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Title: Switchgrass Biofuel Research: Carbon Sequestration and Life Cycle Analysis (a.k.a. Second Generation Biofuels: Carbon Sequestration and Life Cycle Analysis)

Soil emissions have been inadequately characterized in life cycle assessment of biofuels (see section 3.2.3). This project measures the net differences in field-level greenhouse gas emissions (CO2, N2O, and CH4) due to corn residue removal for cellulosic ethanol production. Gas measurements are then incorporated into life cycle assessment of the final biofuel product to determine whether it is in compliance with federal greenhouse gas emissions standards for biofuels (Renewable Fuel Standard 2, RFS2). The field measurements have been conducted over three years on two, quarter-section, production-scale, irrigated corn fields (both roughly 50 hectares, as this size of field is necessary for reproducible eddy covariance flux measurements of CO2; chamber measurements are used to determine N2O and CH4 emissions). Due to a large hail storm in 2010, estimates of the emission from residue could not be separated from the total CO2 flux in 2011. This led us to develop soil organic carbon (SOC) modeling techniques to estimate changes in CO2 emissions from residue removal. Modeling has predicted emissions of CO2 from oxidation of SOC that are consistent (<12%) with 9 years of CO2 flux measurements at the two production field sites, and modeling is also consistent with other field measurements (Liskamore » et al., submitted). The model was then used to estimate the average change in SOC and CO2 emissions from nine years of simulated residue removal (6 Mg biomass per hectare per year) at the sites; a loss of 0.43 Mg C ha-1 yr-1 resulted. The model was then used to estimate SOC changes over 10 years across Nebraska using supercomputing, based on 61 million, 30 x 30 meter, grid cells to account for regional variability in initial SOC, crop yield, and temperature; an average loss of 0.47 Mg C ha-1 yr-1 resulted. When these CO2 emissions are included in simple life cycle assessment calculations, emissions from cellulosic ethanol from crop residue are above mandated levels of 60% reduction compared to gasoline (Liska, in press). These approaches are both technically effective and economically feasible. This work has been extensively peer reviewed.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Biological Systems Engineering. Dept. of Agronomy and Horticulture
  2. Univ. of Nebraska, Lincoln, NE (United States). School of Natural Resources
  3. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Agronomy and Horticulture
  4. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Biological Systems Engineering
Publication Date:
OSTI Identifier:
1111347
Report Number(s):
DOE-NEBRASKA--EE0003149
DOE Contract Number:
EE0003149
Resource Type:
Technical Report
Research Org:
Univ. of Nebraska, Lincoln, NE (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS