August 10, 2007

Measuring the environmental performance of individual biofuel plants is increasingly important for this fast-growing industry.

University of Nebraska-Lincoln agricultural researchers have developed a tool to assess greenhouse gas mitigation and energy efficiency of corn-based ethanol plants.

Institute of Agriculture and Natural Resources researchers have been working on the Biofuel Energy Systems Simulator for two years. The initial version of this software, designed for corn-based ethanol production, is available free at http://www.bess.unl.edu/. The computer modeling software analyzes energy yield and efficiency, greenhouse gas emissions and resource requirements for individual biofuel production systems. Called BESS for short, this "seed-to-fuel" tool quantifies lifecycle carbon savings and environmental impact of individual biofuel systems. It factors in energy use and greenhouse gases from crop production, ethanol conversion, byproduct use, waste disposal and transportation.

A new tool from the University of Nebraska-Lincoln will enable ethanol plants, like this one at Fairmont, to measure their greenhouse gas mitigation and energy efficiency. ( 2005 University of Nebraska Board of Regents. All rights reserved.)

Environmental and economic expectations are high for biofuel production.

Determining how well individual plants measure up will be critical to the industry's long-term success and sustainability, said UNL agronomist Ken Cassman, director of the Nebraska Center for Energy Sciences Research who led this research.

"On average, ethanol plants are thought to reduce greenhouse gas emissions. It's clear some do a better job than others," Cassman said. In the future, the marketplace is likely to reward the most environmentally efficient biofuel plants.

"This research lays the foundation to have the best data available to look at not only average biofuel production systems but also state-of-the-art systems that are far better at conserving resources," he said.

Accurately quantifying the environmental impact of individual biofuel systems is increasingly important for environmental, public policy and economic reasons, Cassman said. In the future, it is quite likely that biofuel plants will need to certify their energy efficiency and greenhouse gas emissions to meet renewable or low-carbon fuel standards being developed in several states and countries, he said.

Verifying that plants are meeting society's environmental goals is key to continued public support. There's also income potential. Once a greenhouse gas emissions standards certification system is established for the industry, individual plants will be able to quantify their greenhouse gas mitigation potential and sell those savings, or offsets, in the rapidly expanding carbon-credit market.

Ken Cassman

"It's important to create appropriate, scientifically sound, accurate, customized certification methods for biofuel systems based on research in the Corn Belt," Cassman said.

This new software draws from ongoing UNL research in several areas, including efficient, environmentally sound crop production; soil carbon sequestration; and feeding cattle with distillers grains. It also draws from the innovation occurring as the industry continues to mature.

"We're ideally positioned to be a national leader in developing the framework for a standardized assessment tool that the scientific community can agree upon to validate that plants are meeting environmental goals," Cassman said.

BESS is designed for easy use by ethanol plant operators, crop producers, researchers, regulators, policymakers or others concerned with optimizing biofuel systems' economic and environmental performance. It's backed by detailed software development and extensive, well-documented scientific data.

"Its strength is that it is transparent. Every parameter is validated by a published reference and you can actually see the parameters for each component," Cassman said. Users can change default assumptions to customize the analysis for their particular biofuel system, or to explore energy efficiency and greenhouse gas consequences under different scenarios.

BESS estimates net energy efficiency and net greenhouse gas emissions for each component in biofuel production and the whole system. It provides three types of analyses: energy yield and efficiency; greenhouse gas emissions and global warming potential; and resources requirements, such as land, fertilizer and water. The UNL system is more flexible and customizable than existing energy and emissions models for corn ethanol production, Cassman said. Users can simulate factors unique to their operation to precisely evaluate their energy and greenhouse gas production. It's also the only system that estimates resource requirements used for specific biofuel production systems.

The initial version of BESS is based on corn-based dry-milling ethanol production. The team plans to develop versions for soybean biodiesel and biomass ethanol production from switchgrass and corn stover, which eventually will allow performance comparisons of biofuel systems with different feedstocks.

Researchers are making their tool freely available because they want it widely used. The BESS software and user manual can be downloaded at http://www.bess.unl.edu/.

A grant from the Western Governor's Association and the Nebraska Energy Office helped fund this research, which was conducted in cooperation with IANR's Agricultural Research Division.

Vicki Miller
IANR News