Wrams Gunnarstorp outside Bjuv in Skåne is a family owned forestry and farming business with forest and agricultural land spread across three farms. Since 2007 they have operated a biogas plant, despite having limited access to livestock manure.
Rudolf Tornerhjelm took a particular interest in the biofertiliser produced after the biogas process
“We obtain forty five thousand cubic metres of fertiliser that we can use on our own fields and distribute to others. It is a challenge to distribute the fertiliser without sending lorries back and forth”, he explains.
Imported machinery
They have invested in importing two new machines from the United States to combine fertiliser application with water. The machines are lighter than traditional tractors with slurry tanks. This reduces soil compaction which is a problem in arable land.
By using nutrient rich water from Ekobalans, extracted during the dewatering of the biofertiliser, and by monitoring the mixture with technical control systems, they achieve precision in the application.
Ulrik Svedin
Diluting the mixture with water reduces ammonia losses which improves the utilisation of nitrogen in the fertiliser.
Ulrik Svedin
“We process fifty thousand cubic metres of raw material per year, with permission for up to sixty five thousand cubic metres. And the biogas plant is connected to the Swedish gas grid which makes things much easier”, says Rudolf Tornerhjelm.
Biorefinery
The collaboration with Ekobalans has led to the development of a type of biorefinery for fractionation of phosphorus and nitrogen from the biofertiliser, in other words the nutrient rich components that remain after anaerobic digestion.
Gunnar Thelin explains the drying process and the separation of nitrogen and phosphorus from the biofertiliser.
Ulrik Svedin
“We can separate ninety five per cent of the phosphorus into a solid fraction while seventy five per cent of the nitrogen remains in the liquid phase, also called nutrient water. This makes it possible to meet the entire nitrogen requirement of the crop without exceeding the maximum allowed dose of phosphorus”, says Gunnar Thelin from Ekobalans.
They have also developed a pelletised biofertiliser from the solid phase as a finished product for garden use.
Challenges
Despite their progress there are challenges, especially concerning the solid fraction. Drying requires a large amount of energy and the process is currently paused. According to Gunnar Thelin at Ekobalans the issue is to find the right scale and market.
“We need greater volume, lower production costs and time for technical optimisation. It is also difficult to compete with conventional fertiliser producers who do not pay for their environmental impact”, he says.
Rudolf Tornerhjelm adds:
“This is no longer an experiment. It needs an industrial application.”
Wrams Gunnarstorp has invested in a system in which water from an excavated reservoir is mixed with nutrient water from the biofertiliser in a pump house before being transported to an irrigation system that delivers the mixture to the fields. The application is frequent and precise which benefits crop growth and reduces weeds.
Water reservoir for the future
A major investment is the new water reservoir, five hectares wide and up to seven metres deep. It collects drainage water from the fields and runoff from the forested ridge.
“We want to show the next generation that we took responsibility. The reservoir can be used for forest fires and for irrigation. When the water returns to the fields it reduces nutrient leakage into the sea”, says Rudolf Tornerhjelm.
Rudolf Tornerhjelm describes the investment in a reservoir as part of the biogas system at Wrams Gunnarstorp where they produce biogas, fertiliser pellets and nutrient water.
