DOE

The objective of this research project was to assess whether standard forestry best management practices (BMPs) are sufficient to protect stream water quality from intensive silviculture associated with short-rotation woody crop (SRWC) production for bioenergy. Forestry BMPs are designed to prevent the movement of deleterious quantities of nutrients, herbicides, sediments, and thermal energy (sunlight hitting stream channels) from clear-cuts and plantations to surface waters. Until now, there have been no watershed-scale studies examining the effectiveness of traditional forestry BMPs as applied to SRWC production for bioenergy. The demand for woody bioenergy feedstocks is expected to increase, especially in the southeastern United States where the climate, topography, and land ownership are favorable for wood production. Therefore, it is important to evaluate the environmental effects of SRWC production for bioenergy and the efficacy of BMPs.

This study used a watershed-scale experiment in a before-after, control-impact design to examine the environmental effects of short-rotation loblolly pine (Pinus taeda) production for bioenergy and evaluate the efficacy of BMPs for protecting surface water quality. Environmental measurements included water and soil quality (i.e., nitrogen, phosphorus, suspended solid, pesticide concentrations in water, nitrate leaching, nitrogen mineralization, denitrification, ecosystem nitrogen budget, conservative tracer modeling), hydrology (i.e., overland flow and concentrated flow tracks, interflow [shallow lateral subsurface flow], groundwater dynamics), and productivity and stand-level ecophysiology (i.e., tree growth, carbon, water, and energy fluxes). Most of these environmental metrics were measured before (for ~2 years) and after (for ~6 years) harvest, planting, and managing short-rotation loblolly pine for bioenergy on more than 50% of the land area in two treatment watersheds and also in one mature timber reference watershed. The three study watersheds are located in the Upper Fourmile Creek watershed at the Savannah River Site in South Carolina. All silviculture practices in the two treatment watersheds followed South Carolina Forestry BMPs (e.g., minimized soil compaction and bare ground exposure; inhibited hydraulic connections between bare ground and surface waters; provided forested buffers around streams).

The silvicultural plan used in the watershed-scale experiment was designed to achieve high yields of loblolly pine over a short rotation (10–12 green tons/acre/year at 10–12 years), and we intentionally pushed the system in terms of high rates of fertilizer applied. Tree growth and net ecosystem exchange (carbon flux) data demonstrated that the objective of accelerating growth was achieved. In the fourth growing season, aboveground biomass of trees averaged 12,000 kg/ha and carbon sequestration was 466 g C/m2/y. The carbon sequestration rate of the loblolly pine was 1–8 years ahead of conventional southern pine stands grown for pulp production. However, our plot-scale study that manipulated levels of fertilizer and herbicide applications found that the most efficient production system based on the ecosystem N budget was a silvicultural treatment of herbicide without fertilizer; tree growth was 90% of that achieved with operational-scale fertilizer additions and nitrate leaching was lower than in the fertilized treatments. At the operational (watershed) scale, only 30–60% of the nitrogen applied in fertilizers was sequestered in pine after the fourth growing season. Overall, some components of the silvicultural treatments were efficient (i.e., early control of competing plants) and some aspects were not (i.e., early fertilization). These results suggest that nitrogen fertilizers were applied in excess in the first three years and highlight the importance of evaluating water quality responses and efficacy of BMPs under these intensive silvicultural applications.

Despite the high fertilizer applications in the watershed-scale experiment, there were minimal effects of SRWC production on stream water quality, suggesting that forestry BMPs appear to be effective at protecting surface waters. However, nitrate concentrations were elevated in shallow subsurface flow (interflow) and in concentrated flow tracks. Nitrate concentrations also increased in groundwater following harvest and the first fertilizer application. The highest nitrate concentrations measured in groundwater were <2 mg N/L, which is below the US Environmental Protection Agency regulatory limit of 10 mg N/L. These low-gradient watersheds are dominated by groundwater flow paths, and there are several lines of evidence suggesting that some of the elevated nitrate in groundwater should have reached the streams during the 6-year-long posttreatment monitoring period. Groundwater modeling suggests that although transport times to the stream might be on the order of a decade, transport from near-stream portions of the plantations are shorter (1–3 years). Conservative (i.e., non-reactive) tracer modeling also suggests that nitrate concentrations would be elevated in streams following the silvicultural treatments if nitrate travelled conservatively (i.e., nitrate is not taken up or transformed along the groundwater flow path). Estimates of denitrification suggest that this microbial process is important in removing nitrate in groundwater both in the sandy upland areas and in the organic-rich riparian zones (streamside management zones) that are characteristic of this region. Overall, the magnitude of these processes suggests that BMPs in these low-gradient, Coastal Plain watersheds are sufficiently robust to mitigate a relatively low nitrogen fertilizer use efficiency. Phosphorus-based fertilizers were also applied as part of the watershed-scale study, but there were no changes in soluble reactive phosphorus concentrations in stream or groundwater, likely because phosphorus is much less mobile than nitrate and the subsoils contain clays that bind phosphorus.

Aside from fertilizer fate, other important water quality parameters are the fate of applied pesticides and the transport of sediments and associated nutrients to streams. We found little evidence of pesticide movement as none of the stream water samples collected posttreatment had detectable levels of pesticides. The pesticides applied in this study are commonly used in southeastern US silvicultural operations and have low mobility and are moderately persistent. We also found very little evidence of sediment transport to streams via overland flow. Concentrated flow track surveys found that the most likely path of solutes by overland flow was from variable source areas that expanded into the plantations during periods with elevated water tables. The greatest sediment input was from an interior ditch of a paved road and was unrelated to silvicultural management of the site. There were no effects of SRWC production on total nitrogen, phosphorus, or suspended solid concentrations in stream water. Therefore, forestry BMPs were effective with respect to pesticide applications, and overland flow and associated sediment transport.

Overall, the lack of effect of short-rotation loblolly pine production for bioenergy on stream water quality suggests that current forestry BMPs are effective at protecting surface waters in the Coastal Plain landscape even with high levels of fertilization and herbicide application associated with SRWC production. These results should be applicable throughout the southeastern Coastal Plain, in watersheds that are characterized by low-gradient uplands with sandy soils and organic-rich riparian zones. Hydrologic processes in the Piedmont differ sufficiently from those in the Coastal Plain that caution should be used when extrapolating these findings to the Piedmont.

The goal of this repository is to promote transparency and ease-of-access to the U.S. Department of Energy Bioenergy Technologies Office (BETO) supported public studies involving techno-economic analysis (TEA). As such, this database summarizes the economic and technical parameters associated with the modeled biorefinery processes for the production of biofuels and bioproducts, as presented in a range of published reports and papers. The database serves as a quick reference tool by documenting and referencing the results of techno-economic analyses from the national laboratories and in peer-reviewed journals.
 
The analyses presented in this database may be distinguished in several regards, such as cost year, feedstock cost, and financial assumptions (tax rate, percent equity, project lifetime, etc.), and reflect details as they were provided in the original studies. Accordingly, the intent of this database is not to directly compare one technology pathway against another, and caution should be taken in interpreting the outputs as such.

Funding Acknowledgement
This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by  the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Bioenergy Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.

Advanced biomass feedstocks tend to provide more non-fuel ecosystem goods and services (ES) than 1st-generation alternatives. We explore the idea that payment for non-fuel ES could facilitate market penetration of advanced biofuels by closing the profitability gap. As a specific example, we discuss the Mississippi-Atchafalaya River Basin (MARB), where 1st-generation bioenergy feedstocks (e.g., corn-grain) have been integrated into the agricultural landscape. Downstream, the MARB drains to the Gulf of Mexico, where the most-valuable fishery in the US is impacted by annual formation of a large hypoxic "Dead zone." We suggest that advanced biomass production systems in the MARB can increase and stabilize the provision of ES derived from the coastal and marine ecosystems of the Gulf-of-Mexico. Upstream, we suggest that choosing feedstocks based on their resistance or resilience to disturbance (e.g., perennials, diverse feedstocks) can increase reliability in ES provision over time. Direct feedbacks to incentivize producers of advanced feedstocks are currently lacking. Perhaps a shift from first-generation biofuels to perennial-based fuels and other advanced bioenergy systems (e.g., algal diesel, biogas from animal wastes) can be encouraged by bringing downstream environmental externalities into the market for upstream producers. In future, we can create such feedbacks through payments for ES, but significant research is needed to pave the way.

Reducing dependence on fossil‐based energy has raised interest in biofuels as a potential energy source, but concerns have been raised about potential implications for water quality. These effects may vary regionally depending on the biomass feedstocks and changes in land management. Here, we focused on the Tennessee River Basin (TRB), USA. According to the recent 2016 Billion‐Ton Report (BT16) by the US Department of Energy, under two future scenarios (base‐case and high‐yield), three perennial feedstocks show high potential for growing profitably in the TRB: switchgrass (Panicum virgatum), miscanthus (Miscanthus × giganteus), and willow (Salix spp.). We used the Soil & Water Assessment Tool (SWAT) to compare hydrology and water quality for a current landscape with those simulated for two future BT16 landscapes. We combined publicly available temporal and geospatial datasets with local land and water management information to realistically represent physical characteristics of the watershed. We developed a new autocalibration tool (SWATopt) to calibrate and evaluate SWAT in the TRB with reservoir operations, including comparison against synthetic and intermediate response variables derived from gage measurements. Our spatiotemporal evaluation enables to more realistically simulate the current situation, which gives us more confidence to project the effects of land‐use changes on water quality. Under both future BT16 scenarios, simulated nitrate and total nitrogen loadings and concentrations were greatly reduced relative to the current landscape, whereas runoff, sediment, and phosphorus showed only small changes. Difference between simulated water results for the two future scenarios was small. The influence of biomass production on water quantity and quality depended on the crop, area planted, and management practices, as well as on site‐specific characteristics. These results offer hope that bioenergy production in the TRB could help to protect the region's rivers from nitrogen pollution by providing a market for perennial crops with low nutrient input requirements.

Highlights
• Opportunities to improve coproduction of wildlife and biomass-for-energy exist at multiple spatial scales.

• At the landscape scale, we review strategies for increasing biodiversity in biomass production systems, drawing examples from plantations, dedicated perennial grasses, and forest thinning systems in the Americas.

• At the scale of one land owner, we describe wildlife-friendly practices to promote land sharing for each production system.

• Dynamic strategies for land sharing can also improve outcomes for wildlife in landscapes containing biomass production systems.

• Implementing practices that minimize wildlife damage to crops are important to address land-owner concerns and to promote adoption of wildlife-friendly practices.

Social and economic indicators can be used to support design of sustainable energy systems. Indicators representing categories of social well-being, energy security, external trade, profitability, resource conservation, and social acceptability have not yet been measured in published sustainability assessments for commercial algal biofuel facilities. We review socioeconomic indicators that have been modeled at the commercial scale or mea-sured at the pilot or laboratory scale, as well as factors that affect them, and discuss additional indicators that should be measured during commercialization to form a more complete picture of socioeconomic sustainability of algal biofuels. Indicators estimated in the scientific literature include the profitability indicators, return on investment (ROI) and net present value (NPV), and the resource conservation indicator, fossil energy return on investment (EROI). These modeled indicators have clear sustainability targets and have been used to design sustainable algal biofuel systems. Factors affecting ROI, NPV, and EROI include infrastructure, process choices, and financial assumptions. The food security indicator, percent change in food price volatility, is probably zero where agricultural lands are not used for production of algae-based biofuels; however, food-related coproducts from algae could enhance food security. The energy security indicators energy security premium and fuel price volatility and external trade indicators terms of trade and trade volume cannot be projected into the future with accuracy prior to commercialization. Together with environmental sustainability indicators, the use of a suite of socioeconomic sustainability indicators should contribute to progress toward sustainability of algal biofuels

Join the U.S. Department of Energy’s Bioenergy Technologies Office on Dec. 6, 2018, at 1 p.m. CST for a webinar on “Biomass Production and Water Quality in the Mississippi River Basin.” In this webinar, Argonne National Laboratory and Oak Ridge National Laboratory will jointly present modeling and analyses of potential implications of biomass production on nutrients and sediments in each of the six tributaries of the Mississippi River Basin. Presenters will describe the methodology, system boundary, and data sources and present water quality estimates for nitrogen, phosphorus, and suspended sediments under historical land use in the Upper Mississippi River Basin, Missouri River Basin, Ohio River Basin, Arkansas White and Red River Basin, Tennessee River Basin, and Lower Mississippi River Basin. The webinar will also provide an estimate of potential changes in water quality and quantity under future biomass production scenarios and discuss opportunities for integrating conservation practices with biomass production. The webinar will include a 15 minute Q&A segment.

Advanced biomass feedstocks tend to provide more non-fuel ecosystem goods and services (ES) than 1st-generation alternatives. We explore the idea that payment for non-fuel ES could facilitate market penetration of advanced biofuels by closing the profitability gap. As a specific example, we discuss the Mississippi-Atchafalaya River Basin (MARB), where 1st-generation bioenergy feedstocks (e.g., corn-grain) have been integrated into the agricultural landscape. Downstream, the MARB drains to the Gulf of Mexico, where the most-valuable fishery in the US is impacted by annual formation of a large hypoxic “Dead zone.” We suggest that advanced biomass production systems in the MARB can increase and stabilize the provision of ES derived from the coastal and marine ecosystems of the Gulf-of-Mexico. Upstream, we suggest that choosing feedstocks based on their resistance or resilience to disturbance (e.g., perennials, diverse feedstocks) can increase reliability in ES provision over time. Direct feedbacks to incentivize producers of advanced feedstocks are currently lacking. Perhaps a shift from first-generation biofuels to perennial-based fuels and other advanced bioenergy systems (e.g., algal diesel, biogas from animal wastes) can be encouraged by bringing downstream environmental externalities into the market for upstream producers. In future, we can create such feedbacks through payments for ES, but significant research is needed to pave the way.

Ecological disturbances are occurring with greater frequency and intensity than in the past. Under projected shifts in disturbance regimes and patterns of recovery, societal and environmental impacts are expected to be more extreme and to span larger spatial extents. Moreover, preexisting conditions will require a longer time to re‐establish, if they do so at all. The word “unprecedented” is appearing more often in news reporting on droughts, fires, hurricanes, tsunamis, ice storms, and insect outbreaks. The causes and effects of these events are often exacerbated by human modifications of natural environments and influenced by technological developments.

Policy makers are interested in estimates of the potential economic impacts of oil price shocks, particularly during periods of rapid and large increases that accompany severe supply shocks. Literature estimates of the economic impacts of oil price shocks, summarized by the oil price elasticity of GDP, span a very wide range due to both fundamental economic and methodological factors. This paper presents a quantitative meta-analysis of the oil price elasticity of GDP for net oil importing countries, with a focus on the United States (US). The full range of estimates of the oil price elasticity of GDP for the US in the data is − 0.124 to + 0.017, accounting for different methodologies, data and other factors. We employ a meta-regression model that controls for key determinant factors to estimate the mean and variance of the GDP elasticity across studies. We use a robust estimation technique to deal with heterogeneity of the data and well-known econometric issues that confront meta-analysis. The resulting regression model is used to simulate the oil price elasticity of GDP for the US, with a mean of − 0.020% and 68% confidence interval of − 0.035 to − 0.006, four quarters after a shock.