Efficiency and ecological impacts of biofuels

As the global demand for energy continues to increase, biofuels, or fuels made from plant material, are frequently identified as an important component of our future energy supply.  However, very little information is available on the environmental and ecological impacts of the large-scale production of biofuels.  Based on calculations of the most optimistic reported net energy values of seven potential sources of biofuel (corn, switchgrass, sugar cane, rapeseed, sunflower, soybean, and low-input high-density biomass), we estimated the amount of arable land that would be required to produce enough biofuels to meet current and projected energy demands.  Currently, the crops with the highest net energy value are switchgrass (118 GJ/ha), sugarcane (109 GJ/ha), and rapeseed (31 GJ/ha).  We compared these land estimates to the availability and distribution of potential arable land based on data from the Food and Agricultural Organization.  Our conservative estimates suggest that, using the crops with the highest net energy values, a minimum of 2.5 to 27.5 times the global potential arable land would be required to produce enough biofuels to meet global fossil fuel demands in 2004. This could dramatically alter the environment by increasing habitat change and fragmentation, altering species diversity and composition, and impacting soil and water quality and availability.  Although the efficiency of biofuel production will continue to increase as technology improves, it is important to consider the potential consequences of conversion to biofuels and develop strategies to minimize the impacts of adding this additional demand on the planet’s resources.