In rural areas of Lombok Island, West Nusa Tenggara Province, Indonesia, cattle raising is an effective measure for improving living standards. However, it carries the risk of water contamination by animal wastes and damages to forests by over-grazing. With the central and provincial governments pursuing plans to accelerate the development of the area through the promotion of livestock, an increase of animal wastes is expected. In this study, the effects of a small-scale biogas plant utilizing cattle waste in a cattle-raising farm household are discussed in terms of its impact on the environment. As a pilot project area, a village in one of the least developed areas in Indonesia was selected. Firewood is the main household energy source, and collection of firewood causes environmental problems. Because the biogas plant provided sufficient methane gas for cooking breakfast and lunch for a family of seven members, the reduction of firewood used for cooking was significant, reaching as much as 70% or about 1.9 ton, equivalent to 3.8m(3) of firewood per family per year. The economic viability of the use of the biogas plant was also studied, and it was found out that the plant is economically feasible under the conditions and circumstances of Lombok Island.