I believe the small sizes of the digesters is a successful project. They usually use the gas for cooking applications, which results in reasonable saving with replacing the LPG gas or kerosene that is commonly used. However, the gas from the bigger digesters have more challenges. They are planned to produce electricity from the biogas. However, with the current prices of the electricity in the country and also low efficiency of the cheap gas engine generators (15-25% of the energy become electricity), this income from the electricity is not feasible!
(A typical underground household digester in Vietnam and Cambodia that convert manure to biogas for cooking and gas lights. I took the picture in Phnom Penh)