Vertical Farming: an increasingly relevant solution for food security in the UK and globally

In this Insight paper, UK Transportation and Industrial Director Peter Farmer makes the case for embracing “Vertical Farming”, the use of aeroponic and hydroponic indoor facilities to intensively grow a range of crops to a high yield and quality standard, helping to secure one key element of the UK food supply. Paul Swainson of Ramboll UK[i] engineers has provided insight in relation to the energy aspects of this paper.

Currently, there isn’t a vast amount of spare industrial space in the UK; industrial ‘shed’ supply in the UK has slightly increased since 2016 but is still less than half that in 2011. While this has corresponded to a reduced vacancy rate, the latter still sits just a little below 7%[ii].

However, a relatively new and exciting entry to the market is helping to reduce the amount of unused building capacity at strategically valuable sites around the country. Vertical farming offers a potential sustainable use for vacant space and new space on industrial brownfield land.

Vertical farming involves growing plants in buildings under fully controlled conditions across many stacked layers, without solar light. Unlike glasshouse production, which relies on sunlight, it makes use of LED lighting to provide different wavelengths of light, according to crop and growth stage needs.

The UK imports 48% of its total food consumed, and the proportion is rising[iii]. The early stages of COVID-19 highlighted concerns about the UK’s food security.

We are also being encouraged to eat more sustainably, which can take many forms – from eating less meat to eating more seasonally. We have, however, become used to being able to eat crops such as tomatoes and cucumbers all year round, and many of these crops are imported and are produced with energy-intensive methods. Vertical farming is one potential solution.

To make this method of food production viable and sustainable, it should use sustainable energy. This is currently an investment-heavy, slow-return business but, while some operations have failed, others are now making it work.

In the UK, the Edinburgh-based Shockingly Fresh has announced plans to develop 40 sites and already has five in production. Ocado has invested £17m in a joint venture with Priva Holdings in the Netherlands, known as Infinite Acres. It has also taken a 58% stake in Jones Food Company, a Lincolnshire-based business producing 420 tonnes of leafy greens each year at a 5,120m2 facility – equivalent in size to 26 tennis courts.

On a smaller scale, Growing Underground[iv], below the busy streets of Clapham in London, produces micro-greens and salad leaves, while LettUs Grow[v], based in Bristol, is providing container-sized “Drop & Grow” units for customers to grow their own.

Growup Urban Farms, in East London, adds fish into the process. When the fish are fed, their waste is converted into fertiliser, with the help of microbacteria, to feed the plants. The plants purify the water, which is then pumped back into the fish tanks.

THE BASICS – WHAT IS VERTICAL FARMING USED FOR?

Vertical farming uses different wavelengths of LED light within controlled indoor envieonments to suit crop and growth stage needs. The system uses soil-free hydroponic or aeroponic technologies[vi].

These systems are arguably not yet viable for heavy root vegetables or large-scale cereal crops; rather, they are used for higher-value, sensitive produce such as herbs, leafy greens (e.g. lettuce, basil and kale) and vine crops (e.g. tomatoes and cucumbers).

They can produce quality-controlled produce 12 months of the year. Vertical farms also achieve a higher crop yield[vii] and the potential for a 48-day seed-to-harvest schedule for crops such as lettuce.

Vertical farms can be set up in almost any space, although economies of scale are important, so vacant or new industrial sheds are ideal. However, we have also explored the idea of modularised and scalable approaches. Vertical farming racking is not dissimilar to traditional storage racking, with spacing depending upon the crop being grown.

THE ARRANGEMENT

Growing trays can be set out statically or in mobile carriages similar to high-density, compact library shelving systems, providing even greater growing density. For the purposes of this explanation, we have divided crops into three groups.

A warehouse of 20,000m2 has a footprint of roughly 1.39 hectares. Assuming a 12m clear internal height, a building, in a single-crop configuration, could achieve a twentyfold[viii] land use intensity increase for small-leaf crops. Alternatively, as we explore below, a mixture of small and medium-leaf and vine crops could still realise a fifteenfold intensity increase, equivalent to roughly 30 hectares. A single crop is possible, but it is more likely that we would introduce a mix or change production, and therefore the rack arrangements would be flexible.

We also need to allow space for seed storage, germination and nursery rooms. There will be basic and process plant rooms, nutrient stores and control rooms as well as administration and staff welfare facilities. If we also build in packing and dispatch functions, further economies can be achieved.

SUSTAINABILITY

The approach has strong sustainability credentials, reducing food miles and using vacant buildings or structures on brownfield land that would otherwise not be suitable for food production. The potential for the intensification of land use, and the fact that these operations can be built on brownfield sites, could also allow for the “rewilding” of farmland. Managed rewilding in line with emerging policy allows land to rebalance, locks in carbon and also re-establishes more diverse ecosystems.

There is a water demand, more so in hydroponics than in aeroponics, but as much as 90% less than in conventional farming and greenhouse production[ix]. There is also a lot that we can do to reduce the impact of this water use, such as recycling and capturing as much as possible. A lot of water passes through the system and is also transpired by the plants, all of which can be reused, while rainwater can be harvested and stored, potentially underground. That being said, the process uses as much as 95% less water than field-farmed food, with yields 390 times higher per square foot, annually[x].

Using non-conventional methods may be disconcerting for some, but the systems and nutrients being used can achieve the highest organic standards.

Energy is possibly the key issue to be addressed. The process is relatively energy-intensive, and energy use is the main factor influencing crop value and yield decisions. We need to start with the load and reduce consumption as much as possible. Therefore, the building specification is important and lighting and air handling must be as efficient as possible. The water delivery systems must be carefully engineered, with full consideration given to water recovery.

As set out in the case studies below, a cellular system, based on standard shipping container-sized modules and an open, multi-level growing rack Controlled Environmental Agriculture (CEA) building, where the building is, in effect, the CEA cell, generally results in a lower energy demand – typically about 125 W per m2 of growing area for the cellular approach compared with 200 W per m2 of growing area for open systems. These would pro rata to 12.5 MW and 20.0 MW total energy demand for 100,000m2 of cellular and open systems, respectively, in an existing 20,000m2 building. The split between LED lighting and other demands (aeroponics, heating, HVAC, etc.) for each approach would also vary, but the following is representative:

  • Aeroponic system 10%
  • LED lighting 60%
  • Heating and HVAC 20%
  • General building services 10%

To maximise the sustainability of the facility, we need to consider:

  • Whether the cells or building are appropriately insulated and how this will impact heating energy demand
  • The spatial opportunities for site-based generation systems, such as CHP or wind turbines on adjacent or remote sites, and energy storage systems
  • The site location in respect of solar energy output from PV cells, which is better in the south-west of the UK than in the north-west
  • Whether the site overlies an aquifer or if there is a body of water nearby for groundwater-source heating and cooling
  • Opportunities or plans for heat networks in the area
  • Other heat supply options such as heat pumps
  • Solar PV plus wind and/or hydrogen-convertible CHP generation, with the option of battery storage to allow for cost-effective battery discharging during higher electricity tariff periods.

A full appraisal can be provided by Ramboll UK upon request.

PROCESSING

As well as growing, we can further increase efficiencies and sustainability by removing further steps in the traditional supply chain. By packaging the produce at the point of production and delivering directly to the point of sale, at least one step in the journey can be eliminated. As well as reducing food miles, this reduces waste and increases freshness and shelf life.

CASE STUDIES

The follow exploratory cases studies explore the potential of medium to large scale options. They include multiple and single, large-scale CEA options.

Case Study 1 – Cellular approach

There is a lot of potential to modularise these facilities. LettUs Grow[xi] already supplies these plug-and-play units. These come in two basic configurations: the first, “Drop&Grow:24”, uses a 40-foot container providing 24m2 of vertical growing space and preparation space, while the second, the “Drop&Grow:48”, provides 48m2 of vertical growing space.

The following case study considers a cellular module system, each containing a four-level growing rack carousel where the container is a closed CEA cell. While this arrangement is less flexible in terms of management, it provides distinct advantages including the ability to add and remove CEAs. This arrangement could also be adapted for the use of temporary land use.

There is a small downside to this approach, in that some efficiencies and economies are lost through the module-by-module approach.

Case Study 2 – Open multi-level arrangement

The following example sets out our ideas, based on the indicative 20,000m2 warehouse-type facility common in the UK. This open system is based on multi-level CEA growing racks where the building is, in effect, the CEA cell. Each system can be stacked vertically and horizontally to fill the available building volume, subject to appropriate spatial and operational requirements.

Case Study 3 – Dome farm arrangement

Considering the potential in a region such as the Middle East, we have developed a high light concept for a large, open CEA farm. We have proposed an efficient dome structure enclosing a single CEA. According to Market Data Forecast, the Middle East and Africa Vertical Farming market was worth US$0.57b in 2020 and is expected to grow at a CAGR of 26.4% to reach US$1.86b by 2025.

The dome is formed in a lattice twin wall to assist with heat rejection, but it is recognised that there will need to be a significant, sustainably powered, heat rejection system.

We have placed some elements such as germination, water cisterns and UPS within the basement levels for security and climate control purposes.

A SOLUTION FOR TWO PROBLEMS

As we have explored, there are three primary barriers to this sector – the length of time for a return on investment, cost and sustainability (particularly with respect to power) and the influence of the first two factors on the cost of produce. Arguably, if we can introduce sufficient scale, social and economic change will make production increasingly competitive.

These facilities can be local to customers as well as concentrated in former industrial areas. As mentioned, they could be scalable and fitted into existing buildings. There is almost no limit to the types of spaces that could be adapted, including tunnels, basements and redundant industrial space, and we could also consider under-used multi-level car parks attached to larger developments. The facilities could also be temporary in nature, such as a box park-type of development, making use of land for a period pending redevelopment.

This is an exciting opportunity, at the micro-level for small communities to the industrial level, where scale will help address some of the investment issues.

The UK is seeing an increase in the popularity of veganism and vegetarianism, as well as sustainably sourced food in general. As demand for vegetables increases and concerns grow about food security, vertical farms could be a key part of the answer, providing a new role for industrial and unused space.

For some environments, such as the Middle East, vertical farming is an obvious move. An indoor farm in Saudi Arabia, for instance, can use solar energy to power LEDs at low cost without shading out other farmland. At present, virtually all vegetables must be imported into the country.

A move to vertical farming will not only allow us to produce the food we need more locally and sustainably, it could also free up agricultural land, allowing for reforestation with hardwoods to absorb relock in CO2 and combat the global climate emergency.

The economics are still marginal, with current successes tending towards the ‘boutique’ product price point. AeroFarms, a large vertical farming and equipment operation in the USA, only started generating a (small) profit eight years into its nine-year existence. So it is a high bar, but a bar that is coming down[xii].


[i] Ramboll is a leading global engineering, science and economics consultancy working across all built environment markets and management consulting. Ramboll creates sustainable societies where people and nature flourish and is committed to climate action to address the climate emergency.

[ii] Spotlight: Big Shed Briefing; Savills. https://www.savills.com/research_articles/255800/294532-0

[iii] Defra

[iv] http://growing-underground.com/

[v] http://www.lettusgrow.com/

[vi] Hydroponics and aeroponics feed plants without the medium of soil. In hydroponic systems, the roots are submerged in water and nutrients are delivered via the water. In aeroponics, the roots are exposed and sprayed with a mist containing water and nutrients, resulting in a humid, fog-like environment. There are advantages and disadvantages to each.

[vii] If you grow lettuce on an agricultural field of 1x1 metre, you can yield 3.9 kg every year. When lettuce is grown on the same acreage in a greenhouse, 41 kg can be harvested.3 Vertical farms can even yield twenty times more lettuce than agricultural fields. - Bayley, J.E., Yu, M., & Frediani, K. (2010), Sustainable food production using high-density vertical growing (Verticrop).

[viii] Assuming an allowance for some support facilities. Our subsequent case study considers a mixed crop and in-site processing and dispatch operation.

[ix] https://greenlivingmag.com/the-future-of-food-hydroponics-aquaponics-and-aeroponics-agriculture/

[x] https://aerofarms.com/story/

[xi] http://www.lettusgrow.com/

[xii] https://www.forbes.com/sites/erikkobayashisolomon/2019/04/05/investing-in-vertical-farming-five-take-aways/

About the Author

Peter Farmer (BArch(Hons) BA Arch(Hons) RIBA)

Director, UK

Peter heads up our Transportation sector in the UK. He undertakes a key role in the continuing development of this sector, related research, masterplanning, due diligence and sustainability.

With over 25 years’ specialist experience across the UK, Central and Eastern Europe, the Middle East, Asia, Australia and the Caribbean, he has an in-depth understanding of the political and business drivers of projects with multiple stakeholders and complex design and delivery teams.

Areas of expertise:

Commercial / Transport

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