Updating greenhouse gas emission estimates in the New Zealand-specific dietary life cycle-assessment (LCA) database

Background. Estimating environmental impacts has become an integral part of dietary assessments. These estimations rely on available life cycle assessment (LCA) data and databases of LCA information, which should be as recent and context specific as possible. Objectives. We aimed to update the existing New Zealand (NZ) dietary LCA database with recently available NZ data and provide documentation to streamline regular future updates. Following the update, we also aimed to investigate the impact of the updated database on emission estimates for dietary intakes in the population. Methods. A search was developed and conducted on November 18th, 2024. Recently published or identified LCA data for food items produced in NZ were integrated into the database. A comparison of the estimates of total greenhouse gas emissions due to dietary intake between the original database and updated database was conducted on existing NZ dietary intake data. Results and discussion. Updates in nine food items resulted in small net emissions decreases in fourteen food categories of the New Zealand Adult Nutrition Survey 2008/09. The estimate of average daily emissions due to dietary intake per adult in NZ decreased by approximately 1%, from 4.99 kgCO₂eq to 4.91 kgCO₂eq. This resulted in a decreased estimate of 350 tCO₂eq per day for the entire population. Small changes in LCA data can accumulate to substantial effects over the entire population; however, a 1% decrease in production emissions over 15 years shows that efficiencies in status quo patterns of food production alone are vastly inadequate to meet Paris obligations. More transformative changes will rapidly be needed.