According to various forecasts, global energy consumption will grow in the foreseeable future. This growth is accompanied by an increasing demand of fossil fuels that is the main source of energy.
We should either replace hydrocarbon fuels with carbonless fuels or learn to synthesise hydrocarbons from atmospheric CO2. The contemporary carbon budget is unbalanced; this is because CO2 emission exceeds its uptake for biomass production. The primary goal of our ecological policy is to try to maintain the CO2 concentration in air at a constant level.
If we could synthesise carbohydrates from atmospheric CO2 at a rate comparable to the anthropogenic CO2 production, this would partially solve the ecological problem. Carbon dioxide is low-energy molecule; obtaining energy-rich hydrocarbons from it requires energy. Nature suggests us to use solar energy for CO2 reduction.
Organisms performing oxygenic photosynthesis acquire CO2 from the atmosphere and combine it with hydrogen (electrons and protons) from ubiquitous water by using solar energy. The main means to obtain hydrocarbons (carbohydrates) from CO2 by sunlight for growing of fuel crop is through photosynthesis.