References Agriculture, Environment

The nutrient efficiency of dairy production can be significantly enhanced by processing the manure. A new technique developed by Valio enables to extract nitrogen and phosphorus as separate fractions. Furthermore, the energy can be utilized as biogas and the amount of water in the manure reduces notably. The active development work of the method started 2012 and the related pilots by the Natural Resources Institute Finland (Luke) have created breakthroughs in this field.

You may have noticed Valio’s target of being carbon neutral in 2035 on billboards or milk cartons. Processing and recycling manure into energy and even fuel for traffic is one of the most important actions to take in order to achieve this target. Valio has worked on the subject for about eight years. The research started in 2012 with laboratory tests and has recently moved on to pilots on Luke’s locations in Maaninka and Siikajoki.

lehmä, lehmiä, ammuu
Luke’s biogas facility in Maaninka, Finland played an important role in pilot studies. Photo: Kirsi Järvenranta.

When the work started, the research problem was stated as follows: how could slurry generated in a dairy farm be processed so that its nutrients are in an easily utilizable form and major proportion of water is extracted? In particular nitrogen and phosphorus need to be isolated in separate fractions. Furthermore, nitrogen should be stabilized so that its evaporative losses are minimized. Grass is the most important feed for dairy cattle and it is also effective in absorbing nutrients. Therefore, the new nitrogen fertilizer was tested on grass. Since slurry-based fertilizer is also suitable for organic farming, tests were conducted on organic barley as well.

Processing slurry creates an efficient fertilizer

The fractionation method proceeds as follows: the raw slurry coming from the barn goes through biogas process and the reject is divided into phosphorus-rich dry manure and nitrogenous liquid solution. After this, the excess water is removed from the nitrogenous fraction and the remaining nitrogen rich solution is processed in order to prevent evaporative losses.

In circular economy, we should talk about ingredients rather than side streams or waste.

The end product of the process is an efficient nitrogen fertilizer. In the future it can be produced on an industrial scale. The functioning of the fertilizer has been studied for three years in Luke’s locations in Maaninka and Siikajoki. The tests have proved that nitrogen fraction is as efficient as the industrial mineral nitrogen fertilizer. For comparison: when the biogas process was lacking from the fractionation method, the grass yield was 15–20 percent smaller.

Slurry processing provides opportunities

When the farm produces milk, various side streams are formed.

Lannoitteen mittausta Maaningalla
Research technician Arto Pehkonen is measuring liquid N fertilizer fractionated from slurry. Photo: Jenni Laakso.

“At the present time of circular economy, one should talk about ingredients rather than side streams or waste,” suggests Juha Nousiainen, responsible of Valio’s carbon neutral dairy chain. Nousiainen has a long career in Valio’s primary production, the last ten years of which in various management posts.

“Finland has a lot of opportunities in utilizing manure. For example, Finland currently produces some 1–2 percent slurry into biogas, while in Denmark the same number is around 20 percent. Technology exists to a large extent, we should just put it to use on a large scale. This calls for investments,” Nousiainen continues.

Senior scientist Kirsi Järvenranta from Luke says that the  assignment was very interesting for Luke and at the heart of its expertise.

“If the end products of this development work get to be utilized as fertilizers at the farms, it has a significant impact on enhancing the nutrient cycle efficiency of grass production. This would be an important step towards carbon neutral agriculture,” Järvenranta says.