An Integrated Landscape Designed for Commodity and Bioenergy Crops for a Tile-Drained Agricultural Watershed

Remote Sensing-Based Estimation of Advanced Perennial Grass Biomass Yields for Bioenergy

A sustainable bioeconomy would require growing high-yielding bioenergy crops on marginal agricultural areas with minimal inputs. To determine the cost competitiveness and environmental sustainability of such production systems, reliably estimating biomass yield is critical. However, because marginal areas are often small and spread across the landscape, yield estimation using traditional approaches is costly and time-consuming. This paper demonstrates the (1) initial investigation of optical remote sensing for predicting perennial bioenergy grass yields at harvest using a linear regression model with the green normalized difference vegetation index (GNDVI) derived from Sentinel-2 imagery and (2) evaluation of the model’s performance using data from five U.S. Midwest field sites. The linear regression model using midsummer GNDVI predicted yields at harvest with R2 as high as 0.879 and a mean absolute error and root mean squared error as low as 0.539 Mg/ha and 0.616 Mg/ha, respectively, except for the establishment year. Perennial bioenergy grass yields may be predicted 152 days before the harvest date on average, except for the establishment year. The green spectral band showed a greater contribution for predicting yields than the red band, which is indicative of increased chlorophyll content during the early growing season. Although additional testing is warranted, this study showed a great promise for a remote sensing approach for forecasting perennial bioenergy grass yields to support critical economic and logistical decisions of bioeconomy stakeholders.

Influence of shrub willow buffers strategically integrated in an Illinois corn-soybean field on soil health and microbial community composition

Soil serves many important ecological functions and is an integral part of our existence as a society. However, concerns for soil health are growing globally, in part due to the negative impacts of agricultural management on soil resources. The production of perennial bioenergy crops on marginal land in row-crop production systems is one solution that could improve land-use efficiency and address the sustainability of cropland management. Because the relationship between crop management and the environment is complex, more research is needed to evaluate the potential benefits perennial bioenergy crop production has on soil health, as well as other ecosystem services. In this study, shrub willow buffers were strategically integrated into a corn-soybean cropping system with the main objective of reducing nitrate-N leaching from grain crop production while producing biomass for bioenergy. Two buffer systems (defined by landscape positions) were included for comparison, one on marginal land with exposure to nitrate-N leaching from upslope grain (southern plots) and one on fertile soils with less nitrate-N leaching potential (northern plots). Evaluation of soil (chemistry, bulk density, microbial community) and shrub willow vegetation properties (fine roots, leaf litter decomposition, and nutrient uptake dynamics), showed that landscape position plays an important role in (1) the dynamics of soil chemical properties, (2) shrub willow's influence and productivity, and (3) the provision of additional ecosystem services such as reductions in nitrous oxide emissions and nitrate-N leaching. In addition, the combination of crop type and landscape position (N-grain, N-willow, S-grain, and S-willow) influenced the species composition of the soil microbial community, resulting in unique and identifiable communities. These results highlight the potential application of shrub willow buffers for ecosystem service provision and support of ecosystem processes; however, understanding the relationship between the microbial community, crop type, and landscape is important for understanding the sustainability of the design.

Performance-Based Payments for Soil Carbon Sequestration Can Enable a Low-Carbon Bioeconomy

Incentivizing bioenergy crop production in locations with marginal soils, where low-input perennial crops can provide net carbon sequestration and economic benefits, will be crucial to building a successful bioeconomy. We developed an integrated assessment framework to compare switchgrass cultivation with corn-soybean rotations on the basis of production costs, revenues, and soil organic carbon (SOC) sequestration at a 100 m spatial resolution. We calculated profits (or losses) when marginal lands are converted from a corn-soy rotation to switchgrass across a range of farm gate biomass prices and payments for SOC sequestration in the State of Illinois, United States. The annual net SOC sequestration and switchgrass yields are estimated to range from 0.1 to 0.4 Mg ha^-1 and 7.3 to 15.5 Mg dry matter ha^-1, respectively, across the state. Without payments for SOC sequestration, only a small fraction of marginal corn-soybean land would achieve a 20% profit margin if converted to switchgrass, but $40-80 Mg^-1 CO₂e compensation could increase the economically viable area by 140-414%. With the compensation, switchgrass cultivation for 10 years on 1.6 million ha of marginal land in Illinois will produce biomass worth $1.6-2.9 billion (0.95-1.8 million Mg dry biomass) and mitigate 5-22 million Mg CO₂e.

Biofuel and bioproduct environmental sustainability analysis

Life cycle analysis (LCA) is a key tool in the evaluation of biofuel and bioproduct sustainability. Recent advances in these analyses include increased incorporation of spatially explicit elements of feedstock growth including changes in soil carbon and fertilization rates. Furthermore, new evaluations of processes to convert biomass to fuels (ethanol, algal-derived fuels, jet fuels, and others) and products have been conducted that examine emerging conversion technologies. Co-product allocation among co-produced biofuels and bioproducts continues to raise LCA methodological challenges; approaches to allocation can drive LCA results. Given the variations in feedstocks, spatially explicit factors, conversion process design, and LCA methodological choices (e.g. co-product allocation), transparency in reporting biofuel LCA methodology and results is critical to enable cross-comparison of studies.

Yield and Water Quality Impacts of Field-Scale Integration of Willow into a Continuous Corn Rotation System

Agricultural landscape design has gained recognition by the international environmental and development community as a strategy to address multiple goals in land, water, and ecosystem service management; however, field research is needed to quantify impacts on specific local environments. The production of bioenergy crops in specific landscape positions within a grain-crop field can serve the dual purpose of producing cellulosic biomass (nutrient recovery) while also providing regulating ecosystem services to improve water quality (nutrient reduction). The effectiveness of such a landscape design was evaluated by the strategic placement of a 0.8-ha short-rotation shrub willow ( Seemen) bioenergy buffer along marginal soils in a 6.5-ha corn ( L.) field in a 6-yr field study in central Illinois. The impact of willow integration on water quality (soil water, shallow groundwater leaching, and crop nutrient uptake) and quantity (soil moisture and transpiration) was monitored in comparison with corn in the willow's first cycle of growth. Willows significantly reduced nitrate leachate in shallow subsurface water by 88% while maintaining adequate nutrient and water usage. Results suggest that willows offer an efficient nutrient-reduction strategy and may provide additional ecosystem services and benefits, including enhanced soil health. However, low values for calculated willow biomass will need to be readdressed in the future as harvest data become available to understand contributing factors that affected productivity beyond nutrient availability.