Ecological intensification by integrating biogas production into nutrient cycling: Modeling the case of Agroecological Symbiosis

There is growing demand to produce both food and renewable energy in a sustainable manner, while avoiding competition between food and energy production. In our study, we investigated the potential of harnessing biogas production into nutrient recycling in an integrated system of organic food production and food processing. We used the case of Agroecological Symbiosis (AES) at Palopuro, which is a combination of three farms, a biogas plant, and a bakery, as a case to explore how biogas production using feedstocks from the farms can be used to improve nutrient cycling, and to calculate how much energy could be produced from the within-system feedstocks. The current system (CS) used in organic farms, and the integrated farm and food processing AES system, were analyzed using Substance Flow analysis. In the AES, annual nitrogen (N) and phosphorus (P) surpluses were projected to be reduced from 95 kg ha −1 to 36 kg ha −1 and from 3.4 kg ha −1 to −0.5 kg ha −1 respectively, compared to the CS. Biogas produced from green manure leys as the major feedstock, produced 2809 MWh a −1 . This was 70% more than the energy consumed (1650 MWh a −1 ) in the systemand thus the AES system turned out to be a net energy producer. Results demonstrated the potential of biogas production to enhance the transition to bioenergy, nutrient recycling, and crop productivity in renewable localized farming and food systems.