Living Lab Skåne – maize straw tested as a biogas substrate

The work in the Accel AgroBiogas Living Lab Skåne is continuing in parallel with activities in the project’s other regions. During the autumn, a new potential biogas substrate has been tested: maize straw, i.e. the straw and stalks that remain after harvesting grain maize.

The test and demonstration are carried out at Assargården in Glumslöv (Landskrona). The grain maize was harvested in mid-October using a conventional combine harvester. The maize kernels are used as feed raw material, among other things for poultry and dog feed, while the straw and stalks are normally left in the field.

To be able to utilise the biomass, the maize straw and stalks were windrowed using a grass mowing unit (butterfly mower, 9-metre working width). The material was then pressed into square bales using a conventional baler. The harvest yielded approximately 70 bales of 1,000 kg each from around 10 hectares, with a dry matter content of about 35 percent. This corresponds to a straw yield of approximately 3.5 tonnes per hectare.

Plant samples – both frozen and dried – have been sent to Aarhus University for analysis of the biogas potential of the maize straw.

After baling, the bales were transported to Assargården’s biogas plant, where they are stored outdoors on a hard surface without cover. In daily operation, approximately half a bale per day is fed into the stationary mixer wagon, which chops and mixes the substrates before they are fed into the biogas plant.

The first experiences from the test show that windrowing, baling and transport worked very well. However, the maize stalks have proven to be somewhat too hard and long for the feeding system, which can cause blockages and thereby limit how much material can be used per day.

One possible further development being discussed is to finely chop the maize straw directly in the field and store it as silage, in order to facilitate feeding into the plant. A next step in the Living Lab work at Assargården could therefore be to test this method in connection with the harvest next autumn.