Indeed the Sun - and a lot of it. However, one advantage of artificial hydrocarbons is that the can be readily transported, as the oil industry demonstrates daily. However, that would still leave the enormous problem of covering millions of square km of suitably sunny land with the appropriate plant and keeping it supplied with fresh water etc.
Humans use roughly 500EJ of primary energy a year whilst about 3,000EJ (equivalent) of biomass is created every year. If all 500EJ of primary fuel (the great majority of which are fossil) was to be replaced by artificial hydrocarbons, that would be equivalent to about 17% of the World's annual biomass generation. That's a lot of land area - in the millions of square km, and getting enough freshwater to (say) the deserts rather than displacing agricultural or natural rain-forest and the like is going to be an engineering project, the like of which has never been dreamed of to date.
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Indeed the Sun - and a lot of it. However, one advantage of artificial hydrocarbons is that the can be readily transported, as the oil industry demonstrates daily. However, that would still leave the enormous problem of covering millions of square km of suitably sunny land with the appropriate plant and keeping it supplied with fresh water etc.
Humans use roughly 500EJ of primary energy a year whilst about 3,000EJ (equivalent) of biomass is created every year. If all 500EJ of primary fuel (the great majority of which are fossil) was to be replaced by artificial hydrocarbons, that would be equivalent to about 17% of the World's annual biomass generation. That's a lot of land area - in the millions of square km, and getting enough freshwater to (say) the deserts rather than displacing agricultural or natural rain-forest and the like is going to be an engineering project, the like of which has never been dreamed of to date.