Evaluation of annual bioenergy crops in the boreal zone for biogas and ethanol production

Three annual plant species, maize, hemp and faba bean were tested for suitability as dedicated biomass crops in Boreal conditions. Biomass yields were 10–15 t ha-1. The crops were analyzed for their composition and tested as raw materials for conversion to methane and to fermentable sugars. The methane yield was 379 ± 16 Ndm3 kg−1 VS−1 from maize, 387 ± 20 Ndm3 kg−1 VS−1 from faba bean and 239 ± 9 Ndm3 kg−1 VS−1 from hemp. Based on the yield per hectare, maize proved to be the most potential raw material source for methane production. Analogous to methane production, maize was the most productive raw material also in standard hydrolysis tests, with a conversion yield of about 80% of the theoretical sugars. Based on the amount of carbohydrates, the highest theoretical yield per hectare was obtained with hemp. However, considering all parameters, including the need for weeding and fertilizers, all three crops studied proved to be attractive options for cultivation in boreal conditions as well as being used as energy crops in boreal climate.

► Maize, fibre hemp and faba bean produced high biomass yields in boreal climate.
► Maize and faba bean showed positive potential in methane production.
► Methane yield from hemp increased to the same level after more extensive milling.
► All potential carbohydrates were not available for ethanol before pre treatment.