Microbial protein as substitute for ruminant meat

The production of ruminant meat has strong environmental impacts, especially related to land use. Microbial protein, produced in bioreactors, is a land-saving nutritious alternative. We analyzed the environmental effects of microbial protein in the context of the whole agriculture and food system by 2050.
Published in Sustainability

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The food system is at the root of a third of global greenhouse gas emissions (GHG)especially from ruminant meat production. That is because more and more forests that store a lot of carbon are cleared for cattle grazing or growing its feed. Today, almost 80% of global agricultural land including cropland and pasture is used for feeding livestock. Furthermore, animal agriculture causes considerable amounts of methane (CH4) and nitrous oxide (N2O) emissions.

Part of the solution to this problem could be existing biotechnology: Nutritious protein-rich biomass with meat-like texture produced via fungal fermentation in bioreactors, what scientists call microbial protein. Microbial protein is different from cultured meat, where animals cells are grown in a petri dish. Cultured meat recently got a lot of public attention. However, this biotechnology is still in an early development stage with many unknowns, particularly with respect to composition and costs of the growth medium. In contrast, microbial protein is commercially available today in grocery stores, for example in the UK or in Switzerland (Quorn). 

Life Cycle Assessment (LCA) studies have estimated considerable lower land use and GHG emissions  of microbial protein, produced in bioreactors using sugar as feedstock, compared to ruminant meat. LCA is a very useful tool to make the environmental impacts of different products comparable to each other. However, LCA factors are usually based on the footprint of current production systems and do not account for future changes in population, income, dietary patterns and technology. Moreover, owing to non-linear effects in the land use system such static factors cannot be used to scale up the effects of replacing ruminant meat with microbial protein in the context of the whole food and agricultural system globally.

microbial protein (left) and minced red meat (right).  Picture credits: Tomas Linder

Our team of researchers from Germany and Sweden included microbial protein in a dynamic land-use modelling framework (MAgPIE) to analyze the environmental effects of substituting ruminant meat in the context of the whole agriculture and food system. Our forward-looking scenarios run until 2050 and account for future population growth, food demand, dietary patterns as well as dynamics in land use and agriculture. 

In our recently published paper in Nature, we found that the substitution of 20 per cent of per-capita ruminant meat consumption with microbial protein globally by 2050 (MP20) would cut annual deforestation and related CO2 emissions roughly in half as it would offset projected future increases of global pasture area compared to a reference scenario without microbial protein. The reduced numbers of cattle do not only reduce the pressure on forests and other ecosystems but also reduce methane emissions from the rumen of cattle and nitrous oxide emissions from fertilizing feed or from manure management. Our modelling framework accounts for the additional sugar needed as feedstock for microbial protein production. In summary, our projections show that for the same protein supply the production of microbial protein requires much less agricultural land and causes fewer GHG emissions from land-use change and agriculture compared to ruminant meat.

When scaled up to replacing 50 or 80 per cent of per-capita ruminant meat consumption globally by 2050, microbial protein further reduces environmental pressures. Most environmental indicators covered in our study, including CH4 and N2O emissions, agricultural water use and nitrogen fixation, decrease linearly with increasing substitution of ruminant meat. However, deforestation and related CO2 emissions show a non-linear saturation effect. The reason for this non-linear relationship is that land-use change typically does not depend on the level of production, but on structural change in agricultural production. In our scenarios, the substitution of ruminant meat with microbial protein strongly reduces the demand for animal feed from pastures and cropland. In the MP20 scenario, i.e. replacing 20 per cent of ruminant meat consumption with microbial protein by 2050, global feed demand from pasture remains rather constant from 2020 onwards, in contrast to an increasing trend in the reference scenario. Therefore, no increase of global pasture area is needed in MP20 by 2050, which explains the strong reduction of deforestation relative to the reference scenario. In the MP50 and MP80 scenario, global pasture feed demand decreases compared to the reference scenario,  which further reduces the overall pressure in the land system. However, since a considerable share of deforestation is already avoided in the 20% case, the land-saving effects are diminishing with increasing substitution levels. 

The fermentation process requires energy for regulating the temperature and other functions of the bioreactor. Therefore, it is crucial that a large-scale transformation of the food system towards microbial protein or other biotechnology-enabled alternatives is complemented by a large-scale decarbonisation of electricity generation. Otherwise, land-related GHG emission savings of substituting ruminant meat with microbial protein, as shown in our study, could be jeopardized by energy-related GHG emissions. 

Microbial protein is a promising and readily available option to reduce the detrimental impacts of ruminant meat production. However, microbial protein should not be perceived as a silver bullet to solve the climate or biodiversity crises. Instead, microbial protein should be integrated into a portfolio of options that address climate change and biodiversity loss simultaneously. For instance, microbial protein could be combined in a sustainable transformation pathway with a shift towards the EAT-Lancet planetary health diet, the protection and restoration of ecosystem, and the decarbonisation of electricity generation.

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