PROFILE
FOR MANY BRITONS , turning the heating on ( or up ) is a reflexive action for a large part of the year . So much so that approximately 47 percent of energy in the UK is used for heating – which is in turn responsible for one-third of the country ’ s carbon emissions . Suffice it to say that decarbonising heat is on the agenda for anyone seeking to reduce the UK ’ s carbon footprint , and one particular solution is increasingly sparking corporate interest : biomethane gas .
What is biomethane and how is it produced ? According to Dr . Kiara Zennaro , the Head of Biogas at the Renewable Energy Association , the UK has the fastest-growing biogas sector in the world . Biogas is produced through anaerobic digestion – a natural process in which plant and animal-derived material is broken down by microorganisms in an airtight container . It ’ s not wholly dissimilar to what occurs in your average garden compost heap , but an anaerobic digester must be a sealed vessel in which bacteria can work without the presence of oxygen .
“ The microorganisms are pretty much the same ”, Zennaro says of the difference between composting and anaerobic digestion . “ They are already in the waste ; you don ’ t have to add anything . In the absence of oxygen , they will break down material , though it will need some stirring and mechanical mixing to make it more effective ”.
The type of organic matter ‘ fed ’ to a digester tends to fall into two categories : municipal food waste and so-called ‘ grain crops ’ grown solely to be used in the process of making biogas .
There are two major by-products of anaerobic digestion , the so-called ‘ digestate ’ matter and biogas . The former can be used as a crop fertiliser because of its nutrient-rich composition , while the latter , a methane-rich gas , can be burned at the site of the anaerobic digestion plant to generate both renewable power and heat .
However , biogas still contains a relatively large amount of methane , CO2 and other impurities . It must be processed in order to be injected into the National Grid , where it can be used for heat and electricity in much the same way as traditional natural gas . This purified form of biogas is referred to as biomethane .
8 June 2016