Biomass Energy Technology

Wood Energy Data

Pre-Processing

Before biomass is converted into an other form of energy often, an intermediate step is involved to facilitate the handling of the biomass as well as improve the quality of the final combustion process. Drying, sizing and briquetting of the feedstock are among these pre-treatment activities.

Drying

The objective of the drying process is to decrease the moisture content of the fuel to a level suitable for use in the subsequent conversion process. Drying can be done via mechanical processes, thermal processes or in the open air. Mechanical drying (centrifuging, pressing) can only be used for very wet materials to be dried to a moisture content of about 50% (wet basis). Obtaining a moisture content below 50% requires thermal drying. Thermal driers suitable for biomass exist in various configurations such as belt driers, rotary driers and flash driers.

A modern dryer uses about 5,000-10,000 kJ thermal energy for the evaporation of 1 kg water. This means that decreasing the moisture content by approximately 10% consumes about 3.5-7% of the heating value of the dry material. It has been found that the overall costs of biomass fuel drying may vary between 7-22 US$/T. When local conditions of solar availability and humidity permit, solar drying is an interesting alternative.

Sizing

Many biomass residues are cut into smaller sizes for easy handling and efficient combustion. Straw and stalk-type materials are chopped by chaff-cutters into granular material for easy transportation. Similarly, wood is cut into chips for their efficient use in boilers. Size reduction is an expensive operation and requires high investment and operation costs (e.g. costs of chipped fuel may vary between 18-36 US$/m3).

Back to the top

Briquetting

Briquetting is a densification process of loose organic material, such as rice husk, sawdust and coffee husk, aiming to improve handling and combustion characteristics. There are various technologies for briquetting of biomass and one can make a distinction in: briquetting with binders, briquetting without binders (screw type, piston type) and bio-coal technology (carbonized briquettes with or without binders). Briquetting is practised on a limited scale in Asia, mainly due to its high production cost. Current research and development activities are aimed at reducing these. Extensive information about briquetting is available in RWEDP's publication about this subject and its manual on technology and practices of biomass briquetting.

India - Other Countries

India

Briquetting systems, India, 1995
Type	Capacity	Yield	mach.costs	plant costs	prod. costs	#Plants	Note/Source
	(kg/hr)	(%)	('000 US$)	('000 US$)	(US$/tonne)
screw press	1000	80	85	180	16.6		machines imported; TERI, 1997
screw press	100	90	7.5	10	16		machine locally made; TERI, 1997
piston press	1000	90	60	120	16.5-18		machines locally made; TERI, 1997
brick kiln carbon.+ semi-mech.briq.	1000 /day	35-40		20	30-35		TERI, 1997
mech carbon.+ briq.plant	5000 /day	30-40		100	18-20		TERI, 1997
low density briq.plant	500		1	4	16		TERI, 1997
Screw press machine	360-600						SEC=30-55 kWh/MT; RWEDP, 1996
Briquetting plant	500-2,000 /plant					29	SEC=53-70 kWh/MT; mainly piston press with capacity of 500 kg/hr; RWEDP, 1996
Briquetting plant	500-750 /machine					40-45	figures for 1999; SEC=38-45 kWh/MT;mainly piston press machines; WEN, 1999
Notes: mach.costs= machine costs, prod.costs= production costs, #Plants= number of plants as of reference year, SEC= Specific Energy Consumption, MT= metric tonne

Other Countries

Briquetting systems
Country	Year	Type	Capacity	Investm.	#Plants	Note/Source
			(kg/hr)	(US$)
Bangladesh	1990	Briquetting plant			1	mainly rice husk as fuel input; APDC, 1993
Malaysia	1995	Briquetting plant		536,000 /plant	6	mainly sawdust as fuel input, produce mainly charcoal briquettes, production cost 786,188 US$/yr for typical plant; RWEDP, 1996
Myanmar	1995	Screw press machine	60	2,000		typical price; WEN, 1995
Nepal	1990	Briquetting plant	500 MT/yr/plant		7	total 3,500 MT/yr; APDC, 1993
Phillipines	1990	Briquetting plant	1-50 MT/day/plant		9	mainly sawdust, charcoal fines and/or ricehusk as fuel input; RWEDP, 1996
Sri Lanka	1989	Briquetting plant	1 MT/day/plant	4,500 /plant	1	pilot project,baling press machine, coir dust as fuel input,production cost 16 US$/MT; FAO, 1990
Thailand	1989	Briquetting plant			9	among which 2 rice husk and 7 sawdust plants; RWEDP, 1996
Thailand	1995	Briquetting plant	500 /plant	50,000	10	among which 2 rice husk and 8 sawdust plants, production cost 50 US$/MT for typical plant; RWEDP, 1996
Notes: #Plants= number of plants as of reference year

Back to the top

Back to overview