This paper presents results from anaerobic digestion of cow manure and whey mix. A pilot scale anaerobic digester, 128 1 in volume, has been developed, to operate under batch and fed-batch conditions. The versatile and unique characteristics of the instrument allowed testing the methane production directly in the farm. The digester performance was evaluated with two calibration tests, the main for a period of 56 days. The study test was divided into three phases, one for each type of feeding operation (batch, fed-batch, batch). The initial phase of digestion resulted in 57 I-CH(4)/kg-VS, the second phase had a yield of 86.6 I-CH(4)/kg-VS and the third one had a production of 67 I-CH(4)/kg-VS. The total methane yield was equal to 211.4 I-CH(4)/kg-VS. Using the obtained pilot plant results to a real scale diary production cycle, it was possible to evaluate an electricity production equal to 8.86 kwh per 1 t/d. The conducted tests did show that there is a good potential to the use of a cow manure and whey biomass mix for biogas production. (C) 2009 Elsevier Ltd. All rights reserved.