biomass energy conversion techniques

7/28/2019 Biomass Energy Conversion Techniques

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1. Biomass:- What is it?

Biomass is a natural product of Solar energy and a renewable source of carbon and hydrogen

which are basic constituents of energy and chemical products. The term bomass include all

plant life-trees, agricultural plants, bush grass etcand organic waste.

1.1 Biomass Energy Conversion Techniques:

The energy content in the biomass can be extracted by various methods. The selection of the

technology would depend on evarious factors such as Type of Biomass, End Use, Energy

content, Location( Urban/Rural) etc The below table shows various methods availble for

energy conversion-


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1.3 Classification of Technologies1.3.1 Direct Method

In this type technology the fuel will be directly burned to produce energy.

Different types of direct Methods are:

a. Incerination/ Combustion Mass Burning of Biomass in presence of excess air Similar to Conventional Fossil Power plants Conversion Biomass to electricity Used for thermal and electricity applications Old technology and is not widely practiced today due to production of Harmful gases.b. Combined Heat and Power

Used in Cogeneration cylces where thermal and electrical power is required. Improves Thermal Power Plant Efficiency Suitable for sugar industry

c. Biofuels Liquid biofuels include pure plant oil, biodiesel, and bioethanol. Biodiesel is based on esterification of plant oils. Ethanol is primarily derived from sugar,

maize, and other starchy crops.

Several processes exist to convert feedstocks and raw materials into biofuels. First-generation biofuels refer to the fuels that are produced through well-known processes

such as cold pressing/ extraction, transesterification, hydrolysis and fermentation, andchemical synthesis. The resultingfuels have been derived from sources such as starch,

sugar, animal fats, and vegetable oil

Second-generation biofuels are produced through more advanced processes, includinghydro treatment, advanced hydrolysis and fermentation, and gasification and synthesis.

They are in Research stage.

Can be used for Transportation segment. Reduces the dependence on fossil fuels forVehicles.

Requires large amount of land for the commercial production of Biofuel. Farmers may be attracted to cultivation of biofuels thus affecting the cultivation of

edible crops.


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d. Cooking and Related Applications

Biomass densification or briquetting. This is the process of compacting loosebiomass feedstocks into a uniform dense form, producing a higher quality fuel.

reduced emissions,and greater control for residential and industrial applications.

Briquettes offereasier transport, storage, and mechanical handling in both household

andindustrial settings.

Stalks, husks, bark, straw, shells, pits, seeds, sawdustvirtually any solid organic byproduct of agricultural or silvicultural harvestingcan be used as a

feedstock.


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Biomass wastes with relatively low moisture content (less than 15%) are most suitable

for efficient production of briquettes.

Ethanol gel. Ethanol gel is a clean-burning fuel that consists of gelatinized ethanol boundin a cellulose thickening agent and water

1.3.2 Indirect Methoda. Gasification

Conversion of Biomass to Synthesis Gas, which can be used for power generation Incomplete Oxidation of Biomass which produces carbonmonoxide, hydrogen,

Methane and other hydrocarbons

Better than Incerination as harmful gases produced is less. Syngas can be used to run IC engine, fuel for Boiler, Energy produced can be stored in form of ethanol, gas, etc..

b. Anaerobic Digestion Fermentation of bio degradable subjects Suitable for household wastes Biogas produced can be used locally for house hold cooking purposes. Large numbers of small scale Biogas Digesters have been used throughout many

developing countries.

c.

Biorefineries

A biorefinery involves the co-production of a spectrum of bio-based products (food, feed,materials, chemicals) and energy(fuels, power, heat) from biomass .

A biorefinery is a facility that integrates biomass conversion processes and equipment toproduce fuels, power, and value-added chemicals from biomass.

Analogous to petroleum refinery.


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d. Biochar Biochar is a fine-grained charcoal high in organic carbon and largely resistant to

decomposition.Biochar is produced by heating biomass in the absence (or under reduction)

of air, or pyrolysis. Low-cost, small-scale bio char production units can produce biochar to build garden,

agricultural, and forest productivity, and bioenergy for eating, cooking.

1.4 Prospective Projects:-

Small scale biogas plants can be installed in rural houses which can be used as cookinggas

Biomass gasification plants can be used for rural electrification- Decentralized powergeneration

Large scale cultivation of biofuel plants in waste land. Biofuels can replace fossil fuels fortransportation

Co generation using biomass should be made mandatory in industries to improve plantefficiency.

Agricultural wastes should used for power generation thereby improving the earnings offarmers.


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2. Waste to Energy Systems

2.1 Potiential of Waste to Energy Systems in India- Overview

About 115000 tons of solid waste is generated per day in the country. This figure couldbe twice as much by 2020.

Municipal solid waste is a potential source for recyclable and inert materials and canproduce value added products, in addition to energy recovery.

Business opportunities in waste to energy exist in all three stages of waste to energyWaste Transportation, Waste Management Facilities, and Waste Processing for Energy

Recovery.

Indian government actively encourages private sector participation in MSW value chainthrough a variety of business and operational models.

Currently, biomethanation and incineration are the most prevalent and maturetechnologies for MSW to energy in India. Gasification and pyrolysis are the emerging

technologies.

Inadequate segregation at source, sub-optimal regulations and incentives, inadequatetreatment facilities and immature technologies are some of the key challenges in this

sector.

Key success factors in waste to energy include optimal technology, efficient operations,focus on costs, and emphasis on environmental protection.

2.2 Waste to Energy Conversion Technologies

The most significant WTE technologies are based on biological or thermal methods. It is

essential that technologies identified, based on evaluation criteria consisting of technical,

commercial and environmental aspects, are employed for the WTE projects.

2.2.1 Basic Techniques of Energy Recovery from Waste

Energy can be recovered from the organic fraction of waste (biodegradable as well as non-biodegradable) through thermal, thermo-chemical and biochemical methods.

A brief description of the commonly applied technologies for energy generation from waste is as

follows

a. Anaerobic Digestion/Biomethanation


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In this process, the organic fraction of the waste is segregated and fed into a closed container

(biogas digester). In the digester, the segregated waste undergoes biodegradation in presence

of methanogenic bacteria and under anaerobic conditions, producing methane-rich biogas and

effluent. The biogas can be used either for cooking/heating applications, or for generating

motive power or electricity through dual-fuel or gas engines, low-pressure gas turbines, or

steam turbines. The sludge from anaerobic digestion, after stabilization, can be used as a soilconditioner. It can even be sold as manure depending upon its composition, which is

determined mainly by the composition of the input waste.

b. Combustion/IncinerationIn this process, wastes are directly burned in presence of excess air (oxygen) at high

temperatures (about 800C), liberating heat energy, inert gases, and ash. Combustion results in

transfer of 65%80% of heat content of the organic matter to hot air, steam, and hot water.

The steam generated, in turn, can be used in steam turbines to generate power.

c. Pyrolysis/GasificationPyrolysis is a process of chemical decomposition of organic matter brought about by heat. In

this process, the organic material is heated in absence of air until the molecules thermally break

down to become a gas comprising smaller molecules (known collectively as syngas).

Gasification can also take place as a result of partial combustion of organic matter in presence

of a restricted quantity of oxygen or air. The gas so produced is known as producer gas. The

gases produced by pyrolysis mainly comprise carbon monoxide (25%), hydrogen and

hydrocarbons (15%), and carbon dioxide and nitrogen (60%). The next step is to clean the

syngas or producer gas. Thereafter, the gas is burned in internal combustion (IC) enginegenerator sets or turbines to produce electricity.

d. Landfill Gas recoveryThe waste dumped in a landfill becomes subjected, over a period of time, to anaerobic

conditions. As a result, its organic fraction slowly volatilizes and decomposes, leading to

production of landfill gas, which contains a high percentage of methane (about 50%). It can

be used as a source of energy either for direct heating/cooking applications or to generate

power through IC engines or turbines.


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2.2.1 MSW to energy Systems-Overview


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2.2.1.1 Comparison of various methods


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2.3 Industrial Waste to Energy

The technologies, identified for conversion of different types of industrial waste in to energy are

given as:1 Liquids Biomethanation

2 Solids Gasification/Pyrolysis, Incineration/Combustion

3 Semi-solids Biomethanation, Gasification/Pyrolysis,Incineration/Combustion

Source: Technical Memorandum on Waste-to-Energy Technologies, February 2003

Methods to Convert Non Hazardous Waste to Energy

Industries Prominent Wastes Generated Treatment Option Application

Sugar Mills Sugar bagasses Combustion andGasification

Heat and Power

Pressmud Composting Fertilizer

Sugar molasses Fermentation Ethanol synthesis

Fermentative Yeast biomass Biomethanation Biogas production &

digestate

Slaughter houses Organs, Tissues, Blood, Hides,

Animal excreta and Carcass etc

Biomethanation Biogas production &

digestate

Paper mills Pulp Biomethanation Biogas production &

digestate

Paper shavings Combustion Heat and power

Wood wastes and Paper boards Combustion and

gasification

Heat and power

Dairy Plants Whey and Milk cream Biomethanation Biogas production &digestate

Sago factories Starch materials and peels Biomethanation Biogas production &

digestate


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Tanneries Hides and skins Acid treatments

and

biomethanation

Biogas production &

digestate

Animal Husbandries Animal excreta and body fluids Biomethanation Biogas production &

digestate

Fruits and vegetable

processing units

Pulp wastes Biomethanation Biogas production &

digestate

Analysis of Key Aspects of Waste to Energy Technologies

Criteria Incineration Anaerobic Digestion Gasification/Pyrolysis

A Feedstock

Industrial

Liquid Not suitable Suitable Not suitable

Solid Suitable Not suitable Suitable

Urban

Liquid Not suitable Suitable Not suitable

Solid Suitable Suitable Suitable

Farm

Poultry Suitable Suitable Suitable

Cattle Suitable Suitable Suitable

B Technology features

Technology status

Industrial Proven Proven Emerging

Urban Proven Proven Emerging

Farm Proven Proven Proven

Energy efficiency 85-90% (Based on

calorific value)

50-60% (Based on

volatiles)

90-95% (Based on

calorific value)

C Operating conditionsSystem

configuration

Complex Simple Complex

Process Flexibility Low Good Low

Modular Yes Yes Yes

D Capital, O & M costs


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Relative capital

cost

Very high Medium-high Very High

O & M High Low Limited

Commercial

viability

Less viable than others

owing to costlydownstream air

pollution control

Readily viable Varies considerably

Captive power

requirements

Significant (25-30%) Low (5%) Variable (5-20%)

Area requirements Elaborate Compact Compact

E Environmental

impacts

Can be minimized, but

requires expensive

technology

investments

Minimum Can be controlled to a

significant extent

F Socio-economic impacts

Public

acceptability

Not fully satisfactory Satisfactory Satisfactory

Waste disposal Complete, except for

ash to landfill.

Complete except for

sludge stabilization

Complete, except for

ash

biomass energy conversion techniques

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