The Oil Drum

171 comments on Climate Change and Electricity From Biomass

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odograph on August 1, 2006 - 1:24pm

No, I'm thinking like an engineer ... and trying to frame this as a set of numbers.

If you don't start with a plant production number, what do you start with?

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memmel on August 1, 2006 - 2:22pm

Its not a plant production problem its a matter of determining the best way to convert bulky biomass to a usable form. I'm suggesting simple bioreactors to produce concentrated peat and methane. These would be used to produce what ever output you want if its liquid fuels then the cost is similar to CTL. Since its syn gas. I'm arguing that energy concentration at the source is a must for biofuels and natural digesters are the right thing to do. By overloading the digesters with organic material from surrounding croplands over a multi year period your replicating natural concentration steps that produced peat and thence in time coal. The approach concentrates organic material via two steps overloading from surrounding land and bacterial decomposition to reduce bulk. And its cheap and effective. The one modern magic material needed is a plastic sheet for covering that was not available to our ancestors. You can use ceramic or glass or steal coverings also so its possible without plastic but in this case a decent plastic cover makes the most sense. The ditch can be lined with clay/bricks concerete or agian plastic. My point is my argument is the number one problem with biomass is concetrating it not conversion this is a simple cheap and effective method to concentrate biomass.

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odograph on August 1, 2006 - 2:36pm

I have actually blue-sky'd about adding waste biomass to manure ponds to increase/prolong methane production. In a small (direct use, as I said above) case it might make sense.

Now, currently the output of those ponds is fertilizer, and not waste in the sense of something that must be shipped at some cost to disposal. As I understand it, it can be sold.

If you are going to propose drying and conversion to liquid fuel, that is the step ton concentrate on. For that the numbers of interest are how many tons of psuedo-peat you need, what it costs to process it, and how much liquid fuel it produces.

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memmel on August 1, 2006 - 3:05pm

Going from natural peat production See http://www.fao.org/docrep/t0512e/T0512e0b.htm

Peat The biggest problems in gasification of peat is encountered with its high moisture content and often also with its fairly high ash content. Updraught gasifiers fuelled with sod peat of approximately 30 - 40% moisture content have been installed in Finland fox district heating purposes and small downdraught gasifiers fuelled with fairly dry peat-pellets have been successfully tested in gas-engine applications (25). During the Second World War a lot of transport vehicles were converted to wood or peat gas operation, both in Finland and Sweden.

Now one approach is if the ditch is actually lined say with concrete or clay with embedded pipes and a tight cover can be fitted the entire ditch once drained and allowed to air dry can be blown with methane and in-situ gasified. Also you can introduce more dry organic material on top after draining to add fuel to finish the drying process. So in theory you need not move anything. So the final issue is how much the moisture content can be reduced during the final drying certainly methane and dry organic material can be added to finish the drying. In the case of more organic matter denser woody material such as popular thats say grown for 3-5 years beside the ditch while the ditch was being filled can be cut and used. As far as water content its known that natural peat bogs burn when drained or during droughts so obviously it drops enough for ignition and as I said before added dry organic material and methane can be used to initial and control drying and syngas production. The addition I've made is adding pipes to the bottoms and sides to inject methane if needed. Adding a final dry matter depending on moisture and creating a simple syngas reactor out of the fermenter with a fireproof covering that can be reused. If the covering is slightly wider then the ditch then it can be u shaped and simply buried to get a seal. Old time charcoal production used a similar method. I would not be surprised if you don't need to actually add water as the reaction progresses. Finally if needed or wanted the sludge could be scrapped into a smaller area before in-situ gasification. This could be done if needed by scraping several inches of the top material to a part of the ditch designed to be the gasifier as it dries. This should not be required but probably greatly hastens the drying process and its not a lot of energy.