Solar Energy Perspectives - IEA

Solar Energy Perspectives: Solar fuels
Carbon and hydrogen
As noted in Chapter 1, fossil fuels are remnants of ancient living organisms, which drew their
energy from the sunlight through photosynthesis, associating carbon atoms taken from the air
in carbon dioxide (CO 2 ) molecules, and hydrogen atoms taken from water, building
hydrocarbon chains and releasing oxygen. These hydrocarbon chains carry the energy of
biomass, natural gas, oil and coal.
Some scientists are seeking to mimic photosynthesis and directly generate hydrocarbon
chains with water and CO 2 under sunlight. Using living organisms to capture solar energy
through photosynthesis is generally considered “biomass”, not direct solar energy. Recent
developments however, such as the first facility converting CO 2 captured from a nearby
cement factory into synthetic liquid fuel using microscopic algae and sunlight, evokes an
“industrial solar plant” rather than a plant (Photo 9.2). Its economics are based on the sales
of fatty acids to the agro-food industry, a “by-product” which is more highly valued than the
main product, synthetic oil.
Photo 9.2 Near Alicante, Spain, tubes filled with microscopic algae turn CO 2
and sunlight into synthetic oil
Source: BSF Blue Petroleum.
Key point
Micro-algae are expected to produce fuels and high-value products in bio-refineries.
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© OECD/IEA, 2011