Farmers get energy from waste
New Zealand farmers can get energy from animal waste and reduce greenhouse gas emissions at the same time.
When animal waste decomposes in the absence of oxygen it produces a gaseous mixture of about 70% methane and 30% carbon dioxide. This biogas has an energy content similar to that of natural gas and it can be used to generate electricity, as is already done by trapping gas released by decaying material at some landfills. Making use of this energy reduces the farmer’s energy costs, but has the added advantage of reducing greenhouse gas emissions.
“Both methane and carbon dioxide are greenhouse gases,” NIWA scientist Dr Rupert Craggs said recently, “but methane is twenty times more potent as a greenhouse gas than CO2. Methane emissions are responsible for 20% of global warming since pre-industrial times, and New Zealanders are one of the world’s largest emitters of methane per capita.”
Given the level of dairying in New Zealand, the use of biogas as an energy source is a fairly simple and cost-effective way to reduce our methane emissions.
On-farm methane recovery can significantly reduce energy bills by providing most, if not all, of the electricity, heating, or cooling required by the farm. Annual energy savings should be at least $2,000 for a 300-cow dairy farm, and $7,000 for a 1000-cow farm. Using electricity generated from biogas means the farmer is not using energy that might have been generated from fossil fuels and so is further helping reduce New Zealand’s greenhouse gas emissions.