Rural domestic biogas supply model for Zambia

There is potential of producing biogas in rural areas of Zambia where rearing of cattle and other livestock exists. With feedstock and financial resources, people in rural areas could form groups or co-operatives and install digesters with sizes ranging from 12 to 1000 m3. Generally the initial investment costs decrease with increase in digester size and decrease in the number of digesters to be installed. Economic analysis indicates that these digester sizes would be viable with positives Net Present Values (NPVs) at the nominal base rate of 18% up to about 37% when NPVs start to be negative. The payback period ranges from 1.3 years to about 3 years depending on size and investment costs. Biogas production results in an opportunity cost of US$0.01/ kg dry dung. Biogas would replace the use of biomass for cooking energy needs. Currently burning of biomass on inefficient stoves leads to respirable particulate matter exposure ranges from 125 to 2125 μg/m3 which is above the World Health Organization guidelines. Implementation of biogas production in the Chitete settlement real case example would result into 3.022 GgCO2eq avoided emissions from the use of biomass for cooking using inefficient stoves, manure management and chemical fertilizer application, conserve 9.48 t of nitrogen from avoided biomass consumption for cooking, production of 336 t of organic fertilizer at a net income US$ 224,978 per year, saving of 2171 t of firewood worth US$ 57,000 and 948 t of charcoal worth US$ 95,000 per annum.