New method to reduce emissions of ammonia and methane from manure

By adding tannic acid and fluoride to manure, researchers from the University of Southern Denmark and Aarhus University have managed to significantly decrease the harmful environmental effects of the manure.

‘Lab tests with pig manure show a reduction of ammonia emissions of up to 95 % and a reduction of methane emissions of up to 99 %, depending on the amount of tannic acid and fluoride added. An unexpected, but positive, side effect is that the technology also reduces the smell of manure significantly by halving the odour index,’ says rofessor Henrik Karring of SDU Chemical Engineering, head of the ManUREA Technology research project.

The researchers have filed for a patent on the technology, which consists of mixing tannic acid, which we know from wine, with small amounts of fluoride, which we know from toothpaste. The plan is to eventually develop a granulate that farmers can add to the manure.

‘We will have to further develop the technology to lower the cost for farmers, but we believe that we have a revolutionary technology on our hands when it comes to reducing the environmental effects of Danish pig farming,’ Henrik Karring says. He adds:

‘It is a 3-in-1 technology, because it can reduce ammonia emissions, methane emissions and odour all at the same time.’

Less ammonia emissions

Denmark has committed to reducing ammonia emissions significantly in accordance with the EU NEC directive, because ammonia poses a threat to our nature and causes air pollution.

 The agricultural industry is responsible for approximately 95 % of Danish ammonia emissions and contributes to greenhouse gas emissions. A large part of these emissions comes from manure.

The researchers believe that their new invention will help the agricultural industry reduce its effects on the environment in a simple and efficient way.

A great potential

‘Our lab tests clearly show a great potential for reducing ammonia emissions, methane emissions and odour issues,’ says associate professor Anders Feilberg from the Air Quality Engineering research group at the Department of Engineering, Aarhus University. He is responsible for the lab tests of adding tannic acid and fluoride to pig manure.

But other than its efficiency, the researchers are concerned with the cost of the technology. If the technology is too expensive, farmers will not use it.

‘The agricultural industry is struggling to keep the cost of environmental technologies at a reasonable level. Tannic acid is expensive in large quantities, so we are e.g. working to perfect the dosage to maximise the efficiency and minimise the cost,’ Anders Feilberg explains.

Testing in pig barns

Last year, Henrik Karring received $1,050,000 US from the Ministry of Environment and Food of Denmark. The money will be used to further improve the technology with a special focus on reducing methane emissions and testing the technology in pig barns.

Before discovering the combination of tannic acid and fluoride, the researchers tested around 70 different additives. In addition to perfecting the dosage, the researchers continue to test new additives that might boost the technology.

‘We have actually seen an effect with other additives. We are looking further into that now, so I don’t want to say too much, but it looks promising,’ Henrik Karring says.

Photo: Henning Bagger/Ritzau Scanpix