Conversion of manure into biogas – economic assessment of feasibility of investments

There is a whole range of biomass sources that can be used for biogas production ; however, manure is the most common example. Biogas is a part of the group of gaseous fuels, a product of anaerobic fermentation (digestion) of biomass or biodegradable waste. Its chemical composition is a compound of 2/3 methane and 1/3 carbon-dioxide. Usually, biogas is converted into electric energy and heat with cogeneration units (1 m 3 biogas produces 6.5 kWh energy) or when purified can be used as fuel. To optimize the production of biogas it is necessary to secure the continuous input of biodegradable waste – manure at least 30-40 tons daily containing more than 3% of organic matter, which in the case of cow manure means that biogas facilities should be located at areas of intensive cattle production. It is possible to construct them as individual units. However, in Republic of Croatia there are only several farms with capacity over 500 heads of cows so cost effective approach would include common plants within radius of 50 km.