|Boiling Point No. 39 - Using Biomass Residues for Energy (ITDG - ITDG, 1997, 44 p.)|
Mohammad Aslam, IT Bangladesh, GPO Box 3881, Dhaka, Bangladesh.
Introduction aux besoins en rgie domestique au Bangladesh
Au Bangladesh plus de 90 % des mges utilisent la biomasse comme combustible pour la cuisson. Les mges les plus dnis utilisent des rdus vtaux ou animaux comme la bouse de vache. L'auteur examine les avantages et les contraintes li 'utilisation de ce combustible. Il est notamment soulignue c'est un combustible apprais qui tend tre moins abondant du fait de l'introduction de varis aut rendement dans l'agriculture au diment de l'vage de bovins.
Household energy situation in Bangladesh.
In Bangladesh, 64.8% of the total final energy consumed in 1990 was consumed in the household sector. This high proportion is an indication of the subsistence nature of the economy. The energy needs of the household sector are basic for survival, making their provision on a sustain-able basis a priority. In 1990, of the total energy consumed in the household sector, 91.5% was supplied by biomass fuels and only 8.5% by commercial fuels. To ensure a sustainable supply of energy for the household sector there must be planned development of biomass fuels which are in scarce supply in Bangladesh.
Energy is needed in the household sector for cooking and lighting. Lighting cannot be provided by biomass fuels, so a supply of commercial fuels, such as kerosene and electricity is also needed.
In 1990, it was found that in Bangladesh, 94% of all households used biomass fuels for domestic cooking; households with a comparatively higher income use fuel wood, and lower income households use residue-type fuels (such as sawdust and dung cake). In urban areas, biomass fuels are sold, while rural consumers gather them locally. More residue-type fuels are used in the dry season.
In the household sector, the following possible energy savings exist:
· increasing the efficiency of biomass stoves (rural and urban households);
· improving the efficiency of burners (mainly urban households);
· improving kerosene lamps (rural and urban households);
· providing natural gas cookers with efficient gas burners (urban households);
· improving lighting devices (rural and urban households);
· supplying efficient household appliances.
Very poor households tackle the household energy problem by increasing the time and effort spent gathering fuel, at the cost of quality of life.
The problems in urban areas
In many urban locations, poorer households cannot even afford to buy dung cake (a low-grade biomass fuel). The following methods are adopted to obtain household energy.
· They depend on combustible city garbage for cooking,
· They use organic solvents from the garment industry. These type of fuels give off corrosive fumes, harmful to health,
· They adopt slow and smoky cooking practices to save fuel. These take up valuable time and cause discomfort to the cook,
· In the rainy season they cook only one meal a day rather than several,
· To save kerosene (for lighting) they finish their household activities within daylight hours,
· They dig out tree roots for cooking fuel which involves hard labour; because of ownership restrictions, easily available biomass fuels (such as twigs and branches) are not accessible to them.
The traditional users of dung
The traditional users of cow dung are those who work in agriculture, own domestic cattle and above all, have sufficient surplus of dung to use it as fuel after the main use of dung as fertilizer.
Another group of people who use dung as a fuel are the landless or marginal land owners who work as day labourers employed locally.
The third group who use dung as fuel is the urban slum dwellers, or urban poor households, who do not have access to other cheaper sources of fuel.
Uses of dung
· as a floor coating
Traditionally Hindus consider dung as a source of purity. A portion of dung and clay, mixed to a paste, is used for a regular thin coating on the floors of their homes.
· as whitening agent
The traditional block printers, both in India and in some part of Pakistan, use cow and camel dung as prime bleaching agent for their cotton fabrics.
· as source material for biogas
Small-scale experiments using dung as the raw material for small scale bio-gas plants are being performed in several parts of the country. The results are not satisfactory.
Introduction of high-yielding varieties (HYV) in agriculture and a decline in household cattle and use of dung.
Until recently, farmers, who had domestic cattle, used to save dung in a common pit round the year, together with other domestic bio-wastes. Both the bio-wastes and the dung, when composted together, produce an ideal fertilizer for farms.
Due to the increased population growth, Bangladesh and similar countries have moved from indigenous agricultural patterns to modern HYV agriculture patterns. This produces more food, but the natural balance of the ecology has been greatly affected.
A greater pressure on the land for increased and quick production of cereal crops has meant that many of those lands which had been used as grazing lands have been converted to cereal crops. This has caused a decline in availability of dung for poor people in the rural areas.
Where farmers must grow more food than in previous times, in a shorter period, a small amount of dung can do very little to meet the needs of people today. Chemical fertilizer has so far been the only an answer suggested to meet existing needs. However, farmers have now begun to realize that agricultural growth is diminishing rapidly; that already damage has been caused to the land, and that it will be difficult or impossible to revert to the indigenous way of life. Each year there is an increased need for chemical fertilizer to grow the same or less crops on the same land, the soil is becoming less fertile and more dependent on chemicals.
The collection pattern for dung
Many poor families in rural and urban areas collect dung as their source of income. There is a group of women who traditionally collect dung, make cakes and sell them to the commercial markets.
The traditional collectors of dung are teenaged girls from the poor families. These girls, who traditionally have a low position in the family hierarchy, go in teams to hunt for dung from around the agricultural lands, forests and hills, where people from their community graze their cattle.
The collectors bring back the dung to their homes and convert it to round cakes and cone-like sticks for drying in the open sun.
Dung is considered to be one of the best fuels for the traditional mud stove for the following reasons:
· burns slowly,
· cooks fast,
· generates powerful heat compared to other locally available source of fuel,
· easy to store,
· less fuel and toxicity,
· no direct cost involved (women's work is not considered an economic activity).
Figure 1: Cone-like sticks of dung drying in the sun
Problems related to dung as fuel
· There is a great scarcity of dung and it is not easy to have access to free dung.
· Cattle owners do not allow the dung hunters to collect dung from their fields.
· As dung is being dried as a cake, there is a risk that it will be stolen, so the dung cakes must be guarded when they are drying.
· As the cakes are hand-compressed, they tend to burn faster than fire wood. But users are usually happy with the energy output.
Strategies to mitigate household energy problems
The households in Bangladesh are traditionally male-dominated so few have made alternative arrangements to meet the growing fuel needs in the home.
Women, the kitchen managers, are bound to collect dung and other biomass residues such as branches, seasonal leaves, twigs etc., which can be collected from the surroundings. This reduces the pressure of the fuel needs in the kitchen, but it deprives the soil a great deal. This need is being temporarily met by the increased use of chemical fertilizers.
The supply of household energy is as critical to basic needs as food, shelter and health. It should thus be considered as part of a national development programme. Isolated efforts by interested groups (such as NGOs) achieve limited success.