Utilising biofilters to drastically reduce methane emissions from livestock

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DTU, SEGES, COWI, PFH Miljø & Anlæg and the University of Copenhagen have joined forces to develop, design and test biofilter systems. From the dairy cows’ barns and slurry containers, total methane emissions from Denmark’s approximately 570,000 dairy cows amount to 2.3 million tonnes of CO2 equivalents annually. Similarly, overall pig production produces 1.45 million tonnes of CO2 equivalents per year in methane emissions. Methane gas is formed in the stomachs of livestock and is emitted via their exhalation of air and slurry.

A noticeable reduction of livestock emissions
The project parties are aiming for a cost-effective technological solution utilising biofilters containing methane-eating bacteria. Total emissions from dairy cow barns and slurry containers in Denmark are predicted to be lowered by up to 20%, while the climate impact of pig slurry is expected to be reduced by 15%, according to the project’s estimates. Secondary benefits are also expected, as air filtration in cow barns and slurry containers in the biofilter would reduce ammonia emissions and odour nuisances at the same time.

Outside the barn, the compost is placed in huge containers or buried in the ground. A “point extraction” system is also installed over the dairy cows’ stalls, in which methane-containing air is sucked out of the barn and passed through a filter outside the barn via ventilation pipes. Methane is converted to carbon dioxide and water in this process. The covered dairy cow and pig slurry containers, where the concentrated methane-air over the slurry is sucked out and channeled into the biofilter, will use the same procedure.

A known technology
The technology is already known. At DTU, it has been used to convert methane from old landfills for nearly 15 years. Likewise, project partner COWI has similar experience with biofilters, having provided consulting services for the installation of biofilters in landfills for numerous years. The goal of the current research is therefore to deploy the technology to cow barns and slurry containers which are subject to different conditions.

“At DTU, we’ve long worked with technologies for breaking down methane using biofilters. It’s an effective method that has—for example—proved its worth in old landfills with methane emissions. Biofilters can also make a big difference at farms when they are customised for such use.” says Prof. Charlotte Scheutz, Head of Section Climate and Monitoring, DTU Environment.

Full-scale test systems that work in practice and effectively reduce methane and ammonia concentrations in barn surroundings and slurry containers are the current target for 2021. By the end of 2022, the final version of the filter is expected to be ready.