With COVID-19 and Brexit affecting food imports, CHAP Innovation Network Lead Dr Harry Langford looks at how controlled environment agriculture can add to the UK’s food security by increasing yields, while also benefiting the environment. Controlled Environment Agriculture (CEA) is the production of crops under highly controlled conditions in greenhouses (i.e. glasshouses or ETFE greenhouses) or indoor spaces (e.g. vertical farms).

The rise of the green growth agenda

In 2011, the OECD released its preliminary ‘Green Growth Strategy for Food and Agriculture’ report. It said: “Sustainable productivity growth that reflects the scarcity value of natural resources, and optimises resource use and environmental protection, will be fundamental to meeting the food and nutrition requirements of future generations”. Since then there has been increasing pressure to reduce the carbon intensity and adverse environmental impacts throughout our agri-food chain.

Now, the global Covid-19 pandemic is also having an effect, with more than 150 multinationals having signed a UN-backed statement calling for governments to align their economic relief plans with science-based climate targets, leading to the idea of a ‘green recovery’, sparked by the need to ‘build back better’.

Innovations in resource efficiency, yield resilience and cropping intensity will all be critical to drive green productivity growth in the sector, while ensuring food remains affordable for everyone.

The European Commission published its long-awaited ‘Farm to Fork’ strategy in May, outlining ambitious 2030 targets for landscape diversification (10%), reducing chemical pesticide use (50%), reducing nutrient losses (50%) and reducing fertiliser use (20%).

In the UK, the as yet unratified, Agricultural Bill and the associated Environmental Land Management Scheme (ELMS) aim to reward farmers for environmental protection and public good provision, increasing the sustainable productivity of UK agriculture while shifting towards net zero.

This is all in line with the principles of green growth, save for – perhaps – a slight ignorance around the agri-tech innovations needed to achieve this growth and the mechanisms needed to prioritise these innovations. The NFU report ‘Achieving Net Zero’ outlines some of the practices farmers can use to reduce their emissions: controlled release fertilisers, anaerobic digestion, enhanced hedgerows and strategic woodland planting, and an ambitious swathe of bioenergy cropping with carbon capture and storage. However, more detail is needed on the potential of carbon storage in soils, dietary change, precision digital agriculture and controlled environment agriculture.

CEA is already forging a path towards green growth

Controlled Environment Agriculture (CEA) is the production of crops under highly controlled conditions in greenhouses (i.e. glasshouses or ETFE greenhouses) or indoor spaces (e.g. vertical farms). CEA allows the grower to optimise inputs such as energy, labour, water and crop protection products, with the aim of maximising both crop production/yield and crop quality, as well as extending the fresh produce season through into the winter months.

Temperature, humidity, CO₂ levels and lighting are probably the most important environmental variables to control well within a CEA system, though there are many ways to do this. Temperature and humidity can be controlled using radiant or piped heat, HVAC, passive ventilation, or evaporative cooling; CO₂ levels are typically raised through carbon dioxide generators or, more recently, captured CO₂ from Combined Heat and Power (CHP) engine exhaust systems or biomass boilers. Lighting is either high-pressure sodium or LED, with newer LED lights boasting specific wavelength control to boost blue or red or add in far-red wavelengths, allowing light recipes to be tailored to specific plant varieties.

CEA already boasts some of the highest efficiencies (yield per unit area of land) of any mode of production, with studies indicating ~11 times greater land use efficiency in hydroponic glasshouse systems (Barbosa et al. 2015) and, for vertically farmed lettuces, ~14 times greater than that (Touliatos et al. 2016). Commercial grower Green Spirit Farms produces the equivalent of 81 ha of farmland harvested year-round within its 11-ha vertical farm, across a range of crop types (~8 times more efficient; Al-Kodmany 2018). In the UK, Intelligent Growth Solutions states that the annual output of two of its 9m-high growth towers is equivalent to one crop cycle from one hectare of field production. It is not only the vertical stacking that enables this efficiency, but also the highly tuned LED lighting and optimised environmental conditions, which allow leafy greens to grow up to two and a half times faster than field production (Benke & Tomkins 2017).

Water savings

By 2030, it is estimated that 47% of the world’s population will live in areas with severe water stress, up from 35% in 2005. In this country, south-east England and East Anglia are particularly vulnerable, with climate change predicted to reduce rainfall and the UK’s population set to rise. Water use efficiency within CEA production is typically 70-95% greater than in field agriculture (e.g. ~92% less water used in the Barbosa et al. study), thanks largely to advancements in recirculating hydroponics and improved environmental control.

Perhaps surprisingly, the energy intensity of UK agriculture (energy use per unit of output) actually increased by 19% between 2000-2018 (BEIS National Statistics 2019). While the energy intensity data was not fully factored, within the arable and horticulture sectors this is most likely due to higher fuel consumption of larger agricultural machinery, more digital service uptake in agriculture and an increase in the number of higher-energy glasshouse and vertical farm units.

Having said that, significant work in the CEA sector is bringing energy efficiency savings and beginning to improve energy intensity markedly. Sector-standard LED lighting, for example, already offers an energy saving of 50-70% over high-pressure sodium lighting. Newer advances – such as driverless lighting, ultra-low voltage power and integrating sensing and control – could deliver an additional 30% energy saving.

Energy efficiency

Within the CEA sector, vertical farms have been found to outperform the most efficient glasshouses in terms of energy efficiency (Graamans et al. 2018) and CO₂ use efficiency, although due to solar energy inputs, glasshouses use less energy overall. More recently though, linking green energy to glasshouse production, e.g. via Anaerobic Digestion (AD) with CHP, has seen considerable uptake, and clean energy funds have begun to invest in co-located glasshouses to utilise industrial waste heat, citing a 75% reduction in the carbon footprint of production due to the capture and re-use of wasted energy.

These innovations, among others (e.g. thermal screen technology and ground-source heating and cooling) have significantly improved the energy efficiency and lowered the operational expenditure of glasshouse production in the most modern UK glasshouses.

CEA is already an innovation hot-spot, with vertical farming companies such as CHAP member LettUs Grow, Intelligent Growth Solutions and Vertical Future raising just shy of £10 million through private-sector investment, indicating the support for innovation within the UK agri-tech sector.

Green agricultural growth

Peat usage is still significant within the CEA sector, for everything from babyleaf lettuce production to seedling or transplant production, contributing to the ~1 million cubic metres of peat used each year within UK horticulture. Government legislation will not permit its use beyond 2030, so alternatives definitely need to be found that can maintain the quality, consistency and volume of production that is currently achieved using peat. Other substrates, such as coir or rockwool, are equally unsustainable, so novel substrates need to be developed.

CEA is one of the few industries to successfully incorporate carbon capture and use, from (AD‑)CHP engines, into production. However, a mismatch between supply and demand can result in direct CO₂ emission from gas-to-grid CHP engines.

Venting of glasshouses is needed to maintain relative humidity or for cooling. If this is poorly timed or – particularly during the earlier growth stages – when the plants are smaller, direct CO₂ emission can also occur. While CO₂ use efficiency is typically better within vertical farms than glasshouses, the sector could benefit from innovation in CO₂ use, efficiency and management, to support net zero.

Horticultural energy use has always been significant within agriculture, with data from 2005 (Warwick HRI 2007) indicating that protected crops accounted for 26% of the direct energy use in agriculture, of which 58% (15% of total for agriculture) was attributable to protected edibles. Energy use in CEA, particularly vertical farming, is its biggest downside from a green growth perspective. Typically, vertical farms use 30-176 kWh per kg more energy than greenhouses. Although there is already a lot of innovation in this space, further reductions in energy use, efficiency improvements and integration with renewable energy sources are needed to ensure CEA is commercially viable within the UK.

A need for automation

Within the most automated vertical farms, labour is relatively low, however most glasshouse CEA operations still require a significant labour force. This is particularly true for difficult to automate tasks, such as harvesting. Restrictions on the seasonal labour market – from both Brexit and Coronavirus – have led to growing concern about the divergence between a rapidly reduced labour supply and a slower progression towards fully automated CEA. Robotics and automation solutions within the CEA sector need to be prioritised to ensure production rates can be maintained and expanded.

Crop diversity is also an issue, particularly in the face of growing food security concerns and calls for improved nutrient density within foods. At present, the CEA sector principally grows leafy greens (e.g. lettuce, spinach, babyleaf and herbs), solanaceous and gourd vegetables (e.g. tomatoes, peppers, cucumbers, squash and aubergines) and soft fruits (e.g. strawberries, raspberries and blackberries). The vertical farming sector is struggling to viably grow taller stature, longer lifecycle crops and is principally engaged in microgreen production. The alternative protein market is expanding, and there is a need for more nutrient-dense production in order to effectively balance food production, carbon sequestration and consumer health. Increasing crop diversity within CEA and the nutritive value of existing crops are both significant innovation priorities.

Innovation holds the solution

• CHAP member Digital Farming has successfully produced strawberries in its vertical production system. Beeswax Dyson Farming is currently constructing a low-input, 6-ha soft fruit glasshouse linked to an AD-CHP facility in Lincolnshire. This will focus on energy-efficient strawberry production. A 12.7-ha glasshouse is also under construction in East Anglia, co-located next to an Anglian Water treatment facility to utilise waste industrial heat; this will be operated by Abbey View Produce.
• INDO Lighting has developed some of the most efficient LED lighting on the market, using its Direct Drive technology, with white lights tuned to three different spectral profiles to match critical plant growth stages. French company Rouge Engineered Designs has developed a 4-LED-colour, fully tunable greenhouse light with a control system that senses light intensity and spectrum and dynamically optimises the light spectrum.
• Farm management systems are a particular focus for innovation, with LettUs Grow creating its Ostara system and researching into integrating ‘demand-side response’ into production through a collaboration with Octopus Energy, while Ginium Ltd is developing a hardware-agnostic software system for indoor agriculture.
• CHAP member AEH Innovative Hydrogel has just won an Innovate UK grant to investigate use of its novel hydrogel formulations as low-carbon, re-usable substrates for the vertical farming and hydroponic glasshouse sector.
• Phytoponics is looking to expand the repertoire for vertically farmed produce in the UK by growing Dragon Fruit in the glasshouses of CHAP partner Stockbridge Technology Centre.
• Autonomous guided vehicles are becoming more commonplace in CEA, but robotic harvesting is still in development. CHAP member University of Plymouth’s spin-out Fieldwork Robotics has recently partnered with Bosch to optimise its soft robotic arms for automated fruit picking, and Dogtooth Technologies is partnering with University of Lincoln to further develop its robotic harvester. Work rates are approaching half that of a human picker, with work on added value (e.g. in-situ grading) and cost reduction beginning to make these a serious proposition.
• Hybrid vertical glasshouse systems are receiving increasing attention. Shockingly Fresh is set to construct several across the UK, incorporating the Saturn Bioponics tower system. Growpura plans to scale up its vertical moving hydroponic system thanks to a £4.5M grant from South East Midlands Local Enterprise Partnership.

Resilient food systems

What the agri-food sector ultimately needs is green growth within a sustainable and resilient food system. CEA currently provides a set of tools to achieve this, and innovations in the sector are driving efficiency and productivity improvements. Looking to the future, it is imperative that CEA technologists, growers, and researchers interact with wider food systems. The CEA sector needs to fully understand its green growth potential, as well as the barriers and emerging solutions, to allow it to further improve its credentials, scale up in harmony with a resilient UK food system and drive clean, green growth.

Dr Langford has a background in soil science and geomicrobiology, with a PhD in Environmental Science from The University of Sheffield. He has worked in postdoctoral and scientific coordination roles for the Centre for Ecology and Hydrology and The University of Sheffield, focusing on soil microaggregate structure and landscape-scale environmental observation systems. Before joining CHAP he spent three years working as a Knowledge Exchange Fellow for the N8 AgriFood Resilience Programme, building and leading an innovation cluster on Urban & Controlled Environment Agriculture and delivering knowledge exchange focused on soil health and sustainable agriculture.