In the East Anglian counties of Norfolk and Suffolk, a £120m commercial low carbon greenhouse project is leading the way in sustainable high volume crop production. The 28.3ha of greenhouses across two sites are the brainchild of Low Carbon Farming and funded by the UK’s largest renewable energy investor, Greencoat Capital. They are capable of producing 12% of the UK’s tomato demand, with 75% lower carbon emissions than traditional greenhouses, by using world-first renewable energy technology and circular production.
Mark Dykes, director at Step Associates, is managing the project. “The greenhouse project is a collaborative effort to provide critical proof of concept for post-Brexit food security and meeting 2030 carbon reduction targets,” he says. “Construction started in September 2019 – it took 14 months to build the greenhouses and the heat pump system, and six months for roadworks.”
Greenhouses for a controlled environment
The seven-metre-tall greenhouses are spread across two farmland sites; Crown Point Estate, Norwich and Ingham, Bury St Edmunds, providing 16ha and 13ha of growing space respectively. “We have two 8ha greenhouses at Crown Point Estate and a single greenhouse at Ingham,” explains Mr Dykes.
Each site has over five kilometres of underground pipeline and more glass than the Shard building in London. Constructed by Dutch glasshouse specialist, BOM Group, the greenhouses provide a controlled growing environment where crops are grown hydroponically – in a nutrient-rich water solution instead of traditional soil.
The greenhouses currently (June 2021) grow salad crops – tomatoes, cucumbers, and peppers – vertically from 177km of growing gutters. In comparison to field farming, the greenhouses can grow 10 times more crops with 10 times less water.
Within each greenhouse there are 16 zones which can be heated independently, as well as three walls which can be opened or closed to allow for isolation. “It allows for different crops and stages of growth to be accommodated and means crops can be grown and harvested throughout the year,” Mr Dykes explains.
“Each greenhouse should average four harvests per year, but that is dependent on crop type and rotation – the first harvest was taken in May 2021.”
Environmental computers use artificial intelligence to control the environment, which includes scanning MET Office weather data. The roofs are designed to maximise natural light and diffused glass disperses light across the crops evenly. “The stringent control of the greenhouses ensures biosecurity and consistent, healthy growth of crops.”
Innovation goes beyond scale
But innovation goes beyond scale, and resource engineering is what enables the greenhouses to produce crops with 75% less emissions than traditional commercial greenhouses. The sites were specifically selected for their proximity to Anglian Water’s waste water treatment facilities. “Heat is extracted from cleaned effluent at the water treatment facilities into a heat transfer plant before being transported two kilometres to ground source heat pumps at the greenhouse sites; these works were undertaken by specialist utility Company Clancy Group,” explains Mr Dykes.
“The ground source heat pumps are then able to inject this heat into the greenhouses. Peak thermal demands are 32mw at Crown Point and 26mw at Ingham, taking greenhouse temperatures to 55◦F. This equates to enough thermal power to heat 20,000 homes.
“The waste heat extraction is a first and the development is home to the UK’s largest system of heat pumps. And because it is a renewable energy project we were able to apply for a Renewable Heat Incentive (RHI) grant.”
Electricity for the heat pumps and sites is generated by Combined Heat and Power (CHP) units located at Crown Point and Ingham, producing export capacity of 3.6mw and 2.4mw respectively. “The electricity generated by the CHP units fulfils about 85% of the site’s electricity demands,” he says.
The electricity generated by the CHP units fulfils about 85% of the site’s electricity demands.
Waste heat from the units is recycled and enables greenhouse temperatures to be increased when required. “Heat generated by the CHP units is captured and fed into hot water storage tanks which allows greenhouse temperatures to be taken up to 80◦F.”
The sites also have infrastructure to capture and clean generated carbon dioxide which is fed back into the greenhouses to meet the growing crops’ requirements. Compared to traditional greenhouses these save on average 1.2m tonnes of carbon from the environment.
Water efficiencies are helped by the sheer amount of glass. “We are able to capture the rainfall runoff from the greenhouses and store it – across both sites there is 200,000m3 of water storage,” explains Mr Dykes.
To ensure uninterrupted operation the sites have control measures. “There are two gas boilers and back-up generators, as well as two days’ worth of heat in buffer tanks – it’s been designed to cover all bases in the event of something shutting down.”
A new growing concept
The greenhouses offer a new growing concept. “They are a transferable development – the design can be replicated elsewhere in the country and really offers an opportunity to increase homegrown production,” he adds.
The design can be replicated elsewhere in the country and really offers an opportunity to increase homegrown production.
But how big do greenhouses really have to be? “It comes down to economies of scale,” says Mr Dykes. “Food production efficiencies and the sector’s carbon footprint can be reduced by having these larger, low carbon greenhouses. The larger greenhouses reduce the logistical challenges, emissions and costs of having lots of small greenhouses everywhere.”
And the greenhouses offer opportunities beyond crop production. “Each site has provided 200 new jobs – the range of required work and skill provides broad opportunities.”