Industrial scale straw-to-biomethane conversion. A new business opportunity

A number of laboratory measurements as a function of variations of the pre-treatment showed, that under practical circumstances it is possible to achieve a biogas yield of 400 m3 per tons straw (corresponding to 300 m3 methane per tons volatile solids). The most significant effect was achieved by impregnating the straw with 1 % acetic acid before mechanical treatment. It was additionally shown that an extended incubation, after the me-chanical treatment at 90oC, resulted in a more pronounced effect than incubation at 140oC.

The maximum gas yield was 360 l methane per kg vs (volatile solids). This is equivalent to 290 l methane per kg straw (at 85 % dry matter, 95 % vs) or 450 l biogas per kg straw (at 65 % methane).

A typical annual quantity of straw for anaerobic digestion would be 10.000 tons and more. A biogasplant di-gesting e.g. 100.000 tons liquid manure and 10.000 tons straw will produce a total of app. 6.5 mio. m3 biogas, of which 2.5 mio. m3 stems from the slurry and 4 mio. m3 from the straw.

The result is a sustainable and robust biogas production and an equally sustainable economic performance of the biogas plant.