Digging for Salad: Is the Future of Vertical Farming Underground?

Vertical farming has spent a decade building up: warehouses stacked floor on floor with LED lit racks, chasing efficiency by going vertical. A small, scattered group of projects has spent that same decade quietly testing the opposite direction, down. Four months after securing UKRI funding, a team from the University of Sheffield and Farm Urban is now harvesting the first salad crops grown 1.1 kilometres below the surface, inside a working salt and polyhalite mine in North Yorkshire. It is being billed as the world’s deepest vertical farm, and it is not the only underground experiment currently running. A Canadian startup is drilling farms straight into the ground beneath new buildings, and a Japanese utility company is growing lettuce four floors under its own headquarters. A fourth, earlier attempt, a London farm built into WWII air raid tunnels, shows what can go wrong along the way.

Case 1: Boulby Mine, Physics Research Meets Pak Choi

The STFC Boulby Underground Laboratory, hosted inside the working Cleveland Potash mine near Whitby, is better known for dark matter research than agriculture. Shielded from cosmic radiation more than a kilometre down, it is one of the world’s low background physics sites, the kind of place built to detect signals too faint to survive anywhere closer to the surface. The same tunnels are now home to upright hydroponic growing beds producing lettuce and pak choi, first announced back in March 2026 when the UKRI funding was secured.

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Project co-lead Jacob Nickles says the team is currently harvesting salad crops, with a second trial planned around higher value, salt tolerant species: samphire, sea fennel, quinoa, rocket, basil, mustard, and possibly a tomato variety. Root vegetables, Nickles has said, are off the table because the hydroponic system does not suit their morphology, a claim worth unpacking properly later in this piece, since it is more nuanced than it sounds.

The appeal is largely thermal, the same lever we covered in detail in our breakdown of how to solve vertical farming’s energy problem. Boulby’s ambient temperature holds steady in the 25 to 35°C range, and the mine already has lighting and ventilation infrastructure in place, both of which chip away at the energy costs that make above ground vertical farms expensive to run. There are trade offs too: ambient salt and heat from ongoing mining activity add engineering challenges the team is still working through over the course of the 12 month study.

What makes Boulby a more interesting case than a one off research curiosity is the mine’s own backstory. A few years ago, Cleveland Potash’s future looked uncertain as its original potash reserves ran down. The site survived by pivoting to polyhalite, marketed as polysulfate fertiliser, a product mined almost nowhere else in the world. That shift secured around 580 jobs, most held by workers living within a 12 mile radius on an average salary of roughly £50,000, and the mine recently won a 25 year extension to its operating licence. Nickles points to that same pattern as the wider opportunity: many disused UK mines sit in economically deprived areas, and repurposing them for food production could mean skilled jobs and a second life for old industrial sites, not just cheaper lettuce.

Case 2: GreenForges, Farming as a Drilled In Utility

Where Boulby repurposes an existing mine, Montreal based GreenForges is building underground farms from scratch. Founded in 2019 by Philippe Labrie, the company drills 40 inch shafts, 15 to 30 metres deep, directly beneath new buildings, then lowers growing modules into the hole. Harvesting and maintenance happen by mechanically pulling the crop racks back up to street level.

The logic is the same thermal one driving Boulby, just engineered rather than inherited. In Canada, ground temperature stabilises around 10°C at just 5 metres deep; in warmer climates the company has cited figures around 20°C at 10 metres. Either way, the point is that underground temperature barely moves with the seasons, which is where GreenForges’ engineering manager Jamil Madanat has argued the real energy savings sit.

Commercially, GreenForges is not chasing farm ownership. The plan is to license the underground system to building owners, particularly developers of hotels and apartment complexes, and take a construction fee plus a share of produce sales, a real estate play as much as an agricultural one. It is also, by most available company data, still a very early stage business: no public funding rounds are on record, and independent trackers describe activity levels as low, a different capital position than the institutional, supply chain backed rounds now going to more established CEA operators. Anyone weighing this kind of CAPEX against a conventional build should run the numbers the way we outline in our vertical farm startup cost guide: worth watching, not yet worth calling proven.

Case 3: Kyuden HQ, Underground Farming as Workforce Inclusion

The third case looks almost nothing like the other two. Kyushu Electric Power’s special purpose subsidiary Q-CAP has opened a hydroponic vegetable farm on the fourth basement level of the company’s own headquarters building in central Fukuoka, Japan, according to the company’s own press release. It began operating in April 2026 and was shown to media in June.

There is no mine, no drilled shaft, no claim about geothermal stability. The “underground” here is simply unused basement floor space in an existing office building. The farm grows six varieties of leafy greens, including lettuce and kale, under LED lighting and without pesticides. What sets it apart is the purpose: ten employees with disabilities were newly hired to work the farm as part of Q-CAP’s inclusive employment programme, alongside two managers and support staff. Q-CAP already employs 45 people, 33 of them with disabilities, and holds Japan’s “Moni-su” certification for excellence in disability employment. The vegetables are being sold to Kyuden group employees from July 2026, with retail sales across Fukuoka Prefecture planned if demand grows.

It is a useful corrective to the idea that underground farming is a single trend with a single motive. Kyuden is not chasing energy savings from geology at all. It is using basement space to build a workplace, with the produce as a secondary output.

Which Crops Actually Work Underground, and Which Don’t (Yet)

All three current underground projects converge on the same basic menu: lettuce, pak choi, kale, herbs, microgreens, and Boulby’s planned second round of samphire, sea fennel, quinoa, rocket, basil and mustard. That is not a coincidence, and it is worth asking why, because the usual shorthand explanation, that root vegetables simply cannot be grown hydroponically, does not hold up to scrutiny.

Potatoes actually grow hydroponically without much trouble, in a specific and commercially established sense. Since at least the early 2000s, growers have used hydroponic and aeroponic systems, the same family of growing technology we compare in our CEA vs. hydroponics vs. aeroponics guide, to produce potato minitubers: small disease free seed tubers used to propagate the next generation of field crops, rather than potatoes destined for the plate. A widely cited comparison published in Potato Research found that aeroponic systems produced almost 70 percent higher tuber yield per plant than hydroponic beds, though with smaller average tuber size and a longer growing cycle. NASA’s own aeroponics research, later developed for space life support systems, drew directly on this seed potato work, not unlike how Freya Cultivation Systems’ ultrasonic aeroponics is now being co-developed with the German Aerospace Center for the same reason. So the “morphology” explanation commonly used for why vertical farms skip root vegetables is a simplification. The potato plant itself is not the obstacle. Producing an edible, table sized tuber at food crop scale, rather than a pea sized seed tuber, is.

Two separate obstacles explain that gap between growing the plant and harvesting a useful crop from it. The first is exposure damage: tubers sitting in a nutrient film or mist for weeks accumulate mineral salts that can damage the periderm, the thin skin layer that protects a potato from disease and moisture loss once harvested, a concern raised repeatedly in recent hydroponics literature. The second is energy economics, and this is the bigger one. Root and fruiting crops need dramatically more energy per kilogram of edible product than leafy greens, because most of the plant’s growth goes into building starchy or fleshy tissue rather than the leaf itself, which is also the part hydroponic systems feed and harvest most efficiently, the same 99 percent heat, 1 percent biomass imbalance we quantified for lettuce in our piece on vertical farming’s waste heat economics. Land Institute researcher Stan Cox has estimated that fleshy crops like tomatoes or sweet corn can require roughly 1,200 kWh of lighting electricity per kilogram of dry matter produced under fully artificial light, comparable to a year of running a household refrigerator to grow barely a kilogram of food. That single figure is most of the reason vertical farms of every kind, underground or not, have stuck to greens and herbs rather than staple crops.

Recent research is chipping away at that limit, at least for smaller root vegetables. A 2024 study on vertical hydroponic aeroponic hybrid systems found radishes and turnips could both be grown successfully in an eight week cycle under LED and mixed lighting, with turnips responding far better to vertical growing than radishes: over 450 percent higher root yield compared with a horizontal control, versus roughly 50 percent for radishes. That is early academic work, not a commercial deployment, and it is worth noting the study targeted fast cycling, shallow roots specifically, not the deeper, longer season crops like potatoes or carrots that Boulby has ruled out.

Underground systems add a second, more literal obstacle on top of the economics. Boulby’s grow beds and GreenForges’ shafts are both built around pulling growing racks or modules up and down a vertical or angled channel, a mechanism suited to shallow rooted plants growing in a thin nutrient film or lightweight substrate slab. A tuber bulking up in a deeper growing medium does not fit that harvest mechanism nearly as neatly as a lettuce head sitting on a floating raft. That is the practical half of what Boulby’s team means by root vegetables not suiting the system, sitting on top of the energy economics described above.

The Cautionary Tale: Growing Underground

Before any of these three projects existed, there was Growing Underground, arguably the project that put underground farming on the map in the first place. Founded in London in 2015 by Richard Ballard and Steve Dring, with backing from chef Michel Roux Jr, it converted a WWII air raid shelter 33 metres beneath Clapham into a hydroponic microgreens farm, supplying restaurants and supermarkets across the city. It ran for the better part of a decade, built out BRC and Red Tractor certification, and became something of a poster child for zero carbon urban food production, with Cambridge researchers even building a “digital twin” of the farm to optimise its growing conditions.

The company, trading as Zero Carbon Farms, was dissolved by Companies House in November 2023. It has since been named alongside AeroFarms, Kalera, and AppHarvest in our own analysis of why vertical farming fails as part of a broader wave of business closures largely attributed to rising energy costs, competition from cheaper conventional produce, and financing that got more expensive as interest rates climbed.

That is the uncomfortable footnote for the underground pitch. Growing Underground made almost exactly the same argument Boulby, GreenForges, and Kyuden are making now: constant temperature, renewable power, minimal environmental footprint, and it still did not survive the sector wide cost crunch that took down plenty of above ground competitors too. Going underground solves one input cost. It does not automatically solve the economics of controlled environment agriculture as a whole, and it never solved the crop selection problem either: even at its peak, Growing Underground stayed within the same microgreens and salad leaf category that Boulby, GreenForges, and Kyuden are all still working within today.

So, Underground: Yes or No?

Three very different projects, three very different reasons to dig. Boulby is squeezing a second act out of a mine that has already reinvented itself once. GreenForges is selling underground infrastructure as a service to property developers. Kyuden is using spare basement space to build an inclusive workplace, almost incidentally producing lettuce along the way. None of them are large enough yet to prove underground farming at commercial scale, and Growing Underground is a reminder that a good thermal argument does not guarantee a viable business.

What underground farming does offer, consistently across all three current projects, is a way to sidestep vertical farming’s most persistent cost problem, climate control, without needing a breakthrough in LED efficiency or power prices. What it has not solved, and what none of the four projects in this piece have solved, is the crop ceiling that applies to vertical farming everywhere, underground or not: until the energy cost per kilogram of a fleshy or starchy crop comes down substantially, the menu stays limited to greens, herbs, and the occasional small, fast growing root. Whether the thermal savings are enough to build a lasting business on greens alone is exactly what the next 12 months at Boulby, and whatever comes next from GreenForges and Kyuden, should start to answer.

Further Reading

• How to Solve Vertical Farming’s Energy Problem: 5 Approaches That Actually Work
• Why Vertical Farming Fails and What Actually Works
• How Much Does It Cost to Start a Vertical Farm in 2026?
• The Overlooked Revenue Stream Hiding in Every Vertical Farm’s LED Heat
• CEA vs Hydroponics vs Aeroponics: What Vertical Farms Actually Use in 2026
• Freya’s Ultrasonic Irrigation: Is This What Aeroponics Was Always Supposed to Be?