Among the sources of renewable energy, biogas has one of the greatest potentials for development. The UNO report on renewable energy considers biomass and cogeneration as key technologies for combating climate change. Italy is an energy importer: it imports directly 11.2% of its electricity requirements and almost all of its fossil fuels, which are used to produce 72.8% of the demand (Terna data 2008).

Biogas is therefore a doubly important and interesting source of energy. Firstly it responds to the country’s energy needs. Secondly, it is a renewable energy source, which does not emit additional CO2 into the atmosphere and can therefore actively help to combat the greenhouse effect.

How biogas is formed

Biogas is a mixture of gases which is produced naturally by specialist bacteria, in the absence of oxygen, from organic natural materials. The biomass, placed in hermetically sealed containers (the fermenters), is attacked by the bacteria which break up the complex organic substances (carbohydrates, proteins, fats), simplifying them throughout the four phases of anaerobic fermentation. The biogas consists mainly of methane which, if produced from agricultural raw materials, is typically between 50 and 55%, and carbon dioxide, between 35 and 40%.

This fuel can be used for the production of electrical and thermal energy, via a cogenerator, or can be purified so that it is identical to natural gas of fossil origin. The carbon dioxide emitted during the process is equivalent to the amount fixed by plants during their lifecycle.

All sorts of biomass can be used: energy crops like maize, sweet sorghum or other cereals, dung, agro-industrial processing waste, and even the organic fraction of municipal solid waste. The bacteria, which are living beings, must be guaranteed a balanced diet: it is therefore important to seek expert advice when drawing up the feed plan.