Is Vertical Farming the Future?

A story appeared on the BBC News website talking about a new vertical farming operation in Gloucestershire. The Grantham Centre took this opportunity to look into some of the specifics of the article and ask one question. Is vertical farming the future of agriculture?

So what is vertical farming? In essence it is growing crops in vertically stacked layers, often in controlled atmospheres. Heating and lighting are arranged to optimise growing times to increase yields and maximise profit.

Let’s look at the article in more detail.

Image credit: BBC News
The so-called vertical farm can grow salad three times as fast as traditional outdoor agriculture thanks to its controlled, consistent climate.

This is true. Studies have shown that CEA (Controlled Environment Agriculture) systems can have significantly higher yields per square metre than conventional growing methods. In this study yields of lettuce were over ten times higher. This could be a great benefit for areas where land available for cultivation is low.

“There’s a lot of tech involved, a lot of engineering involved…”

This statement highlights that there is significant material use in vertical farms and other CEA systems. This embodied carbon should be taken into account when determining the relative sustainability of different growing systems. An unheated polytunnel will have a relatively low embodied carbon compared to a new build insulated vertical farm structure.

What the rise of vertical farming does give the opportunity for is the reuse and repurposing of existing buildings. Where these can be collocated with sources of waste heat, say next to industrial units, the embodied and operational carbon can be optimised.

What’s more, the “outdoors” he refers to is in Spain or Morocco at this time of year. British supermarkets sell bags of salad leaves all year round, but in the winter they have to be imported. (…) He explained: “Compared with trucking the crops across Europe, or even air-freighting it, we are saving carbon.”

We eat a lot of lettuce. In 2022 92,000 tonnes of lettuce were grown in the UK and 132,000 tonnes imported. However very little of the salad crops sold in UK shops are airfreighted. The majority of winter supplies actually come from Spain (over 80%). Within the overall carbon footprint of food supply chains, transport is often a very small proportion. A 2005 study commissioned by DEFRA showed that for tomatoes grown in Spain the transport emissions from freight were around a fifth of the total for the product but that overall the Spanish tomatoes had an impact three times less than that of the UK grown equivalent.

It is imperative that when claims are made about products the full lifecycle and wider environmental impacts are compared. Highlighting a single issue, such as food miles, growing time or water use can result in consumers being misled as to the most sustainable choice to make.

All the power is sourced from renewable electricity, and carefully managed.

What is true renewable electricity? In the UK there is a system of Renewable Energy Guarantees of Origin (REGO) Certificates. They are provided to generators of electricity and then can be sold on via retailers to the ultimate consumers. Theoretically this puts a premium on electricity generated from wind and solar and should stimulate developers to build more infrastructure. What this means in practice is that if you procure your energy from a supplier offering a renewable tariff they will have purchased REGO certificates at sufficient volume to cover the power they sell to you and to all their other customers.

Does this mean your electricity is cleaner than anyone else’s? In a word – no. The UK has a national grid into which all power generated is fed. It is then ultimately delivered, via local distribution networks, to consumers. Every year the government produces a grid average emission factor. This is derived from the mix of technologies that have been employed to generate the nation’s power.

To truly claim that the energy used in one particular building, process or product manufacture is renewable the user needs to demonstrate additionality.

That could take the form of “behind the meter” installations such as roof mount solar, or an on-site wind turbine. It could be a private wire from a nearby installation which bypasses the grid infrastructure. Alternatively it could be a Power Purchase Agreement (PPA) with a developer where an organisation agrees to a long term supply contract in order to facilitate the building of renewable power plants.

Image credit: BBC News

How energy is managed could also be crucial to the long term viability of vertical farming, and minimising its environmental impact. Currently the UK energy market is focussed around time of use charging, attempting to match supply and demand with punitive tariffs. Should we move to a carbon based tariff system then operations could be optimised to strike a balance between yield and impact.

(…) Infarm has closed its operations in Europe – making 500 staff redundant.

Vertical farming is heralded as a more resilient way of supplying food to our supermarket shelves. It is also claimed to be more resilient to the impacts of climate change, and more resilient to the impacts on global supply chains caused by wars, pandemics and trade disputes. Infarm’s own website is keen to point this out. Whilst this may be true, the energy intensity of the operation and the need to deliver a return on investment for the significant infrastructure set up costs means that these installations have a different set of vulnerabilities from more traditional growing methods.

Mr Lloyd-Jones said he believed his company had “cracked the code” for growing sustainable food all year round.

So is this a breakthrough in sustainable farming? The article itself does not contain the detail we would need to make that assessment. There are many considerations, as highlighted above, that need to be taken into account in making such a claim. Even simply through a carbon lens there are issues which need to be addressed. That is without looking at wider environmental and societal impacts.

The question then becomes, if producing home grown lettuce is what we want most, should we only eat it in summer? Or if we want to minimise imports, and create the lowest impact UK only crops should vertical farms be turned off in summer and field grown crops used instead?