Techno-economic assessment of anaerobic co-digestion of livestock manure and cheese whey (Cow, Goat & Sheep) at small to medium dairy farms.

Anaerobic digestion of manure is a common practice; however, the low biogas yield of manure can hamper the profitability of systems in small to medium farms. An increase in biogas yield could be achieved by co-digesting animal manure with co-substrates such as cheese whey. A Techno-economic assessment of anaerobic co-digestion of animal manure and cheese whey (cow, goat and sheep), has been carried out. The results obtained showed that for a farm with 250 adult cattle heads, the revenues generated in an anaerobic mono-digestion process are not able to offset the initial required investment. However, the co-digestion of manure with 30% of cheese whey showed a good economic performance and positive returns (Net Present values >0, Internal Rate of Return >11% and a Return of the investment in <10 years). Electricity selling price and biogas production are the key parameters to determine the profitability of the system.