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“Life-cycle assessment” is a term that has been “thrown around a lot,” Martin Heller said. But what exactly is it? In essence, LCA is a methodological framework for tracking the environmental impacts of producing a product, not just during manufacturing but also during the upstream extraction of raw materials, transportation throughout the life-cycle of the product, utilization (e.g., for a car, this would include tailpipe emissions), and disposal at the end of life. In the simplest terms, Heller thinks of it as an environmental accounting tool, one that tags all of these “cradle to grave” impacts together and provides an end result.

The international standards that have been developed to characterize LCA define it as the “compilation and evaluation of the inputs and outputs and the potential environmental impacts of a product system throughout its life cycle” (International Organization for Standardization, 2006, p. 2). The inputs include raw materials (e.g., metals, minerals, water, land) and energy. Outputs include what people normally think of when they think about environmental pollutants: emissions to air, emissions to water, and waste products. When conducting LCA, one also has to consider co-products from systems and their impacts. For example, the production of milk also produces meat as a co-product; thus, the upstream burdens associated with producing those two products need to be allocated between them.

Importantly, LCA is a relative assessment method, which means the end result is relative to some measure, ideally a measure of the function of the system. How that measure, or functional unit, is chosen has significant implications for the end result. The choice of a functional unit is especially important when comparing different systems that provide the same function. Another important feature of LCA to keep in mind, in Hellers's opinion, is that while International Organization for Standardization's standards for LCA have helped to make LCA more consistent from one study to the next, there is still no single method for conducting a LCA. Many of the methodological decisions made in LCA studies depend on the goal of the study and can impact results, meaning comparisons between studies must be done with caution. Also important to keep in mind is that gathering, interconnecting, and managing all of the inputs and outputs can be data-intensive and time-consuming.

The ultimate aim of LCA is to connect all of the inputs and outputs and quantify their environmental significance using impact assessment models. Typical LCAs consider impacts on energy use, global warming potential, eutrophication, acidification, tropospheric ozone, and human toxicity. Other impact categories important to food and agriculture that have been less stressed in typical LCAs include land and water use, biodiversity, and eco-toxicity. According to Heller, developing relevant and meaningful impact assessment models for some of these less-often-used categories is a cutting edge area of current LCA research.

LCA has many uses: identifying hot spots (i.e., places in a system where attention should be re-focused); identifying and evaluating unintended consequences (e.g., production of aluminum to reduce the weight of an automobile and reduce fuel consumption carries a significant environmental burden); identifying and avoiding burden shifting to other life-cycle stages, other environmental impacts, or other geographic regions; comparing alternative products that provide the same service or alternative scenarios within a particular production system; communicating impacts to consumers through standardized product footprints and quantifying Environmental Product Declarations; and informing public policy. LCA has become a large component of sustainable consumption policy in Europe, according to Heller. In the United States, the Environmental Protection Agency is using LCA to evaluate GHG emissions from renewable fuels under the Energy Independence and Security Act of 2007.

Regardless of its use, Heller reiterated the importance of keeping in mind that LCA is, ultimately, “just a tool.” It needs to be considered within its larger context.

Challenges and Future Work
Heller identified four major challenges for future food-related LCA work. First, from a life-cycle assessment perspective, finding the link between nutrition and the environment requires establishing an appropriate nutritional basis for a functional unit. Options include diet quality indexes (e.g., the Healthy Eating Index) and nutrient profiling schemes. Heller encouraged an interdisciplinary dialogue to help establish that functional unit.

Second, Heller made a call for more data, with respect to both availability and quality. The USDA census provides good agricultural production data, with the USDA LCA Digital Commons10 beginning to roll those data into a format that is more useful for LCA, but researchers need more region-specific data. With respect to environmental impact data, environmental impact categories need to be expanded beyond GHG emissions. Also needed is a consistent dataset of food LCA results.

Third, Heller urged consideration of the geospatial specificity of water use impact, land use impact, eutrophication, and other environmental impacts.

Finally, he called for improved ways to weight different environmental impact categories. Making a decision about environmental impact synergies and trade-offs ultimately becomes a value question: which environmental impact is more important? Improving valuation and weighting methods will be very helpful for interpreting future LCA work.