trellisresin lca
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Life Cycle Assessment (LCA)
of Trellis Earth® Bioplastic
Relative to Conventional Polymers
www.TrellisEarth.com
*not for public domain release*
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Sources:
Environmental assessment of bio‐based polymers and natural fibers Dr. Martin Patel, Dr. Catia Bastioli, Dr. Luigi Marini, Dipl.‐Geoökol. Eduard Würdinger Utrecht University, Department of Science, Technology and Society (STS), Copernicus Institute, Padualaan 14, NL‐3584 CH Utrecht, Netherland. This definitive study defines many of the methodologies adopted by the industry in subsequent LCA studies performed on behalf of various commercial clients in the bioplastics industry. http://en.european‐bioplastics.org/
European Bioplastics e.V. published a 2008 Position Paper entitled "Lifecycle Assessment of Bioplastics" in which it outlines methodologies and issues related to bioplastics LCA studies. http://www.altumetrics.com/ Much of the material in this document is taken from the Altumetrics comparison of biopolymers to conventional polymers published in 2011. This report, which focuses on starch based resins (bio‐propylene, chemically equivalent to Trellis Earth(R) bioplastic) in comparison to conventional polypropylene (PP), Polyethylene terephthalate (PET), high impact polystyrene (HIPS) and low density polyethylene (LDPE), the most common alternative materials for food packaging including cutlery.
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Executive Summary Environmental considerations have been and will continue to be an important motivation to
develop and introduce bio‐based polymers and natural fiber composites. This calls for a comparison
of their environmental performance with their petrochemical counterparts. To this end, life cycle
assessment (LCA) can be applied, which is a standardized method to quantify environmental
impacts (ISO, 1997‐1999).
A Life Cycle Assessment (LCA) of the bio‐propylene that is chemically equivalent to the Trellis Earth
(R) brand bio‐resin and four conventional plastic resins was conducted by Altumetrics. The study
compared the pound‐for‐pound impact of bio‐propylene (a trade term for the Trellis Earth(R) brand
of bioresin) against conventional polypropylene (PP), polyethylene terephthalate (PET), high
impact polystyrene (HIPS) and low density polyethylene (LDPE).
This purpose of the study was to potentially to help customers understand the environmental
ramifications of their polymer choices. The boundaries of the study were from cradle to
customer, those that are using the Trellis Earth(R) brand products (up to the point of departure
from the Trellis Earth factory gate).
The plastics were compared by carbon footprint (global warming potential, GWP), resource
depletion, and an environmental score called ReCiPe, which combines environmental impacts into
a single value.
The study found that:
Trellis Earth bioresin had the best overall environmental performance. It had the
lowest carbon footprint (GWP) of any of the plastics. Its carbon footprint was 8% lower
than the best conventional plastic, which was PP, and 76% lower than the worst
conventional plastic, which was HIPS. This was when no credit was given for
plant carbon dioxide absorption. When credit was given, the benefit of Trellis Earth
bioresin was even greater: its carbon footprint was 32% lower than even the best
conventional plastic (PP).
In terms of the ReCiPe single score (which amalgamates environmental impacts into a
single value) Trellis Earth bioresin was found to be superior to all conventional plastics:
it was 23% better than the best conventional plastic, which was again PP.
The Trellis Earth bio‐resin also performed well against conventional plastics in terms of
abiotic depletion, where it was better than all conventional alternatives.
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Contents Executive Summary ....................................................................................................................... 3
Contents ........................................................................................................................................ 4
1 Introduction ............................................................................................................................. 5
2 Life Cycle Assessment............................................................................................................... 5
3 Goal and scope ........................................................................................................................ 7
3.1 Scope ................................................................................................................................ 8
3.2 Inventory Analysis............................................................................................................. 10
3.3 Impact assessment ......................................................................................................... 11
4 Inventory analysis.................................................................................................................. 12
4.1 Trellis Earth bioresin ........................................................................................................ 13
4.3 Conventional plastics ..................................................................................................... 14
5 Impact assessment ................................................................................................................ 1 9
5.1 Global Warming Potential .............................................................................................. 19
5.2 Abiotic Resource Depletion ............................................................................................ 23
5.3 Single environmental score ............................................................................................ 25
6 Sensitivity Analysis ................................................................................................................ 2 6
6.1 A change to the starch and PP content of Trellis Earth bioresin ...................................... 27
7 Conclusion ............................................................................................................................. 29 Appendix A: Description of Impact Categories ............................................................................ 31
5
Introduction Life cycle assessment provides a standardized method for measuring and comparing the
environmental impacts associated with the manufacturing, use and disposal of a product. This
study considers the production of each plastic to Trellis Earth’s factory outbound shipping gate. The
environmental impacts of each of the plastics have been assessed from raw material extraction
through to the production of finished goods.
Life Cycle Assessment Life Cycle Assessment (LCA) is defined by ISO (International Standards Organization) as the
“compilation and evaluation of the inputs, outputs and the potential environmental impacts of a
product system throughout its life cycle” (ISO 14040). In other words, an LCA identifies the material
and energy usage, emissions and waste flows of a product, process or service over its entire life cycle
in order for its environmental impacts to be determined.
Figure 1 illustrates the life cycle system concept of natural resources and energy entering the system
and product, emissions and waste leaving the system.
Figure 1, Typical categories of data collected to describe processes in LCA terms
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Companies undertake an LCA to understand the environmental performance of their product for
a variety of reasons including legislative pressures and supply chain issues. Another reason is the
increasing number of environmentally conscious customers who are demanding products that
combine the benefits of good functionality and low cost with high environmental performance. While
an LCA is a valuable tool, it should be emphasized that it is one of many factors, such as costs,
consumer acceptance and production feasibility, which companies must take into account during
the decision‐‐‐making process.
The technical framework for a life cycle assessment consists of four inter‐‐‐related stages: goal
and scope definition, inventory analysis, impact assessment and interpretation as shown in
Figure 2.
Figure 2, Stages of an LCA (ISO 14040)
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The ISO standards set out the requirements associated with each stage.
The goal and scope definition involves identifying the purpose of the study and the systems to
be studied, including setting the system boundaries and determining the level of detail
included.
In the inventory analysis all materials, substances and energy used and all emissions and waste
released to the environment are identified and quantified over the whole life cycle of the
product (from raw material extraction and processing, through manufacture).
The impact assessment is a technical, quantitative method used to assess the environmental
significance of the inputs and outputs identified in the inventory analysis. The impacts
considered can be divided into subject areas such as resource use, human health, and
ecological consequences.
In the interpretation stage, results are analyzed, limitations explained, conclusions are made
and recommendations are provided.
The following sections outline each of these stages for this project in detail.
Goal and scope The goal and scope of an LCA involves identifying the purpose of the study and information
relating to the systems being studied such as the system boundaries (i.e. what is
included/excluded from the study).
The purpose of this study was to evaluate the environmental impacts associated with Trellis Earth
bioplastic and four conventional plastics prior to their delivery to the customer.
Trellis Earth intends to use the results internally to help develop more environmentally
responsible polymer blends as well as use the results to help buyers evaluate its products with
environmental impacts considered when choosing between bioresin and conventional plastics.
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3.1 Scope
3.1.1 Functional unit Any comparison of life cycle impacts must be based on a comparable function (or “functional
unit”) in order to allow clear interpretation. The functional unit for the study was:
“The production of 1lb of plastic pellets”
All results contained within this report therefore represent the environmental impact
generated by the production of this unit. The pellets are designed to be functionally equivalent.
For example, 1lb of Trellis Earth bioresin is equivalent to 1lb of polypropylene when formed
into a product such as cutlery or deliware. However it is possible that in rare instances unknown
to Trellis Earth some applications may require different amounts of polymer to achieve
equivalent product performance. The discussion within the impact assessment (section 5)
directly compares the products considered on a pound for pound basis since this is the most
common situation when the resins are formed by a customer through extrusion, mo l d i n g
o r f o rm i n g a p p l i c a t i o n s . If a customer uses different amounts of material the results
of this study would need to be adjusted to reflect that situation.
3.1.2 Product systems and system boundaries The system boundaries define the life cycle stages and unit processes included in the systems
to be studied. This study considered one blend of bioplastic:
• Trellis Earth bioresin – containing a blend of polypropylene and starch (and additives).
The following conventional plastics were also considered in the study:
• Polypropylene (PP) – pellets containing conventional PP.
• Polyethylene terephthalate (PET) – pellets containing conventional PET.
• High Impact Polystyrene (HIPS) – pellets containing conventional HIPS.
• Low Density Polyethylene (LDPE) – pellets containing conventional LDPE.
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Each of the plastics considered have been evaluated from “cradle to gate”. Cradle to gate
means that the systems include the extraction of raw materials, the production and
transportation of input materials, and the production of products in Trellis Earth’s
facilities.
However, the system boundary of this study does not include the distribution of the product to
the customer or the disposal of products after use. Therefore, the differing impacts of these
plastics at end of life, such as composting and recycling, are not considered within this
study. Where a customer wishes to carry out an life cycle assessment of its product this study
may be used to contribute to that study to achieve a “cradle to grave” study.
3.1.3 Excluded processes Processes outside the system boundary are not included in the study. In particular these stages
of the life cycle are not included:
• Transport of products from Trellis Earth’s facilities to the customer (this
transportation would be the same for all polymers and so would not change the
results).
• Use of the customer’s product (products are various and not always known to
Trellis Earth, after delivery. In some instances, such as disposal methods, carbon
sequestration would vary, hence this study shows the two carbon extremes so that a
customer can see the range of results within which their product’s results would fall).
• Waste treatment (which would vary depending on the customer’s product).
The exclusion of these aspects is in line with the purpose of this study, which is to help
Trellis Earth R&D and introduce the issues to customers. A customer could build on this study
by including product stages in a life cycle assessment of its own particular product.
In addition to the processes excluded by the system boundaries, a number of other processes
have been excluded from the study. All excluded processes are outlined below:
• The construction, maintenance and demolition of industrial buildings and the
manufacture of machines and equipment was excluded from the study as these
impacts should be absorbed over the whole of the period of use. Experience shows that
these impacts are negligible compared with those linked to their operation.
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• Packaging used to transport materials between the supplier and the producer was
excluded as this impact was found to be negligible when compared to the impact of the
materials contained within them.
3.1.4 Key Assumptions and Limitations
Within any LCA some assumptions are required due to data constraints. The key assumptions
made within this study are outlined below:
• The transportation of all conventional plastics from the supplier to the producer was
based on distances provided by Trellis Earth.
• All road transportation was assumed to be via a 16‐‐‐32 metric ton truck.
• The use of natural gas during plastic product manufacture was assumed to be in a
>100kW modulating boiler.
• The production of conventional plastics was based on Ecoinvent data on polymer
production in Europe.
3.2 Inventory analysis Inventory analysis is the identification, collection and calculation of inputs and outputs of
environmental flows across the system boundaries. The inputs and outputs are scaled to the
functional unit and include both elementary and non‐‐‐elementary flows. Elementary flows are
materials or energy entering the system being studied, which have been drawn from the
environment without previous human transformation, or materials and energy leaving the
system, which are discarded into the environment without subsequent human transformation.
The software tool SimaPro was used to model the systems and calculate the environmental
impacts of the life cycle scenarios studied. SimaPro has been specifically developed by PRé
Consultants in the Netherlands for the calculation of life cycle impacts and is one of the world’s
leading LCA tools.
Life cycle Inventories generally contain hundreds of environmental flows for a single product
system. Life cycle impact assessment (LCIA) translates these flows into potential impacts on the
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environment enabling the evaluation of the systems through a number of impact categories
such as global warming and abiotic depletion.
Where generic average data has been used, data specific to United States was used in the
modeling where possible. However, in some cases the data represents a European average.
Primarily this data was obtained from the Ecoinvent database which contains the elementary
and non‐‐‐elementary flows for over 4000 industrial materials and processes.
3.3 Impact assessment The impact assessment phase of an LCA assigns the results of the inventory analysis to different
impact categories. The impact categories considered in this study were:
• Global Warming Potential (GWP or carbon footprint)
• Abiotic resource depletion
Global warming potential is a measure of how much of a given mass of a greenhouse gas (for
example, CO2, methane, nitrous oxide) is estimated to contribute to global warming. Global
warming occurs due to an increase in the atmospheric concentration of greenhouse gases
which changes the absorption of infra‐‐‐red radiation in the atmosphere, known as radiative
forcing leading to changes in climatic patterns and higher global average temperatures. Global
warming potential is measured in terms of CO2 equivalents.
For GWP, the IPCC 2007 characterization factors were used to translate the greenhouse gas
emissions generated by the life cycle scenarios into a single carbon footprint. These
characterizations factors do not included the absorption of biogenic CO2 from the atmosphere
during biomass growth and the release of biogenic carbon as carbon dioxide and methane
emissions during product degradation. This is a significant issue for polymers that contain
biomass, such as the bioplastics produced by Trellis Earth, since the exclusion of the absorption
of biogenic CO2 from the atmosphere during plant growth eliminates one of the key benefits
of the bioplastics. Therefore, to understand the relevance of this issue, these biogenic
impacts have been included as a sub category within the global warming results. This sub
includes the amount of biogenic carbon dioxide sequestered during production. However,
it does not consider the implications of product degradation and the potential release of
this biogenic carbon as carbon dioxide and methane as this degradation is outside the cradle
to gate scope of the project.
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For abiotic resource depletion, the CML 2 baseline 2000 method, a problem‐‐‐oriented approach
developed by the Center for Environmental Science (CML), Leiden University, the Netherlands,
was used. A description of each of these impact categories is given in appendix A.
To provide a greater understanding of the relevance of certain impact categories, the ReCiPe
method was also used to generate a single environmental score for each scenario. This method
normalizes and weights environmental impact categories and then combines them into a single
score in terms of eco‐‐‐points where 1,000 eco‐‐‐points is the equivalent of an average person’s
annual environmental load. ReCiPe was developed by panels of experts agreeing weightings of
different environmental issues. Any weighting is potentially controversial. For example, some
experts feel that ReCiPe assigns too much importance to GWP, whereas other experts feel this
appropriately reflects the importance of the global warming issue. Some experts even feel that
no weightings should ever be used, meaning no single score methodology should ever be used.
In recognition of this range of views, ReCipe results should be seen as “rule of thumb”
management summary indications rather than as “hard and fast” scientific fact.
The impact assessment reflects potential and not actual impacts and takes no account of the
local receiving environment. In addition, the underlying scientific knowledge, especially for fate
and exposure assessment, is still under development.
Included in the assessment is an evaluation of the GHG impacts both with and without biogenic
carbon. This is the approach recommended in the most recent GHG Protocol adopted by the
Sustainability Consortium. This approach is recommended by the Consortium because it
provides transparency: a reader who feels biogenic carbon should not be included can see
those results, while a reader who feels that it should be included can see those results. In
addition, in the case of Trellis Earth the approach makes sense because it shows the range of
potential results achieved by different Trellis Earth customers.
4 Inventory analysis This section describes the data used to model the life cycles of the five plastics considered
during the inventory analysis stage. The following sections describe the primary data (data
collected from the customer and suppliers) and secondary data (data provided by existing
datasets or assumptions) used to model the production of the bioplastics and conventional
plastics considered from cradle to gate.
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4.1 Trellis Earth bioresin
The diagrams in figure 3 show the cradle to gate life cycle of 1 lb of Trellis Earth bioplastic
pellets produced by Trellis Earth Products, Inc. The following sections outline the data used to
model the life cycle of this product based on the life cycle stages identified in this figure.
Figure 3, The cradle to gate life cycle of 1lb of Trellis Earth bioresin bioplastic pellets.
4.2 Additives The quantity of all additives required to produce 1 lb of bioplastic resin was supplied by Trellis
Earth. All input materials were assessed and modeled using the most appropriate
secondary data available.
4.2.4 Production energy
The production of grid electricity was based on the delivery of medium voltage electricity from
the US grid. The use of natural gas was modeled using European data on the delivery and
burning of natural gas for heat in a >100kW modulating boiler.
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4.2.5 Transport The transportation of materials from material supplier to Trellis Earth was based on
a combination of estimates and primary data provided by Trellis Earth. All distances from
the material supplier to Trellis Earth were provided by Trellis Earth.
4.2.6 Production waste
The disposal of the pellet production waste was based on wastage rates provided by Trellis
Earth. The landfill of pellet production waste was modeled using Ecoinvent data on the
disposal of mixed plastic to landfill and is representative of a Swiss municipal sanitary landfill.
4.3 Conventional plastics The following sections outline the data used to model the life cycles of the conventional
plastics considered in this study.
4.3.1.1 Polypropylene
The diagram in figure 7 shows the cradle to gate life cycle of 1 lb of polypropylene pellets
(as though) produced by Trellis Earth (for normalization purposes). The following section
outlines the data used to model the life cycle of this plastic.
Figure 7, The cradle to gate life cycle of 1lb of conventional polypropylene (PP) pellets.
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The production of polypropylene resin used in the conventional PP pellets was modeled using
Ecoinvent data representing the average of 28 production sites producing a total of 7.2 Mt in
Europe during 1999.
The transportation of polypropylene resin from the material supplier to Trellis Earth was based
on a distance of 940 miles by train provided by Trellis Earth. Rail transport was modeled
using Ecoinvent data representing the use of diesel rail freight in the United States.
The production of the plastic pellets was modeled using primary data on the use of grid
electricity and natural gas and was provided by Trellis Earth. A detailed site assessment was
undertaken and this showed that all the plastics were processed in the same way with the
same energy requirements (mixing, heating and pelletization were the same in each case). This
data was combined with secondary data from the Ecoinvent database on the impact of grid
electricity production and natural gas extraction and use. The production of grid electricity was
based on the delivery of medium voltage electricity from grid in the United States. The use of
natural gas was modeled using European data on the delivery and burning of natural gas for
heat in a >100kW modulating boiler.
The disposal of the pellet production waste was based on wastage rates provided by Trellis
Earth. The landfill of production waste was modeled using Ecoinvent data on the disposal of
mixed plastic to landfill and is representative of a Swiss municipal sanitary landfill.
4.3.1.2 Polyethylene terephthalate
The diagrams in figure 8 show the cradle to gate life cycle of 1 lb of the polyethylene
terephthalate pellets ( a s t h o u g h ) produced by Trellis Earth. The following section
outlines the data used to model the life cycle of these pellets.
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Figure 8, The cradle to gate life cycle of 1lb of conventional polyethylene terephthalate (PET)
pellets.
The production of polyethylene terephthalate resin used in the conventional PET pellets was
modeled using Ecoinvent data representing the production of a total of 569,000 t of
amorphous polyethylene terephthalate from ethylene glycol and PTA in Europe during 2000.
The transportation of polyethylene terephthalate resin from the material supplier to Trellis
Earth was based on a distance of 940 miles by train provided by Trellis Earth. Rail
transport was modeled using Ecoinvent data representing the use of diesel rail freight in the
United States.
The production of the plastic pellets was modeled using primary data on the use of grid
electricity and natural gas and was provided by Trellis Earth. This data was combined
with secondary data from the Ecoinvent database on the impact of grid electricity production and
natural gas extraction and use. The production of grid electricity was based on the delivery of
medium voltage electricity from the US grid. The use of natural gas was modeled using
European data on the delivery and burning of natural gas for heat in a >100kW modulating
boiler.
The disposal of the pellet production waste was based on wastage rates provided by Trellis
Earth. The landfill of pellet production waste was modeled using Ecoinvent data on the
disposal of mixed plastic to landfill and is representative of Swiss municipal sanitary landfill.
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4.3.1.3 High Impact Polystyrene
The diagrams in figure 9 show the cradle to gate life cycle of 1 lb of the high impact polystyrene
pellets ( a s t h o u g h ) produced by Trellis Earth. The following section outlines the data used
to model the life cycle of these pellets.
Figure 9, The cradle to gate life cycle of 1lb of conventional high impact polystyrene (HIPS)
pellets
The production of the high impact polystyrene resin used in the conventional HIPS pellets was
modeled using Ecoinvent data representing the average production of 15 sites of high impact
polystyrene from ethylene and benzene by free radical processes.
The transportation of high impact polystyrene resin from the material supplier to Trellis Earth
was based on a distance of 940 miles by train provided by Trellis Earth. Rail transport was
modeled using Ecoinvent data representing the use of diesel rail freight in the United States.
The production of the plastic pellets was modeled using primary data on the use of grid
electricity and natural gas and was provided by Trellis Earth. This data was combined
with secondary data from the Ecoinvent database on the impact of grid electricity production and
natural gas extraction and use. The production of grid electricity was based on the delivery of
medium voltage electricity from the US grid. The use of natural gas was modeled using
European data on the delivery and burning of natural gas for heat in a >100kW modulating
boiler.
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The disposal of the pellet production waste was based on wastage rates provided by Trellis
Earth. The landfill of pellet production waste was modeled using Ecoinvent data on the
disposal of mixed plastic to landfill and is representative of a Swiss municipal sanitary landfill.
4.3.1.4 Low Density Polyethylene
The diagrams in figure 10 show the cradle to gate life cycle of 1 lb of the low density
polyethylene pellets (as though) produced by Trellis Earth. The following section outlines the
data used to model the life cycle of these pellets.
Figure 10, The cradle to gate life cycle of 1lb of conventional Low Density Polyethylene (LDPE)
pellets.
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The production of the low density polyethylene resin used in the conventional LDPE pellets was
modeled using Ecoinvent data representing the average production of 4.79Mt of LDPE during
1999. The transportation of low density polyethylene resin from the material supplier to
Trellis Earth was based on a distance of 940 miles by train provided by Trellis Earth. Rail
transport was modeled using Ecoinvent data representing the use of diesel rail freight in
the United States.
The production of the plastic pellets was modeled using primary data on the use of grid
electricity and natural gas and was provided by Trellis Earth. This data was combined
with secondary data from the Ecoinvent database on the impact of grid electricity production and
natural gas extraction and use. The production of grid electricity was based on the delivery of
medium voltage electricity from the US grid. The use of natural gas was modeled using
European data on the delivery and burning of natural gas for heat in a >100kW modulating
boiler.
The disposal of the pellet production waste was based on wastage rates provided by Trellis
Earth. The landfill of pellet production waste was modeled using Ecoinvent data on the
disposal of mixed plastic to landfill and is representative of a Swiss municipal sanitary landfill.
5 Impact assessment The following sections outline the results of the impact assessment of the Trellis Earth
bioplastics and conventional plastics identified in section 3.1. The first section (5.1) provides an
overview of the carbon footprint results (Global Warming Potential, GWP). The second
section (5.2) outlines the results for abiotic resource depletion. The third section (5.3)
provides an analysis of the ReCiPe single environmental score results.
5.1 Global Warming Potential The results for the carbon footprint (Global Warming Potential, GWP) of all the plastics are
shown in table 1 and figures 11 and 12. The table and figures show the results excluding and
including the effect of biogenic carbon dioxide absorption during biomass growth. All results
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represent the functional unit (the production of 1lb of plastic pellets). The table shows the
results along with the best and worst option marked either red (worst) or green (best). The
figures show a breakdown of each plastic based on the life cycle stages identified in the
inventory analysis (section 4). The results can be summarized as follows:
• The Trellis Earth bioresin bioplastic had the lowest GWP per lb of any of the plastics
considered (both when the absorption of biogenic carbon dioxide was included and
excluded). It was found to be 8.1% lower than the nearest conventional plastic (PP) when
biogenic carbon dioxide was excluded. This difference rose to 31.7% when biogenic
carbon was included.
Table 1, The Global Warming Potential (GWP) of each plastic with and without the inclusion of biogenic carbon.
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Figure 11, The Global Warming Potential (GWP) of each plastic without the inclusion of biogenic
carbon based on life cycle stage.
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Figure 12, The Global Warming Potential (GWP) of each plastic with the inclusion of biogenic
carbon based on life cycle stage.
The results show that, when biogenic carbon was excluded, the plastic with the lowest GWP
per lb was the Trellis Earth bioresin while the plastic with the highest GWP per lb was HIPS.
In some cases the Trellis Earth bioresin bioplastic was very significantly better (76% lower than
HIPS) and in other cases it was significantly better but by a smaller amount (8% lower than PP).
The compostable bioplastics were all found to be superior to HIPS and competitive with APET.
However, they were found to be inferior to all other conventional plastics. This was due to a
number of factors including the greater transport distances involved (particularly for Ecoflex
from Germany) and the impact of material production. The split of impact between Ecoflex and
PLA was fairly even despite the use of a larger quantity of Ecoflex within each compostable
bioplastic. Therefore the PLA had the largest material contribution, almost entirely due to the
consumption of energy, from grid electricity and natural gas, used to produce it.
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When biogenic carbon was included in the impact assessment of GWP, the Trellis Earth
bioplastic was found to be superior to all other alternatives. The inclusion of the absorption of
carbon dioxide reduced the impact of the Trellis Earth bioresin by over 25% compared to the
original results due to the uptake of CO2 from the air. So the benefit of Trellis Earth bioresin
became even greater. The impact of the conventional plastics remained largely unchanged as
they did not include any renewable material in their composition.
5.2 Abiotic Resource Depletion The results for abiotic resource depletion using the CML impact assessment method for all
plastic pellets are shown in table 2. The table shows the results along with the best and worst
option in each category marked either red (worst) or green (best). All results represent the
functional unit (the production of 1lb of plastic pellets).
Table 2, The impact on resource depletion for each plastic.
Plastic products
Abiotic depletion
(lbs Sb eq/lb)
Trellis Earth bioresin 0.0283
Compostable 3000 0.0320
Compostable 3002 0.0325
Compostable 3010 0.0329
Polypropylene 0.0369
Amorphous Polyethylene Terephthalate 0.0386
High Impact Polystyrene 0.0443
Low Density Polyethylene 0.0377
The Trellis Earth bioresin was found to have the lowest abiotic resource depletion and was 23%
lower than the nearest conventional plastic (PP). Both the Trellis Earth bioresin and compostable
bioplastics were found to be superior to their conventional alternatives due to the reduced
quantity of fossil based plastic used to produce them. This is particularly clear in figure 13
which shows the results based on their life cycle stage. This shows that the impact of starch on the
Trellis Earth bioresin and PLA on the compostable bioplastics was relatively low compared to the
impact of the materials used in the conventional alternatives.
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Figure 13, The abiotic resource depletion of each plastic based on life cycle stage.
5.3 Single environmental score The ReCiPe impact assessment method was used to provide a single environmental score. The
Recipe method normalizes and weights a number of categories based on their relative
importance to provide a single score in eco‐‐‐points where 1,000 eco‐‐‐points is the equivalent of
an average citizen’s annual environmental load. This presents an understanding of the relative
importance of the impact categories considered in the previous section. However any
weighting method is potentially controversial since value judgments are involved (the
importance of one environmental issue compared to another is a human judgment). This
means that ReCipe results should be taken as an interesting management perspective rather
than hard science agreed by all stakeholders. The results were based on a Hierarchist
(balanced) perspective using world normalization factors and are shown in table 3 and figure
14.
The results show that Trellis Earth bioresin bioplastic was superior to all conventional
alternatives. The Trellis Earth bioresin was found to have a 16% lower score than the best
performing conventional plastic (PP). The best performing compostable plastic (Compostable
3000) had an impact only 1% greater than conventional PP, but 9% lower than APET, 24% lower
than HIPS and 1.3% lower than LDPE. For the Compostable bioplastics, the slight advantage
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gained through the use of renewable materials was balanced by the additional transportation
impacts required. However, the use of starch and other materials within the Trellis Earth
bioplastic gave it a clear advantage over conventional polymers.
Table 3, The ReCiPe single score results for each plastic.
Plastic products
ReCiPe World H/A Single Score
(Eco‐‐‐points/lb)
Trellis Earth bioresin 0.1568
Compostable 3000 0.1892
Compostable 3002 0.1904
Compostable 3010 0.1916
Polypropylene 0.1869
Amorphous Polyethylene Terephthalate 0.2082
High Impact Polystyrene 0.2479
Low Density Polyethylene 0.1916
Figure 14, The ReCiPe single score of each plastic based on life cycle stage.
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6 Sensitivity Analysis To provide a greater understanding of the influence of individual materials on Carbon Footprint
(Global Warming Potential, GWP), a range of sensitivity analyses were conducted.
Figure 15 shows the impact per lb of each of the major component materials utilized within all
of the bioplastics (including transportation to Trellis Earth). This shows that when biogenic
carbon dioxide absorption is excluded from the results, PLA and Ecoflex have the highest impact
per lb of the major materials, while starch has the lowest. When biogenic carbon dioxide
absorption is included, the PLA becomes superior to the conventional plastics (HDPE and
PP) dropping 61.5%, but the impact of Ecoflex only drops by 5.3%, making it the worst
option. In addition, the starch provides a negative GWP value meaning it provides a net
benefit to GWP through the absorption of carbon dioxide during growth.
Figure 15, The GWP per lb of each major input material including transportation to site.
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Figure 15 emphasizes that:
• Starch always has the best carbon footprint result, whether or not biogenic carbon is
credited.
• PLA shows very different results depending on whether biogenic carbon is credited: it
has the worst carbon footprint of any of the materials when not given credit for plant
carbon dioxide absorption, but the second best when given this credit.
• Ecoflex only improves slightly if given credit for carbon absorbed (which is to be
expected since it is not a plant based material), and in all cases Ecoflex has a worse
carbon footprint than conventional polymers (because it is derived mainly from the
same conventional monomers as PET, which is one of the higher‐‐‐impact conventional
polymers).
• HDPE and PP have very similar carbon footprints: they have a higher impact than starch
if carbon is not credited, and a higher impact than PLA and starch if carbon is credited.
6.1 A change to the starch and PP content of Trellis Earth bioresin Since starch has the lowest carbon footprint, it means that the environmental performance of
Trellis Earth bioresin improves if starch content is raised. However in reality the product would
become too weak if the starch content was too high.
A sensitivity analysis was carried out to show the benefit of an increase in starch content on
Trellis Earth bioresin (Figure 16). This figure shows that if no starch is included in Trellis Earth
bioresin and the proportions of the other materials remains the same (meaning it is made
up of PP and additives), the carbon footprint is 2.529 lbs CO2 (e)/lb (biogenic carbon included
and excluded). This would mean that Trellis Earth bioresin would still be marginally superior
to conventional PP (the reason it is not identical to PP is that it has additives). However, as the
content of starch begins to increase, the GWP falls (with and without biogenic carbon). The
result excluding biogenic carbon falls at a rate of 0.012 lbs CO2 for every 1% increase in starch
content while the result including biogenic carbon falls at a greater rate of 0.029 lbs CO2
for every 1% increase. Although a 100% starch content does not result in a negative value
like the starch material shown in figure 15, the GWP result including biogenic carbon drops
by 95% to just 0.139 lbs CO2/lb.
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Figure 16, The GWP per lb of Trellis Earth bioresin with increased/decreased starch content.
Conversely, figure 17 shows the implications of increasing the polypropylene (PP) content when
the proportion of the other materials remains the same. This shows that the impact of Trellis
Earth bioresin increases as the PP content increases at a rate of 0.006 lbs CO2 per 1%
increase when biogenic carbon dioxide is excluded. This again shows that as the content of
starch drops, the impact of Trellis Earth bioresin increases. However, even at 100% PP content,
the Trellis Earth bioresin is superior to all other alternatives and identical to conventional PP.
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Figure 17, The GWP per lb of Trellis Earth bioresin with increased/decreased PP content.
7 Conclusion The study found that the Trellis Earth bioresin was better than conventional plastics in terms of
global warming potential, abiotic resource depletion and ReCiPe single score.
The performances of the Trellis Earth bioresin was further found to be aided by the inclusion
of absorbed biogenic carbon dioxide in the measurement of global warming. T h e b ioresin
saw a 21‐‐‐25% drop in its impact when the absorption of CO2 during plant growth was included.
Carbon footprint results need to be taken in context with the use and disposal of the product
produced from the plastic. If the product is used for a significant period of time or does not
degrade, the carbon will remain sequestered within the material, therefore removing it from
the atmosphere for a significant period. Alternately, this benefit may be lost if the
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material is used in short term product and is either incinerated or entirely degrades within a
relatively short period.
The sensitivity analysis found that Starch had the lowest GWP of any of the materials used both
when biogenic carbon was included and excluded. However, even without a starch content, the
Trellis Earth bioresin bioplastic was found to be superior to conventional plastics (because in
this case it is made up of the best of the conventional plastics, PP, plus additives that have a
lower carbon footprint than PP).
To conclude, the results of this study found that:
• Trellis Earth bioresin had the best overall environmental performance. It had the
lowest carbon footprint (GWP) of any of the plastic pellets. Its carbon footprint was 8%
lower than the best conventional plastic, which was PP, and 76% lower than the worst
conventional plastic, which was HIPS. This was when no credit was given for plant carbon
dioxide absorption. When credit was given, the benefit of Trellis Earth bioresin was
even greater: its carbon footprint was 32% lower than even the best conventional
plastic (PP).
• In terms of the ReCiPe single score (which amalgamates environmental impacts into a
single value) Trellis Earth bioresin was found to be superior to all conventional
plastics: it was 23% better than the best conventional plastic, which was again PP.
Appendix A: Description of Impact Categories Abiotic depletion
What is it? This impact category refers to the depletion of non living (abiotic) resources such as fossil
fuels, minerals, clay and peat.
Why is it an issue? In 2006, WWF International reported that mans impact on global resources has
tripled since 1961 and is now 25% above the planets ability to regenerate itself. If the world’s
population shared a western lifestyle, three planets would be required to meet their needs.
How is it measured? Abiotic depletion is measured in kilograms of Antimony (Sb) equivalents.
Global warming
What is it? Global warming potential is a measure of how much of a given mass of a green
house gas (for example, CO2, methane, nitrous oxide) is estimated to contribute to global
warming. Global warming occurs due to an increase in the atmospheric concentration of greenhouse
gases which changes the absorption of infrared radiation in the atmosphere, known as radiative
forcing leading to changes in climatic patterns and higher global average temperatures.
Why is it an issue? If no action is taken to reduce global carbon emissions, average
temperatures are likely to rise by more than 2 degrees Celsius. This change will increase severe
weather such as tropical storms, droughts and extreme heat waves and heavy precipitation.
Stabilization would require emissions to be at least 25% below current levels by 2050.
How is it measured? Global warming potential is measured in terms of CO2 equivalents.
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