Life Cycle Assessments - An Example
Kim et al. (2020) published a paper on a life cycle assessment (LCA) of dietary patterns in the United States.
The authors took into account the major energy and resource inputs at different stages of the supply chain as well as the arising food loss and waste for different dietary scenarios.
Besides the inputs required for primary production, this calculation also included:
- Electricity for store operations and refrigeration, loss of refrigerants due to leakage, natural gas consumption and water usage at the retail stage;
- Transportation for shopping trips, refrigeration, food preparation, dishwashing (incl. use of detergents) and waste treatment on the consumer level; and
- Post-consumer waste treatment, including packaging waste.
The environmental impact of the current average diet in America, which corresponds to a daily energy intake of 2547 kcal in average, was compared to a healthier dietary pattern recommended by the United States Department of Agriculture (USDA), which corresponds to a daily energy intake of 2000 kcal and consists of less added sugar, fat and (red) meat.
The major outcome of the study was that adopting the recommended dietary pattern might actually increase the extent of greenhouse gas emission by approx. 10 % due to a greater production and consumption of fruits and vegetables, juices, dairy products, fish and seafood as well as greater post-harvest losses and consumer-related food waste. However, a modification of the USDA recommended dietary pattern in a way that (red) meat, poultry as well as fish and seafood products were completely avoided resulted in a decrease of greenhouse gas emissions by approx. 20% compared to the current dietary pattern.
Similar trends were also reported for other environmental impact categories, such as ozone depletion, eutrophication, ecotoxicity and fossil fuel depletion. These results demonstrate the implementation of dietary shifts needs to consider as well possible impacts on the environment; otherwise, the positive intentions of a healthier diet might be counteracted by greater environmental impacts.
The study further concluded that food losses and wastes are a significant contributor to greenhouse gas emissions, with the largest part of avoidable food waste being caused on the retailer and consumer level. However, an increased efficiency in the primary production, reached by technological progress, is as important to reduce food waste as behavioral changes of the consumers.
The article moreover provides a good overview on the simplifications and limitations that many LCA studies are suffering from. The most prominent one might be the selection of the system boundaries, e.g., a restriction to food production and distribution without taking into account the consumer level. The consideration of the entire food supply chain, however, may require sophisticated hybrid models, which increase the complexity of the analysis. In the same way, studies focusing solely on the estimation of greenhouse gas emissions may greatly overlook other environmental impacts such as water consumption, depletion of resources and loss of biodiversity that are related to today’s food production as well. Finally, the datasets that are used for modelling are another significant factor affecting the outcome of LCA studies. Since datasets from different resources may not be consistent among each other, depending on the criteria for data collection and grouping, researchers have to compromise when choosing data from one or another source. For these reasons, LCA studies are typically accompanied by analyses of uncertainty (reliability of data) and sensitivity (price variations) as well as a discussion of the study limitations.
In the future, LCA studies will also need to be shifted from “cradle to grave” models towards “cradle to cradle” approaches, which will play a major role in developing a more sustainable food system.
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