Growing crops to produce biomethane produces three times more CO2 than using natural gas, according to a study published in Nature Climate Change.
There has been a rapid increase in growing crops such as maize to produce biome than to help us reach Net Zero, but it seems this option on peat is emitting three times more carbon dioxide than it is using natural gas, according to a study by the UK Centre for Ecology & Hydrology (UKCEH).
The team also shows that the area of the UK dedicated to maize has tripled since 2015. However, emissions from draining these carbon-rich wetlands for agricultural use have been widely overlooked. The analysis focuses on maize and the UK, but the results suggest that crops cultivated on deep-drained peat will produce large amounts of greenhouse gas emissions.
The authors emphasise that we need to consider soil carbon losses associated with bioenergy crops grown on drained peat to make informed decisions about land use. “Biomethane is an important renewable energy source, but it seems unwise to use drained peatland primarily for generating bioenergy in areas where this leads to higher CO2 emissions than the fossil fuel it replaces,” says Professor Chris Evans of UKCEH.
The problem is that more carbon is emitted from drained peatlands than is avoided by not using natural gas. Drainage of these wetlands enables crops to release carbon that has been locked up in their soils for hundreds of years. This released carbon is exposed to atmospheric oxygen, forming CO2 and resulting in significant amounts of additional greenhouse gas.
Every cubic metre of natural gas burned emits the equivalent of 2kg of CO2 while cultivating maize for biogas production on drained peatland results in emissions of up to 6kg per cubic metre of biomethane produced. This figure doesn’t even include the extra greenhouse gas emissions from using fertilisers on maize fields, harvesting and transporting the crop or producing the biomethane.
“The transition to net zero won’t be completely smooth. Along with the successes, there will be failures and unintended consequences,” said Dr Rebecca Rowe of UKCEH. “Our role, as scientists, is to support the Government, land managers, and industry by providing them with the best up-to-date knowledge on the impacts of their actions so they can make informed decisions about energy crop production and land use. This is about working together to ensure a sustainable future.”
The researchers want to point out that their findings do not mean all forms of bioenergy production on drained peat soils will increase emissions. For example, biomass crops on agricultural peatlands managed with higher water levels – paludiculture – is a potentially promising method of mitigating climate change.
Evans et al. 2024. Biomethane produced from maize grown on peat emits more CO2 than natural gas. Nature Climate Change. DOI: 10.1038/s41558-024-02111-1.