Citation:

Niblick, B., J. Bare, H. Golden, J. Compton, B. Morelli, T. Hawkins, AND A. Henderson. Challenges and Opportunities for Regional Nutrient Accounting in Life Cycle Assessment: Nutrient Fate & Transport Section. Presented at ACLCA: LCA XVIII, Fort Collins, Colorado, September 24 - 28, 2018.

Impact/Purpose:

Estimating the environmental impacts associated with nutrients, such as nitrogen and phosphorus, across the life cycle of a product, process, or service is an understudied and complex topic in life cycle assessment (LCA). The standard annual-average approach to LCA inventory flows does not account for the temporal and spatial shifts present in nutrient cycling. Models and tools complementary to LCA can assist (e.g., material flow analysis (MFA) or environmental fate and transport models). However, inconsistent model parameters and differing assumptions can lead to discrepancies between intermediate model outputs and final results. This 90-minute workshop session at the annual North American Life Cycle Assessment Conference (ACLCA) seeks to address these challenges. The session will be applicable to a diverse audience, including system modelers, nutrient experts, and members of government, academia, and industry. Upon successful completion of the session, participants will have a more comprehensive understanding of the status of nutrient modeling in LCA and renewed awareness for opportunities for growth. [Note: The slides attached will be used for the *Nutrient Fate and Transport* portion of the workshop. The other topic slides are being provided by workshop collaborators outside of EPA.]

Description:

Estimating the environmental impacts associated with nutrients across the life cycle of a product, process, or service is an understudied and complex topic in life cycle assessment (LCA). Nutrients, such as nitrogen and phosphorus, cycle through the environment and often exist in a state of imbalance, in large part due to anthropogenic inputs to the environment (e.g., from fertilizer applications or fossil fuel combustion) [1]. The standard annual-average approach to LCA inventory flows does not account for these temporal and spatial shifts in nutrient cycling. Nutrient use and associated environmental impacts (e.g., eutrophication of surface waters) present significant concerns for humanity. In fact, the National Academy of Engineers has identified management of the nitrogen cycle as one of the Grand Challenges for Engineering. Nutrient management necessitates a focus on the issue of fate and transport (F&T): nutrients released at one point in the supply chain can affect environmental quality in other places. Local and regional effects pose management challenges that require data and tools not yet broadly implemented in LCA practice. Life-cycle nutrient data are often aggregated, sometimes based on studies conducted only in Europe, and may assume certain physical geographic characteristics, e.g. soil type or slope. In contrast, site-specific studies can miss system-wide impacts from changes at larger scales. A comprehensive requires multiple tools applied at multiple spatial and temporal scales. Still, a lack of consistency between model parameters and assumptions can lead to discrepancies between intermediate outputs and final results. This session seeks to address these challenges. The 90-minute session will be divided into three 30-minute parts: 1. Roundtable discussion: Session co-hosts will discuss the challenges of modeling nutrient F&T and nutrient-related environmental impacts in LCA. 2. Audience share: What challenges and/or successes have audience members experienced when modeling nutrients in life-cycle systems? 3. Opportunity mapping: Audience and session co-hosts will collaborate to visually map nutrient models and methods to stated stakeholder needs, noting any gaps in knowledge and technology. The session will open with a panel discussion by academic and government researchers engaged in quantifying life-cycle impacts of nutrients using a variety of approaches. Methods to be discussed include LCA, materials flow analysis (MFA), and environmental F&T models. Each method serves a different purpose and has its own set of trade-offs. For example, MFA can provide national inventory estimates for systems-level insights, as demonstrated using the Net Anthropogenic Nitrogen Inputs (NANI) tool [2], whereas integrating hydrological and agricultural process models (e.g., Soil and Water Assessment Tool (SWAT) and the Agricultural Policy/Environmental eXtender model (APEX)) into process-based LCAs may help estimate regionalized impacts. Recent F&T research related to the Tool for Reduction and Assessment of Chemical and other environmental Impacts (TRACI) will highlight how site-specific and regional eutrophication estimates differ from nationally-derived values and how one might evaluate these differences. Building on this evaluative structure, session participants will collaborate to visually map (on paper or electronically) existing nutrient-related methods with stakeholder needs, noting any challenges to connecting stakeholders with decision analyses. Throughout the session, audience members will be encouraged to share perspectives from their own areas of expertise. The topic structure invites a diverse audience, including system modelers, nutrient experts, and members of government and industry.

Record Details: