Optimisation of environmental benefits associated with energy crop production

Negative environmental effects of current agricultural practices, such as emission of greenhouse gases, nutrient leaching, decreased soil fertility, and erosion, may be reduced when traditional annual food crops are replaced by dedicated perennial energy crops. Cultivation of short-rotation forest (Salix) and energy grass (reed canary grass) can also be used to purify municipal waste water and sludge. Furthermore, the content of heavy metals in the soil can be reduced through Salix cultivation. The economic value of these environmental benefits, including reductions in costs to farmers and society as a whole, has been estimated to be from 1 SEK up to 120 SEK per MWh biomass. For comparison, the production cost (excluding transport) of Salix are about 120 SEK per MWh. Purification of waste water in energy crop cultivation has the highest economic value, followed by reduced nutrient leaching through riparian buffer strips, recirculation of sewage sludge, and reduced wind erosion through shelter belts consisting of Salix. The value of other environmental benefits is estimated to be less than 20 SEK per MWh. If 200,000 ha of Sweden's totally available arable land of 2.8 Mha were available for energy crop cultivation, around 12 TWh biomass could theoretically be produced per year, at an average cost of about 15 to 20 SEK per MWh, including the value of environmental benefits. It is assumed that priority is given to cultivations with the highest total value, as several different environmental effects could be achieved on the same cultivation site. If 8000,000 ha were to be available, the corresponding cost of some 40 TWh biomass per year would be around 70 SEK per MWh. (au)