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A varied diet need not cost the Earth

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A diet of locally sourced, seasonal food could reduce CO2 emissions, but does that mean we can never eat an avocado again?

Uncertainty around the Brexit trade negotiations shone a spotlight on where the food we eat comes from. People began to think about what would be on our tables if some food products were no longer available or affordable.

Fortunately, the deal that was reached means that, on the whole, there are no tariffs for food imports or exports between the UK and the EU. The scrutiny of the origin of some food and the environmental cost of bringing it to our shores has shifted the consumer’s focus to the environmental cost of the year-round availability of certain foods.

Around half of the food we eat in the UK is produced here. Eating UK-grown fruit and vegetables when in season means that less CO2 is emitted through transportation.

In 2019, Our World in Data reported that food production is responsible for approximately a quarter of the world’s greenhouse gas emissions. It concluded that the largest contributor is the livestock and fisheries sector.

Raising animals on farms to produce meat, dairy and eggs is responsible for 31 per cent of food emissions. Much of this is methane, which sheep and cattle produce through enteric fermentation in their digestive processes. Methane is emitted when the animal belches. There are also emissions from managing pastures and the fuel used for farm vehicles. In dairy farming, researchers are experimenting with additives introduced to cattle feed, including garlic and cinnamon, to reduce the amount of methane produced in cows’ stomachs, but this does affect the taste of the milk produced.

Fishing also produces CO2 through the use of fuel for fishing vessels. In Scotland and north-east England, fishing boats go further for what is called distant water fishing and can be away for days or weeks at a time, while in the south-west of England, the catch is from coastal waters, with trawlers out for a day or less.

A vegetarian diet also has carbon pitfalls. The US environmental activist group, Environmental Working Group, produced The Meat Eater’s Guide to Climate Change and Health. It reported that cheese consumption resulted in 13.5kg-CO2e/kg. CO2equivalent, or CO2e, is the collective term for greenhouse gases and is the amount of CO2 which would have the equivalent impact of global warming. The CO2e figure for cheese is less than for lamb or beef (39kg-CO2e/kg and 27kg-CO2e/kg respectively) but more than pork or farmed salmon (12kgCO2e/kg), chicken (7kgCO2e/kg), and eggs (5kg/CO2e/kg).

The type of cheese also affects greenhouse gas emissions. Hard cheese requires more milk than soft cheese, and therefore has a higher CO2e because of the emissions from milk production.

Professor Mike Berners-Lee broke down the carbon footprint of many foods in his book ‘How Bad are Bananas?’. He says that UK farm animals convert 10 per cent of calories they consume into meat and dairy for human consumption and argues that it would be more efficient if crops were consumed directly by the UK population.

The perceived wisdom is that eating fruit and vegetables that have not been grown using artificial heating will result in a lower carbon footprint.

Eating local produce, grown without artificial heating and without shipping or air freight, has the lowest CO2 emission. For example, locally grown apples produce 0.3kg-CO2e/kg, compared with apples shipped in from New Zealand, which produce 0.6kg-CO2e/kg. One of the most dramatic figures in Berners-Lee’s calculations is asparagus. Grown in the UK it is responsible for 1.1kg-CO2e/kg but imported from Peru, it increases to 18.5kg-CO2e/kg. Root vegetables can be grown locally all year round and are easy to store without needing refrigeration powered by electricity, resulting in 0.3kg-CO2e/kg.

International trade

The cost of doing business

Brexit has meant some increases in costs for wholesalers. Now that goods cannot travel freely between the UK and the EU, the paperwork required to clear the customs checks adds around €65 (£58) per heading (i.e. category). According to Simon Lane, managing director at fruit importer Fruco, a lorryload of root vegetables may contain broccoli, butternut squash and sweet potatoes, which are three headings, incurring a cost of €195 (£174). This cost is incurred by growers exporting the vegetables and by importers to clear them at the port of entry, adding around £300-400 per lorry. Lane says wholesalers may have to introduce price increases gradually to recoup these costs.

Covid has also brought changes to traditional business models. The UK seafood industry exports around 70 per cent of its catch and imports around 90 per cent. “The UK has a conservative palate,” says Andy Gray, trade marketing manager at industry body Seafish. “It is principally limited to white fish, cod and haddock, and the supply doesn’t meet the demand.” White fish from Iceland, Norway and Russia are imported to supplement the UK’s catch. Other species caught by UK vessels, like Dover or lemon sole, are largely bought by the restaurant trade while langoustine, crab, lobster and finfish (e.g. salmon) are mostly exported. The closure of overseas markets and restaurants in the UK has meant that many fishermen are selling online to customers who are experimenting with new recipes during lockdown. The day’s catch is also being sold at the quayside.

“Customers can buy directly from wholesalers who used to supply restaurants and customers collect from the depot,” says Gray. “We expect this to continue as a direct route to the customer.” When markets open up again, it remains to be seen if fish like turbot or bass will only be sold overseas where they attract a premium price, or if UK consumers will drive up demand.

Similarly, oysters are not being exported, principally to France, but are now being offered to domestic consumers. In the 17th and 18th centuries they were the main source of protein for poor families because they were so plentiful. If they are readily available to buy, wild and farmed oysters may once again become a staple of our diets.

Professor Dave Reay teaches carbon management and education at the University of Edinburgh. He argues that the issue of food miles is more complicated than simply comparing mileage. Although a food product may come from further away, its production may be more efficient and its emissions may be lower than a home-grown option. In his book ‘Carbon-Smart Food’, he estimates that 60 per cent of the carbon footprint of an orange imported to the UK from Brazil is the use of fertiliser, pesticides and fuel for machinery at harvest time. If the orange is used to make juice, he calculates that 22 per cent of its carbon footprint is in distribution.

Consumer food choices play a part in reducing the carbon emission. “If we only demand beautiful vegetables there will be more waste and that will have a knock-on effect for production emissions of food which is never consumed,” says Reay. “If we expect to eat everything we want all year round and ignore the seasons, there will be a production cost in terms of having to ship in food which we can’t grow locally or try and grow it locally under conditions where we are using lots of heat and light.”

For arable farming, crop production is responsible for 21 per cent of food’s CO2 emissions accounts. A contributor is synthetic fertilisers, which contain ammonium and nitrogen, both of which contribute to greenhouse gas emissions. There are also CO2 emissions from agricultural machinery used to cultivate the soil.

Agriculture has led to forests and grasslands being converted for livestock and growing crops, which increased CO2 emissions. Our World In Data estimated land for livestock to produce 16 per cent of emissions and land for arable farming, 8 per cent. The rate of deforestation for cattle ranching in Brazil, for example, means that the CO2 emission of its farmed beef is three times that of British beef. Other factors that contribute to CO2 emissions are savannah burning, ploughing or cultivating the soil.

The labour-intensive production of rice is also responsible for considerable methane emissions. Microbes, which thrive in the low-oxygen, high-carbon environment of the flooded paddy fields, are converted into methane. Introducing different varieties can reduce methane emission and increase productivity.

Seafish, the seafood industry body, argues that aquaculture has reduced its feed conversion ratio over the last 25 years. The feed conversion rate for farmed fish can be as low as 1.3:1, it says, compared with 3.5:1 for pigs and 2:1 for chickens. The carbon footprint for seafood varies according to the species; in all cases there is no farmland to convert or cultivate and unfed aquaculture species, such as mussels, have a particularly low carbon footprint.

Food transportation accounts for 6 per cent of food’s total CO2 emissions, whereas processing, refrigeration and storage account for 18 per cent. Buying from local retailers, markets or directly from producers on a smaller scale can reduce the need for processing and energy for storage. Small quantities of seasonal food for immediate consumption can also contribute to reductions in packaging and waste. Doing this reduces energy consumption by the manufacture of packaging. A redesign, rather than elimination, of packaging is preferable, as durable packaging can prevent food waste.

The energy consumed in refrigerating and processing food has to be weighed against the environmental cost of having to throw away food. In 2017, research found that food waste accounts for 8 per cent of total greenhouse emissions.

Researchers at the University of Belgrade and the University of East Sarajevo, Bosnia and Herzegovina, analysed the levels of CO2 emission in food.

For bricks and mortar food retailers, they noted that the main sources of CO2 emission are electricity, transport, ventilation and heating, refrigeration and waste.

Taking the entire food value chain, from the farm to processing, the researchers found that meat processing has an average emission of 0.66kgCO2e/kg. Vegetable processing has a mean value of 0.07kgCO2e/kg and transportation to a regional distribution centre carries an average emission value of 0.13kgCO2e/kg.

Using renewable energy, improving energy efficiency and refrigeration in stores and maximising the efficiency of its vehicles, US chain Wal-Mart nearly doubled the size of its stores between 2005 and 2014 but limited its CO2 emission, which rose from 18.9 million ton CO2e to 21.9 million in the same period.

Reducing carbon emissions does not mean a poor or limited diet. It could open up a world of new tastes as consumers embrace a broader variety of seasonal food and introduce new food and flavours.

Protein

It’s chicken feed

Producing animal feed for farm animals is the cause of 6 per cent of food’s CO2 emissions. Sugar beet is used as a supplement in cattle feed to provide digestible fibre that helps fermentation in the rumen (the cow’s first stomach) to produce milk.

Sugar beet produced in the UK and fed to UK herds has few food miles, but other animal feed, such as soy bean for chicken feed, has a higher carbon footprint.

Soy production is responsible for deforestation in Brazil and Argentina, and also involves fertilisers, agricultural machinery and long-distance transportation.

Different ways to provide animal protein for animal feed are being researched by the React First project. Nottingham-based Deep Branch Biotechnology has developed a process to use CO2 from industrial emissions to generate a single-cell protein called Proton.

Nottingham Trent University’s Poultry Research Unit is benchmarking Proton’s nutritional quality while the University of Stirling’s Institute of Aquaculture is investigating the feasibility of a microbial single-cell protein with an amino acid profile for the aquafeed industry as an alternative to anchovies shipped from Peru and Chile.

The Institute’s Dr Mónica Betancor explains: “Aquaculture is the fastest-growing food sector, with the UK salmon industry expected to increase significantly. Such growth can only be achieved in a sustainable manner by replacing the traditionally used marine ingredients in aquafeeds – fishmeal and fish oil – for more sustainable options.”

Feeds produced with this protein will require no arable land and minimal water usage for feeds with a carbon footprint that is 65-75 per cent smaller than today’s feeds for farmed fish and chicken.

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