In this blog, I will look at three academic studies using Life Cycle Assessment (LCA) data to evaluate if switching to a vegan diet is better for the environment. I will also investigate individual products to gain a better understanding of the specific environmental problems associated with different foods.
A study on UK dietary habits found that converting from a vegetarian to a vegan diet would reduce greenhouse emissions by an average of 0.92 kg CO2/person/day. Errors arise in estimations of greenhouse gas (GHG) emissions because obtaining accurate information of food consumption is difficult, LCAs are not 100% accurate and their use as proxies for specific supply chains introduces uncertainties. However, errors do not systematically vary across food categories, therefore this analysis allows accurate comparison.
Another study comparing the three diets also found that vegan diets have the smallest environmental impact, based on resource use and ecosystem quality. For each diet, LCA data was used to calculate the environmental impact, expressed in points (figure 1).
In contrast, a more recent study found that omnivorous diets produced worse carbon, water and ecological footprints than the vegetarian and vegan diets, but no significant environmental differences were found between the latter two (figure 2).
Furthermore, through principal component analysis, this study also noted a high level of inter-individual variability, whereby some vegan diets had higher environmental impacts than that of some omnivores. We must look at individual dietary habits rather than looking at the benefits of plant-based diets generally. Therefore, I am going to explore the environmental impacts of individual food products next by looking at GHG emissions, land use, freshwater use and eutrophication.
GHG Emissions
If you want to reduce the carbon footprint of your food, it is better to focus on what you eat not where your food comes from. In contrast to popular belief, eating locally does not substantially impact your carbon footprint because most GHGs emissions from food come from land-use change and farm processes – whereas only 6% of emissions come from transport. Air-freighted food can emit 50 times more CO2eq per tonne-km than boat, but it only accounts for 0.16% of food miles so is not a major cause for concern. The interactive graph below highlights the carbon footprint of different foods.
Figure 3: GHG emissions per 100g of protein
Land use
As mentioned a couple of blogs ago, agriculture is the single largest land use and is a leading cause of biodiversity loss. The graph below shows the land use needed to produce different foods.
Figure 4: Land use per 100g of protein
Freshwater Use
Freshwater scarcity varies across the world, therefore agricultural water demands have less impact in regions with abundant water (more on this next week). Therefore, the following graph showing the water footprint of different foods is weighted by local water scarcity.
Eutrophication
Eutrophication is the excessive richness of nutrients in water, which promotes algae growth and eventually leads to the formation of dead zones. Nitrogen and phosphorus from fertiliser run-off is a leading cause.
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