Global warming is happening; Nobody can deny it. Year after year, the weather is out of control, sea levels are rising and ice caps are melting.
Food accounts for up to 35% of global man-made emissions1. It’s one of the only things we as consumers have control over.
We can choose to eat less meat, eat more sustainably sourced products, and support restaurants and businesses that also reduce carbon emissions.
So how does food production and agriculture impact climate change and contribute to global warming?
Greenhouse gases and their impacts
Nothing is net zero, and even the most sustainable farms produce emissions. Here are the main greenhouse gases and their impacts2:
- Carbon dioxide (CO2): Is emitted during every activity that involves energy consumption (for example, fuel consumption for transportation and electricity consumption for food processing and storage). In addition, carbon dioxide is indirectly released during land use change*.
- Methane (NH4): Is emitted during rice cultivation and animal husbandry (especially enteric fermentation and manure management) and its impact on the climate is 25 times stronger than CO2.
- Nitrous oxide (N20): Is emitted during the production and application of nitrogenous fertilizers and its impact on the climate is 298 times stronger than CO2.
*Land use change is any way humans alter the natural landscape. Some of these changes are permanent destructions, such as the change from forest land to cropland. Other changes, such as abandoning croplands and restoring forests, may attempt to undo previous damage.
Which foods emit the most emissions?
We have classified3 these from the most transmitter to the least. It’s no surprise that beef tops the list.
Beef, lamb and goat: Generally the highest emissions among all food categories due to methane emissions (livestock droppings and cow belching/enteric fermentation) and indirect emissions due to land use change (deforestation). About 21-35 kg CO2e/kg meat.
Chicken and pork: Usually the second highest after beef, lamb and goat but with a significant difference compared to red meat (3-6 kg CO2e/kg meat).
Dairy products and milk: high emissions mainly from livestock (milk and yoghurt 1-1.4 kg CO2e, cheese 2-10 kg CO2e)
Fish and seafood: CO2e values vary a lot here. The usual suspects are feed production for the farmed fish and fuel consumption for the fishing boat.
Fruits and vegetables: Generally very low in CO2e, unless transported by air. Majority of emissions come from fertilizer application and transport (0.05-1.3 kg CO2e)
Cereals and legumes: Generally low in CO2e, most emissions from fertilizer and combine fuel consumption (0.3-0.9 kg CO2e)
Rice: Generally average CO2e but higher than other cereals (2-3 kg CO2e/kg rice). Emissions (methane) come from flooded rice fields.
Greenhouse vs open field
When weather conditions do not allow produce to grow in an open field, heated glass greenhouses are used instead. They require less input (less machinery, fuel and fertilizer) compared to open field operations and the yield is generally higher.
However, they require the construction of glass greenhouses and they require energy in the form of heat and electricity for construction and maintenance.
Electricity and heat generally lead to increased greenhouse gas emissions.
Local food is not necessarily more ecological than imported, seasonality is! When a product is in season, then it must be local!
For most food products, transport accounts for less than 10% of the overall carbon footprint4 (excluding air travel which has a higher carbon footprint and should be avoided).
This is why a tomato grown in peak season in Spain in the open field is more environmentally friendly than a tomato grown out of season in a greenhouse in the UK, although the Spanish tomato has to go to the UK.
Here are the carbon footprints of vegetables grown in the UK in season in the open field, grown in the UK out of season in greenhouses and grown overseas in the open field in season:
Organic vs conventional agriculture
It’s a very nuanced subject. In the case of animals, especially poultry and pork, organic production is less efficient in terms of climate. There is more land occupation for animals, animals live longer, require more food and therefore produce more methane (one of the worst greenhouse gases).
Another disadvantage of organic farming is that it has a lower product yield compared to conventional farming. According to some studies, average yields are 8-25% lower5 in biological systems, and this lack of productivity can create more carbon emissions.
The lower yields are due to lower fertilizer input, the possibility of the crops being attacked by pests and competition for nutrients with weeds and grass.
However, with some crops, the growing conditions and management practices of some organic systems approach conventional yields.
Fruits, vegetables and cereals show a general tendency for organic production to have a slightly lower climate impact (1-2%). This is mainly due to the lesser amount of energy needed to produce synthetic fertilizers.
In terms of the environment, organic farming does not use mineral fertilizers, synthetic pesticides, animal drugs, genetic engineering and food additives that can have adverse health effects.
Pests are managed naturally, crops and livestock are diversified (i.e. crop rotation), and the soil is improved with additions of compost and animal and green manures.
Conventional agriculture is better from a climatic point of view because the animals have a shorter life and are housed in partial to full containment structures and therefore require less land and maintenance.
The main objective is to obtain high yields and high economic inputs. Synthetic fertilizers produce less nitrous oxide than organic fertilizers.
Conventional practices lead to environmental degradation, public health problems, loss of crop variety and genetic biodiversity, and severe impacts on ecosystem services.
In the graph below we see the distribution of the world’s land area today. Half of the habitable land is used for agriculture6.
There is also a very uneven distribution of land use between livestock and crops for human consumption. If we combine the pastures used for grazing with the land used to grow crops for animal feed, livestock accounts for 77% of the world’s agricultural land.
While livestock occupy most of the world’s farmland, they produce only 18% of global calories and 37% of total protein.seven. Agricultural expansion leads to the conversion of forests, grasslands and other carbon “sinks” to cropland or pasture, resulting in carbon dioxide emissions.
Who knew food was so complicated? However, there is hope and steps you can take:
- Seasonal food is key, not local food! Try to buy produce grown in the UK when in season. Out of season, opt for country-specific seasonal imported products.
- Organic fruits and vegetables are slightly better for the environment and the climate.
What we really need is for agriculture to become more sustainable and not deplete our resources.
Share this article with your friends and family and spread the word. The power is in the masses to make the government understand that enough is enough.
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Featured image credit: Klimato