Finding protein-rich foods that align with climate goals can be a challenging task. Isabelle Gerretsen examines data to uncover which dietary choices can effectively reduce emissions.

Reducing individual carbon emissions significantly depends on making sustainable dietary changes.

Food production contributes to 35% of human-caused greenhouse gas (GHG) emissions, with animal products accounting for a large share despite providing only 20% of global calories. Foods like dairy, eggs, fish, and meat are valuable protein sources essential for growth and repair. However, balancing protein needs with climate considerations can be complicated by the variety of products claiming to be “carbon neutral” or “sustainable,” often without substantial evidence. This raises important questions: What does a low-carbon, protein-rich diet look like? How much harm do meat and dairy products cause? Are plant-based proteins like tofu and chickpeas better alternatives? Should one forgo cheese or chicken, and which animal-free options emit the least carbon?

<h3>Meat</h3>

Analysis by researchers Joseph Poore of the University of Oxford and Thomas Nemecek from Agroscope in Switzerland reveals that meat produces 49.9kg of CO2 equivalent (CO2e) per 100g of protein, roughly the emissions of four steaks. Lamb and mutton, generating 19.9kg of CO2e per 100g, come second.

Anne Bordier, director of sustainable diets at the World Resources Institute, notes that meat often overshadows other meats in climate discussions, despite their significant impacts. Ruminants like cows, sheep, and goats release methane during digestion, a potent greenhouse gas with 84 times the warming impact of CO2 over 20 years. Additional emissions arise from growing animal feed and operating livestock farms. Meat from dairy herds has a lower carbon footprint than meat herds because dairy cows provide milk in addition to meat, improving overall efficiency. After producing milk for about three years, dairy cows are slaughtered, and their meat becomes meat.

Non-ruminant animals, including chicken, rabbit, and duck, produce much lower emissions. Chicken emits 5.7kg of CO2e per 100g of protein, almost nine times less than meat. Pig's meat has a footprint of 7.6kg, about 6.5 times lower than meat but slightly higher than poultry.

<h3>Dairy</h3>

Cheese ranks third in agricultural emissions, trailing only lamb and cow's meat. Sophie Marbach, a physicist and researcher, points out that cheese production is carbon-intensive due to cows’ high methane emissions and significant resource demands. Cheese’s GHG footprint—10.8kg of CO2e per 100g of protein—is nearly double that of chicken and higher than pig's meat and eggs.

Different types of cheese have varying impacts. Hard cheeses like parmesan are more carbon-intensive than softer varieties, as they require more milk. Soft cheeses, with higher water content, generally have lower footprints. While cheese from cows, goats, and sheep is similarly impactful due to their ruminant nature, cow’s cheese is often the most efficient because of dairy cows’ high milk yields.

Yogurt, by contrast, has a surprisingly low footprint of 2.7kg of CO2e per 100g of protein, as it requires less milk and its GHG output is distributed across by-products like cream and butter.

<h3>Plants</h3>

Animal products are responsible for 57% of food-related emissions, compared to 29% from plant-based foods. The UK’s Climate Change Committee (CCC) advises reducing meat and dairy consumption by 20% by 2030, increasing to 35% for meat by 2050, to meet climate goals. A vegan diet, eliminating animal products, could cut global food-related emissions by up to 70% by 2050, according to Oxford University research.

Plant-based proteins like peas, pulses, and nuts are among the lowest-carbon options. Producing 100g of protein from peas emits just 0.4kg of CO2e—nearly 90 times less than meat. Lentils produce 0.8kg of CO2e, while tofu generates 2.0kg, largely due to land clearance for soy production.

Innovations like high-protein chickpea powder from US company Nucicer further reduce emissions by increasing protein yield per acre, conserving energy and water. Chickpeas, in addition to being water-efficient, enrich soil by fixing nitrogen, essential for plant growth.

<h3>Fish and Seafood</h3>

GHG emissions from fish and seafood vary widely depending on the species and method of capture. Farmed prawns produce 18.2kg of CO2e per 100g of protein, compared to 6.0kg for farmed fish. Mangrove deforestation for prawn farms exacerbates their impact. Farmed bivalves like mussels and clams, however, have significantly lower footprints, emitting about six times less than prawns and three times less than farmed fish.

Farmed bivalves outperform wild-caught ones due to their minimal energy requirements. Wild bivalves, often harvested through carbon-intensive dredging, disturb seafloor carbon storage, releasing CO2 equivalent to global aviation emissions.

<h3>Lab-Grown Protein</h3>

Emerging alternatives like cellular meat, plant-based meats, and precision fermentation dairy products offer lower-emission options. Cellular meat emits 5.6kg of CO2e per 100g, much less than cow's meat (25.6kg) but higher than plant proteins like pulses and tofu. These products’ emissions stem from the energy-intensive processes in bioreactors.

Precision fermentation, using microbes to produce dairy-like proteins, yields even lower emissions. US company Perfect Day creates animal-free whey protein with a GHG footprint of 0.3kg of CO2e per 100g—35 times lower than traditional dairy.

Solar Foods, a Finnish firm, produces protein powder from bacteria fed with hydrogen and CO2. When powered by renewable energy, these gas-fermented proteins rival the low emissions of plant-based options.

While reducing animal product consumption is key to lowering emissions, other swaps also make a difference. For those unwilling to give up animal proteins, a diet focusing on poultry, eggs, and yogurt offers substantial reductions. According to Marbach, this “low CO2, high-protein” approach can halve an individual’s food-related carbon footprint, whereas a vegetarian diet with heavy reliance on cheese reduces it by only 20%. Ultimately, minimizing animal product reliance is crucial for meeting global climate targets. Simple choices like replacing meat with chickpeas or tofu and scrutinizing seafood sources can meaningfully curb emissions.