Energy and emergy evaluation of potentials for energy self-sufficiency in Danish organic dairy farms by production of biogas and bioethanol

摘要

One obvious way to enhance agricultural resilience is for farms to increase self-sufficiency with necessities such as fuel, fodder and fertilizer. Our research seeks to uncover these potentials for Danish organic dairy farming.udThe setting is a theoretical model of a farm-cooperation of 10 farms of 100 ha each producing only milk and animals for slaughtering and being self-sufficient with fodder and fertilizer. The question is if they can be self-sufficient with energy by means of shared biogas and/ or bioethanol production facilities. The method is mapping of energy, emergy (embodied energy measured in solar energy joules) and mass flows in different scenarios, that are based on empirical data from Danish dairy farms concerning mix of crops, crop yields, livestock input/output and fuel and electricity consumption.udIn various scenarios different utilization of the produced crop is tested. Biogas is produced from manure and either clover grass or maize, and the effluent is fed back to the fields as fertilizer. In another scenario bioethanol is produced from grain and whey originating from the dairy cheese production, and the effluent is fed back to the livestock as a protein-rich fodder. udResults compare the different scenarios in terms of mass, energy and emergy flows, thus including direct and indirect energy. Overall resource and energy efficiency are evaluated.