A low-carbon diet is any diet that results in lower greenhouse gas emissions. Choosing a low carbon diet is one facet of developing sustainable diets which increase the long-term sustainability of humanity. Major tenets of a low-carbon diet include eating a plant-based diet, and in particular little or no beef and dairy. Low-carbon diets differ around the world in taste, style, and the frequency they are eaten. Asian countries like India and China feature vegetarian and vegan meals as staples in their diets. In contrast, Europe and North America rely on animal products for their Western diets.
It is estimated that the food system is responsible for a quarter to a third of human-caused greenhouse gas emissions. More fossil fuels are required for the production of animal-based foods like meat and dairy and have a higher carbon footprint. Large amounts of land are required to raise livestock for beef and dairy products and methane emissions from cattle contribute to the greenhouse gases in the atmosphere. However, carbon emissions from transportation and packaging for plant-based diets are similar in scale to animal-based diets. Local production can be much more energy intensive and inefficient compared to industrialized production.
Overall trends worldwide
A 2014 study into the real-life diets of British people estimated their greenhouse gas footprints in terms of kilograms of carbon dioxide equivalent per day:
7.19 for high meat-eaters (≥100 g/day) 5.63 for medium meat-eaters (50–99 g/day) 4.67 for low meat-eaters (<50 g/day) 3.91 for fish-eaters 3.81 for vegetarians 2.89 for vegans
While the fish-eaters had the lowest footprints out of all the meat-eaters, the vegetarians and vegans were the lowest overall. This is due to the contribution of greenhouse gases in the growth, processing, production, and transport of the plant-based food products eaten by vegetarians and vegans.
A 2020 study found that Asia has the largest percentage of vegetarians at 19%. Close behind Asia is Africa/the Middle East with 16%. South and Central America have just 8% and North America has a mere 6%. This study found that Europe has the smallest percentage of vegetarians at only 5%. There was not conclusive data on the percentage of vegetarians in Australia.
Non-Western diets are built around unprocessed starches. In South America and Africa, the centerpiece of each meal is beans and grains. Peru, in South America, has potatoes as the foundation for their diet. In Asia, rice is a staple in every household no matter the income level. Meat is usually the centerpiece of meals in the Western diet, whereas animal products are often small parts of the meal (or act as condiments) in the non-Western diet.
In India, the practice of the vegetarian diet is usually generational and simply follows the pattern expected of the family. Adherence can also be credited to certain religious groups and social groups. For example, Hindus do not eat beef because they believe that red meat from cattle is impure. Some of the vegetarian staples consumed are a mixture of whole grains along with nuts/seeds and legumes. Dairy is also included in the Indian vegetarian diet, with unique spices and seasonings per region. However, certain populations in India have begun eating meat due to the growing popularity of western diets.
Background on diet and greenhouse gas emissions
In the U.S., the food system emits four of the greenhouse gases associated with climate change: carbon dioxide (CO2), methane, nitrous oxide and chlorofluorocarbons.STAT saying that those four are emitted The burning of fossil fuels (such as oil and gasoline) to power vehicles that transport food for long distances by air, ship, truck and rail releases carbon dioxide, the primary gas responsible for global warming. Chlorofluorocarbons (CFCs) are emitted from mechanical refrigerating and freezing mechanisms – both staples in food shipment and storage.CFC STAT Anthropogenic methane emission sources include agriculture (ruminants, manure management, wetland rice production), various other industries and landfills. Anthropogenic nitrous oxide sources include fertilizer, manure, crop residues and nitrogen-fixing crops production.EPA. 2011. Inventory of U.S. greenhouse gas emissions and sinks: 1990-2009. United States Environmental Protection Agency. EPA 430-R-11-005. 459 pp. Methane and nitrous oxide are also emitted in large amounts from natural sources. The 100-year global warming potentials of methane and nitrous oxide are recently estimated at 25 and 298 carbon dioxide equivalents, respectively.IPCC. 2007. Fourth Assessment Report. The Scientific Basis. Intergovernmental Panel on Climate Change. Sec. 2.10.2.
Steinfeld et al. estimate that livestock production accounts for 18 percent of anthropogenic GHG emissions expressed as carbon dioxide equivalents.Steinfeld, H. et al. 2006, Livestock's Long Shadow: Environmental Issues and Options. Livestock, Environment and Development, FAO. Of this amount, 34 percent is carbon dioxide emission from deforestation, principally in Central and South America, that they assigned to livestock production. However, deforestation associated with livestock production is not an issue in many regions. In the US, the land area occupied by forest increased between 1990 and 2009US EPA. 2011. Inventory of U.S. greenhouse gas emissions and sinks: 1990-2009. United States Environmental Protection Agency. EPA 430-R-11-005. 459 pp. and a net increase in forest land area was also reported in Canada.Environment Canada. 2010. National Inventory Report 1990-2008. Greenhouse Gas Sources and Sinks in Canada. Part 1. 221 pp.
Of emissions they attribute to livestock production, Steinfeld et al. estimate that globally, methane accounts for 30.2 percent. Like other greenhouse gases, methane contributes to global warming when its atmospheric concentration rises. Although methane emission from agriculture and other anthropogenic sources has contributed substantially to past warming, it is of much less significance for current and recent warming. This is because there has been relatively little increase in atmospheric methane concentration in recent yearsIPCC. 2007. Fourth Assessment Report. Intergovernmental Panel on Climate Change. The anomalous increase in methane concentration in 2007, discussed by Rigby et al., has since been attributed principally to anomalous methane flux from natural wetlands, mostly in the tropics, rather than to anthropogenic sources.
Livestock sources (including enteric fermentation and manure) account for about 3.1 percent of US anthropogenic GHG emissions expressed as carbon dioxide equivalents. This EPA estimate is based on methodologies agreed to by the Conference of Parties of the UNFCCC, with 100-year global warming potentials from the IPCC Second Assessment Report used in estimating GHG emissions as carbon dioxide equivalents.
A 2016 study published in Nature Climate Change concludes that climate taxes on meat and milk would simultaneously produce substantial cuts in greenhouse gas emissions and lead to healthier diets. Such taxes would need to be designed with care: exempting and subsidising some food groups, selectively compensating for income loss, and using part of the revenue for health promotion. The study analyzed surcharges of 40% on beef and 20% on milk and their effects on consumption, climate emissions, and distribution. An optimum plan would reduce emissions by 1 billion tonnes per year – similar in amount to those from aviation globally.
High-carbon and low-carbon food choices
Certain foods require more fossil fuel inputs than others. Animal-based foods like meat and dairy have a much higher carbon footprint than plant-based foods. Therefore, it is possible to go on a low-carbon diet and reduce one's carbon footprint by choosing foods that need less fossil fuel and therefore emit less carbon dioxide and other greenhouse gases. Further research finds that even "the lowest-impact animal products typically exceed those of vegetable substitutes". For example, Ritchie explains that "producing 100 grams of protein from peas emits just 0.4 kilograms of carbon dioxide equivalents (CO2eq). To get the same amount of protein from beef, emissions would be nearly 90 times higher, at 35 kgCO2eq."
In June 2010, a report from United Nations Environment Programme declared that a global shift towards a vegan diet was needed to save the world from hunger, fuel shortages and climate change.Felicity Carus UN urges global move to meat and dairy-free diet, The Guardian, 2 June 2010
Also see "Assessing the Environmental Impacts of Consumption and Production" , United Nations Environment Programme (UNEP), Brussels, 2 June 2010. This will mean a huge shift in the diet of the average European, as 83% of their diets are made up of meat, dairy, and eggs. As a major contributor to global carbon emissions, China introduced new dietary guidelines in 2016 which aim to cut meat consumption by 50% and thereby reduce greenhouse gas emissions by 1 billion tonnes by 2030.
More families are choosing to implement vegan and vegetarian diets for adults and children alike. Cundiff and Harris write: "The American Dietetic Association (ADA) and Dietitians of Canada position paper officially recognizes that well-planned vegan and other vegetarian diets are appropriate for infancy and childhood." However, European recommendations for children's diets do not include the vegan diet. They stand that there should be necessary "medical and dietetic supervision" in order for the safety of the vegan child to be kept in mind. It has been noted that "the more restrictive the diet and the younger the child, the greater the risk of nutritional deficiency." The most common nutrients left out of the vegan child's diet are as follows:
Protein (quality and quantity) Iron Zinc Selenium Calcium Riboflavin Vitamins A, D, and B12 Essential fatty acids
Industrial versus pastured livestock
Beef and dairy cattle have extremely high levels of greenhouse gas emissions, due to methane emissions from enteric fermentation, and their very large land footprint. Feed is a significant contributor to emissions from animals raised in Confined Animal Feeding Operations (CAFOs) or factory farms, as corn or soybeans must be fertilized, irrigated, processed into animal feed, packaged and then transported to the CAFO. In 2005, CAFOs accounted for 74% of the world's poultry production, 50% of pork, 43% of beef, and 68% of eggs, according to the Worldwatch Institute. Proportions are significantly higher in developed countries, but are growing rapidly in developing countries, where demand is also growing fast.Danielle Nierenberg, Lisa Mastny, 2005, Worldwatch Paper #171: Happier Meals: Rethinking the Global Meat Industry, p. 11-12 However, in the US, only about 11% of soybean acres and 14% of corn acres are irrigated; in contrast, about 66% of vegetable acres and 79% of orchard acres are irrigated.USDA. 2009. 2007 Census of agriculture. United States summary and State Data. Vol. 1. Geographic Area Series. Part 51. AC-07-A-51. 639 pp. + appendices.USDA. 2009. 2007 Census of agriculture. Farm and ranch irrigation survey (2008). Volume 3. Special Studies. Part 1. AC-07-SS-1. 177 pp. + appendices. Soybean meal for livestock feed is commonly produced after extraction of soybean oil (used for cooking, food products, biodiesel, etc.,Soyatech: http://soyatech.com/soy_facts.htm USDA. 2011. Agricultural Statistics 2010. 505 pp. so that only a fraction of processing is assignable to feed. Such examples illustrate that issues relating to irrigation, fertilization and processing for meat production should also be of concern with regard to production of other foods.