Sustainability

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GLBRC's Sustainability Research Area

Sustainability

Focusing on one attribute comes at a high price.

At the GLBRC, sustainability researchers are exploring complex issues in agricultural and industrial systems. Research focuses on understanding the attributes and mechanisms responsible for the environmental sustainability of biofuel production systems, such as environmental impacts — many of which may be positive — and socioeconomic factors including incentives and policy options

Learn about the Center's research approach

Sustainability Leadership

Scientific Director, Sustainability Lead

A crop and soil scientist and ecosystem ecologist, Robertson focuses much of his research on the role that agriculture plays in greenhouse gas dynamics, and he is internationally known for his expertise in this area. Robertson has been the director...

Sustainability Lead

Jackson’s program focuses on structure and function of managed, semi-natural and natural grassland ecosystems. Research in Jackson’s grassland ecology lab spans many levels of ecological organization, from grass identification at the DNA level to landscape diversity effects on alternative biofuels...

Project Overview

A device used for measuring plant utilization of solar radiation sits in front of plots of switchgrass, corn and poplar growing in the Great Lake Bioenergy Research Center's fields at the Arlington Agricultural Research Station in Arlington, WI.GLBRC Sustainability research ranges from the microbial community level to regional modeling, and researchers conduct fieldwork at different project sites to reflect this diversity of scale. Small plots at Kellogg Biological Station in Michigan and the Arlington Agricultural Research Station in Wisconsin provide locations for measurement-intensive experiments, while investigators work in larger scale-up fields to collect data on carbon balances and biogeochemical processes. Finally, researchers pursue ecosystem-level biodiversity questions across landscapes, including marginal lands, in central Michigan and Wisconsin.

Specific sustainability projects include:

  • Novel biofuel production systems
  • Microbial-plant interactions for improved biofuel production
  • Biogeochemical responses
  • Biodiversity responses
  • Economic responses
  • Modeling, design and testing of drop-in fuels
  • Process synthesis and technoeconomic evaluation for biomass-to-fuels technologies.

 

Sustainability Publications

A reassessment of the contribution of soybean biological nitrogen fixation to reactive N in the environment

Ilya Gelfand; Philip Robertson

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2015

The expansion of soybean (Glycine max (L.) Merr) acreage, increasing yields, and recent nitrogen (N) fertilization recommendations could have a major effect on the contribution of biological N fixation (BNF) in soybeans to reactive nitrogen (Nr) in the environment. We used 15N natural abundance to separate fixed N into grain, aboveground vegetative biomass, and roots along a 9-point N-fertilizer gradient to ask: 1) is the belowground BNF contribution sufficiently different from aboveground to affect regional estimates of soybean Nr production based on harvested biomass, and 2) how does N fertilizer affect soybean yield and BNF’s contribution to different tissues? The contribution of root and vegetative biomass to overall plant BNF was five times lower than that for grain. Including this difference in BNF extrapolations translates to 3.5 ± 0.5 Tg Nr yr-1 for total US soybean production, *37 % lower than earlier estimates that did not differentiate tissue source. Production of Nr ranged between 35 ± 11 and 73 ± 5 g Nr kg-1 grain and was affected by both fertilization and irrigation. In all cases N credits to the next rotational crop were minor. N-fertilization at even very low levels (17–50 kg N ha-1) did not affect yield, but grain N content increased with fertilizer level. The percent BNF contributed to plant N decreased linearly with increasing fertilization, in grain from 49 ± 8 % in unfertilized plots to a plateau of 16 ± 6 % at fertilization C85 kg N ha-1; in aboveground vegetative biomass from 77 ± 4 % to aplateauof11 ± 11 %at146 kg Nha-1;andinroots from 88±12% to a plateau of 41±6% at 146 kg N ha-1. The average whole-plant BNF con- tribution decreased from *84 % in unfertilized plots to a plateau of *34 % at fertilization rates greater than 84 kg ha-1. Results underscore the unnecessary expense and environmental burden of adding N fertilizer to modern soybean varieties, and provide a refined lower estimate for the contribution of soybean N fixation to the US and global Nr budgets of 3.5 and 10.4 Tg Nr yr-1, respectively.

Active site and laminarin binding in glycoside hydrolase family 55

Christopher M. Bianchetti; Taichi E. Takasuka; Sam Deutsch; Hannah S. Udell; Eric J. Yik; Lai F. Bergeman; Brian G. Fox

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2015

The Carbohydrate Active Enzyme (CaZY) database indicates that glycoside hydrolase family 55 (GH55) contains both endo- and exo-beta -1,3-glucanases. The founding structure of the GH55 is PcLam55A from the white-rot fungus Phanaerochaete chrysosporium (Ishida, T., et al. (2009) J. Biol. Chem. 284, 10100-10109). Here, we present high resolution crystal structures of bacterial SacteLam55A from the highly cellulolytic Streptomyces sp. SirexAA-E with bound substrates and product. These structures, along with mutagenesis and kinetic studies implicate Glu502 as the catalytic acid (as proposed earlier for Glu663 in PcLam55A) and a proton relay network of four residues in activating water as the nucleophile. Further, a set of conserved aromatic residues that define the active site apparently enforce an exo-glucanase reactivity as demonstrated by exhaustive hydrolysis reactions with purified laminarioligosaccharides. Two additional aromatic residues that line the substrate-binding channel show substrate-dependent conformational flexibility that may promote processive reactivity of the bound oligosaccharide in the bacterial enzymes. Gene synthesis carried out on ~30% of the GH55 family gave 34 active enzymes (19% functional coverage of the non-redundant members of GH55). These active enzymes reacted with only laminarin from a panel of 10 different soluble and insoluble polysaccharides and displayed a broad range of specific activities, and optima for pH and temperature. Application of this experimental method provides a new, systematic way to annotate GH phylogenetic space for functional properties.

All biomass is local: the cost, volume produced, and global warming impact of cellulosic biofuels depend strongly on logistics and local conditions

Seungdo Kim; Bruce E. Dale

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2015

Current models of cellulosic biofuel systems require that the delivered price of the cellulosic biomass feedstock be kept low. Thus the predicted biorefinery size is relatively small, limiting potential economies of scale. However, it is actually the ultimate selling price of the biofuel that largely determines market penetration. We relaxed the constraint of low delivered feedstock price and explored the resulting effects on biofuel price, biofuel volume produced, and global warming impact (GWI). Feedstock price greatly affects the feedstock supply chains that may develop. Increased feedstock price does not affect the final ethanol selling price very much, but higher feedstock prices greatly increase the amount of ethanol produced. Farmers will supply much more cellulosic biomass at higher feedstock prices, leading to shorter transportation distances with reduced transportation costs and enabling larger biorefineries with improved economies of scale, thereby reducing the ethanol selling price. The cellulosic feedstock supply chain systems were studied as a function of feedstock prices by determining potential feedstock supply clusters and the maximum capacity of cellulosic biorefineries across the United States. Supply clusters were determined by minimizing costs associated with ethanol production. The analysis is based on county-level cellulosic feedstock production data projected in the US Billion-Ton Update report. Each biomass supply cluster is unique in terms of local and regional characteristics (e.g. area, feedstock types), biorefinery capacity, ethanol selling price, and GWI. Very large-scale biorefineries (≥20 000 dry Mg day−1) may be feasible in some regions. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Bioenergy supply and environmental impacts on cropland: insights from multi-market forecasts in a Great Lakes subregional bioeconomic model

Aklesso Egbendewe-Mondzozo; Scott M. Swinton; Shujiang Kang; Wilfred M. Post; Julian C. Binfield; Wyatt Thompson

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2015

Using subregional models of crop production choices in central Wisconsin and southwest Michigan, we predict biomass production, land use, and environmental impacts with details that are unavailable from national scale models. When biomass prices are raised exogenously, we find that the subregional models overestimate the supply, the land use, and the beneficial environmental aspects of perennial biomass crops. Multi-market price feedbacks tied to realistic policy parameters predict high threshold absolute prices for biomass to enter production and less environmental benefice from perennial biomass crops production. Also, regional specialization of biomass production in areas with lower food crop yields is observed.

Biomass potential of switchgrass and miscanthus on the USA’s marginal lands

Varaprasad Bandaru; César Izaurralde; Kaiguang Zhao

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2015

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