Where Should our Salads Come From?

Zeina Chapman, Co-Founder of Liberty Produce, considers how vertical farming could help the UK to increase its food security and become more sustainable

At this time of year, when the sun barely seems to rise above the horizon and our attentions are focused on the rich pickings that the festive season can offer, it can be tricky to motivate oneself to seek out the fresh and nutritious fresh foods that are abundant during the summer months.  Most of us will include some green leaves in our Boxing Day leftovers cold spread, but how many of us really consider where the salad on our plates is actually coming from?

 Where is our salad grown?

Retailers work with large salad suppliers (who are also often growers themselves) to supply produce year-round. In most instances, these suppliers will manage the procurement, processing and packing of products into retailers’ distribution systems.

Climatic constraints on growing seasons mean that in a single year, leafy greens such as baby leaf salads or whole head lettuce may have been sourced from up to three or four different countries in the world. During the summer months (May-October) many of the salad items consumers were seeing in the stores will have been grown in the UK. Outside of the main UK growing season, suppliers will transition to production from the continent, with Spain supplying the bulk of the winter produce we eat, supported by production from others such as Italy, Portugal and the Netherlands.

Managing this supply process is incredibly difficult. Although many salad suppliers are fully integrated, with the ability to draw product from their own growing sites across the globe, predicting the weather and its impact on crop availability is complex. Matching this to consumer demand and volumes required is even harder.

Simply put, shoppers buy more salad when the sun shines. Sustained increases in temperature and sunlight will also cause crops to “flush” resulting in greater volumes.

However, our unpredictable UK summers mean these two events rarely coincide. Suppliers and retailers instead tend to find themselves searching for additional volume when the sun is shining and consumer demand is high, and are then left with excess product from a crop flush, a week to 10-days after the clouds have rolled in.

To ensure full availability in stores, even in peak season, retailers can be forced to take non-UK produce in times of high demand and will then often have to promote heavily following a crop flush, to save it from being wasted.

The salad bag problem

My go-to produce item throughout the year is a salad bag. I’m not alone in this behaviour – in the UK it’s estimated that 480m salad bags are sold each year and it represents the largest volume and value sales area of the salad category. Over the last few years, the salad bag has suffered under the ambitions of creating what was once considered the ultimate consumer-focused convenience item. The avoidable waste, the excessive use of plastic and water, the chemical additions in the form of pesticides in the growing process and the water used in washing are all areas for consumer concern that the market must respond to.

Post-harvest, salad leaves have a very limited shelf life. Once leaves have been washed and dried, they are packed into modified atmosphere packaging (MAP) – plastic bags which are flushed with gas – altering the atmospheric concentrations of oxygen, nitrogen and carbon dioxide with the aim of slowing down respiration, deterioration of the leaves and preventing wilting.

While MAP is incredibly effective and in some cases doubles the shelf life of products, it requires a fully sealed plastic pack. In addition to the single use plastic waste concerns, MAP is effective only to a point for consumers: an unopened salad bag can sit in your fridge looking pristine for days, yet the moment it is opened, even if it’s stored chilled, leaves can quickly turn to a green slime.

Our existing production methods cannot guarantee that contamination in the form of foodborne diseases or foreign bodies is avoided. Producers must go to extreme lengths to limit the exposure of consumers to harmful diseases caused by the likes of E.coli and Salmonella; with salad leaves routinely washed in chlorine.

Controlled Environment Agriculture and how it can help

Controlled environment agriculture (CEA) is the production of crops indoors, within an enclosed structure such as a building, greenhouse or specialised growing unit. The aim of CEA is to provide protection and maintain optimal growing conditions in an environment that controls light, CO2, temperature, humidity, water, pH levels, and nutrients.

Often facilities that employ these techniques are called vertical farms since the available growing space is increased by stacking growing areas on top of each other vertically. The benefits of this approach mean that the growing environment is not affected by the external climate and facilities can be built in almost any location, as neither solar light or soil is needed, only electricity, nutrients, water and seeds. By removing impacts from the external environment, production yields can be maintained year-round and the supply of water and nutrients to the root zone can be totally optimised.

As a result, vertical farming systems are significantly more productive per square meter of growing area, than traditional growing methods; with potential to increase yields up to tenfold. The closed system of a vertical farm allows us to utilise most effectively our resources, including water, energy, space, capital and labour, reducing our impact on the environment. In fact, the IHCEA capability that we recently built in partnership with CHAP recirculates its own water and there is potential for this and similar facilities to generate their own water and plug into renewable energy sources.

Vertical farming also removes the need for the use of pesticides – these poisons are applied to target specific pests but many have wide acting applications with the potential to be toxic to humans and non-target species such as bees, birds and mammals too. As consumers become increasingly aware of the dangers of the use both on human health and the natural environment, the market must respond with a viable solution.

The implications of shifting our food supply chain in this manner are enormous. Year-round production of UK-grown crops would provide stability to our supply chain in terms of availability and price. Crops would be grown on demand, in conditions that optimise their quality, flavour and nutrition, without the natural fluctuations we see currently, as a result of environmental variances such as climate, soil type and irrigation etc. It has huge implications for questions of traceability (which are becoming another facet of current consumer concerns around food production) as the more intricate and complex our global supply chains become, the harder it is to ascertain the full detail and traceability of where and how products have been produced.

Vertical farming enables us to grow produce close to where it is being consumed; drastically reducing the time from field to fork and the food miles for this easily damaged, perishable product. Local production and shorter supply chains mean greater supply chain transparency. Doing this may also remove the necessity for extending the natural shelf life of products through MAP. Technology and processes developed in “closed system” vertical farms are likely to allow for better control of pathogen risks and could mean that the washing process which is currently unavoidable for the control of pathogens in traditionally grown crops could be removed Increased shelf life, improved quality and local production will all reduce food waste, another significant issue in production and consumption of salad bags.

 The Challenges VF still faces

Despite the numerous benefits it can offer, there still remain challenges which must be overcome before VF can achieve its full potential. The cost of capital investment remains as a significant barrier to adoption – high-tech facilities with the tools to fully control the growing environment are expensive. Despite the concerted effort of technology developers to focus on energy efficiency, the energy requirements for VF systems still remains high. These factors mean that the economic viability of VF is currently limited to high value crops such as herbs and micro-greens.

There is also currently a gap in consumer understanding of how and where food is produced and, indeed, how it will need to be produced in the future in order to create sustainable resilient food production systems. This is going to be crucial in gaining the trust and buy-in from consumers for food grown in a CEA systems.

While vertical farming isn’t currently sustainable, a huge amount of work is going into developing the technology that will transform our current food production systems. The Future Farming Hub is already building the tech and educating consumers and industry to revolutionise how we eat and fundamentally benefit supply chains, reduce waste and ensure we become more sustainable.

Liberty Produce is a UK Agri-Tech start-up. It is a CHAP partner through the Innovation Hub For Controlled Environment Agriculture (IHCEA) based at the James Hutton Institute in Dundee. 

If you have any questions about CHAP’s CEA capabilities or would like to reach out to the CHAP team about a specific project, please email us at enquiries@chap-solutions.co.uk


Please note, the opinions expressed in this article are the author’s own and do not necessarily reflect the views or opinions of CHAP.