Environmental Engineering Reference
In-Depth Information
minimum estimate for the year 2000 was close to 40 EJ,
and more liberal assumptions, higher conversion factors,
and addition of minor biomass fuels (grasses, dung)
would raise the total closer to 45 EJ. For comparison,
Hall (1997) estimated that biomass supplied as much as
55 EJ during the early 1990s, the WEC (1998) assess-
ment of global energy resources used 33 EJ, and Turken-
burg (2000) bracketed the total at 45G10 EJ.
China and India are the largest consumers of wood
and crop residues in absolute terms. During the mid-
1990s, China's annual consumption was at least 6.4 EJ
and India's about 6 EJ (Fridley et al. 2001; RWEDP
2000). Brazil and Indonesia rank next, but in relative
terms sub-Saharan Africa, with biomass supplying in ex-
cess of 80% of fuel in most of its countries, comes first
(UNDP 2001). Among the most populous modernizing
nations the shares are still close to 15% in China, roughly
30% in India and Indonesia, and about 25% in Brazil
(IEA 2001). Fuel availability, climatic differences, and
cooking and heating habits explain large consumption
variation; most surveys indicate needs of 0.5-2.5 m
3
of
air-dried wood per capita per year, or about 5-25 GJ.
Published rates for countries whose rural population is
still almost totally dependent on wood, including char-
coal, range from 8-10 GJ for Zambia, Zimbabwe, Mad-
agascar, Kenya, and Ethiopia to about 15 GJ for Angola,
Ghana, Cameroon, Sudan, Nigeria, and Thailand, and up
to 34 GJ for equatorial Gabon, still with extensive tropi-
cal rain forest (Smil 1983; RWEDP 2000). For heavily
deforested, densely populated nations whose people burn
any available phytomass and dried dung, the rates are
much lower, a mere 1.9-3 GJ in Bangladesh, 7-8 GJ in
China, and 6-8 GJ in India. Yet even this low consump-
tion causes extensive environmental degradation because
the loss of vegetation accelerates erosion and reduces the
soil's nutrients, organic matter, and moisture-holding ca-
pacity. The most acutely affected areas are Africa's Sahel
and Namibia, Swaziland, Lesotho, and Botswana, the
Nepali hills, large parts of India and interior China, Ban-
gladesh, Pakistan, Afghanistan, Thailand, and much of
Central America.
The best conclusion would be that those traditional
rural societies still dependent on biomass fuels for all
their household heat consume annually as little as 5-9
GJ per capita of crop residues and dung just for simple
cooking (and even then experience seasonal shortages),
and they are reasonably well off with 15-30 GJ in tropi-
cal and subtropical climates even with inefficient stoves.
Potential savings from introduction of better stoves are
enormous, but actual achievements have been mixed.
Traditional open or partly enclosed fires convert less
than 10% (even less than 5%) of fuel's energy to useful
heat for cooking, and primitive stoves have efficiencies
between 5% and 15%. Unfortunately, many projects to
diffuse improved stoves, built mostly with locally avail-
able materials, were largely disappointing (Kammen
1995).
Many stove designs were still too expensive to be
easily affordable or not sufficiently durable or easy to re-
pair. Moreover, a good design is only a part of a much
broader effort that must also include training of local
craftsmen to build and repair such efficient units, active
promotion of new stoves, and where needed, financial
help in their purchase. The first encouraging success
came with China's National Improved Stove Pro-
gramme, launched in 1982 and initially aimed at 25 mil-
lion units within five years. This effort was gradually
transformed into a commercial venture, and by the end
of 1997 about 180 million stoves were disseminated to
some 75% of China's rural households (Smil 1987; K.
