Abstract
Agriculture is expected to contribute in substituting of fossil fuels in the future. This constitutes a paradox as agriculture depends heavily on fossil energy for providing fuel, fodder, nutrients and machinery. The aim of this paper is to investigate whether organic agriculture is capable of providing both food and surplus energy to the society as evaluated from a model study. We evaluated bioenergy technologies in a Danish dairy farming context in four different scenarios: 1) vegetable oil based on oilseed rape, 2) biogas based on cattle manure and grass-clover lays, 3) bioethanol from rye grain and whey, and 4) a combination of 1) and 2). When assessing the energetic net-contribution to society from bioenergy systems, two types of problems arise: How to aggregate non-equivalent types of energy services, and how to account for non-equivalent types of inputs and co-products from the farming? To avoid the first type, the net output of liquid fuels, electricity, useful heat and food were calculated separately. Further, to avoid the second type, all scenarios were designed to provide self-sufficiency with fodder and fertilizer and to utilize co-products within the system. This approach resulted in a transparent assessment of the net-contribution to society, which is easy to interpret. We conclude that if 20% of land is used for energy crops, farm-gate energy self-sufficiency can be achieved at the cost of 17% reduction in amount of food produced. These results demonstrate the strong limitations for (organic) agriculture in providing both food and surplus energy.
Highlights
Agricultural production depends on fossil energy for providing fuels, fertilizer, pesticides, fodder, and machinery (Østergård et al, 2010; Pelletier et al, 2011)
We model farm-level production and consumption of energy and analyze a reference scenario and four bioenergy scenarios which aim at increasing energy output
Different strategies aiming at increasing energy production by means of vegetable oil, biogas, and bioethanol are explored
Summary
Agricultural production depends on fossil energy for providing fuels, fertilizer, pesticides, fodder, and machinery (Østergård et al, 2010; Pelletier et al, 2011). Agriculture is expected to contribute in substitution of depleting fossil energy sources for the society (Farrell et al, 2006; EU, 2009; Cherubini, 2010). The production of biofuels from energy crops will require replacing land for food with land for energy. It has Integrated Food and Bioenergy System been shown that even drastic land use changes may only provide 7–20% of total Danish energy supply in economically feasible scenarios (Callesen et al, 2010)
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