| Boiling Point No. 17 - December 1988 |
NH Ravindranath and R Shailaja, ASTRA, Indian Institute of Science, Banglore 560 012, India
In rural areas of South Karnataka, in India, biomass is used as fuel mainly for cooking, heating bath water and for producing lime and bricks. ASTRA rural energy studies have shown that cooking is the dominant use of biomass as fuel and tree wood (twigs and branches and logs) is the dominant type of fuel used. In this paper a simple method to estimate the biomass use as energy and different strategies for growing biomass is presented.
Estimation of biomass use as fuel
The first step in any attempt to grow biomass, is to estimate its requirement. A simple method, is to select, say 15 families from the given village, consisting of various categories of households.
The biomass use could be estimated by school students or teachers or voluntary agencies. Spring balance, which is very cheap, could be used for measuring the fuel use. In each selected house weigh a bundle of fuelwood using a spring balance and ask the housewife to use it. After 24 hours record the weight of the remaining fuel and the size of the family. The difference would give the fuel used per day. The measurements should be repeated preferably for a period of one week or at least for 3 days to consider the day to day variations. Thus the fuel requirement could be estimated per year for a given family or for the community. Similarly fuel use for heating bath water could be estimated for a sample of families. Fuel use for brick or lime production in any village could be estimated by collecting data on number of bricks made or kgs of lime produced per year. Using the standard data on fuel required to produce 1 kg of lime (0.75 kg) or 1 brick (0.3 kg) total fuelwood requirement could be estimated. The aim here is to get an idea of the magnitude of biomass fuel that has to be produced and not to make a detailed investigation into the energy consumption patterns.
Efficiency of biomass fuel
It has to be noted here that the quantity of biomass estimated is for a given stove or kiln technology. The biomass requirement could be reduced by considering fuel efficient cook stove or bath water stove or kiln. In fact it is much easier and cheaper to conserve 1 ton of biomass that to produce 1 ton of biomass. Thus fuel efficient stoves/kilns should become an integral component of any biomass production or tree planting programme.
Biomass production or tree planting
Tree planting or biomass production strategies could be considered at individual family level or community level.
1. Biomass energy plantations: Growing high density monoculture plantations of fast growing and coppicing tree species is one of the approaches. Eucalyptus species, Prosopis juliflora and Leucaena leucocephala are some of the species which grow fast and coppice well. Density in the plantation could vary between 8000 - 10000 plants/ha. If the fuel requirement is 500 kg per capita/year, the area required at a biomass productivity of 10 t/ha/year, would be 500 mē per capita..
2. Village biomass forest: In this approach all the village needs of biomass namely: fuel, fodder, timber, leaf manure, oil seeds, tamarind etc would be incorporated into the village forest plan. The biomass requirements could be estimated by sample measurements using spring balances and household surveys. To meet the various biomass needs a multi-species and multi-tier forest has to be grown in the village community land with different spacings in different tiers. A planting pattern is presented in Table 1 and Figure 1.
3. Growing trees along bunds and rows: In this part of India large scale fragmentation of land has taken place leading to smaller crop plots in the range of 0.02 ha to 0.1 ha. If a farmer owns 1 ha in, say, 10 plots of size 50 m x 20 m, he will have a bund length of 1220 m. It is possible to plant 1220 trees at a spacing of 1 m between the trees. Landless could be encouraged to grow trees near their houses and along road sides. If 2 kg/tree/year is taken as the productivity then the number of trees required to be planted is 250, along 250 m of bund length, to get 500 kgs per capita per year.
Note: a bund length of 1220m would therefore be sufficient for a family of five - Ed.
4. Grow coconut trees: There are a number of plantation crops like coconut and arecanut that provide significant quantity of fuels as by-product. Coconut is an important source of fuel for cooking and bath water heating in South Karnataka. An average tree provides about 65kg of dry fuel needs per head. There is a need to explore other economic trees which provide fuel as a by product.