Browsing by Subject "biofuel"

Now showing 1 - 4 of 4
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    Partitioning of evapotranspiration using a stable isotope technique in an arid and high temperature agricultural production system
    (Elsevier, 2017-01) Lu, Xuefei; Liang, Liyin L.; Wang, Lixin; Jenerette, G. Darrel; McCabe, Matthew F.; Grantz, David A.; Department of Earth Sciences, School of Science
    Agricultural production in the hot and arid low desert systems of southern California relies heavily on irrigation. A better understanding of how much and to what extent irrigated water is transpired by crops relative to being lost through evaporation would improve the management of increasingly limited water resources. In this study, we examined the partitioning of evapotranspiration (ET) over a field of forage sorghum (Sorghum bicolor), which was under evaluation as a potential biofuel feedstock, based on isotope measurements of three irrigation cycles at the vegetative stage. This study employed customized transparent chambers coupled with a laser-based isotope analyzer to continuously measure near-surface variations in the stable isotopic composition of evaporation (E, δE), transpiration (T, δT) and ET (δET) to partition the total water flux. Due to the extreme heat and aridity, δE and δT were very similar, which makes this system highly unusual. Contrary to an expectation that the isotopic signatures of T, E, and ET would become increasingly enriched as soils became drier, our results showed an interesting pattern that δE, δT, and δET increased initially as soil water was depleted following irrigation, but decreased with further soil drying in mid to late irrigation cycle. These changes are likely caused by root water transport from deeper to shallower soil layers. Results indicate that about 46% of the irrigated water delivered to the crop was used as transpiration, with 54% lost as direct evaporation. This implies that 28 − 39% of the total source water was used by the crop, considering the typical 60 − 85% efficiency of flood irrigation. The stable isotope technique provided an effective means of determining surface partitioning of irrigation water in this unusually harsh production environment. The results suggest the potential to further minimize unproductive water losses in these production systems.
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    Producing energy while sequestering carbon? The relationship between biochar and agricultural productivity
    (Elsevier, 2014-04) Kauffman, Nathan; Dumortier, Jerome; Hayes, Dermot J.; Brown, Robert C.; Laird, David A.; School of Public and Environmental Affairs
    A partial solution to problems associated with anthropogenic greenhouse gas (GHG) emissions could be the development and deployment of carbon-negative technologies, i.e., producing energy while reducing atmospheric carbon dioxide levels. Biofuels have been considered a possibility but have faced limitations due to competition with food production and GHG emissions through indirect land-use change (ILUC). In this article, we show how emissions from ILUC can potentially be reduced by producing food and bioenergy from biochar amended soils. The possibility of yield improvements from biochar would reduce the land requirement for crop production and thus, lead to a reduction in emissions from ILUC. In our application, biochar and bio-oil are produced via fast pyrolysis of corn stover. Bio-oil is subsequently upgraded into a fuel suitable for use in internal combustion engines. Applying the U.S. regulatory method used to determine biofuel life cycle emissions, our results show that a biochar-induced yield improvement in the U.S. Midwest ranging from 1% to 8% above trend can lead to an ILUC credit between 1.65 and 14.79 t CO2-equivalent ha−1 year−1 when future emissions are assessed over the next 30 years. The model is generalizable to other feedstocks and locations and illustrates the relationship between biochar and crop production.
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    Production and Spatial Distribution of Switchgrass and Miscanthus in the United States under Uncertainty and Sunk Cost
    (Elsevier, 2017-08) Dumortier, Jerome; Kauffman, Nathan; Hayes, Dermot J.; School of Public and Environmental Affairs
    The U.S. cellulosic biofuel mandate has not been enforced in recent years. Uncertainty surrounding the enforcement of the mandate in addition to high production and harvest cost have contributed to a delay in the widespread planting of bioenergy crops such as switchgrass and miscanthus. Previous literature has shown that under uncertainty and sunk cost, an investment threshold is further increased due to the value associated from holding the investment option. In this paper, we extend the previous literature by applying a real option switching model to bioenergy crop production. First, we calculate the county-level break-even price which triggers a switching away from traditional field crops (corn, soybeans, and wheat) to bioenergy crops under various scenarios differing by commodity prices, production cost and biomass price expectations. We show that the resulting break-even prices at the county-level can be substantially higher than previously estimated due to the inclusion of the option value. In a second step, we identify counties that are most likely to grow switchgrass or miscanthus by simulating a stochastic biomass price over time. Our results highlight two issues: First, switchgrass or miscanthus are not grown in the Midwest under any scenario. Under low agricultural residue removal rates, biomass crops are mostly grown in the Southeast. Second, under the assumption of a high removal rates, bioenergy crops are not grown anywhere in the U.S. since the cellulosic biofuel mandate can be covered by agricultural residues.
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    Where does all the biofuel go? Fuel efficiency gains and its effects on global agricultural production
    (Elsevier, 2021-01) Dumortier, Jerome; Carriquiry, Miguel; Elobeid, Amani; School of Public and Environmental Affairs
    Increasing biofuel production over the last decade and biofuel policies in Brazil, the European Union, and the United States have changed the global agricultural landscape in terms of land-use, commodity prices, and trade. Increasing fuel efficiency and electrification of the vehicle stock is projected to lower gasoline, diesel, and biofuel demand in the future. In this analysis, we quantify the effects of a 30% reduction in ethanol consumption in the U.S. and the European Union triggered by higher vehicle fleet fuel efficiency on global agricultural markets. Our results show decreases in global commodity prices by 1.9%–6.6% and a slight decrease in global cropland by 0.3%. Major changes occur in trade patterns with U.S. corn exports increasing by 30.3%. Global greenhouse gas emissions are lower due to the overall reduction in cropland. Gasoline and diesel consumption of the vehicle fleet is not changing rapidly but is a long-term process because vehicles are on average in operation for 10 or more years. Consequently, there are important long-term policy implications from changes in fuel efficiency requirements or ethanol blending limits that affect commodity prices, trade, and greenhouse gas emissions.