• Saving of expenditures on fuel, on average 6-9 kg of fuelwood and 0.2 liters of kerosene per household on a daily basis;
• Saved time to utilise in other income generation activities or for leisure;
• Enhanced soil productivity because of the use of bio-slurry (added N,P,K values);
• Reduction in the quantity of chemical fertilizers used due to the use of biodigester effluent;
• Reduction on health care expenditures due to decrease in smoke-borne diseases;
• Provide employment for local people, masons, supervisors and suppliers of appliances;
• Private sector development;
• Livestock health development.

• Reduction in smoke borne diseases (dizziness, headache, eye-burning, respiratory tract-infection, nausea etc.);
• Improved household sanitation due to attaching of latrines into bio-digesters, absences of black soot, ashes, firewood/dung cakes in kitchen;
• Decreased number of flies near the stables;
• Decrease in burning accidents.

• Preservation of forest;
• Reduction in green-house gases especially methane;
• Prevention in land-fertility degradation due to excessive use of chemical fertilizers;
• Elimination of smell from dung storage ponds at pig farms;
• Reduced pollution from pig dung being dumped in surface water.

• Extra time for social activities;
• Enhanced prestige in the community;
• Reduce workload, especially for women;
• Bright light to help in quality education and household works;
• Increase in rate of enrolment of girls in school because of the liberty from fuel collection.

One biodigester with 4 m³ capacity can produce up to 1.44 m³ of biogas per day, which is enough to burn single burner stove for 3.5 to 4 hours. Assuming that 80% of the produced gas (1.15 m³) is used per day, it can replace 6 kg of firewood, or 2 kg of charcoal, or 0.7 litre of kerosene, or 0.5 kg of LPG or 1.8 units of electricity.

Payback Period of 4 m³ capacity biodigester with the cost of US$393.5 (in April 2010Sept. 2009)

It is clear from the above table that biogas has higher replacement value if it is used to replace kerosene and LPG; however, these fuels are not commonly used by the rural households. The replacement values for firewood and charcoal are equal. The minimum and maximum savings because of the use of biogas are US$ 153 for firewood/charcoal and US$ 166 for kerosene per year. Even without any subsidy, the payback period of a 4 m³ biodigester is less than 3 years if used to replace firewood/kerosene, which is financially viable.

6 m3 is the most popular plant with the average cost of 480USD. Upon construction completion, NBP provides a flat rate of subsidy 150 USD per plant. The below table shows the estimated cost of the plant and farmer investment in different size of the plants updated in May 2009 as follows:

For farmers who lack of cash, they can receive special loan from PRASAC or Amret Microfinance Institution of 150-1000 USD with very low interest 1.2% per month and duration up to 24 months.

Biodigester provides a large number of benefits as follows: 

• Saving 12USD/family/month from buying fuel wood or charcoal, petroleum and charging battery.
• Reduction of deforestation; saving fuel wood in average 6-9 kg/day/family. 
• Reduction of air pollution, global warming, and improve household sanitation.
• Improve agricultural productivity and crops intensification by using digested bio-slurry as organic fertilizer.    
• Reduction of workload, especially women and girls in collecting fuel wood and cooking time approximately saving 2 hours/day.