The development of alternatives to animal-sourced foods has increased during the past few decades as a response to the negative environmental impacts of livestock production. These alternatives include foods that are produced by the industrial-scale culture of animal, plant and microbial cells. Studies have shown that, per unit of mass, cell-cultured foods can have a lower environmental footprint than that of proteins from livestock1, but comparisons of global-level assessments have been lacking. Writing in Nature, Humpenöder et al.2 report the first global analysis of the environmental benefits that could be achieved by substituting beef with mycoprotein from cell culture.
Cell-cultured foods are produced by cultivating cells in bioreactors — usually, steel tanks — containing nutrients and other factors needed for cell growth. The cultivated cells can be used either directly as food or to synthesize substances (such as proteins or fatty acids) that make up food ingredients3. Most cell types source their carbon from glucose, which is generally obtained from agricultural crops, although some microbial cells can obtain carbon from methane or carbon dioxide4. Cropland is therefore required to produce feedstocks for most cell-cultured foods.
Humpenöder et al. investigated the environmental impacts of replacing beef with mycoprotein5. Many cell-cultured food products are still in development, but mycoprotein-based products are already widely available in supermarkets in many countries. Mycoprotein is an ideal substitute for meat because it is rich in protein and contains all the essential amino acids that humans obtain from nutrition. The products are textured and shaped to resemble common meat products, including processed foods (such as sausages and burger patties) and ingredients for cooking (such as minced beef or chicken breast).
The authors modelled the changes in land use, greenhouse-gas emissions, water use and nitrogen fixation (the biological process by which nitrogen gas is converted into compounds that can be used as nutrients by other organisms) that would result from replacing 20%, 50% and 80% of global beef consumption with mycoprotein. They used a ‘middle of the road’ socio-economic scenario as a baseline for estimates of the increases in population, income and livestock demand between 2020 and 2050. Their assessment of the environmental impact of mycoprotein culture considered the cultivation of sugar cane as a source of glucose, but ignored the effects of producing other nutrients and the energy required for the cell-culturing processes. In effect, the study therefore simply compared the land-use impacts of beef and sugar-cane production. The estimated quantity of sugar cane produced was based on the glucose requirements of culturing an amount of mycoprotein equivalent to that of the beef protein being replaced.
The modelling shows that the increase in beef consumption in the baseline scenario would require expansion of global pasture and cropland areas, causing a doubling of the annual deforestation rate between 2020 and 2050. Substituting 20% of beef consumption with mycoprotein halves the annual deforestation rate (Fig. 1). Over the same period, the scenarios assuming 50% and 80% substitution levels result in a decline in global pasture area and substantial reductions in annual deforestation rates.
The relationship between the percentage of beef substitution and the annual deforestation rates in 2050 is nonlinear. Because the pasture area required in 2050 at the two highest substitution levels is lower than that in 2020, there is no need to clear forest for beef production in these scenarios, and some of the land that was once used for pasture can be converted to cropland. Moreover, in all of the substitution scenarios, the annual deforestation rates decline during the first 15–20 years and increase afterwards. This can be explained by structural changes in agriculture that occur over time, such as changes in agricultural yields and in the level of land degradation. Compared with the baseline scenario, all substitution levels resulted in large reductions in greenhouse-gas emissions from livestock production and land-use changes, but only minor changes in agricultural water use and nitrogen fixation.
Studies known as product-level assessments have previously estimated the environmental impacts of cell-cultured foods, per unit produced. Humpenöder and colleagues’ study is a first step towards assessing how production affects specific types of land use and associated greenhouse-gas emissions over time. However, the study does not provide a complete picture of the environmental consequences of the transition from beef to cell-cultured foods. That’s because its scope is limited to impacts associated with land use, and it does not consider all the ingredients and other resources needed for mycoprotein production.
Future research should expand the scope of the current study by considering the environmental impacts of other factors involved in food production. For example, product-level assessments have shown that producing cell-cultured food can require more electricity than does raising livestock1. The environmental impacts of energy generation therefore need to be considered, taking into account future capacity to expand sustainable electricity supplies. Glucose sources other than sugar cane should also be assessed; these could include crops such as sugar beet or grains that can be cultivated in boreal regions, as well as by-products from the production of other types of food or animal feed6.
It should be noted that Humpenöder and colleagues’ modelling is likely to overestimate the impacts of beef production and underestimate those of culturing mycoproteins. Beef production provides many by-products, such as milk, hides for leather production and fat for the chemical industry. If beef production were reduced, the by-products would need to be made in alternative ways, which would increase environmental impacts. Furthermore, large reductions in beef consumption would require a parallel reduction in the consumption of dairy products, at least in regions where most beef originates from dairy systems7.
Further research into the environmental consequences of producing cell-cultured foods should include a wider range of products. These could include proteins produced by microorganisms that use CO2 or methane as a carbon source4; milk and egg proteins produced by microbial cells8; and cultured meat made of animal cells1. The estimates of the environmental impacts would be improved by using scenarios that consider the availability and realistic adoption rates of cell-cultured foods in different socio-economic contexts. Global assessments will also be needed to find ways of making food systems more sustainable through innovative technologies combined with dietary changes, sustainable agricultural practices and reduced food waste.