1,720,997 research outputs found
The economics of cellulosic biofuels: Farm to fuel cost analysis of the supply chain
No full textCellulosic biofuels have become an important source of renewable energy. The 2007 Renewable Fuel Standard is to achieve 36 billion gallons in 2022, of which 16 billion gallons are cellulosic biofuels. With the force of mandate and the potential benefits, people are paying increased attention to cellulosic biofuels. However there is no commercial cellulosic biofuel plant to date and there is significant uncertainty about the costs of producing feedstocks and biofuels themselves. Economic analysis of these elements of the supply chain of cellulosic biofuels is needed to understand this uncertainty with a view towards expansion of cellulosic biofuels to meet the mandate. This research studies four feedstocks representing two types of crops: the annual crops corn stover and sorghum, and the perennial grasses switchgrass and miscanthus. Biochemical and thermochemical conversion technologies are also studied. Combining data from field experiments and existing studies in the literature, the farmgate and delivered feedstock cost, and the breakeven fuel price are obtained for each combination of feedstock and conversion pathway. This study also designs a moisture penalty charged by the biorefinery to the farmers based on the cost of drying biomass to the level required by the conversion pathways considered. Corn stover is found to be the lowest cost feedstock and the thermochemical conversion pathway costs less than the biochemical pathway. A high biomass sorghum variety and perennial grasses planted on pasture land are additional suggested feedstocks in order to meet the Renewable Fuels Standard at the lowest cost. The impacts of uncertainties associated with the parameters biomass yield and fertilization costs are found to be the most important parameters determining breakeven cost of production. In addition, the moisture content of the delivered biomass also has impact on the costs
Using carbon offsets to fund agricultural conservation practices in a working-lands setting
No full textThe nitrogen cascade concept indicates that agriculture serves as a significant link between emissions of the potent greenhouse gas (GHG) nitrous oxide and losses of nitrate to surface waters. Conservation practices have the potential to exploit this link, as their implementation is found to reduce fluxes of GHGs and nonpoint source (NPS) water pollution. Several studies have recognized this link and have documented the potential to improve environmental quality through the use of programs which retire land, the funding for which can be offset by the sale of carbon credits. However, the ability to use land for both agricultural production and environmental conservation is important. As such, this study examines the intensely-farmed Wildcat Creek Watershed in West-Central Indiana to evaluate the potential for implementing agricultural conservation practices to reduce NPS water pollutants and fluxes of GHGs in a working-lands setting. The extent to which carbon pricing can affect practice implementation costs and the optimal distribution of these practices throughout the watershed is also explored. Results from this study indicate that carbon offsets can sharply reduce conservation practice implementation costs and therefore have the potential to reduce greater amounts of NPS pollution for a given cost of implementation. However, the extent to which various practices can be used to abate NPS pollutants and GHGs is heavily dependent on the implementation period considered. Further, this study found that fertilizer management, which is relatively difficult to enforce in practice, significantly influenced the optimal allocation of practices. This study provides a novel framework for analyzing the impacts of conservation practices that may prove useful in formulating innovative policy tools aimed at improving environmental quality in multiple environmental media. The findings of this study indicate that the potential exists to use carbon offsets to improve water quality and reduce GHG fluxes in a working-lands setting
Profit-maximizing responses to climate change in commodity agriculture: Does adaptation matter?
Get PDFAccumulation of greenhouse gases in the atmosphere has led to rising temperatures, and is expected to lead to a change in climate. Crop yields are vulnerable to these changes. Adaptation is expected to be key to combating climate change impacts, but the effectiveness of adaptation strategies is not well understood. Hence, there is a need to assess the impacts of climate change on agriculture and devise profitable adaptation strategies to combat its effects. This study uses historical and three projected climate data sets to simulate yields using the crop model Daycent, empirical relationships between weather and agronomic variables that influence farm management decisions, and a linear optimization model (Purdue Crop/Livestock Linear Program, PCLP-GAMS) to: 1) Provide an integrated assessment of the farm-level impacts of climate change; 2) Identify farm-level adaptation practices and estimate their cost; and 3) Solve for profit-maximizing crop rotations and management adaptations. This approach is applied to a representative corn and soybean farm for a case study located outside Rensselaer, Indiana The extent and direction of climate change impacts depend on climate projections and crops. The NCAR projection is associated with an increase in corn yields into the future whereas GFDL and UKMO projections lead to a decrease in corn yield. Soybean yields increase for all future projections. Among the adaptation practices considered, irrigation, split application of fertilizer, rotating corn with soybeans and switching to continuous no-till were found to have a positive influence on corn yield. Soybean yields, although affected by a changing climate, do not respond to the adaptation practices simulated. Economic optimization results suggest that there is the potential to slightly increase net income with the adoption of some adaptation practices investigated in the 2041-2070 mid-century period. The study provides a holistic framework to analyze the agronomic and economic impacts of climate change and associated adaptation practices that are more complete than previous research. The results are helpful for farmers, crop advisors and policy makers struggling to understand the impact of a changing climate on commodity agriculture and identify economically viable adaptation strategies
A spatially explicit watershed scale optimization of cellulosic biofuels production
Get PDFAs environmental deterioration and global warming arouses more and more attention, identifying cleaner and more environmentally friendly energy sources is of interest to society. In addition to environmental concerns, both the high price of gasoline and the fact that the United States has heavy reliance on petroleum imports has driven policymakers to find alternative energy sources. Producing biofuels from energy crops is one such alternative. They can result in relatively lower greenhouse gas emissions compared to traditional energy sources. Up to now, corn grain is the most researched energy crop. Cellulosic perennial crops such as switchgrass, miscanthus and fast growing trees are also promising energy crops and are expected to help with the energy supply. The 2007 Renewable Fuel Standard requires 16 billion gallons of a total of 36 billion gallons of renewable fuels to be cellulosic biofuels by 2022. Many studies are being done to evaluate costs and feasibility of different potential feedstocks and the first commercial-scale cellulosic biorefinery is scheduled to begin operation in 2014. This study estimates the costs of two dedicated cellulosic biofuel crops, switchgrass and miscanthus, makes comparisons with corn stover, and develops a Matlab program that uses a Genetic Algorithm to minimize production cost subject to production and pollution constraints for the Wildcat Creek Watershed in Indiana, USA. Results indicate that if the biorefinery fuelshed is limited to the boundary of the watershed, miscanthus must be planted to achieve the minimum amount of biomass production required (1,307,065 metric tons per year under thermochemical conversion) while also reducing pollutant levels (total sediment, N and P). Switchgrass has similar environmental advantages but higher cost given the crop parameterizations assumed in the accompanying Soil and Water Assessment Tool (SWAT model) simulations. Corn stover production is the cheapest among all three bio feedstocks considered and would minimize delivered feedstock cost for a biorefinery if the fuelshed is not limited to the watershed boundary. Pollutant loadings from corn stover removal scenarios vary, but they all result in higher water pollution than perennial grasses under the assumed management (tillage, nutrient replacement, stover removal rate, etc.). There is a clear tradeoff between cost and environmental quality when satisfying the Renewable Fuel Standard using different feedstocks
Three essays on water quality policy and valuation
Get PDFSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-12-04 without embargo termsThe student, Seojeong Oh, accepted the attached license on 2023-06-29 at 02:41.The student, Seojeong Oh, submitted this Dissertation for approval on 2023-06-29 at 02:41.This Dissertation was approved for publication on 2023-07-05 at 16:22.DSpace SAF Submission Ingestion Package generated from Vireo submission #19479 on 2023-12-04 at 17:00:18Nutrient pollution is one of the most significant environmental challenges worldwide, with agriculture often the primary driver of this problem. In the US Corn Belt, excess nutrients discharged from crop fields impair water quality and associated ecosystem services at local water bodies while inducing the hypoxic dead zone in the Gulf of Mexico far downstream. These result in considerable welfare losses locally and nationally, leading to calls for more effective nutrient reduction policies. Research and policy efforts to date have shown that addressing agricultural nutrient pollution is challenging. One of the critical reasons is that conventional pollution control instruments, such as standards, emissions trading, or taxes, are often not readily available to implement. For example, diffuse and stochastic features of agricultural nutrient emissions make it hugely costly to identify who emits how much and predict the impacts of farm management decisions on water quality, which form the basis of control policy instruments. Moreover, the fact that regulators are unwilling to restrict farm activities compounds the challenge by limiting the scope of policy choices and the design for optimal policy. Regulators have relied on cost-sharing and other voluntary approaches to address agricultural pollution, but continued poor water quality and limited tax resources raise doubts about achieving water quality goals through the status quo policy set. Therefore, it is essential to investigate whether existing policies are sufficient to advance water quality, what forms alternative approaches can take, and how much benefit these nutrient reduction policies would create for society. In this dissertation, I address these questions in the context of the US Corn Belt. The first chapter examines the potential outcomes of water quality trading where a sewage treatment plant can purchase phosphorus (P) abatement credits from farmers to satisfy a pending P effluent limit. Given that proper trading ratios are critical to water quality trading, this study implements trading ratios as the ratios of marginal social damage from each pollution source. To estimate sources’ marginal damage, I utilize the benefit estimates of water quality improvement obtained from the choice experiment in Chapter 3. In addition, the study investigates alternative P trading schemes to address sediment deposition and P pollution at a local lake, predominantly resulting from farmers. I integrate detailed hydrological knowledge and the watershed’s characteristics to develop these alternative markets. The results show that introducing P markets can induce significant reductions in P and sediment from agricultural sources, with the outcomes enhanced in alternative markets developed. Moreover, these trading markets can lead to significant cost savings for the point source, with an estimated amount of about 1.6 to 2.0 million dollars for meeting the new P limit. The second chapter explores alternative regulatory paradigms to reduce nutrients from the perspective of the general public's preferences. US agencies have long used the pay-the-polluter (PTP) approach in which the government pays agricultural polluters to adopt conservation practices on a voluntary basis to address nutrient pollution. However, limited fiscal resources and continued poor water quality has led to calls for a new paradigm, the polluter-pays-principle (PPP), in which agricultural polluters must clean up their nutrient emissions. Whereas PTP relies on public cost-sharing with farmers, PPP can induce food price increases that result from farm regulation. Little is known about the general public’s preferences with respect to these paradigms. This paper addresses this gap using data from a randomized survey conducted in three Midwestern US states that have significant agricultural nutrient pollution—Illinois, Iowa, and Indiana. I find that, overall, people favor the PPP approach over the PTP approach. Comparing PPP with varying stringency and PTP, multinomial logit regression results suggest that respondents are more likely to support PPP than PTP when given the choice of the most stringent PPP type. Examining specific PPP features, I find that assigning clean-up responsibilities to sources equal to their pollution level positively impacts support for PPP, while combining pollution trading with farm regulation has a negative impact. In addition to the perception that PPP is fairer than PTP, PPP approval is associated with the belief that the PPP approach could make desirable changes to the level of government involvement in agriculture, food safety/quality, and nutrient reduction effectiveness. The last chapter develops a choice experiment to estimate the benefits of nutrient reductions in the US Corn Belt to mitigate the hypoxic dead zone in the Gulf of Mexico. The study area covers the three largest contributing states, Illinois, Indiana, and Iowa, whose nutrient reductions are vital to achieving Gulf hypoxia targets. I find that the public places large values on various ecosystem services, including aquatic biodiversity, aesthetics of increased farm landscape diversity associated with conservation practices, and water-based recreational activities. Moreover, the results indicate that upstream residents have a strong preference for water quality far downstream in the Gulf of Mexico as characterized by reducing the size of the dead zone. The analysis of observed taste heterogeneity indicates that public preferences vary depending on familiarity with nutrient pollution issues, users versus non-users of ecosystem services, and different age groups. The findings inform policies to improve water quality in the Gulf of Mexico and local water bodies in the US Corn Belt
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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