Greenhouse gas emissions Archives

Tengiliður

Guðrún Svana Hilmarsdóttir

Sérfræðingur

gudrun.svana@matis.is

Understanding and reducing the greenhouse gas emissions of bottom trawl fisheries is of importance, as it directly impacts efforts to mitigate climate change and promotes sustainable fishing practices. As a considerable part of global landings is fished using demersal trawls and vessel renewal is often mentioned as an important mitigation measure. This study compares the greenhouse gas emissions of older and newer trawlers in the Icelandic fleet, using Life Cycle Assessment methodology with the functional unit “1 kg of demersally trawled fish at landing”. The global warming potential (kg CO2-eq) from older Icelandic bottom trawlers was assessed and compared to the newer ones, where older vessels were in some cases being decommissioned. A total of 11 trawlers were assessed, providing a cross section of the Icelandic bottom trawler fleet, with respect to age, size, catch composition and onboard operations. The results show that freezer trawling was more energy-intensive compared to trawlers landing their catches chilled/superchilled. Fleet renewal alone does not explain the reduction in fuel use and greenhouse gas emissions in the Icelandic bottom trawl fleet between 2012 and 2022, highlighting the need for a comprehensive approach considering multiple factors such as catch composition, fishing ground, and vessel characteristics, which explained 87% of the emissions. Catching indicated increased fuel consumption compared to steaming. The greenhouse gas emissions allocated to each demersal fish species ranged on average from 0.5 to 1.0 kg CO2-eq/kg of the weight of demersal fish landed, and from 1.4 to 2.7 kg CO2-eq/kg of the edible part of demersal fish landed (mass allocation), where redfish stood out as having the highest emissions.

Abstract

Background

Health authorities are increasingly integrating environmental sustainability considerations into food-based dietary guidelines. However, concerns persist about the accuracy of the data used to assess environmental impacts, as well as the extent to which these guidelines are followed in practice.

Aim

To compare dietary greenhouse gas (GHG) emissions estimates using different top-down and bottom-up life cycle assessment (LCA) databases; and to estimate GHG emissions of food consumption within the ranges set for meat and dairy in recently proposed environmentally sustainable diets.

Methods

Dietary GHG emissions were estimated for participants in the 2019–2021 Icelandic National Dietary Survey (n = 822) using three publicly available LCA databases from Denmark, the US, and France. GHG emissions among participants whose consumption was aligned with the EAT-Lancet diet, the 2021 Danish food-based dietary guidelines and the 2023 Nordic Nutrition Recommendations were also quantified.

Results

The mean dietary GHG emissions among participants were 6.3, 6.1, and 6.1 kg CO₂-eq/day based on the Danish (top-down), US (bottom-up), and French (bottom-up) databases, respectively. The relative ranking of foods was also consistent across all three databases. For example, the relative contribution of total CO₂-eq (% range for the three databases) was highest for red meat (39–51%), followed by dairy (10–17%) and beverages (9–13%). The contribution from plant-based foods (6–10%), seafood (4–11%), and poultry/eggs (<5%) was modest. The dietary habits of most participants (86%) were outside the ranges for meat and dairy consumption as set by the three sustainable diets. However, participants reporting consumption within the ranges for meat and dairy had mean GHG emissions ranging between 4.2 and 4.7 kg CO₂-eq/day, depending on the diet. In comparison, the mean for participants not adhering to the sustainable diets was 7.7 kg CO₂-eq/day. These results are higher than those reported in other Nordic and European studies, likely due to high consumption of lamb, beef, and dairy, and low consumption of plant-based food.

Conclusion

All three LCA databases provided similar estimates for total dietary GHG emissions and relative ranking of different food groups. Based on current dietary habits in Iceland, adherence to environmentally sustainable diets would lead to a substantial reduction in dietary GHG emissions.