Synergy between vertical farming and the hydrogen economy

Abstract

By 2050, the world population will rise to 9.7 billion, and
two-thirds of the world’s inhabitants will reside in urban
areas, according to a forecast by the United Nations (UN
2022). This calls for innovative farming because history
shows that without the Green Revolution techniques of the
1960s, an additional area of 1761 million hectares megahectares
would have been required to attain the same agricultural
output, and thus these techniques have avoided the
emission of 590 gigatonnes of equivalent carbon dioxide
(Burney et al. 2010). Unfortunately, the classical techniques
of industrial agriculture are actually inducing massive environmental
degradation, such as soil erosion, habitat destruction,
loss of biodiversity, water pollution, and greenhouse
gas emissions. Paradoxically, the promising solution to these
issues, vertical farming, is also intensive though it is also
ecological in many aspects (Fig. 1, Kozai and Niu 2016a).
Here, we discuss the potential synergies of vertical farming
and wind, solar and hydrogen fuels.

Full text

Vol.:(0123456789)
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Environmental Chemistry Letters
https://doi.org/10.1007/s10311-023-01648-5
EDITORIAL
Synergy betweenvertical farming andthehydrogen economy
AhmedI.Osman1· DavidRedpath1· EricLichtfouse2· DavidW.Rooney1
© Springer Nature Switzerland AG 2023
By 2050, the world population will rise to 9.7billion, and
two-thirds of the world’s inhabitants will reside in urban
areas, according to a forecast by the United Nations (UN
2022). This calls for innovative farming because history
shows that without the green revolution techniques of the
1960s, an additional area of 1761million hectares mega-
hectares would have been required to attain the same agri-
cultural output, and thus these techniques have avoided the
emission of 590gigatonnes of equivalent carbon dioxide
(Burney etal. 2010). Unfortunately, the classical techniques
of industrial agriculture are actually inducing massive envi-
ronmental degradation, such as soil erosion, habitat destruc-
tion, loss of biodiversity, water pollution and greenhouse
gas emissions. Paradoxically, the promising solution to these
issues, vertical farming, is also intensive though it is also
ecological in many aspects (Fig.1, Kozai and Niu 2016a).
Here, we discuss the potential synergies of vertical farming
and wind, solar and hydrogen fuels.
A circular plant factory
The well-insulated airtight opaque building enables internal
conditions to be controlled. Also, existing buildings can be
retrofitted without altering their exterior appearance. The
internal growth area with a multi-tiered hydroponic system
increases the area available for plant growth; each tier being
equipped with artificial light-emitting diode lighting to sup-
ply the light required for plant growth. The plants grow in
a hydroponic medium, and there is a heating, ventilation
and air conditioning system with circulating fans for space
conditioning and air circulation. The carbon dioxide supply
system is used for increasing the concentration of carbon
dioxide to improve plant growth and sequester carbon. The
nutrient supply system supplies the required fertilisers for
plant growth. These nutrients can be artificial or organic
nutrients derived from anaerobic digestates or via aquapon-
ics. The water transpired by plants is captured in the con-
denser of the air conditioning systems, then returned to the
nutrient supply system, thus minimising water usage.
98% lesswater usage
Vertical farming was developed during the early 1970s for
long-distance space exploration because area is limited on
spacecrafts (Zabel etal. 2016). Essentially, vertical farm-
ing can be located anywhere, provided there is a plentiful
supply of energy, water, nutrients and a suitable structure
to contain the multilevel hydroponic growth system. Water
usage is reduced by 98% compared to open-field agriculture
because 95% of the water from the evapotranspiration of
plants can be collected by the air conditioning system and
reused (Avgoustaki and Xydis 2020b). When combined with
aquaponics, which integrates aquaculture with hydroponics
into a system where the input of plant nutrients is provided
via the food supplied to the fish, the requirement for artificial
fertilisers and pesticides is minimal (Kozai 2013). Switching
from conventional open arable farming to enclosed verti-
cal farming reduces the total amount of land required for
crop production, negates the requirement for imports of out-
of-season produce, and reduces food miles and associated
carbon footprints (Despoina Avgoustaki and Xydis 2020).
In the United States of America, it was estimated that, on
theaverage, the distance food is transported to retail outlets
is 2000kms (Smit and Nasr 1992). The increased deploy-
ment of vertical farms would lead to reduced food waste, as
fresher produce lasts longer.
* Ahmed I. Osman
aosmanahmed01@qub.ac.uk
Eric Lichtfouse
eric.lichtfouse@icloud.com
1 School ofChemistry andChemical Engineering, Queen’s
University Belfast, BelfastBT95AG, NorthernIreland, UK
2 State Key Laboratory ofMultiphase Flow inPower
Engineering, Xi’an Jiaotong University, Xi’an710049,
Shaanxi, People’sRepublicofChina

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200 timesmore productive
Typically, a vertical farm with ten tiers has a productivity
100 to 200 times that of conventional open-field agricul-
ture (Kozai 2013); a theoretical investigation estimated a
potential increase of 514 times (Banerjee and Adenaeuer
2014). With continuous production, vertical farms offer
permanent rather than seasonal employment opportuni-
ties in agriculture (Kalantari etal. 2018). Recent research
has identified that small tuberous root vegetables are par-
ticularly useful for growth enhancement using elevated
carbon dioxide concentrations as the roots are effective
carbon sinks, so photosynthesis in the leaves is increased
using the sieve tubes in the stems, which transport carbo-
hydrates more efficiently (Kozai Toyoki etal. 2020). Previ-
ous research reported that increasing the atmospheric con-
centration in controlled environments, such as from 800 to
1000 parts per million (ppm)in a verticl farm, increased
yields of C3 plants by up to 100% (Poudel and Dunn 2017).
More resources andcapital needed
Whilst vertical farms are more resource efficient, they
are more resource and capital-intensive than open-field
agriculture or greenhouse cultivation (Stein 2021, Plant
Factory 2022). It was estimated that the electrical energy
required for lighting when cultivating basil all year round
was 1030kWh/m2/yr, providing an annual yield of 50kg/
m2 (Avgoustaki and Xydis 2020b). The capital expenditure
for a building containing a vertical farm with a 15-tier sys-
tem, and a vertical separation distance of 50 cm between
the tiers, was estimated at $4000/m2 (Kozai and Niu
2016b). A vertical farm in Denmark using a six-tiered
growing system for producing basil had capital expendi-
ture costs of €1430/m2 (Avgoustaki and Xydis 2020c).
Recycling green oxygen fromhydrogen
production
Vertical farming also allows synergies with the green hydro-
gen economy and the increasing use of renewable power
generation. In particular, this can help grid balancing, by
using thecurrently curtailed wind power. It was estimated
that, by doing this, the initial capital expenditure of vertical
farms could be repaid in 4 to 8years (Xydis etal. 2021).
Green oxygen generated during the electrolysis of water for
the production of green hydrogen, which is normally con-
sidered as waste, could potentially be supplied to the plant
roots via the circulating nutrient solution. Supersaturating
the nutrient solution with pure oxygen rather than air dou-
bles the yield of hydroponically grown crops and addition-
ally inhibits fungal growth on roots (Suyantohadi etal. 2010;
Chérif etal. 1997).
Securing an indigenous energy and food supply with stra-
tegic energy storage levels removes the reliance on any other
external sovereign regimes for food and energy, essentially
providing complete independence for any nation adopting
these technologies. By identifying clearly the agricultural
Fig. 1 The main components
of a vertical farm: An internal
multitiered grow area for plants
with hydroponics and artificial
lighting; a carbon dioxide sup-
ply system; a nutrient supply
system; a heating, ventilation
and air conditioning system, a
well-insulated airtight opaque
building, and an environmental
control system. Modified from
Kozai (2013)
Air tight opaque
building
Plants, hydroponics,
artificial lightin
g
Heating, ventilation,
air conditioning
Carbon dioxide
Nutrient
sE
nvironmental control
Vertical farming

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applications and economic advantages of using green oxy-
gen generated from water electrolysis, the higher costs asso-
ciated with green hydrogen production could be reduced,
improving the payback period and stimulating the emerging
hydrogen economy.
Grid balancing
Using vertical farms for grid balancing or “flexible connec-
tions” also reduces the costs associated with grid reinforce-
ment. From 2020 to 2021, the installed capacity of wind rose
by 47.8% from 59 to 113 gigawatts (GW), whereas genera-
tion rose by only 17% (IEA 2022). The lack of flexibility
associated with transient renewable power generation, such
as wind or solar photovoltaics, means that some countries
assume a capacity factor of only 10% for wind turbines. (IEA
2020). Lighting provided for vertical farms can be switched
off for short periods, allowing these to act as grid balanc-
ing services assisting the integration of transient renewable
energy generation technologies, and research by Avgoustaki
etal. (2021) reported thatintermittent lighting increased bio-
mass production by 47%.
Synergy withhydrogen andwind energies
The costs of wind energy curtailment from 2011 to 2021
for the United Kingdom is increasing (Fig.2, Matson and
Knighton 2022). The planned increase in the generation of
green hydrogen in the United Kingdom to 5Gigawatts and
the expansion of installed offshore wind energy generation
capacity to 50Gigawatts by 2030 suggests that developing
vertical farming technology would simultaneously supply
an indigenous hydrogen economy, asustainable source of
energy and secure food supplies. This would also support the
transition to net zero by 2050 by increasing the capacity fac-
tor of renewable energy generation and reducing greenhouse
gas emissions from the agricultural sector. As the quantity
of renewable energy generation in the United Kingdom has
increased, so has the problem of curtailment along with its
associated costs. A 2022report produced for the DRAX
company estimated the cost of wind energy generation cur-
tailment in 2020 and 2021 as £806million.
Curtailed wind energy could power vertical
farms
If the curtailment value of 2021 stayed the same by 2030,
assuming thatthe target of 50Gigawatts of offshore wind is
met, then the quantity of curtailed energy from this expan-
sion in offshore wind capacity would be 4465Gigawatt
hours. Regarding the unit growth area, Avgoustaki and Xydis
(2020a) reported that 0.176kW/m2 was required for lighting.
Kozai and Niu (2016a) reported that for a well-insulated,
airtight building, lighting constitutes 80% of the total elec-
trical input, with the cooling systems requiring 16% and the
other components 4%. Assuming that the daily photoperiod
is 16h, then the lights would operate for 5840h annually,
Fig. 2 Installed wind capac-
ity, in megawatt (MW), and
wind energy curtailment, in
megawatt-hour (MWh)/MW
installed capacity, for the United
Kingdom from 2011 to 2021

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requiring 1028kWh/m2/yr, cooling would require 206kWh/
m2/yr and the other electrical components 51kWh/m2/yr, so
in total 1.285MWh/m2/yr is required to run a vertical farm.
The quantity of curtailed United Kingdom wind energy in
2021, 2,299,296Megawatt hours, could have powered the
equivalent of 1.79million m2 of vertical farm. If a similar
level of curtailment was occurring globally, then the 2021
installed capacity of 113Gigawatts would indicate a curtail-
ment of 10.1million Megawatt hours sufficient to power
7.85million m2 of vertical farm.
As vertical farms use artificial lighting, curtailed energy
generated during periods of low demand could be used to
grow food and replace imports of exotic or out-of-season
produce as they do not have seasonal variations in output.
This would decrease food miles and provide a revenue stream
for the currently wasted curtailed electricity (Avgoustaki
etal. 2021), potentially providing a market for green oxygen
to increase yields and hence annual profits. In 2021, 58% of
food consumed in the United Kingdom was of domestic ori-
gin; however, the value of food imports at £45,852million
was 56% higher than exports at £20,240million (DEFRA
2022). Assuming that vertical farms were collocated with
the new hydrogen and industrial hubs being developed on
the east coast of England, waste carbon dioxide from flue
gas emissions or blue hydrogen production would be read-
ily available, which could be used to potentially increase
yields by 100% and additionally sequester carbon. Using
green oxygen could potentially improve yields by a further
100%. Assuming that curtailed electricity generated from
offshore wind was supplied to vertical farms at its 2024/2025
clearing price of £41.61/MWh (UKGOV 2019), it could be
determined if vertical farming was an economically cost-
effective for the United Kingdom under these conditions and
thus indicate if it is a cost-effective solution to curtailment.
A protable basil vertical farm
To investigate this, the capital expenditure(CAPEX), opera-
tional expenditure(OPEX), with thegrowing conditions for
basil and vertical farm building details provided from the
previous studies by Kozai and Niu, (2016a) and Avgoustaki
and Xydis (2020a) wereused, all costs were adjusted to 2023
values and then converted to pounds. The building used to
contain the vertical farm was assumed to be similar to that
shown in Fig.1, as described by Kozai and Niu (2016b),
with the area available for growing as 900 m2, including 3
racks with 15 tiers. For growing basil in a vertical farm, the
research by Avgoustaki and Xydis (2020a) stated that 10 har-
vests per year were achievable, resulting in an annual yield
of 50kg/m2/year. The influence of adding carbon dioxide to
the grow chamber was assumed to increase yields to 100kg/
m2/yr if combined with using green oxygen to 200kg/m2/
yr. The cost of basil was assumed as £6.36 (TRIDGE 2022).
Annually the cash flow for this theoretical vertical farm
was calculated as £286,200; if carbon dioxide augmentation
improved yields by 100%, this would rise to £572,400 with
a 50% increase over thestandard configuration and byusing
green oxygenit would be £1,144,800, which is 75% greater
than the standard configuration. These figures were used for
an initial estimate of the impact that vertical farming could
have on the United Kingdom. The adjusted CAPEX and
OPEX expenditure values collected from the two studies
are shown below. The payback period in years for each sce-
nario is shown in Fig.3; this calculation assumed that half
of the CAPEX was borrowed and repaid at a discount rate of
10% over ten years, that electricity costs were £41.61/MWh
and that the plant lifespan was 20. The information in Fig.3
shows that vertical farms could be an economically cost-
effective investment as well as provide a solution to currently
wasted curtailed wind energy. A standard configuration is
repaid in 6.1years, and this reduces to 2.9 and 1.8years if
carbon dioxide and combined carbon dioxide and oxygen
can be successfully integrated, respectively.
The synergies between vertical farming, biogenic carbon
sequestration, curtailed renewable energy generation and
using currently wasted green oxygen from the emerging
green hydrogen sector are shown by Fig.4. Vertical farming
can be used by any country to transform curtailed renewable
energy into a revenue stream, make use of green oxygen and
6.1
2.9
1.8
0
2
4
6
8
Standard Carbon dioxide
augmentation
Carbon dioxide and
oxygen augmentation
Payback
period (years)
Fig. 3 The payback period for a standard vertical farm, carbon
dioxide-augmented vertical farm and combination of carbon diox-
ide, and oxygen-augmented vertical farm, at a discount rate of 10%,
a growing area of 900 m2, 50% of the CAPEX is borrowed, and the
loan is repaid over 10years. The CAPEX and OPEX for a vertical
farm with a growing area of 900 m2; the values shown were derived
from research by (Avgoustaki and Xydis 2020a) and Kozai and Niu,
(2016b) and used to determine the economic cost-effectiveness of
vertical farms making use of currently curtailed energy assuming that
electricity was supplied at the cost of £41.61/MWh. MWh refers to
megawatt-hour. In vertical farming, the CAPEX required for setting
up the facility amounts to £588,140. Regarding OPEX, the break-
down is as follows: £48,122 is allocated for electricity, £1,466 for
real estate lease, £182 for water, £119 for nutrients, £1,454 for seeds,
£531 for packaging and £110,025 for labour. This leads to a total
operational expense of £113,777

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develop an indigenous food supply. Adding additional car-
bon dioxide and green oxygen can reduce payback periods
to under 2years. Vertical farms are secure from the extreme
climatic events expected from climate change. Compared to
conventional open-field agriculture, vertical farms clearly
have many advantages; new crop varieties are being devel-
oped, with vertical farms now producing pharmaceutical
products from plants, orchids, roses, paprika, maize, straw-
berries and tomatoes (Bosman van Zaal 2023).
In conclusion, vertical farming has the potential to pro-
vide a sustainable solution to reducing curtailed renewable
energy, reducing the environmental impact of food produc-
tion and converting currently wasted curtailed energy and
green oxygen into a revenue stream. Governments, busi-
nesses and investors should support research and develop-
ment in vertical farming, creating a sustainable and resilient
food system for future generations. The policy should be
developed to encourage developers of wind farms to sup-
ply curtailed energy at its clearing price to vertical farms
to encourage their further deployment. Globally in 2021,
curtailed wind energy was sufficient to power 7.85million
m2 of the vertical farmdescribed by this research.
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