UNEPInternational Environmental Technology Centre1

Converting Waste Agricultural Biomass into Useful Energy

Surya Prakash ChandakSenior Programme Officer

International Environmental Technology CentreDivision of Technology, Industry, and Economics

United Nations Environment Programme(UNEP DTIE IETC)

HP: www.unep.org, www.unep.fr, www.unep.or.jp

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What is biomass

Broad term generally refers to any plant or animal matter.

Waste Biomass – Main Categories

• Waste agricultural biomass• Forestry residues• Wood• Animal residues• Organic waste from cities and

dwellings

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Why convert waste agricultural biomass into energy/materials ?

• Reduced carbon emissiona) Due to obviating use of fossil fuelsb) Due to avoidance of open burning and rotting

(methane emission)• Enhanced energy security• Enhanced access to energy particularly in rural

areas• Reduced problem of management, treatment and

disposal• Additional revenue for farmers• Job creation

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Global availability of waste agricultural biomass

1 Exa joule = 1018 Joules : 1 KiloJoule = 0.239 Kcals: 1 EJ = 24 million tons oil (approx.)

Region MaizeStraw

WheatStraw

RiceStraw

Bagasse TOTAL

Africa 0.48 0.25 0.20 0.54 1.47

US & Canada

2.95 1.93 0.13 0.19 5.20

Latin America

0.71 0.38 0.29 3.58 4.94

Asia 1.74 3.65 8.96 3.19 17.54

Europe 0.61 2.39 0.04 0.00 3.04

Oceania 0.23 2.26 0.06 0.22 2.77

TOTAL 6.72 10.86 9.68 7.72 31.98 (765 million tons oil

(in EJ/year)

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Geographic distribution of availability of waste agricultural biomass

Region Maize* Wheat** Rice Cotton Sugar# Total

China 8 6 15 3 2 33

India 3 3 8 1 3 18

All Asia 13 13 39 5 6 77

Brazil 2 0 1 1 4 8

All South America

5 1 1 1 5 13

Africa 5 1 1 1 1 9

TOTAL of Asia, S. America and Africa

23 15 41 7 12 100

*including millet and sorghum**including barley#including minor agro industry

(in percent of total)

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Technologies for converting waste agricultural biomass into energy

Waste Agricultural Biomass to Energy – Technology Options

Basic Process Type of Technology

Examples of types of waste handled

Biochemical (anaerobic)

Fermentation Fruit and vegetable market waste, waste from fruit/vegetable processing industries

Biochemical (aerobic)

Fermentation Sugar/starch containing wastes like waste palm trees

Thermo-chemical

Pyrolysis Crop residues such as wheat straw, rice straw, rice husk, coconut shell

Thermo-chemical

Gasification Crop residues such as wheat straw, rice straw, rice husk, coconut shell

Thermo-chemical

Direct Combustion

Crop residues such as wheat straw, rice straw, rice husk, coconut shell

Physical Processing

Briquetting Waste saw dust, waste wood chips

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Interesting features of converting waste agricultural biomass into energy

• Availability of energy source at the place which is energy-starved and conventional energy (electricity and fossil fuels) systems are difficult to reach there• Abundant availability -- a large amount is currently wasted by either burning open or by allowing it to rot in the field• Little or no pollution; generally no emissions of toxic gases like sulfur oxides and nitrogen oxides• Provides a clean fuel for both domestic and commercial use – current patterns of using WAB directly in households usually gives rise to emission of smoke and gases which are very harmful to human health• Can provide and alternative source of income to farmers• Can spur rural economic development due to enhanced energy availability thus generating jobs• Climate neutral

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Constraints in converting waste agricultural biomass into energy• Dispersed availability spread over wide areas hence challenges of collection• Usually voluminous material hence high transportation cost per unit weight – compacting prior to transportation may be required• Lower calorific value as compared to fossil fuels particularly oil and gas• Some WAB has high moisture content (e.g. fruit and vegetable waste) • Some WAB is easily putrescible (e.g. fruit and vegetable waste) • Seasonal availability and variations•Matching of demand and supply of energy – energy load in rural areas varies widely over the day

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Features for considerations when converting waste agricultural biomass into energy

• Systems required for collection and compacting• Considerations for future costs of WAB although it may be available free at present• Considerations for alternatives if WAB is being used for some other purposes presently e.g. as domestic fuel, animal feed, mulching for soil etc.• Cost of transportation in case of large size WAB2E systems• Disposal of ash particularly for WAB like rice husk• Flexibility in WAB2E systems to use different WAB• Storage of WAB to meet the needs during lean seasons• WAB2E systems to have high turn down ratios and/or systems to store energy

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What needs to be done for converting waste agricultural biomass into energy

• Assessment of WAB quantities generated and quantity available for conversion into energy – careful consideration of seasonal variations• Characterization of WAB• Study of possible systems for collection, compaction and transportation• Assessment of present cost structure and projections into future, including cost of transportation• Assessment of present energy demand (type and amount) and projections into future• Assessment of funds availability• Assessment and selection of WAB2E technology• Development of a management system for sustainable operations• Supportive policy framework

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What this project on converting waste agricultural biomass into energy aims at

• Building capacity on various aspects of WAB2E: assessment of quantification and characterization, assessment of prevailing management systems, assessment and selection of technologies

• Provide hands-on experience by working at a selected site

• Demonstration of an appropriate technology which can be further replicated

• Getting together technology suppliers and entrepreneurs to facilitate commercial uptake of WAB2E systems

• Support to government on framing conducive policies

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THANK YOU

For further information:http://www.unep.org