Production of biogas from processing industry

General lack of oil throughout the world had increased our dependence on energy. Natural energy sources including oil, natural gas, and solid fuels are important energy sources nowadays, but also sources of heavy carbon-dioxide emission. Satisfying basic human needs is doubtlessly associated with agricultural and industrial production, which is directly connected with corresponding energy consumption. An increase in industrial activities brought about a series of grave environmental problems (soil, water and air pollution). It resulted in setting new goals in production, i.e. more energy along with less pollution. The Republic of Croatia, as a Kyoto signatory and future EU member, has accepted the commitments from the "Green" and the "White" books on reducing CO2 emission. They, namely, set the year 2010 as a final deadline for reducing CO2 emission by 50%. On the basis of that, the European Parliament and the Council of Europe issued Directives on Liberalization of electrical energy market as well as guidance on systematic development and use of biofuel as the alternative energy source. There is a wide selection of biomass sources that can be used for biofuel production; the most important ones being biodiesel, bioethanol and biogas. According to its definition, biogas belongs to the group of gaseous fuels produced by anaerobic digestion of biomass and/or biodegradable waste. As to its chemical composition, biogas is a mixture of 2/3 methane and 1/3 carbon dioxide. There is a wide range of substratum kinds that can be used for biogas production, such as cereal chaff, bread and dough leftovers, yeast and yeast-like leftovers, various kinds of sludge remaining after production of edible oils and fats, starch sludge, gelatin waste, kitchen and restaurant waste, etc. Biogas is usually converted to electrical and thermal energy by means of cogeneration units (1m(3) of biogas produces 6,5kWh of energy) or it is purified and used as a low-pressure gas for gas stoves, gas water boilers, cooling devices and stationary motors.