BIOGAS PRODUCTION FROM CATCH CROPS: A SUSTAINABLE AGRICULTURAL STRATEGY TO INCREASE BIOMASS YIELD BY CO-HARVEST OF CATCH CROPS AND STRAW

Catch crop cultivation combined with its use for biogas production would increase renewable energy production in the form of methane, without interfering with the production of food and fodder crops. The low biomass yield of catch crops is the main limiting factor for using these crops as co-substrate in manure-based biogas plants and the profit obtained from the sale of biogas barely compensates for the harvest costs. A new agricultural strategy to harvest catch crops together with the residual straw of the main crop was investigated to increase the biomass and thereby the methane yield per hectare. Seven catch crops harvested together with the stubble of the main crop (spring wheat) were evaluated. The effects of stubble height and harvest time for different catch crops/straw blends were studied. Biomass yields were up to 3.6 t of TS ha-1 of which the catch crop constituted around 10% of the total biomass. Leaving the straw on the field until harvest of the catch crop in the autumn could benefit biogas production due to the organic matter degradation of the straw taking place on the field during the autumn months. This new agricultural strategy may be a good alternative to achieve economically feasible biogas production from catch crops and straw