Bioenergy sustainability

This is a joint report between three national labs, ORNL, INL, and ANL, that describes outcomes from a workshop. The Bioenergy Solutions to Gulf Hypoxia Workshop gathered stakeholders from industry, academia, national laboratories, and U.S. federal agencies to discuss how biomass feedstocks could help decrease nutrient loadings to the Gulf of Mexico (Gulf), a root cause of the large hypoxic zone that forms each summer. More broadly, workshop participants discussed the current state of environmental markets in the United States and the state of the science on nutrient management and monetization of the ecosystem services and environmental and social benefits derived from growing energy crops.

A diverse group of participants presented informative perspectives during five sessions: (1) Framing the Problem, (2) Technologies and Practices to Improve Nutrient Management, (3) Monetizing Ecosystem Services, (4) Strategies to Advance Progress, and (5) Research Gaps and Strategies. Multiple breakout discussions designed to elicit stakeholder inputs were interspersed within the presentations.

One approach to assessing progress towards sustainability makes use of multiple indicators spanning the
environmental, social, and economic dimensions of the system being studied. Diverse indicators have different
units of measurement, and normalization is the procedure employed to transform differing indicator
measures onto similar scales or to unit-free measures. Given the inherent complexity entailed in interpreting
information related to multiple indicators, normalization and aggregation of sustainability indicators
are common steps after indicator measures are quantified. However, it is often difficult for stakeholders
to make clear connections between specific indicator measurements and resulting aggregate scores of sustainability.
Motivated by challenges and examples in sustainability assessment, this paper explores various
normalization schemes including ratio normalization, target normalization, Z-score normalization, and unit
equivalence normalization. Methods for analyzing the impacts of normalization choice on aggregate scores
are presented. Techniques are derived for general application in studying composite indicators, and advantages
and drawbacks associated with different normalization schemes are discussed within the context of
sustainability assessment. Theoretical results are clarified through a case study using data from indicators
of progress towards bioenergy sustainability.

Water sustainability is an integral part of the environmental sustainability. Water use, water quality, and the demand on water resource for bioenergy production can have potential impacts to food, feed, and fiber production and to our social well-being. With the support from United State Department of Energy, Argonne National Laboratory is developing a life cycle water use assessment tool for biofuels production at the national scale with multiple spatial resolutions. This open-access web-based model – WATER (Water Assessment Tool for Energy Resources) – ties hydrologic cycle to energy production supply chain with a focus on feedstock production and biorefinery conversion stages. The model employs water footprint accounting to quantify the consumption of blue water, green water, and grey water in the fuel production at regional, state, and county resolution for the entire United States. Direct and indirect water uses are considered, which includes electricity generation and petroleum fuel and natural gas production. It is capable of simulating future climate scenarios. Currently, WATER includes biofuel produced from corn grain, corn stover, switchgrass, miscanthus, and soybean. The model is designed to allow for evaluation of production pathways at the region where the specific feedstock grown; for comparison of biorefinery locations based on water sustainability metric, and for analysis of the interplay of policy, feedstock, pathway, and location factors and the trade-offs among environmental, economic, and social impacts.

Excess nutrients from agriculture in the Mississippi River drainage, USA have degraded water quality in
freshwaters and contributed to anoxic conditions in downstream estuaries. Consequently, water quality is a
significant concern associated with conversion of lands to bioenergy production. This study focused on the
Arkansas-White-Red river basin (AWR), one of five major river basins draining to the Mississippi River. The
AWR has a strong precipitation gradient from east to west, and advanced cellulosic feedstocks are projected to
become economically feasible within normal-to-wet areas of the region. In this study, we used large-scale
watershed modeling to identify areas along this precipitation gradient with potential for improving water
quality. We compared simulated water quality in rivers draining projected future landscapes with and without
cellulosic bioenergy for two future years, 2022 and 2030 with an assumed farmgate price of $50 per dry ton.
Changes in simulated water quantity and quality under future bioenergy scenarios varied among subbasins and
years. Median water yield, nutrient loadings, and sediment yield decreased by 2030. Median concentrations of
nutrients also decreased, but suspended sediment, which is influenced by decreased flow and in-stream processes,
increased. Spatially, decreased loadings prevailed in the transitional ecotone between 97° and 100° longitude,
where switchgrass, Panicum virgatum L., is projected to compete against alternative crops and land uses at
$50 per dry ton. We conclude that this region contains areas that hold promise for sustainable bioenergy production
in terms of both economic feasibility and water quality protection.

There is an inextricable link between energy production and food/feed/fiber cultivation with available water resources. Currently in the United States, agriculture represents the largest sector of consumptivewater usemaking up 80.7%of the total. Electricity generation in the U.S. is projected to increase by 24 % in the next two decades and globally, the production of liquid transportation fuels are forecasted to triple over the next 25-years, having significant impacts on the import/export market and global economies. The tension between local water supply and demand across water use sectors needs to be evaluated with regards to risk evaluation and planning. To this end, we present a systematic method to spatially and temporally disaggregate nationally available 5-year county-scalewater use data to amonthly 1/8° scale.Our study suggests that while 81.9 % of the U.S. exhibits unstressed local conditions at the annual scale, 13.7 % is considered water scarce; this value increases to 17.3 % in the summer months. The use of mean annualwater scarcity at a coarser basin scale (~373,000 ha)was found to mask information critical for water planning whereas finer spatiotemporal scales revealed local areas that are water stressed or water scarce. Nationally, ~1%of these Bunstressed^ basins actually contained water stressed or water scarce areas equivalent to at least 30 % and 17 %, respectively, of the basin area. These percentages increase to 34 % and 48 % in the summer months. Additionally, 15 % of basins classified as "unstressed" contained water scarce areas in excess of 10 % during the summer.

A Workshop for Oak Ridge National Laboratory (ORNL), the US Environmental Protection Agency (EPA), and their collaborators was held on September 10-11, 2009 at ORNL. The informal workshop focused on “Sustainability of Bioenergy Systems: Cradle to Grave.” The topics covered included sustainability issues associated with feedstock production and transport, production of biofuels and by-products, and delivery and consumption by the end users. The workshop had two overall goals, to share information about their activities in this area and to identify immediate and long-term needs and opportunities for collaboration.  The workshop also created opportunities to present key issues of bioenergy sustainability and discuss work that is ongoing to address these issues; to develop a systems perspective on bioenergy sustainability
and to identify questions that lead toward a workable definition of bioenergy sustainability.

In order to aid operations that promote sustainability goals, researchers and stakeholders use sustainability assessments.  Although assessments take various forms, many utilize diverse sets of indicators numbering anywhere from two to over 2000. Indices, composite indicators, or aggregate values are used to simplify high dimensional and complex data sets and to clarify assessment results. Although the choice of aggregation function is a key component in the development of the assessment, there are fewliterature examples to guide appropriate
aggregation function selection. This paper applies the mathematical study of aggregation functions to sustainability assessment in order to aid in providing criteria for aggregation function selection. Relevant mathematical properties of aggregation functions are presented and interpreted. Cases of these properties and their relation to previous sustainability assessment research are provided. Examples show that mathematical aggregation properties can be used to address the topics of compensatory behavior and weak versus strong sustainability, aggregation of data under varying units of measurements, multiple site multiple indicator aggregation, and the determination of error bounds in aggregate output for normalized and non-normalized indicator measures.