Concentrated solar energy is most commonly used for electrical power generation. However, a Colorado company, Sundrop Fuels, has a unique approach to the production of biofuel by that marries the mirrors and tower of concentrated solar power with their process for the production of bio-based fuels.
Instead of burning biomass for the energy needed to create biofuel, Sundrop uses concentrated solar as their energy source to gasify a range of feedstocks including agricultural waste, energy crops, and wood waste. The Sundrop process can produce a range of fuels including gasoline, diesel, and aviation fuel. Many other biofuel processes produce ethanol which has a lower energy density than other fuels, meaning that more of it must be used for an equal amount of work. (Flex-fuel cars get fewer miles per gallon from ethanol than from gasoline, but the ethanol fuel costs less per gallon, and the ethanol is not derived from petroleum.)
Sundrop uses the high temperatures from the concentrated solar array to vaporize the biomass feedstock and form syngas, a mixture of carbon monoxide and hydrogen. As with other biofuel processess, the syngas is the basic building block which is turned into useful fuel.
Sundrop's process has other efficiencies that provide additional benefits. By using solar energy, the process yields 100 to 125 gallons of fuel per ton of biomass, which is more than twice what other biofuel producers obtain. The process also requires far less water, needing only a half gallon of water per gallon of fuel produced, versus 6 or 7 gallons required in other systems. The process also creates electrical power from the waste heat generated in the reaction tower.
One of the only significant drawbacks that the Sundrop process faces is the distance between areas with excellent solar access (and few cloudy days) and ready sources of biomass.
The Sundrop process is expected to be able to create gasoline, without subsidies, for less than $2 per gallon. The company is constructing a pilot plant and aims to have a full, commercial-scale plant with a capacity of 100 million gallons by 2015.
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