my new hero

[kandrathe]

Treated sewage.  Know of any good studies covering the "flushed" biomass as a potential fuel source?

Something tells me that the analogous "human chip" exploitation based on the buffalo chip fires Indians used on the Great Plains has a low harvestable power density, but not a zero fuel density. (Higher in nitrates, I suspect.)

Occhi
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Combustion is generally an inefficient chemical reaction, and much of the energy produced is lost as heat into the environment. I still think one of the better ideas for sewage to energy is in using microbial fuel cells.

The solar to plant, plant to fuel, fuel to kinetic energy process is very inefficient. Perhaps better physics will help us find a way to power vehicles without so much environmentally unfriendly and complex chemistry providing the potential energy. Maybe trade in the motor for a very large wind up spring. :) Rather than gas stations, we just have rewinding stations.

The current process using corn grain requires 29% more energy than the ethanol fuel produces. Using switchgrass requires 50% more; wood biomass: 57% more. Biodiesel production using soybeans requires 27% more energy than the biodiesel fuel produces. Biodiesel production from sunflower: 118% more. source

But, we are just beginning to work with ethanol, so I expect efficiencies to increase. After the farming related energy expenditures, the other is the heat required to boil the ethanol out of the fermented mash. I'm sure we could do better with more focus on reducing energy expenditures in farming, and in producing the ethanol with non-fossil energy sources. Our biggest problem is the limited amount of solar energy captured in plants.