Abstract
Researchers and federal and state agency officials have long been interested in evaluating location-specific impact of bioenergy energy crops on water quality for developing policy interventions. This modeling study examines long-term impact of giant miscanthus and switchgrass on water quality in the Cache River Watershed (CRW) in Arkansas, United States. The bioenergy crops were simulated on marginal lands using two variants of a Soil and Watershed Assessment Tool (SWAT) model. The first SWAT variant was developed using a static (single) land-use layer (regular-SWAT) and for the second, a dynamic land-use change feature was used with multiple land use layers (location-SWAT). Results indicated that the regular-SWAT predicted larger losses for sediment, total phosphorus and total nitrogen when compared to location-SWAT at the watershed outlet. The lower predicted losses from location-SWAT were attributed to its ability to vary marginal land area between 3% and 11% during the 20-year modeling period as opposed to the regular-SWAT that used a fixed percentage of marginal land area (8%) throughout the same period. Overall, this study demonstrates that environmental impacts of bioenergy crops were better assessed using the dynamic land-use representation approach, which would eliminate any unintended prediction bias in the model due to the use of a single land use layer.
Highlights
The United States Energy Independence and Security Act (EISA) of 2007 was intended to bring energy security through increased biofuel production
Because calibration of nutrients depends on hydrology, a comparable trend of under-prediction was observed for Total Nitrogen (TN)
Over-predicted TN outputs were observed during June to September in 2009 and 2010, during which relatively high precipitation was received in the watershed
Summary
The United States Energy Independence and Security Act (EISA) of 2007 was intended to bring energy security through increased biofuel production. A critical driver of interest in biofuel crop production was a target of producing 36 billion gallons of renewable fuels by 2022 [3]. This target was first revised downward to 16.3 billion gallons in 2015 and increased to 17.4 billion gallons by 2016, respectively, because of a variety of reasons such as constraints in accommodation of increasing volumes of ethanol in the transport fuel market, limitations. Despite downward revision of the targeted renewable fuel production from 36 to 17.4 billion gallons by 2022, the need to study environmental footprint of biofuel crop production is still relevant for EPA
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