The Brogas facility on Gotland produces approximately 30 gigawatt hours of biogas per year, corresponding to around three million litres of petrol. But the operation represents more than energy production alone. It is part of a broader, integrated energy system.
“We aim to increase volumes over the coming years. Our goal is to run our tractors and lorries on renewable fuel and on the biogas we produce ourselves. This is important for the environment and for our future market,” says Magnus Ahlsten, founder of Brogas.
Opportunities
The visiting group from the Biogas Solutions Research Center, BSRC, is given a guided tour of the biogas plant in Bro. Food waste and residues from restaurants and the food industry in Visby are delivered here. Behind the plant, a large pile of livestock manure towers over the site.
The manure is full of potential. It has an energy value in the form of biogas, but as with all organic material, or substrate, used in biogas production, most of the material remains after the gas has been extracted. These residues contain valuable nutrients such as phosphorus and nitrogen, which can be returned to agriculture as biofertiliser.
Nutrients remain
Calculations from Linköping University indicate that biogas production on Gotland could increase from today’s 36 gigawatt hours to 165 gigawatt hours. Anaerobic digestion of livestock manure alone could generate approximately 110 gigawatt hours, provided that all available manure were utilised. The study also takes transport and production costs into account.
The results show that Gotland could become more than self sufficient in phosphorus. The organic residual products correspond to around 137 tonnes more phosphorus than the recommended level of phosphorus fertilisation for the crops grown on the island. For nitrogen, the potential is lower. According to the LiU report, fertilisation needs on Gotland are approximately 2.4 times higher than the amount of nitrogen available in the identified residual products.
Phosphorus could be
exported from Gotland
“With more optimal use of the nitrogen and phosphorus in biofertiliser, it would be possible to export phosphorus from Gotland. Imports of nitrogen could also be reduced to some extent. The key benefit is that nutrients in local substrates are returned directly to the soil on Gotland,” says Madeleine Larsson, Associate Professor and Deputy Director of the Biogas Solutions Research Center.
Magnus Ahlsten welcomes the fact that the conditions have been thoroughly reviewed, but believes that the actual energy potential will be somewhat lower.
“In my view, it may be possible to reach around 100 gigawatt hours, which would be sufficient. Not all manure can be collected, and transport costs must be considered to ensure that it is economically viable to bring manure to the facilities.”
