Low-carbon diet

A low carbon diet refers to making lifestyle choices to reduce the greenhouse gas emissions (GHGe) resulting from energy use. It is estimated that the U.S. food system is responsible for at least 20 percent of U.S. greenhouse gases. This estimate may be low, as it counts only direct sources of GHGe. Indirect sources, such as demand for products from other countries, are often not counted. A low carbon diet minimizes the emissions released from the production, packaging, processing, transport, preparation and waste of food. Major tenets of a low carbon diet include eating less industrial meat and dairy, eating less industrially produced food in general, eating food grown locally and seasonally, eating less processed and packaged foods and reducing waste from food by proper portion size, recycling or composting.

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, methane, nitrous oxide, and chlorofluorocarbons. 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 (CO2), the primary gas responsible for global warming. Methane gas (CH4) is 23 times more powerful at trapping heat than carbon dioxide and is a byproduct of livestock production and landfills. Nitrous oxide (N₂O) is 200 times more heat-trapping than carbon dioxide and is emitted as a result of over-tilling and excessive irrigation practices. Finally, chlorofluorocarbons (CFCs) are emitted from mechanical refrigerating and freezing mechanisms – both staples in food shipment and storage.

High carbon and low carbon food choices

Certain foods require more fossil fuel inputs than others, making it 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. Vegans contend that the best choice for reducing individual greenhouse gas emissions is an organic vegan diet. An organic vegan diet may reduce greenhouse gas emissions by 1.5 tons per year (compared to the standard American diet). Choosing exclusively plant based (vegan) foods for one meal out of every five (20%) may cut greenhouse gas emissions by the same amount as switching from a standard to a hybrid-powered car, though this would depend on what the plant foods are, how they are grown, how they are packaged, how (and how far) they are transported, how they are stored, and so on. There is conflicting data however, on the long-term health impacts of vegan diets. One study of vegan children found that more than half had rickets during winter months. but many vegans report no health problems. Cundiff and Harris write: "The American Dietetic Association (ADA) and Dietitians of Canada position paper on vegetarian diets officially recognizes that well-planned vegan diets are appropriate for infancy and childhood. The American Academy of Pediatrics concurs. "

Industrial v. pastured livestock

Beef and dairy cattle can be particularly high in their levels of greenhouse gas emissions. Feed is a significant contributor to emissions from animals raised in Confined Animal Feeding Operations (CAFOs) or factory farms, as corn or soy beans must be fertilised, 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.

By contrast, grass-fed cattle are estimated to account for 40% less greenhouse emissions, due to much lower carbon emissions from feed production, and also higher digestibility of grass by cattle, resulting in less methane production. This number, however, does not take into account their crucial role in establishing a healthy pastoral ecosystem, which can function as a highly efficient system for carbon sequestration. Rotational grazing of ruminants (cattle, sheep, goats, etc.) and birds (chickens, turkeys, etc.) on untilled pasture land promotes rapid topsoil accumulation, representing a major carbon sink. Polyface Farm in Virginia, U.S.A., a pioneering farm in rotational grazing or "grass farming", has built up its topsoil at a rate of about one inch per year, which is well over one hundred times the rate of a healthy forest, increasing soil organic matter levels by an average of .14% per year or 2.7 tons of carbon per acre per year. Polyface's claims have not been independently academically peer reviewed, and the soil's carbon sequestration would have to be weighed against the positive methane and nitrous oxide emissions from the animals. There is increasing criticism of Polyface because they buy in non-organic feed for their poultry and pigs who do not eat pasture and so carbon accumulation means a net loss elsewhere. Additionally, Polyface purchases their hens from a CAFO hatchery where male chicks are destroyed.

Additionally, 37 percent of all anthropogenic methane comes from industrial livestock production, generated by the digestive system of ruminants such as cows, sheep and goats. Because CAFO production is highly centralised, the transport of animals to slaughter and then to distant retail outlets is a further source of greenhouse gas emissions.

Diets heavy in meat and dairy have a major impact on greenhouse gas emissions; it is estimated that livestock production is responsible for 18 percent of worldwide greenhouse gas emissions. This is the second-largest source of greenhouse gas emissions, and more than all forms of transportation combined. One simple way to reduce carbon dioxide and methane emissions from the diet is to eat less beef, lamb and dairy.

Distance traveled and method of transit

See also: Food miles

Transport of food across great distances of land or sea in high speed or refrigerated ships or airplanes is a contributor to carbon dioxide emissions in the food industry. Some studies have argued that growing food only accounts for 21% of the energy required for many food products. Transportation (14%), processing (16%), packaging (7%), food retailing (4%), restaurants and caterers (7%) and home refrigeration and preparation (32%) account for the rest. Another study, by researcher at Carnergie Mellon University, found that carbon missions from transport account for 11% of the total carbon emissions of food, of which the transportation from producer to consumer accounts for 4%.

When looking at total Green House Gases (not just carbon dioxide), 83% of emissions come from the actual production of the food because of the methane released by livestock and the nitrous oxide due to fertilizer.

The word locavore describes a person attempting to eat a diet consisting of foods harvested from within a 100-mile radius.

Some studies have criticized the emphasis on local food, claiming that it romanticizes local production, but does not produce very much environmental benefit. Transportation accounts for a relatively small portion of overall energy consumption in food production, and locally produced food may be much more energy intensive than food produced in a more optimal area. Additionally the emphasis on "inefficient" local producers over more efficient ones furhter away may be damaging.

Processing, packaging and waste

Highly processed foods such as granola bars come in individual packaging, demanding high energy inputs and resulting in packaging waste. These products contribute up to a third of total energy inputs for food consumption, as their ingredients are shipped from all over, processed, packaged, trucked to storage, then transported to retail outlets. Bottled water is another example of a highly packaged, wasteful food product. It is estimated that Americans throw away 40 million plastic water bottles every day, and bottled water is often shipped trans-continentally. Carbonated water must be chilled and kept under pressure during storage and transport so as to keep the carbon dioxide dissolved. This factor contributes greater energy usage for products shipped longer distances. Drinking purified tap water is a lower carbon choice.

See also

• Sustainable food system
• Carbon diet
• Farm to fork
• The 100-Mile Diet
• Vertical farming

Additional references

• Annika Carlsson-Kanyama, Marianne Ekstrom, Helena Pipping Shanahan, “Food and life cycle energy inputs: consequences of diet and ways to increase efficiency,” Ecological Economics, 2003
• Miguel Llanos, “Plastic bottles pile up as mountains of waste,” (2005), MSNBC

External links

• School-to-home Carbon Reduction Plan
• Low Carbon Diet
• Empowerment Institute Low Carbon Diet