Solar fuels and photosynthesis: Resources and labour

Vast farmland, rare catalysts and sunlight focused 2,500 times

What this tab covers The natural resources (land, water, materials, fuel or feedstock) and the labour needed to capture this energy, per unit, with the reason each is needed.

Photosynthesis needs land, water and nutrients on a vast scale. Artificial routes need far less land per unit of fuel but rely on concentrated sunlight, specialised semiconductors, precious-metal catalysts, and water and CO2 as feedstock. Labour figures for these research-stage routes do not exist.

Natural resources

Resource	How much	Why it is needed
Land (photosynthesis)	48 million km2 for agriculture, 80% of it for livestock and 16% for food crops⁶	Sunlight is spread thinly and crops convert under 2% of it, so large areas are needed.
Land (artificial routes)	No per-unit figure in the sources used⁵	Mirror fields or panels must collect enough sunlight; desert land unsuitable for crops can be used.
Water and CO2 feedstock	Inputs for every route; jet fuel combustion emitted about 1,027 Mt of CO2 in 2019⁵⁸	Hydrogen comes from splitting water; carbon for hydrocarbon fuels must come from CO2 captured from air or industry.
Catalysts and semiconductors	No per-unit quantities; the record photoelectrochemical device uses rhodium³	Catalysts lower the energy needed to form hydrogen and oxygen; semiconductors absorb light and separate charge. Scarce metals are a barrier to scale.
Concentrated sunlight	About 2,500 suns (thermochemical); concentrated light also used for the photocatalytic record⁴⁵	Concentration raises temperatures and reaction rates so that small, expensive reactors produce more.

Labour

Phase	How much	Skills	Why it is needed
Research and pilot plants	No figure in the sources used⁵	Materials scientists, electrochemists, chemical and optical engineers	All artificial routes are still in laboratories and test facilities.
Agriculture and forestry (photosynthesis)	No figure in the sources used (see the Biomass tile)⁶	Farmers, foresters, agronomists	Planting, tending and harvesting turn photosynthesis into usable energy.

Sources

Monolithic Photoelectrochemical Device for Direct Water Splitting with 19% Efficiency (Cheng et al., ACS Energy Letters 3, 1795-1800) American Chemical Society, 2018
Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting (Zhou et al., Nature 613, 66-70) Nature, 2023
A solar tower fuel plant for the thermochemical production of kerosene from H2O and CO2 (Zoller et al., Joule 6(7), 1606-1616) Cell Press, 2022
Half of the world's habitable land is used for agriculture Our World in Data, 2024
Researchers produce jet fuel from sunlight, CO2 and water (citing IEA for 2019 jet fuel emissions) The Chemical Engineer (IChemE), 2022