Cost-effective use of straw for biogas

Challenge

In Denmark, 2-3 million tons of straw are produced annually, but are not used; instead, they are cut and left on the fields. This represents a significant and untapped resource that biogas plants could use instead of energy crops like beets, grass, and maize, which are set to be phased out over the next few years. However, this is not without challenges. Firstly, straw costs 700 DKK per ton. Secondly, it is difficult to handle and introduce into the plant, as it can contribute to the formation of floating layers in the biogas plant. Last but not least, the gas yield from straw is only 2/3 of the yield per kilogram of dry matter compared to energy crops.

Solution

The project aims to identify the most cost-effective method for shredding and pre-treating straw in a way that makes it easy to introduce into the biogas plant, while increasing biogas production compared to untreated straw. The project is designed as a trial-based feasibility study, leading toward a full-scale demonstration project.

The project is co-financed by the Ministry of Education and Research.

Impact

The project will determine the most optimal solution for how straw can be most effectively added to biogas plants, with the greatest climate and economic impact. The solution will be applicable to all 200 biogas plants currently operating in Denmark.