A regionalized life cycle inventory model to account for human excretion of food products is presented, constituting an update of a previous model published by the author in 2008.
The updated model provides country-specific estimates on toilet activities (use of toilet paper, tap water, soap) and wastewater/excreta management, the latter addressing not only wastewater collection and treatment as done in developed countries, but also decentralized options such as septic tanks, latrines, and open defecation. The model currently supports inventories for 92 countries, linked to the ecoinvent database. The model is tested here with three products (banana, breadcrumbs, cheese) in five countries (Bangladesh, Denmark, Niger, Israel, USA), where the results for human excretion, per kg food ingested, are compared to food production in terms of global warming and aquatic eutrophication.
Results and discussion
The results show that besides a wide geographical variability, the environmental impacts of sanitation linked to food consumption have a higher magnitude than previously anticipated. In global warming, human excretion impacts can be of similar and even higher magnitude than food production, as far as products with a low carbon footprint are concerned, such as bananas. This relevance decreases for products with a higher carbon footprint such as cheese. Regarding aquatic eutrophication, the results suggest a potentially high relevance for human excretion in countries with poor sanitation, while the opposite holds true in countries with advanced treatment of wastewaters.
We stress the importance of including human excretion in LCA studies of food products, especially when the goal is to identify life cycle hotspots or to assess dietary shifts.
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Muñoz, I. Country-specific life cycle inventories for human excretion of food products. Int J Life Cycle Assess 26, 1794–1804 (2021). https://doi.org/10.1007/s11367-021-01961-7