Cow dung is the main source of producing methane, as one of the greenhouse gases. To decrease this pollution, cow dung can be transformed into biogas, and consequently, the produced biogas can be used as a fuel for electrical generators. This problem is addressed in the so far researches without proposing the appropriate mathematical models. In this paper, the optimal sizing problem of the biogas-based generators (BGs) is formulated for a livestock farm by modeling the anaerobic digester process and the gas storage tank. To protect the system operator's decisions against the uncertainty of the cow dung, the proposed model is reformulated as a risk-based model using the information gap decision theory. The obtained capacity of the BG and the storage tank for a livestock farm with 2000 cows are 433.24 kW and 628.056 m3, respectively. Also, the designed system prevents releasing approximately 522-ton pollution. The results show the appropriate performance of the system operator to use the produced gas to be directly sent to the BG and/or to charge the storage tank. The results show that with increasing the risk-aversion parameter, the capacity of the BG and the storage tank decrease which leads to decreasing the total profit.
