, sustainability requires that a degradable material breaks down
completely by natural processes so that the basic building blocks can be used again by nature
to make a new life form (Gautam, 2009).
Plastics made from petrochemicals are not a product of nature and cannot be broken
down by natural processes. Also, there is no data presented about complete biodegradability
within the one growing season/one year time period. It is assumed that the breakdown
products will eventually biodegrade. In the meanwhile, these degraded, hydrophobic, high
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 17
surface area plastic residues migrate into the water table and other compartments of the
ecosystem causing irreparable harm to the environment (Gautam, 2009).
PE is a synthetic polymer with -CH2-CH2- repeating units in the polymer backbone.
Among different types of synthetic polymers, PE is considered to be highly resistant to
biodegradation. Several features of PE have been identified to make it resistant to
biodegradation: (1) highly stable C-C and C-H covalent bonds, (2) higher molecular weight
(MW) of PE polymer, that makes them too big to penetrate cell walls of microbes, (3) lack of
readily oxidizable and/or hydrolyzable carbonyl, amide, and C=C double bond groups etc. in
the polymer backbone, (4) lack of chromophores that can act as catalysts for synergistic
photo and biodegradation, and (5) highly hydrophobic nature. Because of these features, PE
has been considered almost inert to biodegradation and a literature review revealed differing
views among authors regarding whether to consider PE as a biodegradable polymer or not
(Gautam et al., 2007).
Some plastic articles may take 500 years to decompose (Gorman, 1993; UNESCO,
1994). Due to the long-life of plastics on marine ecosystems, it is imperative that severe
measures are taken to address the problem at both international and national levels, since
even if the production and disposal of plastics suddenly stopped, the existing debris would
continue to harm marine life for many decades (Derraik, 2002).
Synthetic polyolefins are inert materials whose backbones consist of only long carbon
chains. The characteristic structure makes polyolefins non-susceptible to degradation by
microorganisms. It takes several centuries until it is efficiently degraded (except when
exposed to UV from sunlight) (Yamada et al., 2001). Introduction of microorganisms for the
specific digestion of polymer materials is another more intensive approach that ultimately
costs more but it circumvents the use of renewable resources as biopolymer feed-stocks.
Although microorganisms are researched to target and breakdown petroleum based plastics
but this method only reduces the volume of waste and does not help in the preservation of
non-renewable resources (Andreopoulos, 1994).
According to Yamada et al. (2001) degradation always follows photo degradation and
chemical degradation. Otake et al. (1995) reported the changes like whitening of the
degraded area and small holes on the surface of PE film after soil burial for 32 years.
Biodegradation of LDPE film was also reported as 0.2% weight loss in 10 years (Albertsson,
1980). Polyvinyl chloride (PVC) is a strong plastic that resists abrasion and chemicals and
has low moisture absorption. There are many studies about thermal and photodegradation of
PVC (Braun and Bazdadea, 1986, Owen, 1984) but there only few reports available on
biodegradation of PVC.
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 18
In Europe, some countries allow the addition of paper and biodegradable polymers to
the bio-waste fraction (Venelampi et al., 2003). Wilde and Boelens (1997) have proposed
three characteristics of bioplastics and/or paper that would render them suitable for use in
composting and organic recovery. These characteristics are: biodegradation, disintegration
and no effect on compost quality.When plastics are exposed to UVB radiation in sunlight and
the oxidative and hydrolytic properties of the atmosphere and seawater, polymers can be
oxidized, forming hydroperoxides that lead to polymer chain scission (Billingham et al.,
2000). However, these would require further degradation before they would become bio-
available. The mineralization rate from long-term biodegradation experiments of both UV-
irradiated samples (Albertsson and Karlsson, 1988), In addition, the burning of
polyvinylchloride (PVC) plastics produces persistent organic pollutants (POPs) known as
furans and dioxins (Jayasekara et al., 2005).
On the other hand, it is important to have comparable international standard methods
of determining the extent of biodegradation. Unfortunately, the current standards have not, so
far, been equated to each other and tend to be used in the countries where they originated
[e.g. ASTM (USA), DIN (Germany), JIS (Japan), ISO (international standards), CEN
(Europe)]. Many, that are otherwise harmonious, differ in the fine details of the testing. There
is an urgent need to standardize all details so that researchers may know that they have all
worked to the same parameters (Shah et al., 2008).
2.9 PROBLEMS IN RECYCLING AND INCINERATION OF PLASTIC GARBAGE
According to conventional economics, recycling does economically efficient if it costs
more to recycle materials than to send them to landfills or incinerators. Many critics also
point out that recycling is often not needed to save landfill space because many areas are not
running out of it (Tierney, 1996). It is hard to understand why recycling is held to a different
standard and thus forced to cover its own costs. As well, the lower charges for depositing
wastes in landfills in North America and the lower prices paid for recycled plastic shows that
recycling is not a priority for most governments, businesses and individuals, causing grave
consequences around the globe (Porter, 2000). An ecoprofile analysis shows that the
incineration of plastics with heat recovery is the most environmentally friendly and resource
compatible process if it is not technically and economically easy to sort different types of
plastic material (Kikuchi et al., 2008).
McKinney and Schoch (2003) discussed three reasons that affect the recycling rates of
plastic bags. First, plastics are made from many different resins, and because they cannot be
mixed, they must be sorted and processed separately. Such labour-intensive processing is
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 19
expensive in high-wage countries like the United States and Canada. Most plastics also
contain stabilizers and other chemicals that must be removed before recycling. Second,
recovering individual plastic resins does not yield much material because only small amounts
of any given resin are used per product. Third, the price of oil used to produce petrochemicals
for making plastic resins is so low that the cost of virgin plastic resins is much lower than that
of recycled resins (Miller, 2005). Hence, recycling is not a simple solution to lessen the
ecological footprint of the plastic encroachment.
Recycling can be divided into further important categories, such as mechanical
recycling and chemical recycling. Chemical recycling is virtually a thermal method that
yields a liquid with high sulphur and nitrogen content. This is a disadvantageous property for
further utilization (Miskolczia et al., 2004). However, with used thin films, recovery is often
not economically feasible, more oil being used to provide the energy for collection and
sorting from other refuse than is saved by the recovery of the plastics material (Philip et al.,
1993). Although it is important to individually separate various types of waste plastic with a
high accuracy, it must also be environmentally helpful to sort mixed waste plastics according
to their final destination (waste-to-energy application or landfilling) by a simple approach.
Without proper measures, there may be no alternative but to dump them at a landfill. The
plastic densities change with the order PVC > PET > PU> PS > ABS > PE > PP. The number
of floatable plastics increases with an increase in the liquid density. After pre-sorting by the
current process, the mixed waste plastics contain 2.2% Cl. If these plastics are combined with
a waste-to-energy project the Cl content is too great for the same (Kikuchi et al., 2008).
However, mechanical recycling has some limitations. Firstly, the recycled plastics lose
their properties steadily and their final appearance is different. Besides, small contaminations
by other polymers give low quality plastics because of the material incompatibility, and
therefore they can only be used in lower-quality applications. Finally, mechanical recycling is
limited to thermoplastics (Aguado et al., 2006). However, recycling appeared to be a viable
way to reduce pollution and environmental damage when it was first introduced as a waste
reduction technique but use of plastics that are compostable or easily degraded must be
encouraged to reduce toxic emissions when plastic material is recycled or decomposed
(Kolybaba et al., 2003).
With regard to recycling the situation is very specific in India since the percentage of
plastics recycling is much higher than that in most developed and in many developing
countries e.g. China 10%, South Africa 16%, compared to ~ 47% in India (Muthaa et al.,
2006). The recycling sector in India has developed autonomously because of the particularly
low cost of labour and on account of the fairly large market for second-grade (lower-quality)
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 20
products. Recycled products are available at a 20–40% lower price than the same products
manufactured from virgin plastics. The cost per hour in India (according to report issued by
the Plast India Foundation) is 35 times less than in Germany, 19 times less that in the United
States and 6 times less than in Taiwan (NetPEM, 2001).
The pollution that occurs in the disposal stage is largely during incineration. A large
amount of plastic wastes is burnt in incinerators and burning of these chlorine-containing
substances releases toxic heavy metals and emits noxious gasses like dioxins and furans. The
latter two are two of the most toxic and poisonous substances on earth and can cause a variety
of health problems including damage to the reproductive and immune system, respiratory
difficulties and cancer. In fact, dioxin has been shown to have hormonal activity and is an
endocrine disrupt or disruptor (Hicks et al., 2005). On the other hand Incineration coupled
with energy recovery, that has received great support from the industry and Government in
India, could minimize the immediate waste disposal problems in India; but this could also
aggravate pollution problems if strict standards are not enforced. Further there are huge costs
associated with incineration, if it has to be profitable and carried out in an environmentally
friendly manner. Another key aspect is composition of municipal solid waste in India. The
waste has a very low calorific value and additional fuel is required to carry out incineration
effectively. This would further add to the costs associated with incineration. Another
important complication arising from introduction of incineration in India is that it may
adversely affect the recycling industry (Narayan, 2001).
2.10 BIODEGRADABLE POLYMERS AND BIO-PLASTIC (ISSUES AND SCOPE)
As a known fact, sustainability requires that a degradable material breaks down
completely by natural processes so that the basic building blocks can be used again by nature
to make a new life form. Plastics made from petrochemicals are not a product of nature and
cannot be broken down by natural processes hence the use of biodegradable is the need of the
hour to implement immediate application for biodegradable plastics (Gautam, 2009).
Marlet (2004) has shown that plastic bags are preferable to paper bags throughout their
life cycle due to lower energy needs for production and environmental pollution. Hill (2005)
was unable to show significant advantages or disadvantages of bags produced from one type
of plastic over those made from other kinds of plastic, including recyclable material (Ayalon
et al., 2009). Furthermore, comparison with the paper bag alternative, which is accepted by
the public as the „„greener” choice, reveals that the paper bag uses almost 10 times as much
material as that needed to produce a single-use plastic bag. The production process also
requires the use of cellulose derived from trees an important environmental resource for
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 21
sequestering greenhouse gasses. Moreover, the process of producing paper bags demands the
use of larger volumes of water than plastic bags and the degradation process of paper bags in
landfills releases greenhouse gasses. No difference was found between plastic and
biodegradable bags in reference to the problems associated with a whole life cycle, and both
these alternatives are preferable to the paper bag alternative (DEHA, 2002).
The great advantage of bioplastic is the conservation of fossil resources and reduction
in CO2 emissions. It makes them one of the most important innovations for sustainable
development. Plastics, with their current global consumption of more than 250 million tonnes
consume 5% crude oil. This consumption may appear comparatively small, however it does
emphasise how dependent the plastics industry is on oil. Making, disposal and recovery of
bioplastics have the additional advantage of using renewable resources. According to IBAW
(2004), the use of biodegradable plastics has doubled between 2001 and 2003 to 40,000
tonnes.
So far the paper and board sector has been by far the largest bio-polymer producer. Its
world-wide production amounted to approximately 365 million metric tonnes (Mt) in 2006
(FAO, 2008). Non-food starch (excluding starch for fuel ethanol), cellulose polymer and
alkyd resins are also important bio-polymers but they are much smaller in terms of
production volumes. In total, they account for approximately 20 Mt /yr, of that non-food
starch takes the lion‟s share (75% or 15 Mt), followed by cellulose polymers (20% or 4 Mt,
excluding paper) and alkyd resin (5% or 1 Mt) (Shen et al., 2009).
Bioplastics (Biopolymers) obtained from growth of microorganisms or from plants that
are genetically-engineered to produce such polymers are likely to replace currently used
plastics at least in some of the fields (Lee, 1996). The global interest in PHAs is high as it is
used in different packaging materials, medical devices, disposable personal hygiene and also
agricultural applications as a substitute for synthetic polymers like polypropylene,
polyethylene etc. (Ojumu et al., 2004).
2.10.1 Types of Biodegradable Plastics
According to Shen et al., (2009) there are three principal ways to produce bio-based
plastics,
i) To make use of natural polymers which may be modified but remain intact to a large
extent (e.g. starch plastics)
ii) To produce bio-based monomers by fermentation or conventional chemistry and to
polymerize these monomers in a second step (e.g. polylactic acid)
iii) To produce bio-based polymers directly in microorganisms or in genetically modified
crops.
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Naturally occurring biopolymers are derived from four broad feedstock areas Animal
sources provide collagen and gelatin, while marine sources provide chitin that is processed
into chitosan, are the most promising source for future development and expansion. Many
naturally occurring organisms (plant and animal) have potential to be modified and employed
as biopolymers. Microbial biopolymer feedstocks are able to produce polylactic acid (PLA)
and polyhydroxy alkanoates (PHA). The remaining two categories are the agricultural feed-
stocks. This variety of polymers falls into the categories of hydrocolloids, and lipids and fats.
Starch is an agricultural feedstock that is a hydrocolloid biopolymer (Martin et al., 2001;
Salmoral et al., 2000; Chandra and Rustgi, 1998). Amylose, the linear polymer, comprises
approximately 20% w/w of starch while amylopectin, the branched polymer, constitutes the
remain (Tharanathan, 2003).
Plastics can be made from other glucoseintensive materials such as potato scraps, corn,
molasses, and beets (Kings et al., 1992; Sharpley and Kaplan, 1976). As cornstarch is a
native agricultural product, replacement of petroleum-based plastics with starch-based
plastics could reduce our need to import petroleum or could conserve petroleum for other
uses. Starch is totally biodegradable. Degradation or incineration of starch in plastics would
recycle atmospheric CO2 trapped by the corn plant and would not increase potential global
warming (Swanson et al., 1993). Starch in many ways, as a filler and bonding agent as well
as a strengthen additive, is a good objective for the research in the making and development
of biodegradable materials (Andersen and Hodson, 2001; Yoo et al., 1995). Recently, starch
graft copolymers, starch-plastic composites and starch itself have been proposed as plastic
materials (Swanson et al., 1993). Natural filler materials may be incorporated into synthetic
plastic matrices as a rapidly biodegradable component. Often, granular starch is added to
polyethylenes in order to increase the degradation rate of the plastic material (Kolybaba et al.,
2003). Glycerol is often used as a plasticizer in starch blends, to increase softness and
pliability. Starch granules that have been plasticized with water and glycerol are referred to as
plasticized starches (Martin et al., 2001). Plastic materials that are formed from starch-based
blends may be injection molded, extruded, blown, or compression molded (Kolybaba et al.,
2003).
Cellulose has a very long molecular chain, which is infusible and insoluble in all but
the most aggressive solvents (Chandra and Rustgi, 1998). Therefore, it is most often
converted into derivatives to increase solubility, that further increases adhesion within the
matrix (Kolybaba, et al., 2003). Flax fibers continue to receive the majority of the
consideration of Canadian researchers, as they are mechanically strong and readily available
as agricultural by product or waste (Kolybaba et al., 2003). Chemical treatment (acetylation)
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 23
of the fibers is performed in order to modify the surface properties, without changing the
fiber structure and morphology (Frisoni et al, 2001). Bledzki and Gassan (1999) concluded
that fibers that have been thoroughly dried prior to being added to the matrix show improved
adhesion as opposed to fibers with a higher moisture content. Research has shown that
polyvinyl alcohol is an appropriate polymer to use as a matrix in natural fiber reinforced
composites, as it is highly polar and biodegradable (Chiellini et al., 2001).
Due to similar material properties to conventional plastics the biodegradable plastics
(polyesters), namely polyhydroxyalkanoates (PHA), polylactides, polycaprolactone, aliphatic
polyesters, polysaccharides and copolymer or blend of these, have been developed
successfully over the last few years. The most important are poly(3-hydroxybutyrate) and
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (Hocking and Marchessault, 1994;
Steinbuchel and Fuchtenbusch, 1998).
2.10.2 Economical Aspects of Biodegradable Plastic /Polymers
Bio-based plastics represent an emerging, very dynamic field with a very positive
development potential for the future. Bioplastics development is just beginning. Their market
share is currently well under one percent. The market is growing and in many application
areas e.g. packaging or agricultural films, the number and quantity are increasing
dramatically. Today, the combined volume of these non-food non-plastics applications of
starch and man-made cellulose fibers is 55 times larger than the total volume of the new bio-
based polymers (approx. 20 Mt versus approx. 0.36 Mt in 2007). The new bio-based
polymers may reach this level in 20-30 years from now. The use of starch for paper
production only amounts to 2.6 Mt and is hence still seven-folds larger than today‟s
worldwide production of bio-based plastics. By 2013, the world-wide capacity of bio-based
plastics could increase to 2.3 Mt and by 2020 to 3.5 Mt. (Shen et al., 2009). Starch is
inexpensive (about 10 cents/lb) and is available annually in multimillion ton quantities from
corn produced in excess of current market needs in the United States (Swanson et al., 1993).
Bio-based and biodegradable plastics are a very promising innovation for both industry
and the economy. The recommended products, that may be made out of compostable /
biodegradable plastics, are Agricultural Mulch Film, Nursery Bags, Garbage Bags / Wet
Waste Disposal Bags, Special Food Wraps, Coating on Paper/Jute/Textile, specialized fishery
items, plastic water bottles to be carried during expedition in mountains, cutlery to be carried
in boats / ships / trains, foam packaging products medical sector etc. Bioplastics sector
registers continuous growth: As estimated by IBAW, pan-European consumption of
bioplastics in 2003 was at 40,000 tons. This indicates that consumption has doubled from
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 24
2001. Especially in Great Britain, Italy and the Netherlands the market development was
dynamic (ICPE, 2010).
All over the world, industries are using various systems to manufacture biodegradable
bags. Om-Bioplast Ltd in Pune (India) uses carbohydrates to manufacture plastic that
disintegrate under UV radiation and also degradable by microorganisms. ECOSAC LTD,
official supplier of Ecosac Biodegradable/Compostable Packaging in the UK and Ireland. In
the US, BIO Group USA is the sales partner for Europe‟s major manufacturer of 100%
biodegradable and 100% compostable „„plastic‟‟ bags and films produced from cornstarch
(Mohee and Unmar, 2007).
According to Shen et al. (2009) the market of emerging bio-based plastics has been
experiencing rapid growth. From 2003 to the end of 2007, the global average annual growth
rate was 38%. In Europe, the annual growth rate was as high as 48% in the same period.
There are very large opportunities for the replacement of petrochemical by bio-based plastics.
World-wide, bio-based plastics add up to a total production capacity of 0.36 Mt in 2007 and
to 1.5-4.4 Mt in 2020. In terms of size, both small and medium enterprises (SMEs) and large
companies are active in the area of bio-based plastics. In most cases the SMEs were the
pioneers that made the first steps in technology development, production and
commercialization. These SMEs have partly grown to a remarkable size in the last ten years.
Successful reconstruction of the chemical industry using bio-based feed-stocks can be seen as
Third Industrial Revolution. The progress made in bio-based plastics in the past ten years is
very impressive. Also in research and development major activities are ongoing, contributing
to the increased attractiveness of chemical sciences and chemical technology for a new
generation of scientists and engineers. Even by 2020, the European production of biobased
plastics is projected not to exceed 2 kg per capita, while petrochemical plastics may amount
to 166 kg per capita (the current values are 0.27 and 103 kg per capita respectively). On the
other hand, the advantages of the slow substitution of petrochemical plastics are that
technological lock-in.
The concept of biodegradable plastics is new in India and research is still in
preliminary stage in the development of biopolymers due to higher cost and lack of
initiatives. The cost of biodegradable plastics is 2- 10 times more than conventional plastics
e.g. Oxo/Photo Degradable plastics film / bags - Rs.90 to 120 per kg and Biodegradable
plastics film / bags - Rs.400 to 500 per kg (Gautam, 2009).
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2.10.3 Decomposition of Biodegradable Plastic/Polymers
The decomposition of the biodegradable material sharply depends on the condition
provided (open heap, land-filling, different type of normal or controlled decomposing).
Decomposition rate varies with many factors like humidity, temperature, aerobic or anaerobic
conditions, depending on the formulation used, and the microorganisms required. Even the
material that is subjected to decomposition itself has its different susceptibility towards
decomposition. Polymers that are based on naturally grown materials (such as starch or flax
fiber) are susceptible to degradation by microorganisms (Kolybaba et al., 2003). When
biodegradable material (e.g. starch or cellulose) is used as an additive to a conventional
plastic matrix, is attacked by the microbes. The microbes start to digest the starch and when
the starch component has been depleted, the polymer matrix begins to be degraded by an
enzymatic attack results in the slowly reduced weight of the matrix until the entire material
has been digested (Huang et al., 1990). In an experiment Philip et al. (1993) tested some 33
different commercial formulations of polythene containing starch as an additive in five
different natural and seven different laboratory-model environments combinations, at time
intervals of up to one year. It was founded that of the 232 plastics/environments/time
combinations, fewer than 10% showed statistically significant degradation and
biodegradation tended to be faster in those with a high starch. As the microorganisms utilize
or remove the starch present in the polymer there would be some physical or mechanical
damage on the specimen (Austin, 1991). The process is called depolymerization. When the
end products are CO2, H2O, or CH4, the degradation is called mineralization (Hamilton et al.,
1995; Frazer, 1994).
It is important to note that biodeterioration and degradation of polymer substrate can
rarely reach 100% and the reason is that a small portion of the polymer will be incorporated
into microbial biomass, humus and other natural products (Atlas and Bartha, 1997; Narayan,
1993). The evaluation of visible changes in plastics can be performed in almost all tests.
Effects used to describe degradation include roughening of the surface, formation of holes or
cracks, de-fragmentation, changes in color, or formation of bio-films on the surface. These
changes do not prove the presence of a biodegradation process in terms of metabolism, but
the parameter of visual changes can be used as a first indication of any microbial attack (Shah
et al.,2008). Many biopolymers are designed to be discarded in landfills, composts or soil.
The materials will be broken down, provided that the required microorganisms are present.
Normal soil bacteria and water are generally all that is required, adding to the appeal of
microbial reduced plastics (Selin, 2002).
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2.10.4 Problems and Challenges
Products must be developed that satisfy real needs of the public. Performance must
meet public expectations and costs must be competitive to those of extant plastic materials
used for the same applications. Study of the influence of compounding variables on
morphology, physical properties, and biodegradability can provide basis for tailoring
properties of starch plastics to fit specific applications Lower material performance of some
bio-based polymers e.g. starch-based materials fell short in strength and impact properties is
also a big challenges that need to be successfully addressed (Swanson et al.,1993).
On the other hand, high cost for production and processing is major obstacle for the
development and establishment of biodegradable objects e.g. the cost of starch in Europe is
clearly higher than in the US. However, according to Shen et al. (2009) further, for starch
blends, the main cost component is the modification of starch and this area is of great thrust
for considerable for improvement. Use of agricultural land and forests, with maintaining
economical viability against the food production demand will be a limiting factor if bio-based
products increase in next decades. Adverse effects on biodiversity will be the other
environment and ecological issues.
As bio-polymers are modified for the bio-plastic purpose or incorporated with the
traditional non-degradable plastic, sustainable disposal, biodegradation and recycling of these
semi-biodegradable hybrids are another environmental, economical and technical concern
(Swanson et al., 1993).
2.11 CITATION OF RELEVANT PATENTS
Many inventions and research related to developments of different types of
biodegradable containers are compiled and registered as patents. Here examples of some
patents, mainly those of relevant to substitutes of polybags or useful for nursery purposes, are
cited;
Biby et al. (2001) documented a patent, entitled “Water resistant degradable foam
thermoformed sheet”, in that making of such foam that is the extrudate of a mixture of a
biodegradable polymer, starch, talc, and a blowing agent is provided. This foam is water-
resistant and in some variations waterproof making it an effective packing material that is
biodegradable, and thus, it can be disposed. In addition, the foam may be extruded into sheets
to form various articles. „Biodegradable cellulosic material and process for making such
articles‟, is another patent by Wyatt and Wyatt (1994). In this patent a process is described
for making a shaped biodegradable cellulosic article from cellulose-containing material
having a water content of less than about 50 percent by weight.
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 27
In his patent no. 7036272, Hermann (2006) disclosed a plant container consisting of
decayable and ecologically safe materials is collapsible and assembled from its parts
consisting of a pre-cut casing and a bottom made of dimensionally stable wire mesh or
biologically degradable plastic and a decayable organic material attached. The plant container
can be inexpensively transported and easily assembled just before it is put to use. It is
permeable to water and air, prevents the accumulation of wetness, root rot and mildew,
hinders the formation of spiraling roots and promotes a safe growth of the plant. The plant
container is robust and dimensionally stable and therefore suited for use with planting
machines. Patent No: 246163 entitled „Molded starch-bound containers and other articles
having natural and/or synthetic polymer coatings‟ by Simon (1999) described suitable
inorganically filled mixtures are prepared by mixing together a starch-based binder, a solvent,
inorganic aggregates, and optimal admixtures, e.g., fibers, mold-releasing agents, rheology-
modifying agents, plasticizers, coating materials, and dispersants, in the correct proportions
to form an article that has properties similar to articles as paper, paperboard, polystyrene,
plastic, or other organic materials and useful particularly in food and beverage containers.
Invention entitled as „Biodegradable or compostable containers‟ patented by Joe and
Christine (2003), provides an improved method and materials for biodegradable containers
using of a pre-gelled starch suspension that is unique in its ability to form hydrated gels and
to maintain this gel structure in the presence of many other types of materials and at low
temperatures. Patent no. 3852913, „Shaped biodegradable containers from biodegradable
thermoplastic oxyalkanoyl polymers‟ by Clendinning et al. (1974) disclosed the shaped
containers fabricated from material comprising biodegradable thermoplastic oxyalkanoyl
polymers, e.g., epsilon-caprolactone polymers, said containers possessing a medium to
germinate and grow seed or seedling, and optionally, a seed or seedling in such medium. The
resultant of scientific work entitled „Peat containers for the planting of containerized‟ by
William (1976) (Patent No: 3990180) describes manufacturing of an article that involves a
plug shaped receptacle or hollow container made of peat, pre-shaped and reacted at
conditions of temperature and pressure sufficient to cause reaction and polymerization of the
naturally occurring functional groups of the peat.
Theuer (2005) disclosed a research as „Plant pot that fertilizes when it biodegrades‟,
regarding a bio-pot that improves on present bio-pots in three ways. First, the current
invention remains sturdy until it and the growing plant it contains are transplanted into the
ground. This sturdiness is the result of a thin coating on the interior and exterior bottom of the
bio-pot that protects the pot from biodegradation before it is transplanted. Second, the current
invention competes in price with pots made from traditional petroleum-based plastic. Finally,
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 28
the invention improves plant growth that results after transplantation and the invention
biodegrades releasing the unique ingredient alluded to above, fertilizer.
The invention „Biodegradable container for liquid and/or semi-solid products united‟
by Dayton and Park (2010) provides methods and systems for constructing a container for
storage and transport and may be entirely biodegradable and/or recyclable. The body of the
container and/or bottle may be manufactured from paper pulp and assembled from a plurality
of dissimilar parts made of a biodegradable plastic resin and assembled to form a container
and/or bottle. The paper pulp may be treated inside and outside to make it water and air tight
but when exposed to extreme biodegrading influences it may breakdown into compostable
material. Other way is that it may be recycled again. In their patent named „Hydrophobic
biodegradable cellulose containing composite materials‟ Ioelovich and Figovsky (2001)
disclosed a invitation related to the field of manufacturing waterproof and biodegradable
cellulose containing composite materials like paperboard, cardboard and other cellulose
containing materials using natural polymers starch and its derivatives, dextrin, alginates,
lecithin, casein, gelatin, soybean protein and some synthetic polymers like methyl-
carboxymethyl- or hydroxyethyl-cellulose, polyvinyl alcohol, polyacrylic acid and other
hydrophilic polymers or their combinations used for manufacturing of cellulose composite
materials, like sized and coated paper, paper-and cardboard etc. It is well known to add
hydrophilic polymers to the pulp for sizing of cellulose material. The hydrophilic polymers
are also used for coating the surface of cellulose materials. The coated cellulose materials are
in fact composites and since the material of coating is biodegradable such composites are
environmentally friendly. The disadvantage of such composites is associated with the fact
that they are hydrophilic and not stable against humidity, water and aqueous solutions.
Invention named „Container‟ patented by Single (2005) relates to containers for
transporting plants. The invention relates to an easily assembled container to allow access to
inspect the root ball of a plant within the container. In this plant containers side walls and
base have holes or apertures that permit air to circulate around the container. This feature
facilitates air pruning of the roots as the root structure expands by virtue of the plant growing
in the container. Such a plant growth container and air pruning feature is also disclosed in
U.S. Pat. No. 5,099,607 entitled „Plant growth container‟ by Lawton (1992). This patent
discloses a container in that plants are to be grown and comprises of a flexible rectangular
section of material moulded into a lattice of recesses and corresponding protuberances. Roots
are guided into the recesses that converge to holes providing the air interface for air pruning
to take place. This plant growth container has the advantages of being easily adaptable in
diameter and is reusable.Similar plant growth container is also disclosed patent no. 4,939,865
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 29
named „Method and container for growing transplantable plants‟ by Whitcomb and Stephens
(1990). This patent describes a container comprising a set of upwardly extending removably
joined side panels having a lattice of protuberances and corresponding recesses converging to
holes. Whitcomb (2010) also presents patent entitled as „Plant container and method‟ with an
improved container and method for growing a plant to be subsequently transplanted. Another
patent no. 7481025 by Whitcomb (2009) also disclosed same type of plant container provided
with the facility for proper lateral root development.
Patent nos. 4,863,655 („Biodegradable Packaging Material and method of preparation
thereof‟ by Lacourse and Altieri, 1989) and 5,362,776 (Molded biodegradable packaging, by
Hornstein, and Landrum, 1998) disclose preparation of cellulose composite materials for
packaging that comprise cellulose fibers and hydrophilic binders like starch, gelatin,
polyvinyl alcohol, polyethylene glycol and polyethylene oxide. Despite these materials are
biodegradable they are not sufficient waterproof. Cellulose composite materials having
various hydrophobic protected coating layers have been proposed. Such protected coatings
contain various compounds, e.g. polyolefin and additives (Patent no. 5,296,307 by Bernstein,
1994, entitled „Laminated paper polyolefin paper composite‟) copolymers of olefins and
unsaturated carboxylic acids and pigments (Patent no. 3,970,629 by Izaki et al., 1976, entitled
„Composition for paper coating‟) a mixture of polyvinyl chloride and ethylene-acrylic
copolymer (Patent no. 4,365,029 entitled „Integral overwrap shield‟ by Frangipane et al.,
1995).
Patent nos. 3,985,937 ‘Method of forming a strengthened bond in a paperboard product
and products therefrom‟ by Culhane et al. (1995), 4,117,199 entitled „Process for producing
moisture and water-proof paper‟by Gotoh et al. (1978), 4,395,499 by Rosenski and
Fernandez (1983) entitled „High strength pigment binders for paper coatings containing
carboxylated vinyl ester alkyl acrylic interpolymers‟, 4,599,378 entitled „Vinyl
acetate/ethylene copolymer emulsions for paper coating compositions‟ by Hausman et al.
(1985), 5,763,100 entitled „Recyclable acrylic coated paper stocks and related methods of
manufacture‟ by Quick et al. (1998) and 5,744,547 entitled „Processes for producing vinyl
acetate polymer and saponified product of vinyl acetate polymer and resin composition‟ by
Moritani et al. (1998) are disclosed hydrophobic coatings for protection of cellulose
substrates containing aqueous latex of synthetic rubbers, polyvinyl esters, polyacrylates,
various copolymers, paraffin wax, organically acids, fillers and some other additives. The
coatings were applied on cellulose substrate in a form of aqueous latex and dried then. These
cellulose composite materials are waterproof, however their biodegradability is not sufficient
and therefore they cause pollution.
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 30
There are known also papers treated by silicon organic substances e.g. Patent nos.
3,856,558 entitled „Apparatus for treating cellulosic fiber-containing fabric to improve
durable press and shrinkage resistance‟ by McClain and Shattuck (1996) and 4,349,610
entitled „Method for waterproofing paper‟ by Parker (1982). Ioelovich and Figovsky (2001)
stated that these coated papers are sufficiently waterproof however they are bio-stable and
thus polluted the environment.
2.12 COMMERCIALLY AVAILABLE BIODEGRADABLE PRODUCTS
DOTPOT is a company of Arcadia that provides 100% organic and 100%
biodegradable pots for nursery purposes (Dotpot, 2010). These pots are claimed to be made
of all natural wood fibers, compressed peat moss and free from glues or binders allowing the
plant roots to grow right through the pot during a normal production cycle. The walls of the
pot do not impede plant growth. This creates a vigorous, non-girdled root system that spreads
out evenly and uniformly. The highly porous technology of the DOTPOT allows excluding
drain holes from the pots. Without glue or binders, air and water flow freely through the
entire container without the need of drain holes. The „Organic Materials Review Institute‟
(OMRI) has certified organic production, handling, and processing of the company.
Biodegradable pots known as „coir -pots‟ are also provided by company „Fertile Fibre
Limited, Hereford, UK‟ (Fertilefibre, 2010). Fertile pots are claimed to be biodegradable
fiber pots composed of long coir fibers are manufactured without the use of glues or binders.
These are not peat pots because water, air, and roots will penetrate the walls of the fertile pots
also there is no need for drainage holes. The natural root structure that develops helps to
ensure a successful transplant.
„GREENPOLY‟ is a Chinese company that produces Natural Vegetable Fiber Pot and
exports them. This company claims that these are made of natural vegetable fibers, and 100%
biodegradable resin include PCL (polycaprolactam), PVA (polyvinyl alcohol), PBS
[polybutylene succinate], PHBV [polyhydroxybutyrate-hydroxyvalerate], PHAs
(polyhydroxyalkanoate), PLA (polylactic acid). PCL and PVA always act as carrier resin for
100% biodegradable resin, both PCL and PVA originate from petroleum, but recognized as
biomaterials (Greenpoly, 2005).
„GREENEEM‟, an Indian company (Greeneem, 2010) manufactures biodegradable
cultivation pot made of coconut fibers named as Coco Coir Pot that is used for horticulture,
in ornamental plant, vine and tree nurseries, as well as for the domestic gardening market. It
has exceptionally high permeability to water, air and roots. Coco Coir Pots are claimed to be
very much suitable for faster cultivation, an excellent root system and re-establishment
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 31
without any shock from transplanting. When plants are grown in a Cocoa Coir Pot, the roots
quickly penetrate the pot walls. Contact with the air stops the roots from growing, root buds
start to appear and secondary roots start to develop throughout the pot. This phenomenon is
known as "aerial root pruning".
A U.K. Company named ECO-PACK produce, agro-fiber packaging material made of
more than 90% natural agricultural cellulose fibers (Eco-Pack, 2008). This company claims
that its products are pulp free, emissions free and chemical free. ENVIROARC, an Australian
company (Enviroarc, 2010), claims to be first company in the world that prefers bamboo pulp
for the use in the manufacturing of biodegradable ware. Raw material is 100% organic with
no contaminants, and an uninterrupted supply of raw material allows high volume production
as Bamboo grows naturally easily and quickly (without the need of fertilizers). EnviroArc
products are 100% natural hygienic suitable for use with foods oven proof can withstand heat
of upto1800C microwavable, acid, alkali and oil resistant. Period of degradation is adjustable.
Biodegradable products manufactured by a company named as ECOFORMS (Ecoforms,
2009) are made of Grain husks (primarily rice hulls) and natural binding agents (a
combination of starch based, water soluble binders and biodegradable additives). Under
normal conditions, a pot will last five years. These products are meant to be used and reused
above ground only. They will degrade in the landfill. Although they are not certified organic,
they are ideal for organic production. They contain non-polluting, earth-friendly ingredients.
2.13 NURSERY BAGS & CONTAINERS RELATED RESEARCH (TYPE/ SHAPE/
SIZE / DESIGN)
Plant production in containers is relatively new (Hani, 2009). The production of
container seedlings has increased considerably in the last decades (Dominguez et al., 2006).
In 1984, nearly all of the 10 million long leaf pine (Pinus palustris Mill.) seedlings, planted
in the southern United States, were produced in bare-root nurseries. Two decades later, about
48 million container-grown longleaf pine seedlings were produced that amounts to more than
70% of the total production (South et al.,2005). This rapid shift in stock type occurred
because survival of this species is often less than desired when bare-root stock is planted
(Boyette, 1996). Use of container stock increased average survival by perhaps 22% points
(South et al., 2005). Different container types have been developed that purport to improve
seedling growth and development in the nursery (Dominguez et al., 2006). Containers are
unique and unnatural environments for plants. The perched water table and restricted root
system, containers require changes and adjustments relative to plants grown in landscape
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 32
with natural soils i.e. bare root stock (Hani, 2009). Root restriction is an inherent problem
with container grown trees (Arnold, 1996).
In developing countries polybags are usually filled with native soil and placed on the
ground during production of the nursery crop (Mexal, 1996). Polybags are the most common
used plant growing vessel because of their low cost, apparent simplicity and convenience ,
however all these simplicity and low cost can be deceiving (Jones, 1993). Polyethylene bag
grown seedlings have a deformed taproot, because seedling roots tend to grow in spirals once
they hit the smooth inner surface, this inevitably lead to plants with restricted growth, poor
resistance to stress and wind-throw and even early dieback due to ensnarled root masses or
pathogens (Edwin et al., 2005; Jaenicke, 1999; Jones, 1993). Root spiraling (egression,
kinking, curling) is usually concentrated in the bottom of pots and has been observed in poly
bag seedling production (Aldrete et al., 2002; Sundstrom and Keane, 1999; Dumroese and
Wenny, 1997). Root development problems such as curling, matting and twisting are the
inherent problems of poly bags (Jones, 1993). These started to appear early at the time of
propagation and pose adverse effects into mature trees (Kevin, 2009; Edwin, et al., 2005;
Mexal, 1996; Josiah and Jones, 1992; Sharma, 1987). These deformations can affect seedling
performance several years after outplanting (Halter and Chanway, 1993; Lindstrom, 1990).
Kevin (2009) estimates that in waxflower planting the extent of loss due to planting of root
bound plants, range from 20 to 100% in different cases. Diseases such as collar rot
(Rhizoctonia spp. and Cylindrocladium spp.) were reported in the plants with knotted root
system after a few years in the field (Reid, 2004). Pruning off curled roots from the bottom of
spiralled roots systems has been used to negate the effects of spiralling (Owston and Seidel,
1978) but does not appear to be successful for many wildflowers-Seaton pers comm. (Kevin,
2009).
Another problem may arise when seedling roots reach the bottom of the bag, they may
enter the soil (Edwin et al., 2005). It also resulted in severing of roots during transplanting
and made subsequent harvest more difficult for the laborer. The resulting cutting or tearing of
roots to free nursery stock from soil adversely affects seedlings survival and growth (Hani,
2009; Dumroese and Wenny, 1997; Jones, 1993).
A relationship exists between root curling and the length of the root system, that is
controlled by time in tubes. It appears that one of the problems of the round tube system is
that if plants are left too long in tubes after root strike, spiraling occurs (Kevin, 2009).
Overgrown seedlings at planting out often lead to low-quality seedlings with root
deformation or J-rooting (Edwin et al.,
2005; Mangaoang and Harrison, 2003). Survival of
plants in the field was dependent on the age of tube stock (Salonius et al., 2000, 2002;
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 33
Burdett, 1978; Smith, 1962). In a research carried by Kevin (2009) plants that were held in
tubes from 7 to 16 weeks showed 20 to 30% losses in survival when out-planted. Plants that
had been held in tubes for 12 months before planting decreased to 50% of planting numbers
within 4 months of planting and all plants had died 12 months after planting. Kevin (2009)
advocates to minimize the nursery time for plants before planting out in the field.
It was understood from the studies that the plants grown in improved containers have
greater advantages than those grown in plastic and traditional containers (Hani, 2009). Root
trainers are better alternative to polybags as potting containers. Many alternative container
types have been designed to reduce the incidence of deformed roots (Gilman et al., 2003).
Root trainers are usually rigid containers with internal vertical ribs that direct roots straight
down to prevent spiraling (Jones, 1993). In a root trainer stock system, the containers are set
on frames above the ground (trays fixed on stands) to allow natural air-pruning of roots as
they emerge from the containers. The hole in the bottom of the cell facilitates natural air
pruning and drainage of excess water (Edwin et al., 2005). For a better criteria of plant
growing container Mullan and White (2002) concluded that the important factor in deciding a
cell shape is to prevent the development of a few dominant roots, and so produce a fibrous
root system that promotes the formation of a large number of active root tips on all sides;
holds the root ball together enabling easy handling without damage; once out-planted will
establish root apical dominance and lose the appearance of a planted root plug and develop a
natural root form; allows easy extraction to minimize damage in the field during planting.
Root trainer systems produce further benefits in simplifying nursery operations such as
disease and insect control, transportation and handling, and monitoring and sampling. Also,
the reusability of root trainer containers offsets their initial higher costs when compared to
poly-bags (Jones, 1993).
Edwin et al.
(2005) carried experiments on (Eucalyptus deglupta) and Mangium
(Acacia mangium) and found that Root deformation of seedlings was absent in hiko trays (a
tray set of root trainer) but high in the polybag seedlings. The nursery trial results indicate
that seedlings grown in hiko trays, although having significantly smaller diameter, height and
number of leaves but farmers and ACIAR researchers approved that these seedlings are of
high quality exhibiting straight shoot, trained roots and homogenous growth (Edwin et al.,
2005).Studies have shown that root trainer-grown seedlings have more vigorous and rapid
root growth than seedlings grown in poly-bags and most importantly, out planting survival
with the long-term survival is greatly ensured (Jones,1993). Although all type of containers
produced seedlings with some root spiralling, including those containers with ribs
(Dominguez et al., 2006) and the degree of deformation varies within and between species
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 34
(Kinghorn, 1978) but Improved container design can affect flexibility and 'shelf life' of plants
in the nursery (Hani, 2009).
Increased container size has been reported to cause increased canopy growth. The
large container volumes led to increased dry matter production that increased plant growth
rate in respect of shoot height, diameter, number of branches-leaves and biomass (Vizzotto et
al., 1993; Alvarez and Caula, 1993; Peterson and Krizeki, 1992; Peterson et al., 1991;
Gilliam et al, 1984; Biran and Eliassaf, 1980; Ruff et al., 1978; Richards and Rowe, 1977)
Seedlings in small containers results in root restriction that reduce canopy growth (expressed
as shoot length ,diameter , fresh weight and dry accumulation and leaf area) (Hanson et al.,
1987; Richards and Rowe, 1977; Vizzotto et al., 1993; Alvarez and Caula, 1993). Root
restriction reduces dry matter production but this has not been attributed to nutrient
deficiency (Peterson et al., 1991; Peterson and Krizeki, 1992; Ruff et al., 1978). The
relatively small size of seedlings in root trainers is attributed to the size of the container and
do not affect survival rate after outplanting. Large seedlings can become stunted when
planted in the field (Kevin, 2009; Edwin et al., 2005). Typically, larger seedlings cost more
initially (Davis et al., 2007), but can outperform smaller seedlings in the field (Dominguez et
al., 2006). The proportional balance of the shoot and root systems is important (Edwin et al.,
2005). O‟Reilly et al., (2002), recommended 3:1 shoot to root ratio (dry weight basis) for
most species seedlings ready to be planted which is a useful indirect measure of the balance
between the transpiration area and water-absorbing area.
Donahue et al., (1983) has also stated that growing media should have high water
movement, good drainage and aeration. The excess water not used by a seedling produces a
waterlogged condition that impairs aeration; this in turn reduces photosynthesis, translocation
and growth (Sutherland and Day, 1988). Alternatively, plants grown in more open surfaces
(walls and bottom) could have suffered from higher levels of moisture loss and hence the
reduction in root growth could be a form of stress response (Hani, 2009).
Each species responded differently to the type of container used (McConnughay and
Bazzar, 1991; Krizek et al., 1971). The type of nursery container used during production can
have a dramatic impact on root morphology of container-grown plants (Gilman, 2001;
Arnold, 1996). Shape of the container also influences the biomass production and root
architecture (Hani, 2009). In a study by Keever et al. (1985) the top dry weight of Euonymus
increased linearly in response to both increased pot diameter and pot depth, with greater
response from increased diameter. Keever et al. (1985) also observed that plant root growth
increased in deep pots. According to Schuch and Pittenger (1996), trees grown in tall
containers had 58% more root dry weight and 39% more shoot dry weight than when grown
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 35
in regular containers of the same volume. Larger container size is well correlated with larger
seedling size at the end of the nursery production cycle (Pinto, 2005). Generally, larger
container volumes have greater water and nutrients availability, along with more space for
root development that result in seedlings with larger height and diameter, greater nutrient
content thus better seed ling growth (Hsu et al., 1996; McConnughay and Bazzar, 1991).
With all the variables the ratio of container depth to container diameter is also an
important indicator of seedling development in the nursery, and the optimum ratio was 4
(Dominguez et al., 2006). The equal container volumes better growth would result with
containers with larger diameters (Hocking and Mitchell, 1974). Container depth has a greater
influence on species with dominant taproots and better for longer taproot system such as
Quercus (Dominguez et al., 2006). However, species with heavy lateral root development do
not grow well in narrow and long containers. Many others viz., Carlson and Endean (1976),
Hanson, et al. (1987), Dominguez et al. (2006) also found significant relationship between
the depth/diameter index of the container and the size of the plant. Growing density is also
correlated with seedling morphology and nutrient concentration in the nursery (Dominguez et
al., 2006). High density leads to plants with small stem diameter and less height growth
following outplanting (Landis et al., 1990).
Very few studies have assessed the relationship between seedling growth and container
shape without confounding influences from changes in container volume it is not easy to find
published comparisons for the results (Sutherland and Day, 1988). In a greenhouse
experiment conducted by (Hani, 2009) to investigate the influence of conventional plastic
containers and root trainers (spring ring containers) on root and shoot growth of two tree
species (Acacia saligna and Eucalyptus viminalis) it was revealed that in case of Acacia
saligna the leaf number, leaf area and total biomass production was not influenced by
container types. Root length was greater in root trainer and spring rings. However, root fresh
and dry were greater in conventional pots. In Eucalyptus viminalis plant height was higher in
conventional nursery pots, while the root fresh and dry weight was the same in both
conventional and spring ring pots. Leaf number, leaf area, total top fresh and dry biomass
were not significantly influenced by container types. The difference in shoot fresh and dry
weight was found to be negligible in both conventional pots and spring rings. This clearly
reveals that the top growth of Eucalyptus was same in all treatments as there was no marked
significant variation among treatments regarding the total top biomass showed that shoot
growth was not affected by the differences in containers shapes (Hani, 2009). Schuch and
Pittenger (1996) grew Eucalyptus citriodora in two different shapes of container and also
found no differences in shoot dry weight. Same results were found by Evans and Hensley,
(2004) where container type did not significantly affect dry shoot weights of Vinca and
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 36
Geranium when grown under simulated field conditions. Mark (2003) demonstrated that there
were no statistical differences in the growth parameters among four types of five types of
container shapes and designs.
2.14 AIR INDUCED ROOT PRUNING
Air root pruning is the technique wherein root tip exposure to air movement desiccates
and kills the root tip in a suitable container. As roots get pruned, the area behind the root tip
is stimulated to produce branches providing many more secondary roots (Whitcomb, 2005).
This root pruning presumably results in a more branched (fibrous) root system, which may
facilitate field transplanting and container production (Harrise et al. 2001).There are many
types of these air root pruning containers and bags and they vary greatly in their ability to air-
prune (Gilman et al. 2010). There are many patents are registered on root pruning
containers/bags e.g. Henry (1993), Henry and Henry (2007), Lawton, (1989) and Whitcomb,
(1985). In several research Air root pruning has been demonstrated for tree species using
open bottomed containers (Lovelace, 1998; Hoppé et al., 2005; Hoppé and Harun, 2005).
March and Appleton (2004) found no differences in shoot and root dry weights for Quercus
rubra (red oak) when different air root pruning container types were used. It was shown by
Gilman et al. (2002) that the caliper of Live Oak (Quercus viginiana Mill) was not affected
by root pruning, but slight impact on the height was seen. Gamble and Harun (2005) found
that those plants raised in containers which provided air pruning demonstrated accelerated
growth. Marshall and Gilman (1998) reported that AcceleratorR air root pruning containers
caused an increase in number of descending roots compared to smooth sided containers
probably due to the corrugated sides. Gilman et al. (2002) also reported that height of the
seedlings were reduced slightly but not found significant statistically and root weight: shoot
ratio was reduced when root pruning was carried out but root pruned seedlings had better
survival rate.
2.15 ROLE OF COPPER IN ROOT PRUNING
In the case of chemical induced root pruning, Copper compounds have been
extensively researched. Stinson and Keys (1953), Pellet et al. (1980), Ruehle (1985), Arnold
and Struve (1989) experimented copper compound as root pruning agent. Containers treated
with copper-based paints are now commonly used by growers to reduce root circling and to
increase root system febricity (Struve et al., 1994). Struve (1993), Arnold (1996) and Thomas
et al. (1996) applied 100 gm Cu(OH)2/liter in latex carrier at interior surfaces of containers
whereas Armitage and Gross (1996) applied copper hydroxide formulation (0%, 3.5%, 7%
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 37
and 11%) to plug trays. Neither foliar nor any other copper toxicity symptoms are reported in
these studies whereas roots get pruned on the contact with copper-treated containers/bags
wall. Copper-induced changes in root system morphology are associated with improved
mechanical stability (Burdett, 1978) and increased survival (Struve, 1993) of seedlings after
out-planting. Dumroese and Wenny (1997) carried out an experiment in which copper-treated
seedlings of Pinus ponderosa Dougl. produced a much finer, fibrous root system that was
well-distributed throughout the polybag but untreated seedlings were developed abundance
spiraling roots concentrated in the bottom of the polybag. Seedlings grown in copper-treated
polybags had heights, root collar diameters, and biomass values that were similar to those of
seedlings grown without copper whereas in the non-treated polybagss roots were spiraled
matted, often very thick, usually devoid of secondary roots, sometimes kinked, and probably
accounted for the 33% greater root volume, 32% greater root mass, and significantly lower
shoot-root ratio than that of copper-treated seedlings. An absence of copper promoted
surfaces resulted in accumulation of roots at container bottoms have also been reported by
others (Arnold and Struve 1989; Schuch and Pittenger, 1996). Same results were found in
Copper compounds treatments in nurseries experiments viz., in temperate conifers (Wenny
and Woollen, 1989; McDonald et al., 1984, 1981; Burdett, 1978; Saul, 1968), in temperate
hardwoods (Arnold 1996; Arnold and Struve, 1993; Arnold and Young, 1991), and in
subtropical hardwoods (Schuch and Pittenger 1996; Sparks, 1996; Svenson et al., 1995).
When Burdett and Martin (1982) chemically pruned conifer seedling root systems with
copper carbonate, they found that the treated plants were shorter than the controls. The
reduction in root mass of treated seedlings in our study may have been attributable to an
absence of roots at the interface between polybag and medium, as was concluded by Furuta et
al. (1972) for Eucalyptus viminalis Labill., and/or by the reduction of thick spiraled roots at
the bottom of polybags. Furthere it increases the shoot-root ratios significantly when
seedlings grew in contact with copper which again a good indication (Dumroese and Wenny,
1997). On the other hand several studies have shown that height and biomass were unaffected
by copper-coated containers (Wang, 1990; Wenny, 1988; Wenny and Woollen, 1989). South
et al. (2005) reported an increase in the biomass of the copper treated seedlings. Regan and
Davis, 2008 reported better seedling growth after outplanting of copper treated container
grown seedlings of western white pine (Pinus monticola).
Roots of seedlings exposed to the copper coating did not penetrate bottom drainage
holes (Dumroese and Wenny, 1997; Schuch and Pittenger 1996; Svenson et al., 1995; Arnold
and Struve, 1993). On the behalf of the several studied discussed here it can be concluded
that copper is toxic to roots, and roots will self-prune on contact with the copper-treated cell
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 38
wall. After outplanting, these root tips will grow more lateral roots, particularly in the upper
profile of the root plug (Campbell et al., 2006; Dumroese, 2000; Wenny and Woollen, 1989;
Burdett et al., 1983).
Crawford (1997) discussed a practical and commercial example of copper application
(The Spin-Out Coating) to improve nursery seedlings roots development in the container
media. When root tips reach the sides of the container, inhibits root elongation and deflection
and stimulates root branching. As the plant produces new roots, they are pruned, resulting in
a very fibrous root system. Thus Spin Out prevents the “cage root” condition where roots are
only present on the outside of the root ball. SpinOut-treated geotextile fabric prevents weeds
from becoming established by controlling roots that attach and grow through the fabric. This
concept has been also modified where SpinOut-treated fabric is cut into circles or discs and
placed on the tops of pots to control weeds as an alternative to herbicides. Treated fabric also
controls zoospores of Phytophthora crytogea and reduce the spread of disease from infected
to non-infected plants on a sand-bed. Capillary mats used for irrigation of greenhouse crops
remain free of algae growth when treated with Spin Out. Application of spinout coating was
found also helpful to reduce chlorosis in the plants.
In the case of direct availability or contamination of copper in the soil a less quantity
affects the plant health. Strandberg et al. (2006) reported that highest biomass was reached at
intermediate copper concentrations i.e. 200 mg/kg. In his experiment Kjaer and Elmegaard,
1996, studied copper effect on the seedlings of black bindweed (Polygonum convolvulus L.)
with the different dosages of copper sulfate and also found that dosages above 200 mg kg-1
reduced biomass and seed production. Aging of the copper-contaminated soil had only small
effects on bioaccumulation of copper, copper toxicity, and extractable soil copper fractions.
Soil copper had no effect on emergence of cotyledons (Bruus et al., 2000). Cu is a plant
micronutrient (Mutsumi et al., 2010; Michael et al., 2003) essential in several enzyme
systems with minimum requirements generally of 1–5 mg/kg in plant tissue, while at
concentrations higher than 20–30 mg/kg, depending on plant species, it may cause toxicity
(Marschner,1995).Toxicity symptoms include chlorosis, reduced growth, and root
abnormalities. Various mechanisms for dealing with elevated copper levels are found in
plants (Murphy et al., 1999; DeKnecht et al., 1995; Turner 1994; Ernst et al., 1992). Penta
hydrated Copper (II) Sulphate has many roles in different fields but in particular in plant
tissue culture copper salt is used to supply copper ion a micro nutrient (Ganapathi et al.,
2008). In a study copper was added as a CuSO4 solution and the sulfate concentration proved
less toxic than nitrate and chloride (Bruus et al., 2000).
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 39
2.16 COPPER AS BIOCIDE
According to the information rendered by Borkow and Gabbay (2005) the first
recorded use of copper in agriculture was in 1761, when it was discovered that seed grains
soaked in a weak solution of copper sulphate inhibited seed-borne fungi. The greatest
breakthrough for copper salts as fungicides undoubtedly came in the 1880's with the
development of a lime-copper formulation by the French scientist Millardet "Bordeaux
mixture." Within few years Burgundy mixture, also was prepared from copper sulphate and
sodium carbonate (soda crystals) and is analogous to Bordeaux mixture. Use of Bordeaux and
Burgundy mixtures against various fungus diseases were proved very successful in the
agriculture horticulture and forestry throughout the world. The use of copper sulfate for algae
control is still very common, primarily because of its low cost and eases of application.
Copper sulphate has been used to inhibit timber and fabric decay, since it renders them
unpalatable to insects and protects them from fungus attack. Copper sulphate has been in use
since 1838 for preserving timber and is today the base for many proprietary wood
preservatives. Today copper is used as a water purifier, algaecide, fungicide, nematocide,
molluscicide, and as an anti-bacterial and anti-fouling agent.
Copper also displays potent anti-viral activity (Yamamoto et al., 2001; Sagripanti and
Lightfoote, 1996; Sagripanti et al., 1993; Mitun et al., 1983). Copper Metal ions, either alone
or in complexes, have been used for centuries to disinfect fluids, solids and tissues (Block,
2001; Dollwet and Sorenson, 2001). Copper was found to be one of the most toxic metals to
heterotrophic bacteria in aquatic environments. Albright and Wilson (1974) found that
sensitivity to heavy metals of microflora in water was (in order of decreasing sensitivity): Ag,
Cu, Ni, Ba, Cr, Hg, Zn, Na and Cd. More than 23 copper compounds including copper
sulfate, are identified so far for their different applications as bactericide, algicide, fungicide,
molluscicide and acaricide (Borkow and Gabbay, 2005). Penta hydrated Copper (II) Sulphate
solution has anti fungal and anti-bacterial activity. It was also found suitable for surface
sterilization in tissue culture experiments (Ganapathi et al., 2008).
The mechanism of copper antifungal and anti-algae activity has not been well studied.
It has been suggested that the copper ions form electrostatic bonds with negatively charged
areas on the microorganism‟s cell walls. These electrostatic bonds create stresses that lead to
distorted cell wall permeability, reducing the normal intake of life sustaining nutrients
(Borkow and Gabbay, 2005). In contrast to the low sensitivity of human tissue to copper
(Hostynek and Maibach, 2003; DPT, 2002) microorganisms are extremely susceptible to
copper. Copper toxicity to microorganisms may occur through the displacement of essential
Chapter – 2 ………………………………………………….. Review of Literature ………..……………….…………………..…….. 40
metals from their native binding sites, from interference with oxidative phosphorylation and
osmotic balance, and from alterations in the conformational structure of nucleic acids,
membranes and proteins (Borkow and Gabbay, 2005).
The supposed mechanism of cyto-toxicity effect of copper sulphate has been proposed
by Carubelli et al. (1995). They found that the cyto-toxic effect may be mediated by a free
radical attack on proteinaceous components of the phage through a site specific generation of
hydroxyl radicals on protein-bound transition metal ions. According to Bartlett et al. (2001)
copper may attack sulfur containing amino acid residues in the proteins used for
photosynthesis inside an algae cell. As a result, photosynthesis is blocked and lead to cell-
lysis and death.
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