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The coal bio-gas seems interesting but I find the discussion of the conversion and utilization of the various products unclear. It seems the hot gas, 47.5% of the total energy stream, can be converted to electricity at 50% efficiency, so that portion yields 25.75% efficiency for electric conversion, or an EROI of ~1.3. But the charcoal and medium hot gas providing an efficiency of 93% and an EROI of 17.5 is just confounding and relates to an entirely different calculation - effectively a dazzling aside - as when we return to converting this 52.5% of the total stream to electricity with different types of fuel cells we get 50% efficiency for part and 75% for the rest for a combined efficiency of 60% and an overall EROI of 2.5, which is not too inspiring.

But if all those processes could be scaled down so that they could be used to charge a battery in a moving vehicle directly it might be a solution to the mobile fuel requirement, even if it is more polluting than battery operation from electricity supplied by wind and/or solar.

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Fri Jul 26th, 2013 at 02:00:15 PM EST
Any EROI calculation depends on what you call the product. If you call the product of coal production coal, you get one EROI, if you call it electricity from a thermal power plant, you get another.

The thermodynamic losses from conversion of a biomass feedstock in a sealed, semi-pressurized container into biocoal and medium-BTU gas is very low.

Now, you may have a chemical process in which you can directly use warm medium-BTU gas, and another chemical process in which you can directly use charcoal, and for that situation, the EROI would be quite high, dominated by the energy investment into the production of the biomass feedstock, and given the flexibility to choose biomass feedstocks that require no artificial fertilizer or forced drying, the EROI of the production of those end-products would be quite high.

OTOH, you may be interested in electricity production, in which case the medium-BTU gases could be converted by already existing fuel cells at 50% efficiency and the biocoal into electricity at anywhere from 30% to 80% efficiency, but in any case a substantially lower EROI when electricity is the end-product than when biocoal and medium-BTU gas are the end-product.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Mon Jul 29th, 2013 at 06:27:15 PM EST
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