Photo: Arla Foods



Biofilters breaking down methane could be a key step towards cost-effective reduction of the carbon footprint of Danish dairy cows and pig production. The new GUDP project BIOMET just kicked off development and testing of large-scale filter models. Arla and Danish Crown believe the project holds a vast potential for climate and businesses alike.

Today, total methane emissions from Denmark’s approximately 570,000 dairy cows amount to 2.3 million tonnes of CO₂ equivalents annually from the dairy cow barns and slurry containers. Likewise, the total pig production results in methane emissions equal to 1.45 million tonnes of CO₂ equivalents per year. A new GUPD-funded project—Biomet—intends to address this problem: The Technical University of Denmark (DTU), SEGES, COWI, PFH Miljø & Anlæg, and the University of Copenhagen will demonstrate the potential of biofilters as an important and cost-effective technological solution for the reduction of the big climate culprit—methane gas—which forms in the stomachs of the livestock and is emitted via their exhalation air and slurry.

The expectation for the project is that the total emissions from dairy cow barns and slurry containers in Denmark can be reduced by as much as 20 per cent, while the reduced climate impact from pig slurry is expected to be 15 per cent. Important secondary gains are also expected, as filtration of the air in cow barns and slurry containers in the biofilter will concurrently reduce emissions of ammonia and odour nuisances.


In specific terms, the parties will develop, design, and test biofilter systems. The filter consists of compost filled with methane-eating bacteria. The compost is placed in large containers or buried in the ground outside the barn. So-called ‘point extraction’ is also established over the dairy cows’ stalls, and via ventilation pipes, the methane-containing air is sucked out of the barn and through the filter outside the barn. Here, the methane is reduced to carbon dioxide and water. The same process is intended to be used in the covered dairy cow and pig slurry containers, where the concentrated methane air over the slurry is sucked out and channelled into the biofilter.


The technology is already known, as it has been developed to convert methane from old landfills. At DTU, the technology has been used for nearly 15 years, while COWI has similar experience with biofilters from several years of advisory services in the establishment of biofilters in landfills. In the current project, the task will thus be to transfer the technology to cow barns and slurry containers under different conditions.

Testing the technology in full-scale is vital to the success of the project. Until now, DTU and SEGES have performed measurements in laboratories and small pilot systems, but full-scale test systems are required to measure the full effect of the technology. The goal is therefore to develop functional full-scale test systems with point extraction and biofilter in 2021 which work in practice and effectively reduce methane and ammonia contents in barn environments and slurry containers. The final version of the filter is expected to be ready by the end of 2022.


Another important focus in the project is to perform specific calculations of the cost of the method per reduced tonne of CO₂ equivalent and tonne of ammonia. The parties’ initial expectations are that the biofilters will prove to be a cost-effective solution relative to their value, as the method is fairly simple and based on known technology with comparatively low establishment and maintenance costs.

Arla and Danish Crown are showing great interest in the potential of the project and will contribute support and knowledge. Based on the project results, the two parties will also calculate how large climate gas reductions the two industries can each achieve if their suppliers use the biofilters.


Technical University of Denmark (DTU):
Role: Project manager, research and development
Quote by Professor Charlotte Scheutz, DTU Environment:

“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.”

SEGES (Danish Agriculture and Food Council):
Role: Research and development
Quote by Trine Barret, Head of Livestock Innovation, SEGES:

”Danish agriculture aims to be a climate-neutral in 2050, at the latest. That calls for specific solutions, and I believe the BIOMET filter can be a step on the way to reducing methane emissions from cow barns and slurry containers. At SEGES, we look forward to contributing our agricultural insight and ensuring that the project develops solutions that can be used and implemented in Danish agriculture.”

Role: Project manager and engineering consultant
Quote by Christian Buck, Project Manager, Department of Environment and People, COWI:

”This project is immensely interesting and holds a vast potential for supporting the green transition in agriculture. We are excited to contribute COWI's experience in biofilter technology and establishment of full-scale systems. It’s also key to the success of the project that the cost of the method matches the value, so the business case will also be one of our priorities.”

PFH Miljø & Anlæg:
Role: General contractor
Quote by Peter Hvidt, owner

”We look forward to bringing our long-established knowledge in environmental construction works to the project. When developing solutions for cow barns and slurry containers, we will use our experience from the SEGES pilot system with biofilter at a cow barn in Thorsø in East Jutland as well as the biofilters designed to reduce methane emissions from old landfills across Denmark.”

University of Copenhagen:
Role: Research and development
Quote by Bjarne Schmidt Bjerg, Associate Professor at the Faculty of Health and Medical Sciences, University of Copenhagen:

”Dairy and beef production comes with major climate and environmental challenges, which will be easier to solve if we succeed in capturing a large part of the emission of gases in a small part of the vast air change that takes place in a modern dairy cow barn.”

Danish Crown:
Role: Knowledge partner
Quote by Preben Sunke, COO, Danish Crown:

”Danish Crown aims to halve the carbon footprint per kilo of beef by 2030 and we’re well underway. The last part – and not least our vision to be climate neutral in 2050 – requires a knowledge acceleration, which makes close collaboration between scientists and businesses absolutely vital. To us, the BIOMET project holds a significant potential, so we’ll follow the project and take part in testing the systems, and we strongly believe that the systems will be able to contribute considerable reductions of emissions from our owners’ barns and slurry containers.”

Role: Knowledge partner
Quote by Kristian Østerling Eriknauer, Vice President, CSR, Arla Foods:

”Arla Foods has set the ambitious goal of becoming CO₂e neutral across our business in 2050, one partial target being to achieve a 30 per cent reduction in 2030. To achieve that ambitious goal, we need research and innovative solutions, especially in farms, which account for most of our greenhouse gas emissions. We’re excited to test these filters that break down methane in practice, hoping that they will be one of several solutions that help reduce our emissions of greenhouse gases towards 2050.”

The BIOMET project has received DKK 4.6 million in funding from GUDP, the green development and demonstration programme under the Ministry of Environment and Food of Denmark.

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COWI employee Søren Kragh Pedersen

Søren Kragh Pedersen
Head of Group PA & PR
Communication, Denmark

Tel: +45 2025 7018