Anaerobic digestion for biogas production is known as an effective way of organic waste management. However, in countries rich in fossil fuels resources, its application is very limited. The present research aimed to find whether farm biogas plant could be economic in Iran, where low price natural gas and electricity are available in the most of the regions. Capital cost, net income, internal rate of return, and return of investment of a farm biogas plant was calculated assuming three different scenarios for a 400 head dairy farm; 1) Combined heat and power biogas plant by treatment of 4,562 t y−1 manure: power injection to the grid, and heat to be used in farm or be sold to the potential nearby clients, 2) biogas plant only for power generation by treatment of 4,562 t y−1 manure: power injection to the grid, and 3) No power generation: Treatment of 1,200 t.y-1 for substitution of current heating and cooking fuel (liquefied petroleum gas and diesel) by biogas. The technical and economic calculations were based on biomethane potential test (BMP). The economic analysis results showed that the return of investment in all scenarios was less than 4 years. The surplus net income of the farm from digester including energy and bio-fertilizer production from the three scenarios were 32,000, 38,000, and 6,400 US$ per year. Overall, all three scenarios are economically feasible in Iran, if the biogas plant is constructed domestically.

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