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Contrasting effects of bioenergy crops on biodiversity

Agriculture is driving biodiversity loss, and future bioenergy cropping systems have the potential to ameliorate or exacerbate these effects. Using a long-term experimental array of 10 bioenergy cropping systems, we quantified diversity of plants, invertebrates, vertebrates, and microbes in each crop. For many taxonomic groups, alternative annual cropping systems provided no biodiversity benefits when compared to corn (the business-as-usual bioenergy crop in the United States), and simple perennial grass–based systems provided only modest gains. In contrast, for most animal groups, richness in plant-diverse perennial systems was much higher than in annual crops or simple perennial systems. Microbial richness patterns were more eclectic, although some groups responded positively to plant diversity. Future agricultural landscapes incorporating plant-diverse perennial bioenergy cropping systems could be of high conservation value. However, increased use of annual crops will continue to have negative effects, and simple perennial grass systems may provide little improvement over annual crops.

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Genetic tools for engineering Zymomonas mobilis , Cereibacter sphaeroides and Novosphingobium aromaticivorans to improve production of bioenergy compounds

Limited genetic tools for non-model bacteria are one of the limiting factors for genetic studies. This review compiles genetic tools used for three non-model alpha-proteobacteria, such as Zymomonas mobilis, Cereibacter (Rhodobacter) sphaeroides, and Novosphingobium aromaticivorans, which hold significant potential to produce industrially essential bioenergy compounds due to their distinctive metabolic pathways and resilience in extreme environments. Each of these strains has a unique genetic profile that enables them to efficiently carry out key reactions relevant to producing bioenergy compounds, such as converting sugars into bioenergy compounds and breaking down lignotoxins. Genetic tools can further optimize these strains for enhanced bioenergy compound production. This review explores the metabolic advantages of these organisms. It highlights the available array of genetic toolkits that can be shared among them to unlock their full potential for sustainable biofuel production.

Biofuel↗

Sustainable Forest Bioenergy Initiative

In the state’s Electricity Restructuring Act of 1998, the Commonwealth of Massachusetts recognized the opportunity and strategic benefits to diversifying its electric generation capacity with renewable energy. Through this legislation, the Commonwealth established one of the nation’s first Renewable Energy Portfolio Standard (RPS) programs, mandating the increasing use of renewable resources in its energy mix. Bioenergy, meeting low emissions and advanced technology standards, was recognized as an eligible renewable energy technology. Stimulated by the state’s RPS program, several project development groups have been looking seriously at building large woody biomass generation units in western Massachusetts to utilize the woody biomass resource. As a direct result of this development, numerous stakeholders have raised concerns and have prompted the state to take a leadership position in pursuing a science based analysis of biomass impacts on forest and carbon emissions, and proceed through a rulemaking process to establish prudent policy to support biomass development which can contribute to the state’s carbon reduction commitments and maintain safeguards for forest sustainability. The Massachusetts Sustainable Forest Bioenergy Initiative (SFBI) was funded by the Department of Energy and started by the Department of Energy Resources before these contentious biomass issues were fully raised in the state, and continued throughout the substantive periods of this policy development. Thereby, while SFBI maintained its focus on the initially proposed Scope of Work, some aspects of this scope were expanded or realigned to meet the needs for groundbreaking research and policy development being advanced by DOER. SFBI provided DOER and the Commonwealth with a foundation of state specific information on biomass technology and the biomass industry and markets, the most comprehensive biomass fuel supply assessment for the region, the economic development impact associated with biomass usage, an understanding of forest management trends including harvesting and fuel processing methods, and the carbon profile of utilizing forest based woody biomass for the emerging biomass markets. Each of the tasks and subtasks have provided an increased level of understanding to support new directives, policies and adaptation of existing regulations within Massachusetts. The project has provided the essential information to allow state policymakers and regulators to address emerging markets, while ensuring forest sustainability and understanding the complex science on CO2 accounting and impacts as a result of biomass harvesting for power generation. The public at large and electricity ratepayers in Massachusetts will all benefit from the information garnered through this project. This is a result of the state’s interest to provide financial incentives to only biomass projects that demonstrate an acceptable carbon profile, an efficient use of the constrained supply of fuel, and the harvest of biomass to ensure forest sustainability. The goals of the Massachusetts Sustainable Forest Bioenergy Initiative as proposed in 2006 were identified as: increase the diversity of the Massachusetts energy mix through biomass; promote economic development in the rural economy through forest industry job creation; help fulfill the state’s energy and climate commitments under the Renewable Energy Portfolio Standard and Climate Protection Plan; assist the development of a biomass fuel supply infrastructure to support energy project demands; provide education and outreach to the public on the benefits and impacts of bioenergy; improve the theory and practice of sustainable forestry in the Commonwealth. Completed project activities summarized below will demonstrate the effectiveness of the project in meeting the above goals. In addition, as discussed above, Massachusetts DOER needed to make some modifications to its work plan and objectives during the term of this project due to changing public policy demands brought forth in the course of the public discourse on this topic. We found that some tasks needed to be adjusted to meet changed conditions. Shortly after the start of SFBI, DOER recognized that establishing demonstration plots within state owned lands was not possible as the state enacted a temporary freeze on all timber harvesting on state lands, to allow for the completion of an assessment of current impacts of this activity and time to develop prudent policies on land conservation. Even more significantly, the state’s energy and environmental Secretary asked DOER to place a “sustainability” criterion for biomass in the RPS regulations, and the passage of the landmark Global Warming Solutions Act in 2008 committed DOER to very carefully consider and assure that biomass energy supported by the RPS met carbon reduction thresholds aligned with the state’s reduction commitments. These needs led to some adjustment of the SFBI scope and objectives to meet the policy challenges. Most notably was the funding and commissioning of the report by the Manomet Center for Conservation Sciences which provided the sustainability and carbon impact framework necessary for DOER to move policy forward prudently. The “Manomet Study” has moved this emerging policy issue substantially forward, gained national and international significance, and provided a new look at how the forest sequesters carbon and the effect of the removal of growing stock for energy on future carbon sequestration and atmospheric flux. This activity provided information that supports the objectives of SFBI but to accommodate this work, several subtasks were combined and addressed within the framework of the Manomet research study. The expected outcomes of the SFBI include the development of biomass energy systems that support sustainable forest management, new investment in forestry and fuel supply infrastructure, biomass energy generation that contributes to greenhouse gas mitigation, and job creation in project development and operation and in the rural forestry sector.

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Community Input on the Need, Scope, and Development Roadmap of a Proposed National Virtual Biosecurity for Bioenergy Crops Center (NVBBCC)

Brookhaven National Laboratory (BNL) was awarded a pilot project in FY22 under the U.S. Department of Energy (DOE) Office of Science Biopreparedness Research Virtual Environment (BRaVE) initiative, to define research priorities, needs, and requirements for a national virtual center devoted to the biosecurity of bioenergy crops. The mission of the proposed center, referred to as the National Virtual Biosecurity for Bioenergy Crop Center (NVBBCC), would be to provide the scientific basis and tools to detect, characterize, model, and mitigate biothreats to bioenergy crops. This function will be essential to ensure the projected increased US reliance over the next few decades on key plant-based energy products, such as biojet fuel. The NVBBCC is envisioned as a distributed, virtual center with multiple national laboratories at its core to maximize the use of existing unique facilities and expertise across the DOE complex. A major goal of the pilot project was to develop a roadmap for establishing NVBBCC through a series of meetings to gather community input. A total of about 150 individuals, drawn from DOE laboratories, the USDA, academia, NIH, DHS and the private sector participated in six planning meetings held in FY23. Four of the meetings were focused on specific research topics (disease detection, dispersion and disease propagation, biomolecular characterization of plant-pathogen interaction, and mitigation strategies). These four meetings were followed by a meeting that focused on computational needs to support collaborative, data-intensive research within a distributed center as well as workforce development. A final meeting focused on establishing and maintaining preparedness within NVBBCC to respond to an emerging disease within bioenergy crops and how it would collaborate and coordinate with USDA and DHS.

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Stepping into the Midwest Bioeconomy: Stakeholder Engagement and Geospatial Tools to Assist in Perennial Bioenergy Crop Decision Making and Entrepreneurship

This project, “Ecosystem Services and Farm Entrepreneurship Technical Assistance,” was a three-year project originally planned for FY22–FY24. Due to a late start and a few extensions, it is being completed in early FY25. This project explored opportunities to support the deployment of a bioeconomy with a circular, more sustainable supply chain. Using a tool developed by Argonne to identify agricultural areas suitable for use in the bioeconomy, we sought to create opportunities in the bioeconomy as biomass producers, bioenergy users, and environmental entrepreneurs. We proposed to focus at the beginning on enhancing the tool’s capabilities, while engaging with key stakeholders to improve and expand the tool’s functionality for all potential stakeholders in the bioeconomy. We believe that expanding our tools and technologies, coupled with conversations in agricultural spaces, will be needed as we continue to explore how best to offer farmers whole-of supply-chain opportunities to participate in the bioeconomy. Through this project we have continued to gain a better understanding of the ways in which farmers, landowners, bioenergy users, and environmental entrepreneurs may approach the bioeconomy. In addition, as we improve our analytic toolkit, we can continue to refine our communication and the ways in which we can valuate the bioeconomy. Refining these tools allows us to dive deeper into conversations around plausible policies and drivers for future bioeconomy investment and engagement by stakeholders. By working with farmers and agricultural landowners to enable a sustainable bioeconomy business model, enhance their energy options, and recover resources from their waste streams, this project directly responds to the Bioenergy Technology Office’s (BETO) priorities of building a resilient energy economy. It addresses BETO’s focus on fostering the development and adoption of energy technologies that enable the conversion of waste to energy, efficient land use, and robust job creation. By establishing a technical assistance program that develops capabilities and practices in agricultural areas to implement a bioeconomy future, this program will develop an important linkage between technology being developed at U.S. Department of Energy national laboratories and the agricultural communities of the Midwest. This project focuses on farmers with lower productivity farmland. Because less productive lands create a more difficult revenue stream for conventional crops, these farmers may therefore be more open to alternative agricultural land management regimes. Consequently, the technical assistance program and the methodologies for targeting perennial bioenergy crop application on marginal land provide a distinct opportunity to engage with and invest in the bioeconomy in these economically stressed areas. Stakeholders in this project include farmers and landowners, local conservation organizations (NRCS, SWCS, etc.), universities, non-profit environmental and agricultural entities, farm consultants, environmental regulators, and industry, including the industries working on conversion technologies, anaerobic digestion, pyrolysis, and biochar generation, and the companies interested in trading or purchasing/supporting the valuation of ecosystem services (ES).

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Systematic Review on Effects of Bioenergy From Edible Versus Inedible Feedstocks on Food Security

Achieving food security is a critical challenge of the Anthropocene that may conflict with environmental and societal goals such as increased energy access. The“fuel versus food”debate coupled with climate mitigation efforts has given rise to next-generation biofuels. Findings of this systematic review indicate just over half of the studies (56% of 224 publications) reported a negative impact of bioenergy production on food security. However, no relationship was found between bioenergy feedstocks that are edible versus inedible and food security (Pvalue=0.15). A strong relationship was found between bioenergy and type of food security parameter (Pvalue < 0.001), sociodemographic index of study location (Pvalue=0.001),spatial scale (Pvalue < 0.001), and temporal scale (Pvalue=0.017). Programs and policies focused on bioenergy and climat emitigation should monitor multiple food security parameters at various scales over the long term toward achieving diverse sustainability goals.

food security↗

Bioenergy: America's Energy Future

Bioenergy: America's Energy Future is a short documentary film showcasing examples of bioenergy innovations across the biomass supply chain and the United States. The film highlights a few stories of individuals and companies who are passionate about achieving the promise of biofuels and addressing the challenges of developing a thriving bioeconomy. This outreach product supports media initiatives to expand the public's understanding of the bioenergy industry and sustainable transportation and was developed by the U.S. Department of Energy Bioenergy Technologies Office (BETO), Oak Ridge National Laboratory, Green Focus Films, and BCS, Incorporated.

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Synthetic Gene Circuits to Enhance Production of Transgenic Bioenergy Crops (Final Scientific/Technical Report)

This project applied the principles of Synthetic Biology to the field of bioenergy crop improvement. Our goal was to produce a developmental toggle switch, a genetic switch that would permit at-will control of plant developmental states. Upon receiving an external signal, for example by spraying a chemical, a plant would be “toggled” to an embryonic state, transformed with a desired bioenergy trait, and then toggled back to a normal plant state. To accomplish this, over 200 synthetic repressible transcriptional promoters and their respective repressor proteins were designed, assembled and tested in Arabidopsis and sorghum. After being quantitatively characterized with the aid of mathematical models, some of these genetic parts were then used to assemble genetic toggle switches, and quantitative measurements of their function were determined in plant cells or intact plants. Evidence from genetically modified plants suggests a toggle switch capable of turning “ON” with application of an external substance, and capable of turning “OFF” with application of a second external substance. Attempts to transform a toggle circuit into sorghum, a crop plant, showed initial promise, but will require more time to accomplish in full. This research shows that the techniques of Synthetic Biology, a research area with large accomplishments in microbes, can also work for plants and bioenergy crops. Our methodologies have been and will be published and a patent application filed. This information will be enabling to the area of plant-based bioenergy.

59 BASIC BIOLOGICAL SCIENCES↗

Our Commitment to Bioenergy Sustainability

The U.S. Department of Energy’s Bioenergy Technologies Office (BETO) is committed to developing the resources, technologies, and systems needed to support a thriving bioenergy industry that protects natural resources and ad- vances environmental, economic, and social benefits. BETO’s Sustainability Technology Area proactively identifies and addresses issues that affect the scale-up potential, public acceptance, and long-term viability of advanced bioenergy systems; as a result, the area is critical to achieving BETO’s overall goals.

bioenergy, sustainability, bioenergy sustainabilit↗

Combining Eddy Covariance Towers, Field Measurements, and the MEMS 2 Ecosystem Model Improves Confidence in the Climate Impacts of Bioenergy With Carbon Capture and Storage

ABSTRACT Carbon dioxide removal technologies such as bioenergy with carbon capture and storage (BECCS) are required if the effects of climate change are to be reversed over the next century. However, BECCS demands extensive land use change that may create positive or negative radiative forcing impacts upstream of the BECCS facility through changes to in situ greenhouse gas fluxes and land surface albedo. When quantifying these upstream climate impacts, even at a single site, different methods can give different estimates. Here we show how three common methods for estimating the net ecosystem carbon balance of bioenergy crops established on former grassland or former cropland can differ in their central estimates and uncertainty. We place these net ecosystem carbon balance forcings in the context of associated radiative forcings from changes to soil N 2 O and CH 4 fluxes, land surface albedo, embedded fossil fuel use, and geologically stored carbon. Results from long term eddy covariance measurements, a soil and plant carbon inventory, and the MEMS 2 process‐based ecosystem model all agree that establishing perennials such as switchgrass or mixed prairie on former cropland resulted in net negative radiative forcing (i.e., global cooling) of −26.5 to −39.6 fW m −2 over 100 years. Establishing these perennials on former grassland sites had similar climate mitigation impacts of −19.3 to −42.5 fW m −2 . However, the largest climate mitigation came from establishing corn for BECCS on former cropland or grassland, with radiative forcings from −38.4 to −50.5 fW m −2 , due to its higher plant productivity and therefore more geologically stored carbon. Our results highlight the strengths and limitations of each method for quantifying the field scale climate impacts of BECCS and show that utilizing multiple methods can increase confidence in the final radiative forcing estimates.

Falvo, Grant [Department of Plant, Soil and Microb↗

The impact of biotechnological advances on the future of US bioenergy

Abstract Modern biotechnology has the potential to substantially advance the feasibility, structure, and efficiency of future biofuel supply chains. Advances might be direct or indirect. A direct advance would be improving the efficiency of biochemical conversion processes and feedstock production. Direct advances in processing may involve developing improved enzymes and bacteria to convert lignocellulosic feedstocks to ethanol. Progress in feedstock production could include enhancing crop yields via genetic modification or the selection of specific natural variants and breeds. Other direct results of biotechnology might increase the production of fungible biofuels and bioproducts, which would impact the supply chain. Indirect advances might include modifications to dedicated bioenergy crops that enable them to grow on marginal lands rather than land needed for food production. This study assesses the feasibility and advantages of near‐future (10‐year) biotechnological developments for a US biomass‐based supply chain for bioenergy production. We assume a simplified supply chain of feedstock, logistics and land use, conversion, and products and utilization. The primary focus is how likely developments in feedstock production and conversion technologies will impact bioenergy and biofuels in the USA ; a secondary focus is other innovative uses of biotechnologies in the energy arenas. The assessment addresses near‐term biofuels based on starch, sugar, and cellulosic feedstocks and considers some longer‐term options, such as oil‐crop and algal technologies. Published 2015. 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

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Assessing multimetric aspects of sustainability: Application to a bioenergy crop production system in East Tennessee

This paper connects the science of sustainability theory with applied aspects of sustainability deployment. A suite of 35 sustainability indicators spanning six environmental, three economic, and three social categories has been proposed for comparing the sustainability of bioenergy production systems across different feedstock types and locations. A recent demonstration-scale switchgrass-to-ethanol production system located in East Tennessee is used to assess the availability of sustainability indicator data and associated measurements for the feedstock production and logistics portions of the biofuel supply chain. Knowledge pertaining to the available indicators is distributed within a hierarchical decision tree framework to generate an assessment of the overall sustainability of this no-till switchgrass production system relative to two alternative business-as-usual scenarios of unmanaged pasture and tilled corn production. The relative contributions of the social, economic and environmental information are determined for the overall trajectory of this bioenergy system s sustainability under each scenario. Within this East Tennessee context, switchgrass production shows potential for improving environmental and social sustainability trajectories without adverse economic impacts, thereby leading to potential for overall enhancement in sustainability within this local agricultural system. Given the early stages of cellulosic ethanol production, it is currently difficult to determine quantitative values for all 35 sustainability indicators across the entire biofuel supply chain. This case study demonstrates that integration of qualitative sustainability indicator ratings may increase holistic understanding of a bioenergy system in the absence of complete information.

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Field–scale evaluation of ecosystem service benefits of bioenergy switchgrass

Purpose-grown perennial herbaceous species are nonfood crops specifically cultivated for bioenergy production and have the potential to secure bioenergy feedstock resources while enhancing ecosystem services. This study assessed soil greenhouse gas emissions (CO 2 and N 2 O), nitrate (NO 3 -N) leaching reduction potential, evapotranspiration (ET), and water-use efficiency (WUE) of bioenergy switchgrass (Panicum virgatum L.) in comparison to corn (Zea mays L.). The study was conducted on field-scale plots in Urbana, IL, during the 2020–2022 growing seasons. Switchgrass was established in 2020 and urea-fertilized at 56 kg N ha –1 year –1 . Corn management followed best management practices for the US Midwest, including no-till and 202 kg N ha –1 year –1 fertilization, applied as urea–ammonium nitrate (32%). Our results showed lower direct N 2 O emissions in switchgrass compared to corn. Although soil CO 2 emissions did not differ significantly during the establishment year, emissions in subsequent years were over 50% higher in switchgrass than in corn, likely due to increased belowground biomass, which was over five times higher in switchgrass. Nitrate-N leaching decreased as the switchgrass stand matured, reaching 80% lower than in corn by the third year. Differences in ET and WUE between corn and switchgrass were not significant; however, results indicate a trend toward reduced WUE in switchgrass under drought, driven by lower aboveground biomass production. Our study demonstrates that switchgrass can be implemented at a commercial scale without negatively impacting the hydrological cycle, while potentially reducing N losses through nitrate-N leaching and soil N 2 O emissions, and enhancing belowground C storage.

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Finding Promising Candidates for Wet Growing Conditions: The Effect of Two Row Spacings on Biomass Production of Four Bioenergy Prairie Cordgrass Populations in a Wet Marginal Land

Demand for energy and the environmental consequences associated with fossil fuel emissions has created a need for alternative energy sources. To avoid conflict over the conversion of existing agricultural land from food production to fuel production, bioenergy crops could instead be cultivated on marginal land. Here, this study compared the performances, biomass yield, tiller density, and lignocellulosic bioenergy feedstock composition of four prairie cordgrass populations with two-row spacings cultivated on a waterlog-prone marginal land, as well as three other bioenergy candidate crops used as controls: big bluestem, M. × giganteus , and switchgrass. Across all populations and spacings, annual biomass yield of prairie cordgrass was 13 Mg ha −1 . Row spacing had significant impacts on prairie cordgrass productivity, with higher biomass yields observed in the 45 cm spacing than in the 90 cm spacing. Feedstock composition (cellulose, hemicellulose, ADL, and ash concentration) was not influenced by row spacing and did not deviate from expected values for growth on agricultural lands. However, biomass yields of the control species M . × giganteus and switchgrass planted in 45 cm spacing were higher than the prairie cordgrass. Our results provide evidence that prairie cordgrass could be a good energy crop with comparable biomass yield production to the energy crops M . × giganteus and switchgrass on waterlogged marginal land.

Bioenergy crops↗

Optimizing bioenergy sorghum productivity and nutrient removal in Illinois: Impact of nitrogen fertilization under diverse marginal conditions

Bioenergy sorghum (Sorghum bicolor L. Moench) is a promising crop for contributing to the United States bioenergy supply. However, the varying limitations of the marginal lands targeted for its cultivation present a management challenge. This two-year study aimed to investigate how the limitations associated with marginal cropland impact the effects of nitrogen fertilization on the yield of bioenergy sorghum and the uptake of 11 macro- (N, P, K, Ca, Mg, and S) and micronutrients (Fe, Mn, Zn, Cu, and B). The study contrasted prime cropland in central Illinois (Urbana) with three marginal cropland sites in southern (Ewing) and central Illinois (Fairbury and Pesotum). These marginal cropland sites are characterized by varying limitations, including low soil fertility (P and K limitations), leaching and erosion, and flooding, respectively. Four nitrogen rates (0, 56, 112, and 168 kg N ha –1 ) were tested under eight environments. The average yields and ranges of sorghum biomass were 20.2 (17.0–23.2) Mg ha –1 in Urbana, 18.1 (13.1–19.8) Mg ha –1 in Ewing, 13.8 (9.0–17.3) Mg ha –1 in Fairbury, and 23.3 (14.6–33.0) Mg ha –1 in Pesotum. Optimal N rates were 56 N in Pesotum and 112 N in Urbana, Ewing, and Fairbury. Tissue macronutrient contents in Urbana were generally higher than in the marginal croplands, while micronutrient contents did not show discernible trends. Increasing N rate generally correlated with the macronutrient removal except in Ewing. Comparable sorghum biomass yields were observed between prime and marginal croplands (averaging 18.3 Mg ha –1 ), but optimal N rates varied between 56 N and 112 N. This suggests that yield gaps can be narrowed by applying the optimal N rates for the respective locations. However, increased removals of macronutrients, especially P and K, with increasing yields indicate the need to revise fertilizer recommendations, particularly for soils deficient in these nutrients.

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Land use for bioenergy: Synergies and trade-offs between sustainable development goals

Bioenergy aims to reduce greenhouse gas (GHG) emissions and contribute to meeting global climate change mitigation targets. Nevertheless, several sustainability concerns are associated with bioenergy, especially related to the impacts of using land for dedicated energy crop production. Cultivating energy crops can result in synergies or trade-offs between GHG emission reductions and other sustainability effects depending on context-specific conditions. Using the United Nations Sustainable Development Goals (SDGs) framework, the main synergies and trade-offs associated with land use for dedicated energy crop production were identified. Furthermore, the context-specific conditions (i.e., biomass feedstock, previous land use, climate, soil type and agricultural management) which affect those synergies and trade-offs were also identified. The most recent literature was reviewed and a pairwise comparison between GHG emission reduction (SDG 13) and other SDGs was carried out. A total of 427 observations were classified as either synergy (170), trade-off (176), or no effect (81). Most synergies with environmentally-related SDGs, such as water quality and biodiversity conservation, were observed when perennial crops were produced on arable land, pasture or marginal land in the ‘cool temperate moist’ climate zone and ‘high activity clay’ soils. Most trade-offs were related to food security and water availability. Previous land use and feedstock type are more impactful in determining synergies and trade-offs than climatic zone and soil type. This study highlights the importance of considering context-specific conditions in evaluating synergies and trade-offs and their relevance for developing appropriate policies and practices to meet worldwide demand for bioenergy in a sustainable manner.

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Investment risk in bioenergy crops

Here, perennial, cellulosic bioenergy crops represent a risky investment. The potential for adoption of these crops depends not only on mean net returns, but also on the associated probability distributions and on the risk preferences of farmers. Using 6-year observed crop yield data from highly productive and marginally productive sites in the southern Great Lakes region and assuming risk neutrality, we calculate expected breakeven biomass yields and prices compared to corn ( Zea mays L.) as a benchmark. Next we develop Monte Carlo budget simulations based on stochastic crop prices and yields. The crop yield simulations decompose yield risk into three components: crop establishment survival, time to maturity, and mature yield variability. Results reveal that corn with harvest of grain and 38% of stover (as cellulosic bioenergy feedstock) is both the most profitable and the least risky investment option. It dominates all perennial systems considered across a wide range of farmer risk preferences. Although not currently attractive for profit-oriented farmers who are risk neutral or risk averse, perennial bioenergy crops.

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Emerging wild virus of native grass bioenergy feedstock is well–established in the Midwestern USA and associated with premature stand senescence

The North American native prairie grass Panicum virgatum (switchgrass) is a primary bioenergy feedstock candidate. Its widespread distribution and genetic diversity enable the possibility of developing this perennial grass for high production in a variety of conditions, including on marginal lands. A critical concern in feedstock development and deployment is the risk of novel pathogen emergence. Here we investigate the landscape-scale prevalence and epidemiology of a little-studied North American virus first detected in switchgrass and other grasses in bioenergy trials in the US Midwest. Switchgrass mosaic virus (SwMV, Genus Marafivirus, Family Tymoviridae) is transmitted by leafhoppers and phylogenetically sister to Maize rayado fino virus, a significant pathogen of maize in parts of the Americas. Our goal was to determine whether SwMV is uniquely limited to specific bioenergy trials or well-established and circulating more broadly. We used molecular diagnostics to quantify naturally occurring SwMV infection in leafhoppers and switchgrass in naturalistic stands throughout a large Midwestern landscape, and quantified leafhopper abundances and stand performance. Our analysis revealed that this apparently wild virus is well-established and widespread. Infection was present at nearly all sites, across diverse landscape contexts, with prevalences ranging as high as 33%–60%. Infection appeared to accumulate and persist in stands over time. It was associated with increases in premature stand senescence but not with reductions in stand height. Although wild viruses are believed to evolve benign relationships with their natural hosts, these data suggest that SwMV has potential to impact yield components. Viruses are frequently overlooked in crop development efforts, but represent the majority of emerging plant pathogens. For SwMV, it is imperative to quantify its impact on host performance, to identify the extent of any host resistance, and to assess any risks of virus spillover to agricultural plantings of other Poaceae species, including maize and sorghum.

59 BASIC BIOLOGICAL SCIENCES↗