Lighting the way?

Closed crop growing systems are going mainstream, but they have their critics, says Gavin McEwan.

LED-based methods of growing crops are becoming more efficient as technologies improve year on year - image: USDA
LED-based methods of growing crops are becoming more efficient as technologies improve year on year - image: USDA

This year will see high-tech urban farming in the UK begin to move from demonstration projects to full commercial-scale developments. But questions remain as to whether such capital- and energy-intensive options are the most financially and environmentally sustainable.

Britain has been slow to embark on such systems but now in east London, GrowUp Urban Farms has been granted planning permission to build what it claims to be the country’s first commercial-scale aquaponic urban farm, combining salad and herb growing with fish rearing in a 550m2 disused warehouse.

When complete this will produce over 20,000kg of leaves and 4,000kg of tilapia fish throughout the year, most of which will be sold to local restaurants. It will incorporate a stacked vertical growing system with LED lights to grow the plants, and will also include a small visitor centre.

Funding has come from Ignite Social Enterprise European non-profit partnership Climate-KIC, and a grant from the government’s Agri-Tech Catalyst.

Explaining the idealism behind the project, co-founder and chief executive Kate Hofman says: "We are creating jobs in our local area and I hope these will be the first of many as we expand.

Generating social and environmental benefit is something that Tom [co-founder Tom Webster] and I care passionately about." But she insists the development can wash its face. "Our backers very much want to know what sort of return it will bring. With a turnover of £360,000 a year, we expect to break even after two and a half years," she says.

"Our business model is for a range of crops. We could make a lot of money just growing micro-greens for restaurants, but that wouldn’t meet the aim of providing healthy sustainable food in volume. The majority of the revenue will come from salads – 25 per cent will be everyday salad and herb mix bags to the local area. The nitrogen-rich waste from the fish is good for the leaves. For fruits like tomatoes and peppers you would need to supplement with things like phosphorus."

A further synergy between the two crops comes with energy use, she says. "We will start by taking power off the mains. LEDs are fairly energy-efficient but when you have 2,000 close together they do give off heat. We are capturing that to heat the water – tilapia like it warm.

"GrowUp has trialled the format in a re-purposed shipping container which it will now scale up," she explains. "There is a minimum viable size, but part of the reason for the InnovateUK funding is to find out what the limits and boundaries are. There are lots of exciting developments going on in many countries right now – the question is, which is most efficient?"

The turnaround from approval to full production is likely to be swift, with the system up and running by August and the first baby leaves harvested in September, she says.

Planning permission

Elsewhere, an aquaculture system combined with conventional glasshouse growing is awaiting planning permission in north Lincolnshire. In London, Growing Underground began growing hydroponic, LED-lit micro-leaves and herbs in a disused air-raid shelter in Clapham last summer.

But some are critical of these schemes. Mike Hamm, professor of sustainable agriculture at Michigan State University, points out that only a handful of crops can ever be viably grown using enclosed systems, pointing out that as commodity crops, wheat and other grains "would be important if these systems are to truly feed a city", but these would in fact be "a terrible choice for indoor production".

Citing a study by Cornell University emeritus professor Dr Louis Albright, he says wheat grown in a tiered, artificially-lit system would require three Empire State Buildings to feed the city of New York and the resulting bread would have to be priced at $11 "just to cover the lighting cost", he says.

Lettuce comes out better from the study but a 100 per cent artificially-lit crop would still require a price of 10 cents more per head to cover the expenditure on energy, which if sourced conventionally, would expend around 4kg of CO2 per head. For tomatoes, the CO2 cost comes out at 8.7 kg per kg of fruit.

"It begs the question of why it makes sense to put a lot of intellectual activity and resources into something that negates the direct use of our one absolutely renewable resource – the sun – and totally replace it with artificial light," Hamm says.

Instead, he calls for greenhouses and polytunnels on the urban periphery and on brownfield sites to "have potential to improve the sustainability and resilience of our food system and ensure sustainable livelihoods for a diversity of farmers. This is not the case for 100 per cent artificially-lit systems."

Stockbridge Technology Centre has been trialling LED-based growing of a range of crops at its LED4Crops facility since 2012, and its science director Martin McPherson strongly refutes this argument.

"It fails to take account of the drivers that are going to be important in the next few decades: 9-10 billion people to feed, potential climate disruption, increased urbanisation, reduced land availability, labour and skills, increased concern about contamination, or the converging of a whole series of different technologies which will continue to improve the efficiency of LED lighting, photovoltaic technology, sensor and automation systems," he says.

"There appears to be an assumption that we will always be able to import a proportion of our food supplies from overseas – currently 80 per cent in the case of tomatoes. Retailers are already concerned about resilience in the food chain, hence their growing interest in more local production."

Plant light responses

He stresses is the way in which greater understanding of plant light responses "is going to revolutionise our ability to manipulate food production, including plant architecture, colour, flavour, aroma, nutritional value, and potential health benefits", he adds, "and to do it consistently all year around without interference from the weather ".

"We will continue to use the energy from the sun through improving solar technology," he says.

"But plants don’t use the full solar spectrum and at times the intensity of the sun’s energy is damaging to plants, so energy is wasted protecting the plant. Instead, we can use specific selected optimised light wavelengths much more efficiently to provide bespoke light regimes for optimised quality production of a wide range of food crops."

He concedes that in the short term, closed production systems "will play a relatively minor role in mainstream UK horticulture", and suggests: "Niche roles like propagation, micro-herbs and ornamental production are areas which we will see early adoption but it will happen elsewhere for a variety of different reasons. Large-scale adoption will depend on the rate of success of the early start-ups but I am convinced that it can aspire to have an impact on UK food production, so long as we accept we may have to pay more for high quality year-round locally grown pesticide-free produce."

University of Nottingham and HydroGarden enjoy hydroponic link-up

The University of Nottingham and equipment supplier HydroGarden have begun research to investigate the differences in energy use and productivity between a hydroponic system with only LED lighting, and one that combines natural and artificial lighting sources.

As part of the project, supervised by Professor Mark Gillott and undertaken by undergraduate student Matthew Woodward, two of HydroGarden’s vertical hydroponic systems have been installed in the university’s £1.9m Creative Energy Homes Project, which comprises seven eco-houses purpose-built to investigate the integration of energy-efficient technologies and which attract over 3,000 visitors a year.

The move follows the launch of HydroGarden’s Project Urban Grow, now branded as VydroFarm, at the university’s Vertical Farming and Urban Agriculture (VFUA) Conference last September.

It features vertical racks on tracks that can be moved together to save space and maximise production density. Incorporating Valoya LED lights, it can be monitored and controlled remotely via smartphone, tablet or PC.

One such system has been installed in the basement of the eco-house, the other by its main entrance. Both will be used to grow a variety of salad crops. Their weight and nutrient content will be compared as well as the energy required to produce them.

Woodward said: "I’ll be looking at how building design can be adapted to incorporate vertical farming systems working in synergy with the building services systems."

Gillott added: "This is a great opportunity to investigate the energy and building integration issues associated with moving food production into our cities. We see this as part of a solution for ensuring global food security."

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