Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling
19 February 2020

Scale-Aware Analysis of Energy, Land, and Water Systems Dynamics: Nitrate Release Under Scenarios of Biomass Co-Firing in the Midwestern U.S.

Fine-scale modeling of interacting energy, land and water systems is necessary in order to capture the environmental implications of widespread biomass co-firing in the Midwestern United States.

Science

Challenges at the intersection of energy and food production, environmental impacts, natural resources, and critical infrastructures are increasingly crossing not only disciplinary boundaries, but involve interactions across policy domains and natural and economic systems that have historically been studied independently.  Growing out of several research communities, there is an increased focus on intersections such as energy-water-land and environmental and other coupled systems dynamics, giving rise to a new community in multi-sector dynamics.  As the importance of considering cross-system interactions increases, a methodological question that arises concerns the appropriate scale and scope of analysis. The majority of studies in this space employ one of two approaches: 1) a high-level model or integrated framework of models that resolve multiple systems but at relatively coarse scale, potentially with downscaled outcomes for key variables; or 2) a model or empirical analysis with a finer scale resolution focused on the primary system of interest. However, in some cases, it may be necessary to bridge these two approaches in order to capture the critical feedbacks across sub-systems. Understanding when this is required and when these feedbacks can be neglected remains an open research question in the literature that we explore in this paper using a fine-scale, gridded multi-sector dynamic framework. 

Impact

As scientists seek to better understand the linkages between energy, water, and land systems, they confront a critical question of scale for their analysis. Indeed, many researchers exploring this nexus of systems restrict themselves to a small area, such as a single watershed or an individual power plant, in order to ensure that they can accurately capture local processes. While such studies provide important scientific insights, if the impacts from governance/institutional interventions are extrapolated to a regional or national scale on the basis of unit-level analyses, the critical aggregate impacts on energy, land, and agricultural markets and systems may either be missed or overestimated. Indeed, this is the case with a hypothetical co-fire intervention considered in this paper. We find that forty-six percent of the coal-fired plants in the upper-MISO region stop generating electricity instead of co-firing biomass at the 15% level, and the capacity factor of other plants falls in many cases. Ignoring these interactions in the electricity market would have led to an overestimation of the demand for biomass in the neighborhood of these power plants. Furthermore, the impacts of additional total corn production, and additional nitrogen fertilizer use, on prices results in a reduction in corn production outside of the regions supplying biomass for co-firing power plants. These are impacts that would be missed altogether if we have undertaken the analysis solely at the level of individual power plants or watersheds, or restricted to only one domain such as the power system or agricultural markets. A separate strand of literature exploring the energy-water-land nexus takes a more aggregate view of the problem, restricting themselves to a coarser regional resolution in favor of offering national or even global coverage. Here, the risk is that the analysis will not be sufficiently refined to capture different local processes. If, for example, we have modeled the entire MISO region as a single electricity generating unit, we would have also missed the fact that some power plants will cease generation under the co-firing mandate scenario explored in this paper.  More serious is the fact that, by treating the entire region as one unit of analysis, we would have registered only a modest increase in nitrate releases (just 5% across the upper MISO region). This would have obscured the extremely large increases in leaching in particular regions. For example, in southern Illinois, in close proximity to the power plants along the Mississippi River, the increase in nitrate release reaches 60% over baseline. Furthermore, leaching is already a significant challenge in Illinois.  Averaging over the entire region obscures the potential environmental dynamics and effects.

Summary

As scientists seek to better understand the linkages between energy, water, and land systems, they confront a critical question of scale for their analysis. Many studies exploring this nexus restrict themselves to a small area in order to capture fine-scale processes, while other studies focus on interactions between energy, water, and land over broader domains but apply coarse resolution methods. Detailed studies of a narrow domain can be misleading if the intervention scenario under consideration is broad-based and has consequences for energy, land, and agricultural markets. Regional studies with aggregate low-resolution representations may miss critical feedbacks driven by the dynamic interactions between subsystems.  This study applies a novel, gridded energy-land-water modeling system to analyze the local environmental dynamics associated with scenarios of biomass co-firing of coal power plants across the upper MISO region. We use this framework to examine the impacts of a hypothetical biomass co-firing technology intervention of coal-fired power plants with corn residues. We find that this scenario has a significant impact on land allocation, fertilizer application, and nitrogen leaching. The effects also impact regions not involved in co-firing through agricultural markets. Further, some MISO coal-fired plants would cease generation because the competition for biomass increases the cost of the biomass and because the higher operating costs of plants that co-fire are no longer competitive with other generation sources. The factors that make some plants not economically viable are not captured by analyses undertaken at the level of an individual power plant. We also show that a region-wide analysis of this co-fire mandate would have registered only a modest increase in nitrate leaching (just +5% across the upper MISO region). This would have obscured the extremely large increases in leaching at particular locations -- as much as +60%. Many of these locations are already nitrate hotspots. Fine-scale analysis, nested within a broader framework, is necessary to capture these critical environmental interactions within the energy, land and water nexus. 

Contact
John Weyant
Stanford University
Publications
Sun, S, B Ordonez, M Webster, J Liu, C Kucharik, and T Hertel.  2020.  "Fine-Scale Analysis of the Energy–Land–Water Nexus: Nitrate Leaching Implications of Biomass Cofiring in the Midwestern United States."  Environmental Science & Technology 54(4): 2122-2132.  https://doi.org/10.1021/acs.est.9b07458.