Energy Self-sufficiency from an Emergy Perspective Exemplified by a Model System of a Danish Farm Cooperative

Contemporary food production is highly dependent on fossil fuel for production of fertilizer and as diesel for field operations. One way to enhance agricultural resilience is to increase self-sufficiency at the farm level with necessities such as energy, food, fodder, nutrients and seed. It is even better if the farm is a net energy producer since energy used for processing, distribution and trade of farm products should be supplied also by agriculture in order to increase the resilience of food supply systems.

In this project we analyze these potentials based on a model system of a multifunctional Danish organic farm cooperative with a small biogas plant shared between five farms. We model the energy, matter and emergy flows in a crop rotation scenario developed by the Danish organic farmers association including grass-clover lays, cereals, oilseed rape and legumes; also we consider the emergy flow for labor in different ways.

The five farms produce bioenergy (biodiesel from oil seed rape and electricity and hot water from anaerobic fermentation of grass-clover), food and fodder (cereals and legumes) and green manure (effluent from biogas production). All green manure, about half of the biodiesel and a little electricity and heat are used on the farms; the remaining products are supplied to the society.

Different emergy indices for resource use efficiency are evaluated and compared to results from other bioenergy studies. The roles of nutrient balances and green manure are discussed.