A model for fossil energy use in Danish agriculture used to compare organic and conventional farming

Knowledge about fossil energy use in agricultural systems is needed, because it can improve the understanding of how to reduce the unsustainable use of limited energy resources and the following greenhouse gas emissions. This study describes and validates a model to assess fossil energy use in Danish agriculture; gives an example of how the model can be used to compare organic and conventional farming; and discusses the implications and potentials of using the model to simulate energy use in scenarios of agricultural production. The model is a development of an existing model, which was too coarse to predict measured energy use on Danish farms. The model was validated at the field operational, the crop type, and the national level, and can supplement the Intergovernmental Panel on Climate Change manual to quantify fossil energy use and subsequent carbon dioxide emissions from agriculture. The model can be used to model energy use as one indicator in a multi-criteria evaluation of sustainability, also including other agroecological and socio-economic indicators. As an example, energy use for eight conventional and organic crop types on loamy, sandy, and irrigated sandy soil was compared. The energy use was generally lower in the organic than in the conventional system, but yields were also lower. Consequently, conventional crop production had the highest energy production, whereas organic crop production had the highest energy efficiency. Generally, grain cereals such as wheat have a lower energy use per area than roughage crops such as beets. However, because of higher roughage crop yields per area, energy use per feed unit was higher in the roughage crops. Energy use for both conventional cattle and pig production was found to be higher than that for organic production. With respect to fossil energy use per produced livestock unit, agro-ecosystems producing pigs were in both cases less energy effective than those producing cattle. Fossil energy use for three scenarios of conversion to organic farming with increasing fodder import was compared to current conventional farming in Denmark. The scenario with the highest fodder import showed the highest energy use per livestock unit produced. In all scenarios, the energy use per unit produced was lower than in the present situation. However, the total Danish crop production was also lower. In conclusion, the model can be used to simulate scenarios, which can add new information to the discussion of future, sustainable agricultural production.