Minimizing land use and nitrogen intensity of bioenergy

The environmental impacts of bioenergy products have received a great deal of attention. Life cycle analysis (LCA) is a widely accepted method to quantify the environmental impacts of products. Conducting comprehensive LCAs for every possible bioenergy alternative is difficult because of the sheer magnitude of potential biomass sources and energy end products. The scopes of LCAs are often simplified to compare multiple products on the basis of greenhouse gas emissions and net energy balances, and may neglect equally important considerations such as nitrogen and land use. This study determines the most desirable energy crops on the basis of nitrogen and land use. The theoretical minimum nitrogen and land use requirements of fourteen bioenergy feedstocks are evaluated. These results can help prioritize certain feedstock crops for more in-depth life cycle analyses and can be used to inform policies on dedicated energy crops. The results of the study indicate that sugar cane has the best nitrogen and land use profile of the analyzed feedstocks. Sugar cane is the largest contributor to bioenergy production worldwide and is an effective policy choice from a nutrient and land use perspective. Conversely, soybeans and rapeseed are the least effective biomass sources with respect to land use and nitrogen requirements, yet these crops are also used to meet biofuel production targets worldwide. These results indicate current energy policies either do not consider or undervalue nitrogen and land use impacts, which could lead to unsustainable recommendations. Interestingly, when both nitrogen and land intensity are taken into account, reasonably small differences are seen between the remainder of the analyzed feedstocks, indicating an inherent trade-off between energy yield and nitrogen impacts.