Converting cow manure into heat and electricity

A plant in Japan will convert manure from local dairy cows into biogas that will power a generator system

Spotted: Methane is a potent greenhouse gas produced when organic matter decomposes without oxygen present – a process called anaerobic digestion. If this process is uncontrolled, it releases methane into the atmosphere, adding to global warming. However, if anaerobic digestion is controlled through man-made ‘digesters’, the methane can be captured and used as a renewable energy source. Moreover, the byproducts of anaerobic digestion—fertiliser and water—can be used to help grow crops and replenish aquifers.

Cows may make for a quaint pastoral scene, but they are a major source of methane. Cattle belch out the greenhouse gas as they digest their food, and decomposing cow manure also adds to atmospheric methane. In fact, livestock are responsible for 44 per cent of all man-made methane emissions.  

One company, Anaergia, is tackling the problem with plans for Japan’s largest manure-to-energy facility. The plant, which is set to be located in Kasaoka, Okayama, will process up to 250 tonnes of manure per year from local dairy farms using anaerobic digestion. In addition to preventing methane emissions, the plant will generate renewable electricity and heat, as the biogas produced will be used to power a combined generator system.

To compare emissions of different greenhouse gases on the same footing, scientists use a unit called carbon dioxide equivalent (CO2e). The plant is expected to prevent the annual emission of around 13,500 tonnes of CO2e – equivalent to taking around 2,900 cars off the road for a year. The project is also expected to generate enough renewable electricity to power approximately 2,200 households.

Springwise has spotted a number of innovations aiming at reducing methane emissions, such as a specially-formulated animal feed that reduces the amount of methane generated in the guts of cows. Food waste can also leak methane, and one startup is using a similar process to create biogas from food discarded by nearby businesses.