Resumen
Most households in rural developing countries depend on firewood from public forests or agricultural bio-wastes for cooking. Public forests, though, are declining due to an increasing population and inefficient use of wood. Use of agricultural wastes on the other hand involves loss of soil nutrients since these resources are used as a substitute for inorganic fertilizers. Biogas energy can be an alternative in providing clean energy for cooking as well as improving soil fertility with the slurry. However, the labor spent on producing biogas can limit its use as a source of energy and fertilizers. Therefore, this study aims to determine the labor requirement of different mono and co-digestion biogas energy systems. The assessment is made by using simple models involving different schemes of resources collection and transportation based on reported relevant literature. The analysis shows that biogas production can be labor intensive when transportation of feedstock, water, and slurry is involved. Transporting these resources over a one kilometer (km) distance requires about ten times the amount of time spent on firewood collection and transportation. The largest part of the time for biogas production activities is spent on water collection and transportation. Low labor biogas production is possible only if all the resources are available nearby (not transported). One of the advantages of the biogas energy system is to use the slurry for soil enrichment. However, this can only be realized when the slurry is converted to compost or directly applied on nearby lands. In general, biogas production involving resources (feedstock, water and slurry) transportation is not a viable alternative to save the time spent on the traditional use of firewood. However, a community biogas system involving resource system integration is an option to provide clean energy with acceptable labor requirements of production.