|Boiling Point No. 39 - Using Biomass Residues for Energy (ITDG - ITDG, 1997, 44 p.)|
by Smail Khennas, International programme manager for energy, ITDG, Myson House, Railway Terrace, Rugby, Warwicks, CV21 3HT.
Figure 1: Use of dung and crop residues in developing countries
Despite the penetration into people's lives of more efficient stoves, and to a lesser extent the policies carried out in urban areas to substitute petroleum products such as liquefied petroleum gas (LPG) to biomass energy, the pressure on wood fuels remains unabated. Even when they are available, petroleum products are not affordable to poor people, who are the main users of wood-fuels. Bio-residues (dungs from animals and different types of crop residues) are already widely used in some countries and there is still a great potential to be tapped.
However when bio-residues are taken out from agricultural lands, the ecosystem may be affected, resulting in a diminution of the productivity or a need for more chemical fertilizers to maintain the same level of production. It is estimated that some 60% of the world's population live in rural areas of developing countries and rely on agriculture for their livelihood. It is therefore crucial to include this dimension before carrying out any policy aiming at a wider utilization of bio-residues in rural areas.
It is estimated that about one billion people rely on residues as their principal cooking fuel. In many areas, particularly in Asia, the commercialisation of bio-residues is a source of modest income but at the same time it is a burden for poor people. Very often the utilization of bio-residues is associated with a very low efficiency and therefore a higher level of smoke emissions and a negative impact on health. The conversion of bio-wastes to a more dense form such as briquettes increases the efficiency and, if the process is well managed, it can lead to the introduction of technical change and the development of small enterprises in low income, areas.
Although the technologies so far used for briquetting are high cost, there are prospects to use low cost technologies, for example low pressure technology which is suitable for some biomass residues. Apart from briquetting, other technologies such as a hand operated compacting press may be considered. It is believed that the investment to develop and manufacture this type of equipment is very low. The technical change in the area of bio-residues may increase the supply of improved biomass fuels for poor people and create an enabling environment to sustain the business while the environmental impact is minimized.