James A. Duffield
United States Department of Agriculture
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Archive | 1998
John Sheehan; Vince Camobreco; James A. Duffield; Michael S. Graboski; Housein Shapouri
This report presents the findings from a study of the life cycle inventories (LCIs) for petroleum diesel and biodiesel. An LCI is a comprehensive quantification of all the energy and environmental flows associated with a product from “cradle to grave.” It provides information on raw materials extracted from the environment; energy resources consumed; air, water, and solid waste emissions generated.
Transactions of the ASABE | 2003
H. Shapouri; James A. Duffield; M. Wang
Studies conducted since the late 1970s have estimated the net energy value (NEV) of corn ethanol. However, variations in data and assumptions used among the studies have resulted in a wide range of estimates. This study identifies the factors causing this wide variation and develops a more consistent estimate. We conclude that the NEV of corn ethanol has been rising over time due to technological advances in ethanol conversion and increased efficiency in farm production. We show that corn ethanol is energy efficient, as indicated by an energy output:input ratio of 1.34 and 1.53 under a best–case scenario.
Transactions of the ASABE | 2008
A. Pradhan; D. S. Shrestha; J. Van Gerpen; James A. Duffield
Although several studies have found biodiesel to be a renewable source of energy, there has been a claim that it is not. This article investigates models used to calculate the net energy ratio (NER) of biodiesel production to point out the reasons for the contradictory results, compares their strengths and weaknesses, and proposes a uniform model for interpretation of the final result. Four commonly referenced models were compared for their assumptions and results. The analysis revealed that the most significant factors in altering the results were the proportions of energy allocated between biodiesel and its coproducts. The lack of consistency in defining system boundaries has apparently led to very different results. The definitions of NER used among the models were also found to be different. A unified model is proposed for biodiesel energy analysis to answer the renewability question. Using the unified boundary, a range of probable NERs was calculated using bootstrapping. The mean NER on a mass basis was 2.55 with a standard deviation of 0.38. The economic sustainability ratio (ESR) is defined as the monetary value ratio of biodiesel to biodiesels share of the energy inputs. The average ESR was found to be 4.43 with a standard deviation of 0.6.
Transactions of the ASABE | 2011
A. Pradhan; D. S. Shrestha; A. McAloon; W. Yee; M. Haas; James A. Duffield
The first comprehensive life-cycle assessment (LCA) for soybean biodiesel produced in the U.S. was completed by the National Renewable Energy Laboratory (NREL) in 1998, and the energy inventory for this analysis was updated in 2009 using 2002 data. The continual adoption of new technologies in farming, soybean processing, and for biodiesel conversion affects the life-cycle energy use over time, requiring that LCA practitioners update their models as often as possible. This study uses the most recently available data to update the energy life-cycle of soybean biodiesel and makes comparisons with the two past studies. The updated analysis showed that the fossil energy ratio (FER) of soybean biodiesel was 5.54 using 2006 agricultural data. This is a major improvement over the FER of 3.2 reported in the 1998 NREL study that used 1990 agricultural data and significantly better than the FER of 4.56 reported using 2002 data. The improvements are primarily due to improved soybean yields and more energy-efficient soybean crushing and conversion facilities. The energy input in soybean agriculture was reduced by 52%, in soybean crushing by 58% and in transesterification by 33% per unit volume of biodiesel produced. Overall, the energy input reduction was 42% for the same amount of biodiesel produced. The addition of secondary inputs, such as farm machinery and building materials, did not have a significant effect on the FER. The FER of soybean biodiesel is likely to continue to improve over time because of increases in soybean yields and the development of increasingly energy-efficient technologies.
Journal of Agricultural and Applied Economics | 2000
Irfan Y. Tareen; Michael E. Wetzstein; James A. Duffield
The objective of the research presented in this paper is the development of a stochastic adoption threshold. The option pricing approach for modeling investment under uncertainty is extended for the case of comparing two stochastic input prices associated with inputs that are perfect substitutes in a production process. Based on this methodology, a threshold decision rule influenced by the drift and volatility of these two input prices is developed. Theoretical results established an empirical link for measuring the tradeoff of a relatively more expensive input (biodiesel) with lower price drift and volatility compared with a lower but more volatile priced input (petroleum diesel).
American Journal of Agricultural Economics | 1992
Lewell F. Gunter; Joseph C. Jarrett; James A. Duffield
A major concern in development of the 1986 Immigration Reform and Control Act was the potential for reductions in seasonal farm labor supply. Although the act appears to have increased farm labor supply, future immigration policy will likely be affected by similar concerns. Muths model of industry supply and factor demand is adapted to analyze effects of labor supply reductions on selected U.S. crops. Labor factor share and output demand elasticity are the most important factors influencing the impact of labor supply on production, and effects of moderate supply decreases will be small if recent output demand conditions continue.
Transactions of the ASABE | 2012
A. Pradhan; D. S. Shrestha; J. Van Gerpen; A. McAloon; W. Yee; M. Haas; James A. Duffield
This study updates the life cycle greenhouse gas (GHG) emissions for soybean biodiesel with revised system boundaries and the inclusion of indirect land use change using the most current set of agricultural data. The updated results showed that life cycle GHG emission from biodiesel use was reduced by 81.2% compared to 2005 baseline diesel. When the impacts of lime application and soil N2O emissions were excluded for more direct comparison with prior results published by the National Renewable Energy Laboratory (NREL), the reduction was 85.4%. This is a significant improvement over the 78.5% GHG reduction reported in the NREL study. Agricultural lime accounted for 50.6% of GHG from all agricultural inputs. Soil N2O accounted for 18.0% of total agricultural emissions. The improvement in overall GHG reduction was primarily due to lower agricultural energy usage and improved soybean crushing facilities. This study found that soybean meal and oil price data from the past ten years had a significant positive correlation (R2 = 0.73); hence, it is argued that soybean meal and oil are both responsible for indirect land use change from increased soybean demand. It is concluded that when there is a strong price correlation among co-products, system boundary expansion without a proper co-product allocation for indirect land use change produces erroneous results. When the emissions associated with predicted indirect land use change were allocated and incorporated using U.S. EPA model data, the GHG reduction for biodiesel was 76.4% lower than 2005 baseline diesel.
American Journal of Agricultural Economics | 1992
James A. Duffield; Robert Coltrane
Producers of labor-intensive crops fear labor shortages if sanctions under the Immigration Reform and Control Act (IRCA) of 1986 are strictly enforced. They argue that special government programs are necessary to insure an adequate labor supply. On the other hand, farm labor advocates argue that such policies create an oversupply of workers and depress wages. A model of the farm labor market was tested for disequilibrium using cusum and cusum squares criteria. Results give no evidence that the hired farm labor market is chronically out of balance or unable to make equilibrium adjustments.
Inhalation Toxicology | 2007
James A. Duffield
The convergence of a number of social, economic, and political developments, at both the national and global levels, has created much interest in developing biodiesel as an alternative to petroleum diesel. In response to higher energy prices, along with government incentives, the fledgling biodiesel industry is beginning to grow at a rapid pace. However, there are clearly economic limits to biodiesels growth potential and questions are being raised about the future role biodiesel can play in reducing our energy dependence Since vegetable oils and animal fats will continue to be used primarily for food products, biodiesel production can only supply a small portion of our fuel needs. To further increase biodiesel production, we will need to develop new sources of feedstock and develop new technologies to convert a broader spectrum of feedstocks.
Bioresource Technology | 2018
Rui Chen; Zhangcai Qin; Jeongwoo Han; Michael Wang; Farzad Taheripour; Wallace E. Tyner; Don O'Connor; James A. Duffield
This study conducted the updated simulations to depict a life cycle analysis (LCA) of the biodiesel production from soybeans and other feedstocks in the U.S. It addressed in details the interaction between LCA and induced land use change (ILUC) for biodiesel. Relative to the conventional petroleum diesel, soy biodiesel could achieve 76% reduction in GHG emissions without considering ILUC, or 66-72% reduction in overall GHG emissions when various ILUC cases were considered. Soy biodiesels fossil fuel consumption rate was also 80% lower than its petroleum counterpart. Furthermore, this study examined the cause and the implication of each key parameter affecting biodiesel LCA results using a sensitivity analysis, which identified the hot spots for fossil fuel consumption and GHG emissions of biodiesel so that future efforts can be made accordingly. Finally, biodiesel produced from other feedstocks (canola oil and tallow) were also investigated to contrast with soy biodiesel and petroleum diesel.