Bioenergy Feedstock Research Articles

Potential, economic and ecological benefits of sweet sorghum bio-industry in China

BackgroundSweet sorghum (Sorghum bicolor) displays an excellent potential to serve as a non-food bioenergy feedstock for bioethanol production in China due to its high potential yield on marginal lands. However, few studies have been conducted on the potential of sweet sorghum yield and appropriate industrial models in different marginal regions in China. This study explored the spatial distribution of potential sweet sorghum production using the Decision Support System for Agrotechnology Transfer (DSSAT) model and proposed three typical industrial models of sweet sorghum industry to calculate their economic and ecological benefits.ResultsThe results indicate that considering the factors of land use, annual precipitation, soil salinity, soil pH, and accumulated temperature, approximately 32.23 million ha of marginal land are suitable for sweet sorghum cultivation in China, and 130 million tonnes (t) of ethanol can be produced. Further, the development of the sweet sorghum industry under the three models can generate 1425.49 billion CNY potential, approximately accounting for 3.57% of industrial added value in China if measured against 2023 levels, and reduce CO2 emissions by 4.68 million t.ConclusionsThis study provides an innovative perspective for the multi-industry large-scale promotion of sweet sorghum in different marginal lands based on the high spatial resolution Geographic Information System (GIS) data by the DSSAT model with a Life Cycle Assessment (LCA) method, and this applies not only to China but also to the worldwide and other types of energy plants.

Biomass yield potential, feedstock quality, and nutrient removal of perennial buffer strips under continuous zero fertilizer application

Abstract. Perennial-based buffer strips have been promoted as having the potential for improving ecosystem services from riparian areas while producing biomass as livestock feed or as a bioenergy feedstock. Both biomass production and nutrient removal of buffer strips are substantially influenced by the vegetation types for the multipurpose perennial buffers. In this 2016–2019 study in western Illinois, two perennial cropping systems, including forage crops composed of cool-season grass mixtures (forage system) and bioenergy crops made up of warm-season grass mixtures (bioenergy system), were used to establish buffer strips for assessing biomass production, feedstock quality, nutrient removal, and buffer longevity. Treatments for this study reflecting agronomic practices included (1) two harvests occurring in summer (at anthesis) and fall (after complete senescence) and (2) one harvest in fall for the forage system (two-cut vs. one-cut forage) and (3) one fall harvest for the bioenergy system (one-cut bioenergy). Successively harvesting without any fertilizer input resulted in a yield decline in forage biomass over 3 years by approximately 30 % (6.3 to 4.4 Mg DM ha−1 (dry matter) with a rate of 1.0 Mg ha−1 yr−1) in the two-cut forage and by 35 % (4.9 to 3.2 Mg DM ha−1 with a rate of 0.9 Mg ha−1 yr−1) in the one-cut forage systems. The feed quality also decreased over the years by showing declined rates of 12.9 (crucial protein), 0.9 (calcium), 0.7 (copper), and 1.3 g kg−1 DM yr−1 (zinc). Empirical models predicted enteric CH4 emissions from cattle ranged from 225.7 to 242.6 g per cow per day based on the feed nutritive values. In contrast, bioenergy biomass yield increased by 27 % from 4.9 to 6.7 Mg DM ha−1 with a consistent quality (cellulose of ∼ 397.9 g kg−1; hemicellulose of ∼ 299.4 g kg−1), corresponding to the increased total theoretical ethanol yield from 1.8 × 103 to 2.4 × 103 L ha−1 (∼ 33 % increase). Annual nutrient removals of N, P, K, Ca, and Mg were significantly higher in the forage systems (e.g., two-cut: 52.6–106.9 kg N ha−1; one-cut: 44.5–84.1 kg N ha−1) than those in the bioenergy system (e.g., 25.9–34.4 kg N ha−1); however, the removal rate declined rapidly over 3 years (e.g., ∼ 49 % reduction) as the annual biomass yield declined in the forage systems. This on-farm field study demonstrated the potential of the perennial crop used as buffer strip options for biomass production and buffer sustainability at the edge of the field.

Formation and endogenous feedback mechanism of farmers’ bioenergy feedstock planting decisions

Formation and endogenous feedback mechanism of farmers’ bioenergy feedstock planting decisions

Valorization and optimization of Prosopis africana pod and cowpea husk wastes for densified hybrid briquette production

Biomass is an eco-friendly alternative sustainable renewable energy source when agricultural wastes are effectively utilized. It has become critical to assess the suitability of biofuel briquettes as an energy source for cooking, electricity, and fuel for heating. Certainly, the integration of energy sources into energy policies is warranted, considering the huge potential to provide energy for rural communities and the peri-urban poor with alternative fuel. This research describes a technique to generate densified hybrid solid biofuels from biomass waste and valorize them. Prosopis africana pod (PAP) and cowpea husk (CPH) wastes were combined to create high-energy-density fuel briquettes. The experiment involves improving briquette manufacturing parameters using response surface methodology to better understand the impacts of particle sizes, composition, binder concentrations, and densification pressures on briquette performance. The optimal conditions were particle size 150 µm, 50% PAP, 10% binder concentration, and densification pressure 103.42 kN/m2. The optimum values for burning rate, ignition time, specific fuel consumption, and heating value were 0.35 g/min, 2.75 min, 0.186 g/L, and 22.98 MJ/kg, respectively. The findings show the potential for using PAP and CPH biomass waste to produce environmentally friendly energy sources. This increases the potential agro-waste feedstocks for bioenergy in developing countries, reducing energy insecurity while promoting waste management, renewable energy generation, and environmental sustainability.

Multiyear productivity and nitrate‐nitrogen loss from corn and prairie bioenergy cropping systems

AbstractThough corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are widely grown and readily accepted into commodity markets and biofuel facilities, heavy reliance on seeds of those two crops for bioenergy production has been linked to environmental degradation, including nutrient discharge to water, and to constraints on food production. Alternative biofuel feedstock systems might better address this “food–energy–environment trilemma.” Using data from a 9‐ha field experiment in Iowa, we evaluated yields from a 14‐year period for four bioenergy feedstock systems: stover harvested from corn grown with and without an unharvested rye cover crop, and prairie vegetation grown with and without fertilizer. We also assessed sub‐surface drainage flows and NO3‐N concentrations and discharges in leachate from those cropping systems. The continuous corn systems produced mean grain yields of 11.0–11.5 Mg ha−1 year−1, while also yielding about 4 Mg ha−1 year−1 of stover. Mean harvested biomass from the fertilized prairie was 83% greater than from the unfertilized prairie and was superior to stover production in the two corn treatments in 11 out of 14 years. Nitrate‐N losses in drainage water from the corn systems averaged 12–14 kg NO3‐N ha−1 year−1, whereas both the fertilized and unfertilized prairie systems almost eliminated NO3‐N loss. Cover cropping with rye reduced NO3‐N loss in only one out of 13 years and had variable effects on corn yield. Adoption of prairie‐based biofuel systems might be driven by placing perennial feedstocks on environmentally sensitive sub‐field areas and by government policies that favor perennial feedstocks over annual crops like corn.

A miniaturized feedstocks-to-fuels pipeline for screening the efficiency of deconstruction and microbial conversion of lignocellulosic biomass.

Sustainably grown biomass is a promising alternative to produce fuels and chemicals and reduce the dependency on fossil energy sources. However, the efficient conversion of lignocellulosic biomass into biofuels and bioproducts often requires extensive testing of components and reaction conditions used in the pretreatment, saccharification, and bioconversion steps. This restriction can result in a significant and unwieldy number of combinations of biomass types, solvents, microbial strains, and operational parameters that need to be characterized, turning these efforts into a daunting and time-consuming task. Here we developed a high-throughput feedstocks-to-fuels screening platform to address these challenges. The result is a miniaturized semi-automated platform that leverages the capabilities of a solid handling robot, a liquid handling robot, analytical instruments, and a centralized data repository, adapted to operate as an ionic-liquid-based biomass conversion pipeline. The pipeline was tested by using sorghum as feedstock, the biocompatible ionic liquid cholinium phosphate as pretreatment solvent, a "one-pot" process configuration that does not require ionic liquid removal after pretreatment, and an engineered strain of the yeast Rhodosporidium toruloides that produces the jet-fuel precursor bisabolene as a conversion microbe. By the simultaneous processing of 48 samples, we show that this configuration and reaction conditions result in sugar yields (~70%) and bisabolene titers (~1500 mg/L) that are comparable to the efficiencies observed at larger scales but require only a fraction of the time. We expect that this Feedstocks-to-Fuels pipeline will become an effective tool to screen thousands of bioenergy crop and feedstock samples and assist process optimization efforts and the development of predictive deconstruction approaches.

Greenhouse Gas Mitigation Potential of the Enhanced Rice Straw Biogas System in the Philippines

Abstract Rice straw is an agricultural waste produced abundantly every rice cropping cycle. Its disposal or removal from the field is a problem to rice farmers every start of the next cropping cycle due to its labor-intensive collection from the field. One traditional practice is soil incorporation; however, rice straw does not degrade easily, and this management practice releases significant amount of greenhouse gas emissions to the environment. An attempt to solve this issue is to utilize rice straw with cattle manure as feedstock for biogas production and use the energy generated for rice post-harvest processing such as grain drying and milling. An Enhanced Rice Straw Biogas facility was constructed in Victoria, Laguna, Philippines and a trial lagoon run was conducted from June to October 2021. The data from the initial run was used as input to the modified Aston-developed Mass Energy Balance Model to determine the biogas production potential of rice straw and cattle manure as bioenergy feedstocks. The proposed system can produce 8,803,567.99 L (296.19 L/kg VS) of biogas which can be converted to 19,502.97 MW electricity and 84,512.86 MJ heat. From the energy generated per batch, 18,417.21 kg rice grain (dry season) or 15,752.79 kg rice grain (wet season) can be dried and milled, with an excess of equivalent kerosene (696.93 L for dry season or 248.46 L for wet season) and electricity (3,745.12 kWh for dry season or 6,182.23 kWh for wet season). Due to biogas utilization, an estimated 3,351 L of fossil-based kerosene and 12,185.91 kWh of electricity equivalent can be avoided. This low GHG emission rice production system (Aston Model) has a theoretical annual carbon footprint of 153,134 kg CO2e and a 28.21% reduction of greenhouse gas emissions compared to the conventional rice production system.

A REVIEW ON RENEWABLE BIOFUELS AND ITS PROPERTIES: A PROMISING CHOICE FOR THE PRODUCTION OF BIODIESEL

Natural energy resources like coal and petroleum are under extreme pressure due to the world's population expansion, which is driving up energy consumption. The twenty-first century will see more violent drought occurrences, which will have an impact on agricultural production, according to climate prediction models. Developing bioenergy feedstock as a possible alternative for the manufacture of biodiesel might be a workable solution to manage the increasing demand for energy and worldwide climate crisis without diminishing fossil fuel supplies. Therefore, this research paper concentrates on the background sources of biodiesel along with their chemical and technological features. A thorough discussion of their respective benefits and drawbacks is provided, with an emphasis on their industrial use. An overview of the alternative fuels, possible feedstocks, biodiesel production processes, characteristics and their benefits from environmental point of view are also presented.

Wood-Based Bioenergy in North America: An Overview of Current Knowledge

Policy priorities for wood-based bioenergy in North America have undergone fluctuations over time, influenced significantly by the dynamic interplay of sociopolitical factors. Recent years, however, have seen a renewed public interest in wood-based bioenergy in the United States, Canada, and Mexico. This resurgence is driven by fluctuating energy prices and growing concerns about climate change. This review provides an overview of current energy production and consumption scenarios, and highlights critical issues related to the sustainability of bioenergy feedstocks and their economic potential across the three North American countries. Different cross-cutting issues related to public health, climate change, and social acceptance of wood-based bioenergy are thoroughly examined. Within this context, several challenges have been identified, including uncertainties in climate projections, inadequate tree inventories beyond forestlands, deforestation concerns, technological shifts in wood processing, fluctuations in bioenergy demand, and the imperative need for access to reliable markets. Addressing these challenges requires increased research and investment in wood-based energy to enhance energy security, reduce greenhouse gas emissions, and improve economic and social viability in bioenergy production. This proactive approach is vital for fostering a sustainable and resilient wood-based bioenergy sector in North America.

Co-cultivation of microalgae and bacteria for optimal bioenergy feedstock production in wastewater by using response surface methodology

This work uses response surface methodology (RSM) to study the co-cultivation of symbiotic indigenous wastewater microalgae and bacteria under different conditions (inoculum ratio of bacteria to microalgae, CO2, light intensity, and harvest time) for optimal bioenergy feedstock production. The findings of this study demonstrate that the symbiotic microalgae-bacteria culture not only increases total microalgal biomass and lipid productivity, but also enlarges microalgal cell size and stimulates lipid accumulation. Meanwhile, inoculum ratio of bacteria to microalgae, light intensity, CO2, and harvest time significantly affect biomass and lipid productivity. CO2 concentration and harvest time have significant interactive effect on lipid productivity. The response of microalgal biomass and lipid productivity varies significantly from 2.1 × 105 to 1.9 × 107 cells/mL and 2.8 × 102 to 3.7 × 1012 Total Fluorescent Units/mL respectively. Conditions for optimum biomass and oil accumulation are 100% of inoculation ratio (bacteria/microalgae), 3.6% of CO2 (v/v), 205.8 µmol/m2/s of light intensity, and 10.6 days of harvest time. This work provides a systematic methodology with RSM to explore the benefits of symbiotic microalgae-bacteria culture, and to optimize various cultivation parameters within complex wastewater environments for practical applications of integrated wastewater-microalgae systems for cost-efficient bioenergy production.

Aboveground woody biomass estimation of young bioenergy plantations of Populus and its hybrids using mobile (backpack) LiDAR remote sensing

Woody aboveground biomass (AGB) including short-rotation Populus is used as a feedstock for renewable and carbon-neutral bioenergy. While woody AGB can be estimated with allometric equations requiring labor-intensive field data, remote sensing technologies like mobile terrestrial light detection and ranging (LiDAR) can estimate woody AGB quickly and accurately. Therefore, the goals of this study were to develop a model to predict woody AGB of 2-year-old Populus spp. from three taxa (P. deltoides, P. deltoides × P. maximowiczii and P. deltoides × P. trichocarpa) using allometric (height and diameter at breast height (DBH)) or LiDAR-derived metrics from a mobile terrestrial (backpack) system. Likewise, we sought to compare LiDAR-estimated tree height and DBH with field-measured values. We found that a taxa-specific model containing LiDAR-measured tree height, crown volume, and taxa interactions with the height of the 10th percentile, and the density of the lowest interval (density metric 0) explained 84 % of the variation in woody AGB with a root mean square error (RMSE) of 28.7 % and performed slightly better than the allometric model. The best model excluding taxa had a slightly higher RMSE but lower bias than the allometric model. LiDAR-derived tree heights were highly correlated with field-measured heights, but DBH could not be estimated accurately. Therefore, terrestrial mobile LiDAR systems can accurately estimate woody AGB and tree height of Populus in short rotation systems to aid in the fast and efficient quantification of woody bioenergy production and renewable energy resources.

The AFOLU sector’s role in national decarbonization: a comparative analysis of low-GHG development pathways in Brazil, India and Indonesia

ABSTRACT This paper analyses the role that AFOLU (agriculture, forest and other land use) plays in national deep decarbonization scenarios in Brazil, India and Indonesia between 2020 and 2050. It finds that the LULUCF (land use, land use change and forestry) subsector is important for medium-term mitigation (2020–2030) while continuing to contribute to mitigation over the long-term (2030–2050) in the three countries. Mitigation actions in LULUCF include drastically reducing deforestation (Brazil, Indonesia) and peat degradation (Indonesia), re-/afforestation (all), increased sequestration in standing forests (Brazil, Indonesia) and increasing soil carbon in agricultural lands (India). AFOLU further contributes to mitigation in Brazil and Indonesia by producing biomass feedstock for bioenergy. No country significantly reduces N2O and CH4 emissions from either agriculture or via demand-side actions on diets, due to trade-offs with food security, rural livelihoods and economic growth (although all countries reduce the GHG intensity of agricultural products). Furthermore, the paper analyses national policies to manoeuvre co-benefits and trade-offs between mitigation and other sustainable development goals (SDGs), including no poverty (1); zero hunger (2); decent work and economic growth (8); climate action, including both adaptation and mitigation (13); and life on land (15). Common policy areas were identified, including incentives to land managers for conservation or more environmental agricultural practices; changing regulations of land use to protect ecosystems and/or encourage shifts in agricultural practices; and strengthening enforcement capacity of land protection.

Effects of lignin syringyl to guaiacyl ratio on cottonwood biochar adsorbent properties and performance

Lignin syringyl to guaiacyl ratio (S/G) has long been suspected to have measurable impacts on biochar formation, but these effects are challenging to observe in biochars formed from whole biomass. When the model bioenergy feedstock Populus trichocarpa (cottonwood), with predictable lignin macromolecular structure tied to genetic variation, is used as feedstock for biochar production, these effects become visible. In this work, two P. trichocarpa variants having lignin S/G of 1.67 and 3.88 were ground and pyrolyzed at 700 °C. Water-demineralization of feedstock was used to simultaneously evaluate any synergistic influences of S/G and naturally-occurring potassium on biochar physicochemical properties and performance. The strongest effects of lignin S/G were observed on specific surface area (SBET) and oxygen-content, with S/G of 1.67 improving SBET by 11% and S/G of 3.88 increasing total oxygen content in demineralized biochars. Functional performance was evaluated by breakthrough testing in 1% NH3. Breakthrough times for biochars were nearly double that of a highly microporous activated carbon reference material, and biochar with S/G of 3.88 had 10% longer breakthrough time than its lower S/G corollary. Results support a combination of pore structure and oxygen-functionalities in controlling ammonia breakthrough for biochar.

Assessing the potential of a genetically modified Parachlorella kessleri-I with low CO2 inducible proteins for enhanced biomass and biofuel productivity

The biological process is one of the promising approaches for CO2 capture and storage. Recently, biological sequestration using microalgae has gained much interest due to its capability to utilize CO2 as a carbon source to generate valorizable biomass. This algal biomass further can be used as a feedstock for bioenergy and different value-added products. Here, we have heterogeneously overexpressed the low CO2 inducible proteins (LCIA & LCIB) from Chlamydomonas reinhardtii in the marine alga Parachlorella kessleri-I. Incorporation of these two genes boosted the endogenous CCM leading to a hybrid system and improved overall carbon acquisition. The combination of these CCM proteins enhanced the supply of inorganic carbon to RuBisCO with positive effects on growth and biomass productivity. Biochemical analyses revealed that the hybrid CCM in P. kessleri-I was characterised by 2- fold higher carbonic anhydrase activity, increased starch, and 2X more lipid yield in comparison to wild type (WT) strain. Moreover, the semi-continuous cultivation of GM strain with supply of 1 % CO2 led to around 60 % rise in the overall biomass productivity. These traits also persisted in scale-up studies leading to 2X more biomass productivity in the GM strain than WT in 100 L PBR. A comparative life-cycle assessment underlines the sustainability of the process of carbon capture and both biofuel and biochar production from P. kessleri-I with a hybrid CCM.

A spatial analysis of the economic returns to land‐use change from agriculture to renewable energy production: Evidence from Ireland

AbstractCountries are looking to reduce their agricultural sector's carbon footprint while encouraging economic and environmental sustainability. One proposed method of making agriculture more sustainable while maintaining farm incomes is through the production of bioenergy feedstocks. We examine the spatial aspect of the production of renewable energy feedstocks in Ireland. Two feedstocks are looked at—grass silage and short‐rotation coppice (SRC) willow. Spatial microsimulation analysis is utilised to assess the spatial suitability for alternative land uses, simulating land‐use change to compare economic returns with the current agricultural use. A farm‐based carbon subsidy is modelled based on avoided agricultural emissions and carbon sequestered. We find that midlands counties, especially those in the north midlands, have the highest proportion of land where feedstocks would be more profitable than the current agricultural use. Counties on the western seaboard have the lowest proportion of land where feedstocks would give greater returns. The amount of land where feedstocks are more profitable increases as greater carbon subsidies are provided. Of the two feedstocks assessed, SRC willow cultivation is more profitable than grass silage production. The overwhelming majority of land where producing feedstocks would be more profitable has cattle farming as its current use.

Characterization of Wood, Leaves, Barks, and pod wastes from Prosopis africana biomass for biofuel production

One of the approaches for increasing the contribution of biomass to the renewable energy mix is the valorization of biomass to bioenergy. Evaluating the potential of unconventional biomass sources could significantly accelerate the assessment for suitability as feedstock for bioenergy production as a sustainable solution. The study aimed to characterize the Prosopis africana biomass of wood, barks, leaves, and pods towards providing valuable data for scaling up and incorporating these materials into the bioenergy crop database. Characterizations of wood, leaves, barks, and pod wastes from Prosopis africana biomass were investigated based on the proximate, ultimate, and compositional analysis of pulverized samples of the PA biomass to determine their physical, thermal, and chemical properties towards assessing their potential for valorization to bioenergy. The lignocellulosic materials were characterized by scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. The results show that the pulverized sample wastes have porous structures with varying degrees of crystallinity (wood: 89.20 %, bark: 23.90 %, leaves: 32.48 %, pods: 23.08 %), suggesting different susceptibilities to conversion processes. Notably, the wood sample had the lowest moisture content (3.13 %), and the pod sample had the highest volatile matter content (75.83 %), indicating a high potential for biofuel production. The higher heating values (HHV) and lower heating values (LHV) of the samples ranged from 15.23 to 20.49 MJ/kg and 13.83 to 18.79 MJ/kg, respectively. These calorific values are competitive with established lignocellulosic bioenergy feedstocks, positioning PA biomass as promising candidates for solid biofuel applications.

Bioenergy feedstock production in Chlamydomonas reinhardtii (microalgae) cultivated under mixotrophic growth with cellulose hydrolysate from agricultural waste.

In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.

Endophyte-Mediated Populus trichocarpa Water Use Efficiency Is Dependent on Time of Day and Plant Water Status

Endophytes are potential partners for improving the resource use efficiency of bioenergy feedstock systems such as short rotation coppice Populus species. Endophytes isolated from members of the Salicaceae family have broad host compatibility and can improve water use efficiency (WUE) through decreases in stomatal conductance. However, the literature is inconsistent with regard to the environmental conditions and temporal patterns of these benefits. This study investigated how endophyte-mediated changes in Populus trichocarpa ‘Nisqually-1’ stomatal conductance and WUE shift with time and scale in response to water deficit stress. Leaf gas exchange and aboveground productivity were used to evaluate the carbon and water balance of greenhouse-grown plants in response to endophyte inoculation and water deficit. Differences in stomatal conductance between control and inoculated plants were more pronounced (39.7% decrease, Welch two-sample t [14.34 adjusted degrees of freedom] = –2.358, P = 0.033) under water deficit conditions in the late morning during a period of higher light intensity. The decrease in stomatal conductance accompanied a substantial increase in intrinsic WUE (iWUE) for water deficit inoculated plants. However, increases in iWUE did not result in improvements in aboveground productivity or shoot biomass WUE for water deficit inoculated plants. This decoupling between iWUE and aboveground productivity may be an indicator of assimilate allocation to microbial metabolism as an additional carbon sink or a shift in carbon allocation toward belowground biomass. Future work should take a whole plant approach that accounts for diurnal patterns in incident irradiance to evaluate the impact of endophyte inoculation on host WUE and stress tolerance.

Abiotic stress reorganizes rhizosphere and endosphere network structure of Sorghum bicolor

Sorghum bicolor is a promising bioenergy feedstock with high biomass production and unusual tolerance for stresses such as water and nutrient limitation. While the membership of the sorghum microbiome in response to stress has been explored, relatively little is known about how microbe-microbe networks change under water- or nutrient-limited conditions. This is important because network changes can indicate impacts on the functionality and stability of microbial communities. We performed network-based analysis on the core bacterial and archaeal community of an agronomically promising high biomass bioenergy genotype, Grassl, grown under nitrogen and water stress. Stress caused relatively minor changes in bacterial abundances within soil, rhizosphere, and endosphere communities, but led to significant changes in bacterial network structure and modularity. We found a complete reorganization of network roles in all plant compartments as well as an increase in the modularity and proportion of positive associations which potentially could represent coexistence and cooperation in the sorghum bacterial/archaeal community under stress. While stressors are often believed to be destabilizing, we found stressed networks were as or more stable than non-stressed networks likely due to their redundancy and compartmentalization. Together, these findings support the idea that both sorghum and its bacterial/archaeal community can be resilient to future environmental stressors.

Bird Species Use of Bioenergy Croplands in Illinois, USA—Can Advanced Switchgrass Cultivars Provide Suitable Habitats for Breeding Grassland Birds?

Grassland birds have sustained significant population declines in the United States through habitat loss, and replacing lost grasslands with bioenergy production areas could benefit these species and the ecological services they provide. Point count surveys and autonomous acoustic monitoring were used at two field sites in Illinois, USA, to determine if an advanced switchgrass cultivar that is being used for bioenergy feedstock production could provide suitable habitats for grassland and other bird species. At the Brighton site, the bird use of switchgrass plots was compared to that of corn plots during the breeding seasons of 2020–2022. At the Urbana site, the bird use of restored prairie, switchgrass, and Miscanthus × giganteus was studied in the 2022 breeding season. At Brighton, Common Yellowthroat, Dickcissel, Grasshopper Sparrow, and Sedge Wren occurred on switchgrass plots more often than on corn; Common Yellowthroat and Dickcissel increased on experimental plots as the perennial switchgrass increased in height and density over the study period; and the other two species declined over the same period. At Urbana, Dickcissel was most frequent in prairie and switchgrass; Common Yellowthroat was most frequent in miscanthus and switchgrass. These findings suggest that advanced switchgrass cultivars could provide suitable habitats for grassland birds, replace lost habitats, and contribute to the recovery of these vulnerable species.