A Root for the Fuel Problem

An alternative to wood, "rootfuel" is being explored for use in developing countries where the demand for fuel is outstripping forest resources. Rootfuel is the name given to fast-growing non-woody sun-dried taproots of certain members of the Cucurbitaceae family, such as wild dryland gourds and melons. According to the researchers: Eugene B. Shultz, Wayne G. Bragg, and Debra L. Duke, of the Washington University in St. Louis Missouri, rootfuel will produce two times the dry biomass of trees per unit of area on dry deforested lands. Besides providing a fuel source, these curcurbits can control soil errosion. Their abundant roots stabilize the soil, and their large, stiff leaves blunt the force of rain. The scientists are urging people in arid, deforested areas of the Third World where wild curcurbits are found, to use these resources and cultivate them on poor or marginal land where the plants would not compete with food crops. Dr. Shultz and his co-workers have focused on C. foetidissima in their work with the Mazahua indians in Mexico.

Cucurbita foetidissima is a wild New World aridlands cucurbit with a fast-growing inedible carrot-shaped taproot. It grows readily on nutrient-poor slopes where few other plant species can be found. Dr. Shultz has frequently observed C. foetidissima stabilize slopes against erosion. In Arizona, fresh root yields of as high as about 35 metric tons (11 tonnes of dry biomass) per hectare were harvested from an unirrigated, high density summer planting of C. foetidissima. This is nearly twice the dry biomass yield expected for unirrigated tree biomass cropping for the area, given the same lenght of time.

Laboratory analyses performed at the Industrial Testing Laboratories in St. Louis revealed that the heating value of the roots is almost identical to that of wood. An analysis of heat-release rates showed that roofuel releases heat more slowly than wood. Thus rootfuel transfers heat to cooking vessels more efficiently, therefore less rootfuel than wood is needed to cook the same meal. One study showed that only about two-thirds as much rootfuel is needed, compared to wood, to cook the same amount of food, in almost the same amount of time. This means that a family would have to grow or purchase two thirds as much fuel by weight in the form of dried rootfuel, in comparison with wood.

In 1988 women in rural Senegal, Niger, and Mexico tested the root by cooking several types of meals with native wild curcurbit roots. According to them the fuel does not impart any unusual flavors to food cooked with it. In every case, the women who tried rootfuel preferred it to corn stalks, dung cakes or dried cactus leaves. These fuels can impart unhealthy chemicals and bad flavors to the food. Unfortunatly, they are forced to use these fuel as other preferred fuels sources are depleted. In some cases they even preferred rootfuel over wood.

Rootfuel was found to produce a considerable amound of smoke, but since rootfuel is mostly starch, it produces few irritating compounds such as creosote when it is burned. Rootfuel seems to require at least as much ventilation as charcoal and perhaps more. The best stove for cooking with rootfuel is one that permits enough draft, such as three-stone stoves. Stoves must also be modified to accomodate the high ash content of rootfuels. The women who cooked with it found the smoke very similar in odor to that of wood. Increased draft through the stove could alleviate much of the smoke, but city women who can afford charcoal will probably continue to prefer that premium fuel.

The researchers hope the value of rootfuel will foster the cultivation and drying of roots near home for kitchen use, or the production of rootfuel for local markets as a private or cooperative business. Shultz proposes that rootfuel seeds be broadcasted on slopes where errosion control is needed and near the home to reduce the work normally required to harvest wood. A fraction of the larger roots of the curcurbit should be harvested each year to promote the development of the remaining smaller roots. Only a fraction of the total roots should be harvested, however, since a complete harvest would forfeit any errosion control as well as future harvestable fuel. C. foetidissima plants forms colonies which normally reach 30 ft. in diameter. Forsight when planting will prevent rootfuel plants from invading crops.

For more information:

Dr. Eugene B. Shultz Bioresources Development
Washington University, Campus box 1106
One Brookings Drive
St. Louis, MO 63130 USA
Tel: (314) 889-5455