US Renewable Research Articles

Major impacts of the US Renewable Fuel Standard on corn and soybean cultivation

AbstractWe use rich spatial data on observed crop choices and ethanol production to estimate the local impacts of ethanol plants and the overall impact of the 2007 US Renewable Fuel Standard (the RFS2) on crop patterns. We find that the RFS2 increased total corn area by 9.7%, corn monoculture by 16.8%, and soybean area by 6.7%, with notable spatial heterogeneity in both the overall impact and the local effects of ethanol plants. The results indicate an RFS2‐induced shift in the geography of corn and soybean cultivation within the Corn Belt—intensification in the core, and significant expansion near the periphery.

The Risk-Return Trade-Off of US Renewable Energy Sector

This study applies the Fama-French three-factor model to analyze the impact of market risk premium, size, and value factors on the stock returns of eight major renewable energy companies listed on the U.S. stock market. Employing linear regression analysis. The analysis indicates that while market trends heavily influence stock returns, the size and value factors' effects vary across different companies. This study contributes to understanding the financial performance of renewable energy firms and underscores the need for industry-specific risk management approaches to bolster investor confidence and facilitate sector growth. The results serve as a foundational reference for investors and policymakers interested in the renewable energy market's dynamics and its future development trajectory.

Independent Pitch Controller based on Fuzzy Adaptive Tuning PI for Load Mitigation of Large Land Wind Turbine

With the development of wind power generation units towards the mega-scale, the blade root and tower have large load and vibration problems during the operation of wind turbines. In order to extend the operational life of wind turbines, a PI independent pitch control (IPC) strategy with fuzzy adaptive tuning (FAT) is introduced based on the existing wind turbine model and control strategy to achieve optimal control of wind turbine loads. Simulations are carried out by the FAST software of the US Renewable Energy Laboratory to compare the independent pitch and the cooperative pitch. The results show that IPC reduces the load on the blade roots and improves the quality of the electrical energy.

Environmental outcomes of the US Renewable Fuel Standard

The Renewable Fuel Standard (RFS) specifies the use of biofuels in the United States and thereby guides nearly half of all global biofuel production, yet outcomes of this keystone climate and environmental regulation remain unclear. Here we combine econometric analyses, land use observations, and biophysical models to estimate the realized effects of the RFS in aggregate and down to the scale of individual agricultural fields across the United States. We find that the RFS increased corn prices by 30% and the prices of other crops by 20%, which, in turn, expanded US corn cultivation by 2.8 Mha (8.7%) and total cropland by 2.1 Mha (2.4%) in the years following policy enactment (2008 to 2016). These changes increased annual nationwide fertilizer use by 3 to 8%, increased water quality degradants by 3 to 5%, and caused enough domestic land use change emissions such that the carbon intensity of corn ethanol produced under the RFS is no less than gasoline and likely at least 24% higher. These tradeoffs must be weighed alongside the benefits of biofuels as decision-makers consider the future of renewable energy policies and the potential for fuels like corn ethanol to meet climate mitigation goals.

Rentiers of the low-carbon economy? Renewable energy's extractive fiscal geographies

Progressive movements today call for transformative state-led investment in renewable energy and other climate infrastructures—in the United States, a vision that confronts inherited legacies of austerity. I argue that a significant obstacle is the neoliberal toolkit through which the US federal government subsidizes renewables, an indirect, highly opaque system of tax credits and incentives. For forty years, tax subsidies have ‘paid’ private financial players to invest in renewables, via allowing them to claim legal tax shelters against their other income. In this political economic analysis, I question, first, how US renewable energy acquired this peculiar form of public finance ‘through the tax code’, unique in the global industry. Second, I explore how the model has shaped US renewables financing, development, and ownership. I center two decisive moments: the California ‘wind rush’ in the 1980s, and the ongoing renewables boom of the last fifteen years. This history articulates financial experiments and tax sheltering scandals of the Reagan Administration with exploitation returned today in more organized (and lucrative) form, as ‘tax equity’ finance. Via tax equity, a handful of major US banks dominate financing for renewables and other politically embattled public goods. They exert a troubling ability to extract rents for their capital, gatekeep what projects get built and by whom, and stall US renewables development altogether. Today, the practice is increasingly strained by these and other problems—growing public costs, private capacity ceilings, and amplification of sectoral crises. Under Biden, it faces probable reform, but may need more comprehensive reimagination.

Research on Solar Resource Evaluation Method Based on Mathematical Statistics

According to the satellite data provided by the US Renewable Energy Laboratory, the datum of solar resources 25 typical cities in China for 29 years were analyzed by method of principal component analysis and the whole evaluation of this kind of energy was summarized. The indicators for evaluation of solar energy resources, including richness, stability, utilization value and mean of effective sunshine duration, are incorporated into three main parameters. And the score of principal component is considered as the main factor of the resource evaluation. The evaluation and prediction of solar energy in a region are efficient and accurate by this method, which provide guidance for utilization and development of solar energy.

High-resolution techno–ecological modelling of a bioenergy landscape to identify climate mitigation opportunities in cellulosic ethanol production

Although dedicated energy crops will probably be an important feedstock for future cellulosic bioenergy production, it is unknown how they can best be integrated into existing agricultural systems. Here we use the DayCent ecosystem model to simulate various scenarios for growing switchgrass in the heterogeneous landscape that surrounds a commercial-scale cellulosic ethanol biorefinery in southwestern Kansas, and quantify the associated fuel production costs and lifecycle greenhouse gas (GHG) emissions. We show that the GHG footprint of ethanol production can be reduced by up to 22 g of CO2 equivalent per megajoule (CO2e MJ–1) through careful optimization of the soils cultivated and corresponding fertilizer application rates (the US Renewable Fuel Standard requires a 56 gCO2e MJ−1 lifecycle emissions reduction for ‘cellulosic’ biofuels compared with conventional gasoline). This improved climate performance is realizable at modest additional costs, less than the current value of low-carbon fuel incentives. We also demonstrate that existing subsidized switchgrass plantings within this landscape probably achieve suboptimal GHG mitigation, as would landscape designs that strictly minimize the biomass collection radius or target certain marginal lands.

Land management change greatly impacts biofuels’ greenhouse gas emissions

AbstractHarvesting corn stover for biofuel production may decrease soil organic carbon (SOC) and increase greenhouse gas (GHG) emissions. Adding additional organic matter into soil or reducing tillage intensity, however, could potentially offset this SOC loss. Here, using SOC and life cycle analysis (LCA) models, we evaluated the impacts of land management change (LMC), that is, stover removal, organic matter addition, and tillage on spatially explicit SOC level and biofuels’ overall life cycle GHG emissions in US corn–soybean production systems. Results indicate that under conventional tillage (CT), 30% stover removal (dry weight) may reduce baseline SOC by 0.04 t C ha−1 yr−1 over a 30‐year simulation period. Growing a cover crop during the fallow season or applying manure, on the other hand, could add to SOC and further reduce biofuels’ life cycle GHG emissions. With 30% stover removal in a CT system, cover crop and manure application can increase SOC at the national level by about 0.06 and 0.02 t C ha−1 yr−1, respectively, compared to baseline cases without such measures. With contributions from this SOC increase, the life cycle GHG emissions for stover ethanol are more than 80% lower than those of gasoline, exceeding the US Renewable Fuel Standard mandate of 60% emissions reduction in cellulosic biofuels. Reducing tillage intensity while removing stover could also limit SOC loss or lead to SOC gain, which would lower stover ethanol life cycle GHG emissions to near or under the mandated 60% reduction. Without these organic matter inputs or reduced tillage intensity, however, the emissions will not meet this mandate. More efforts are still required to further identify key practical LMCs, improve SOC modeling, and accounting for LMCs in biofuel LCAs that incorporate stover removal.

Developing a cellulosic aviation biofuel industry in Indiana: A market and logistics analysis

With the non-advanced portion of the US Renewable Fuel Standard having been largely met by corn ethanol, many states are looking to cellulosic crops as the next source of biofuels. In Indiana, attention is turning to biojet fuels and renewable diesel as forming the demand for these crops. This paper seeks to determine the optimal manufacturing site locations and supply chain logistics for the conversion of biomass sources to jet fuel and renewable diesel within Indiana. A sequential start-up model is developed for this application, using a mixed integer non-linear (quadratic) program, in which firms sequentially optimize unit costs by choosing the conversion site location, scale, and feedstocks. The results indicate that firms wish to locate conversion sites near biomass sources as opposed to fuel destinations, and that early entrants to the industry gravitate towards counties rich in corn stover, a less expensive residue. However, even with existing subsidies firms would barely break even. Finally, the benefits of the sequential model are elucidated in contrast to a social planner's model, with the key benefit being that the sequential model can generate supply curves independent of demand levels.

Economic implications of incorporating emission controls to mitigate air pollutants emitted from a modeled hydrocarbon‐fuel biorefinery in the United States

AbstractThe implementation of the US Renewable Fuel Standard is expected to increase the construction and operation of new biofuel facilities. Allowing this industry to grow without adversely affecting air quality is an important sustainability goal sought by multiple stakeholders. However, little is known about how the emission controls potentially required to comply with air quality regulations might impact biorefinery cost and deployment strategies such as siting and sizing. In this study, we use a baseline design for a lignocellulosic hydrocarbon biofuel production process to assess how the integration of emission controls impacts the minimum fuel selling price (MFSP) of the biofuel produced. We evaluate the change in MFSP for two cases as compared to the baseline design by incorporating (i) emission controls that ensure compliance with applicable federal air regulations and (ii) advanced control options that could be used to achieve potential best available control technology (BACT) emission limits. Our results indicate that compliance with federal air regulations can be achieved with minimal impact on biofuel cost (~$0.02 per gasoline gallon equivalent (GGE) higher than the baseline price of $5.10 GGE−1). However, if air emissions must be further reduced to meet potential BACT emission limits, the cost could increase nontrivially. For example, the MFSP could increase to $5.50 GGE−1 by adopting advanced emission controls to meet potential boiler BACT limits. Given tradeoffs among emission control costs, permitting requirements, and economies of scale, these results could help inform decisions about biorefinery siting and sizing and mitigate risks associated with air permitting. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Policy Implications of Allocation Methods in the Life Cycle Analysis of Integrated Corn and Corn Stover Ethanol Production

A biorefinery may produce multiple fuels from more than one feedstock. The ability of these fuels to qualify as one of the four types of biofuels under the US Renewable Fuel Standard and to achieve a low carbon intensity score under California’s Low Carbon Fuel Standard can be strongly influenced by the approach taken to their life cycle analysis (LCA). For example, in facilities that may co-produce corn grain and corn stover ethanol, the ethanol production processes can share the combined heat and power (CHP) that is produced from the lignin and liquid residues from stover ethanol production. We examine different LCA approaches to corn grain and stover ethanol production considering different approaches to CHP treatment. In the baseline scenario, CHP meets the energy demands of stover ethanol production first, with additional heat and electricity generated sent to grain ethanol production. The resulting greenhouse gas (GHG) emissions for grain and stover ethanol are 57 and 25 g-CO2eq/MJ, respectively, corresponding to a 40 and 74 % reduction compared to the GHG emissions of gasoline. We illustrate that emissions depend on allocation of burdens of CHP production and corn farming, along with the facility capacities. Co-product handling techniques can strongly influence LCA results and should therefore be transparently documented.

The Pass-Through of RIN Prices to Wholesale and Retail Fuels under the Renewable Fuel Standard

AbstractThe US Renewable Fuel Standard (RFS) requires blending increasing quantities of biofuels into the surface vehicle fuel supply. The RFS requirements are met through a system of tradable permits called Renewable (fuel) Identification Numbers, or RINs. We exploit the large fluctuations in RIN prices during 2013–15 to estimate the pass-through of RIN prices to US wholesale and retail fuel prices. We control for common factors by examining spreads of physically similar fuels with different RIN obligations. Pooling six different wholesale petroleum fuel spreads, we estimate a pooled long-run or equilibrium pass-through coefficient of 1.00 with a standard error of 0.11. This pass-through occurs within two business days. The only fuel for which we find economically and statistically significant failure of pass-through is retail E85, which contains up to 83% ethanol; the pass-through of RIN prices to the retail E85–E10 spread is precisely estimated to be close to zero.

Cropland expansion outpaces agricultural and biofuel policies in the United States

Cultivation of corn and soybeans in the United States reached record high levels following the biofuels boom of the late 2000s. Debate exists about whether the expansion of these crops caused conversion of grasslands and other carbon-rich ecosystems to cropland or instead replaced other crops on existing agricultural land. We tracked crop-specific expansion pathways across the conterminous US and identified the types, amount, and locations of all land converted to and from cropland, 2008–2012. We found that crop expansion resulted in substantial transformation of the landscape, including conversion of long-term unimproved grasslands and land that had not been previously used for agriculture (cropland or pasture) dating back to at least the early 1970s. Corn was the most common crop planted directly on new land, as well as the largest indirect contributor to change through its displacement of other crops. Cropland expansion occurred most rapidly on land that is less suitable for cultivation, raising concerns about adverse environmental and economic costs of conversion. Our results reveal opportunities to increase the efficacy of current federal policy conservation measures by modifying coverage of the 2014 US Farm Bill Sodsaver provision and improving enforcement of the US Renewable Fuels Standard.

Multi-objective regulations on transportation fuels: Comparing renewable fuel mandates and emission standards

We compare two types of fuel market regulations — a renewable fuel mandate and a fuel emission standard — that could be employed to simultaneously achieve multiple outcomes such as reduction in fuel prices, fuel imports and greenhouse gas (GHG) emissions. We compare these two types of regulations in a global context taking into account heterogeneity in carbon content of both fossil fuels and renewable fuels. We find that although neither the ethanol mandate nor the emission standard is certain to reduce emissions relative to a business-as-usual baseline, at any given level of biofuel consumption in the policy region, a mandate, relative to an emission standard, results in higher GHG emissions, smaller expenditure on fuel imports, lower price of ethanol-blended gasoline and higher domestic fuel market surplus. This result holds over a wide range of values of model parameters. We also discuss the implications of this result to a regulation such as the US Renewable Fuel Standard given recent developments within the US such as increase in shale and tight oil production and large increase in average vehicle fuel economy of the automotive fleet.

Managing the nitrogen cycle to reduce greenhouse gas emissions from crop production and biofuel expansion

Public policies are promoting biofuels as an alternative to fossil fuel consumption in order to mitigate greenhouse gas (GHG) emissions. However, the mitigation benefit can be at least partially compromised by emissions occurring during feedstock production. One of the key sources of GHG emissions from biofuel feedstock production, as well as conventional crops, is soil nitrous oxide (N2O), which is largely driven by nitrogen (N) management. Our objective was to determine how much GHG emissions could be reduced by encouraging alternative N management practices through application of nitrification inhibitors and a cap on N fertilization. We used the US Renewable Fuel Standards (RFS2) as the basis for a case study to evaluate technical and economic drivers influencing the N management mitigation strategies. We estimated soil N2O emissions using the DayCent ecosystem model and applied the US Forest and Agricultural Sector Optimization Model with Greenhouse Gases (FASOMGHG) to project GHG emissions for the agricultural sector, as influenced by biofuel scenarios and N management options. Relative to the current RSF2 policy with no N management interventions, results show decreases in N2O emissions ranging from 3 to 4 % for the agricultural sector (5.5–6.5 million metric tonnes CO2 eq. year−1; 1 million metric tonnes is equivalent to a Teragram) in response to a cap that reduces N fertilizer application and even larger reductions with application of nitrification inhibitors, ranging from 9 to 10 % (15.5–16.6 million tonnes CO2 eq. year−1). The results demonstrate that climate and energy policies promoting biofuel production could consider options to manage the N cycle with alternative fertilization practices for the agricultural sector and likely enhance the mitigation of GHG emissions associated with biofuels.

Impact of US Biofuel Policy in the Presence of Uncertain Climate Conditions

We analyze the impact of total and partial waivers of the US Renewable Fuel Standard (RFS) under uncertain changes in climate conditions that affects crop yield distributions. Results show that reducing RFS would make world agricultural consumers better off, and increase the US corn share in the world market while slightly decreasing agricultural commodity prices. However, the higher the RFS reduction the higher the uncertainty on the price changes. On the other hand, price changes would make ethanol and agricultural producers face losses as well as increase gasoline consumption and, therefore, bring larger environmental damages. Overall, RFS reduction generates negative changes in total economic surplus, specifically, small and medium RFS reductions generate changes in the socio-economic variables; however, large reductions do not bring further changes, although uncertainty in welfare results is higher under an increased reduction.

How Effective are US Renewable Energy Subsidies in Cutting Greenhouse Gases?

The federal tax code provides preferential treatment for the production and use of renewable energy. We report estimates of the subsidies' effects on greenhouse gases (GHG) emissions developed in a recent National Research Council (NRC) Report. Due to lack of estimates of the impact of tax provisions on GHG emissions, new modeling studies were commissioned. The studies found, at best, a small impact of subsidies in reducing GHG emissions; in some cases, emissions increased. The NRC report also identified the need to capture the complex interactions among subsidies, pre-existing regulations, and commodity markets.

Technological variation and the US renewable fuel standard

The US Renewable Fuel Standard contains a policy bias that undermines the three-broad policy goals of rural development, energy security, and greenhouse gas reductions. This policy bias, wherein a narrow range of options is expected to address broad societal objectives, contributes to a persistence of first-generation biofuels and limits technical variation. Renewable fuel content requirements have helped to expand the use of ethanol and biodiesel in the short term. However, long-term changes will require greater technological variation to stimulate innovation for the development of sustainable renewable fuel pathways.

Design and simulation of an organosolv process for bioethanol production

Organosolv pulping can be used as a pretreatment step in bioethanol production. In addition to ethanol, organosolv pulping allows for the production of a pure lignin product and other co-products. Based on publicly available information, conceptual process design and simulation model were developed for an organosolv process. The simulation model was used to calculate the mass and energy balances and approximate fossil-based carbon dioxide (CO2) emissions for the process. With a hardwood feed of 2,350 dry metric tons (MT) per day, 459 MT/day (53.9 million gallons per year) of ethanol was produced. This corresponded to a carbohydrate to ethanol conversion of 64 %. The production rates of lignin, furfural, and acetic acid were 310, 6.6, and 30.3 MT/day, respectively. The energy balance indicated that the process was not energy self-sufficient. In addition to bark and organic residues combusted to produce energy, external fuel (natural gas) was needed to cover the steam demand. This was largely due to the energy consumed in recovering the solvent. Compared to a dilute acid bioethanol process, the organosolv process was estimated to consume 34 % more energy. Allocating all emissions from natural gas combustion to the produced ethanol led to fossil CO2 emissions of 13.5 g per megajoule (MJ) of ethanol. The total fossil CO2 emissions of the process, including also feedstock transportation and other less significant emission sources, would almost certainly not exceed the US Renewable Fuel Standard threshold limit (36.5 g CO2/MJ ethanol).

Renewable Energy—Finance: Financing US Renewable Energy Projects in a Post‐Subsidy World

AbstractThe federal renewable energy production tax credit (PTC) was created in 1992 when Congress enacted the Energy Policy Act of 1992. The creation of the PTC for renewable energy generating projects signaled the birth of the modern renewable energy industry in the United States. In the years since its birth, the industry has grown in fits and starts, seeing the creation of the investment tax credit (ITC) in 2005 and no less than six extensions of the PTC.