business food sustainability

Giant greenhouses for Low Carbon Farming

As I’ve mentioned in recent posts about Britain’s food security, the country grows around 60% of its own food. Some categories are lower than others, and fresh fruit and vegetables are among the lowest categories at 23% self-sufficiency. Some of this is tropical fruit that doesn’t grow locally – bananas are Britain’s favourite fruit. But a lot of it is things we could produce ourselves.

When you look at where we import our fresh fruit and vegetables from, it’s often countries with a climate similar to our own. 28% of our vegetables come from Holland, which has the same seasons as we do. The reason it comes from there is that farmers in the Netherlands have invested substantially in heated greenhouses and grow for export. We could be doing the same here, and after Britain has left the EU, the economics may shift anyway.

One company that has spotted this opportunity is Low Carbon Farming, who are building the biggest greenhouses in the country in East Anglia. As their name suggests, they specialise in sustainably heated greenhouses.

The largest of their two sites is in Norwich, and the farm is located near the city’s sewage treatment plant. Heat pumps extract heat from the waste plant and pump it through underground pipes to the 40 acres of greenhouses. Another project draws on the sewage works of Bury St Edmunds, using the heat on a further 30 acres. Electricity is generated by onsite with combined heat and power systems, which also provide CO2 for enhancing growth. A thermal heat store can also bank excess warmth on a hot day and release it slowly over the next two to three days, reducing the need for the heat pumps.

Using a wastewater plant for low carbon heat in this way has never been done before, so they’re claiming a world first. It’s also a good example of how government policy can encourage sustainable ideas. The farms rely on a smart circular economy technology, and it has been able to raise the millions needed to invest because it can tap into the government’s renewable heat inventive scheme. It does the sewage works and the local rivers a favour too. There are regulations about how warm the water can be when discharged from the plant into a river. By tapping the discharge pipe and removing some of the heat, it helps to protect the river ecosystem.

Together, these two new farms will be able to produce 12% of Britain’s tomatoes. One might argue that the most sustainable thing would be to stop eating tomatoes out of season altogether, but this approach would be a big improvement. The Low Carbon Farming approach cuts 75% of the CO2, and their hydroponic vertical growing systems recycle water. Normal field-based growing uses 10 times more water.

Food production is due to start at Low Carbon Farming’s sites in 2021. In the meantime, I hope other places will spot similar opportunities to increase local food production and cut CO2 at the same time.

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