Selecting Metrics for Sustainable Bioenergy Feedstocks
- ORNL
Key decisions about land-use practices and dynamics in biofuel systems affect the long-term sustainability of biofuels. Choices about what crops are grown and how are they planted, fertilized, and harvested determine the effects of biofuels on native plant diversity, competition with food crops, and water and air quality. Those decisions also affect economic viability since the distance that biofuels must be transported has a large effect on the market cost of biofuels. The components of a landscape approach include environmental and socioeconomic conditions and the bioenergy features [type of fuel, plants species, management practices (e.g., fertilizer and pesticide applications), type and location of production facilities] and ecological and biogeochemical feedbacks. Significantly, while water (availability and quality) emerges as one of the most limiting factors to sustainability of bioenergy feedstocks, the linkage between water and bioenergy choices for land use and management on medium and large scales is poorly quantified. Metrics that quantify environmental and socioeconomic changes in land use and landscape dynamics provide a way to measure and communicate the influence of alternative bioenergy choices on water quality and other components of the environment. Cultivation of switchgrass could have both positive and negative environmental effects, depending on where it is planted and what vegetation it replaces. Among the most important environmental effects are changes in the flow regimes of streams (peak storm flows, base flows during the growing season) and changes in stream water quality (sediment, nutrients, and pesticides). Unfortunately, there have been few controlled studies that provide sufficient data to evaluate the hydrological and water quality impacts of conversion to switchgrass. In particular, there is a need for experimental studies that use the small watershed approach to evaluate the effects of growing a perennial plant as a biomass crop. Small watershed studies have been used for several decades to identify effects of vegetation type, disturbance, and land use and agriculture practices on hydrology and water quality. An ideal experimental design to determine the effects of conversion to switchgrass on surface water hydrology and quality would involve (1) small catchment (5-20 ha) drained by a perennial or ephemeral stream, (2) crop treatments including conversion from row crops to switchgrass; pasture to switchgrass (other likely scenarios); controls (no change in vegetation), (3) treatments to compare different levels of fertilization and pesticide application, (4) riparian treatments to compare riparian buffers with alternative cover types, and a treatment with no buffer, and (5) 3-4 replicates of each treatment or BACI (before-after, control-intervention) design for unreplicated treatments (ideally with several years of measurements prior to the imposition of treatments for BACI design). Hydrologic measurements would include soil moisture patterns with depth and over time; nitrogen and phosphorus chemistry; soil solution chemistry - major anions and cations, inorganic and organic forms of carbon, nitrogen and phosphorus; precipitation amount and chemical deposition; stream discharge; and streamwater chemistry. These water quality metrics would need to be put into context of the other environmental and social conditions that are altered by growth of bioenergy feedstocks. These conditions include farm profits and yield of food and fuel, carbon storage and release, and a variety of ecosystem services such as enhanced biodiversity and pollinator services. Innovations in landscape design for bioenergy feedstocks take into account environmental and socioeconomic dynamics and consequences with consideration of alternative bioenergy regimes and policies. The ideal design would be scale-sensitive so that economic, social, and environmental constraints can be measured via metrics applicable at relevant scales. To develop a landscape design, land managers must consider (1) what are the environmental impacts on water and air quality, carbon sequestration, and native plants and animals and their habitats; (2) what is the appropriate spatial and temporal scales at which to examine environmental effects, and (3) how can potential tradeoffs in environmental costs and benefits be considered. Tradeoffs exist across space and time among the economic, ecological, and social consequences of alternative choices. For example, the implications of increased biofuel production from corn at a local scale may be to increase pesticide use, which could negatively affect human health. At a regional scale, nutrient flux may increase and thus degrade water quality. At the scale of the Mississippi River watershed (48% of the U.S.), production may increase the hypoxia zone in the Gulf of Mexico and cause decline of shrimp harvest in the region.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Laboratory Directed Research and Development (LDRD) Program
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 963386
- Resource Relation:
- Conference: China-US Joint Research for Ecosystem and Environmental, Beijing, China, China, 20081015, 20081017
- Country of Publication:
- United States
- Language:
- English
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