The Water Quality and Energy Impacts of Biofuels

Abstract

Concerns over rising fuel prices, national security, and the environment have led to the Energy Independence and Security Act (EISA) of 2007, which established a mandate for the production of at least 36 billion gallons of biofuels in 2022, up to 15 billion gallons of which can come from traditional first-generation biofuels sources such as corn starch-based ethanol. One consequence of ramped-up biofuels production is the risk of additional soil runoff. This runoff, potentially laden with nitrogen and phosphorus compounds from fertilizers, can detrimentally impact water quality. Consequently, the water treatment sector might require additional energy to remove increased quantities of sediment and run-off from nutrients and pesticides in degraded water bodies downstream of agricultural land. At the same time, the cumulative effects of increased eutrophication in the Mississippi and Atchafalaya River Basins have already negatively impacted much of the aquatic life in the Louisiana-Texas continental shelf. A recent report by U.S. Geological Survey measured nitrogen loading in the Mississippi River basin as high as 7,761 metric tons per day, the highest recorded loading in the past three decades, 52% of which is attributed to loading from corn and soybean crops. Massive algae blooms that thrive in nutrient-rich water deplete the water of oxygen when they die, creating a hypoxic region. This hypoxic region, which currently covers a region the size of New Jersey, is considered to be the second-largest dead zone in the world as of 2007. As a result, the Gulf Hypoxia Action Plan of 2008 was established to reduce nitrogen and phosphorous loading by 45% in order to shrink the hypoxic region to 5,000 square kilometers. Thus, at a time when water quality priorities aim to decrease nitrogen and phosphorous loading in waterways, legislative targets are seeking to increase corn starch-based ethanol production to 15 billion gallons a year, and thereby potentially increase nitrogen loading in this region by 10–34% due to runoff. Consequently, the energy intensity for water treatment may have a two-fold challenge. Because water and wastewater treatment is already responsible for 4% of the nation’s electricity consumption, putting more stringent demands on this sector could put upward pressure on energy consumption. This analysis quantifies the impact that the mandated increase in ethanol production might have on the energy required for water treatment in the United States. It reports results from a first-order top-level analysis of the energy impacts of ethanol. The results indicate that the increased production corn-starch based ethanol in the United States is not likely to increase the energy consumed during surface water treatment, but might cause significant increases in the energy consumed during groundwater treatment.