Half a croissant, on a plate, with a sign in front of it saying '50c'
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Fuel & Power Station

Generate electricity & biofuel in one plant
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Background: Modern gas turbine based power stations increase their overall efficiency (~30%) by recovering exhaust heat to run a second stage generator using a steam turbine. These are known as combined cycle gas turbines (CCGT).

My suggestion is, rather than use GT exhaust heat to make additional electricity, would it not be more profitable and ecological to run a biomass pyrolyzier with said heat. A gas turbine can generate exhaust temperatures up to 590°C & pyrolysis of biomass can occur at just below this temperature.

This statement supports my idea: "In a process known as fast pyrolysis, fine, low-moisture biomass fuel particles are heated rapidly to temperatures in the range of 450° to 550° C (842° to 1022° F), resulting in liquid pyrolysis oil but very little gas. The oil produced in fast pyrolysis is 60 percent to 75 percent of the original fuel mass. It can be used as a synthetic fuel oil."

It may seem inefficient to use some energy from one fuel to make another, but it is a question of sustainability. Gaseous fuels are excellent for fixed delivery infrastructures like our 'town' natural gas networks. Liquid fuels are better suited to vehicles where fuel is transported with the power generator (i.e. 'on-board' engines).

I would envisage a scenario utilising biomass from farming cooperative. With the farms collectively generating hundreds of tonnes of agricultural wastes annually, a partnership could be formed with an electricity company in commissioning a GT power station (centrally located between the farms) The GT exhaust gases would be channelled into a pyrolysis plant and liquid fuels would be sold in local towns.

Advantages: It would give boost to farming communities whilst generating low carbon fuels for the surrounding communities (cutting fuel transport impacts). Liquid transport fuels can be made from many 'waste' biological feedstock, such as forestry or wood-mill residues. The magic ingredient needed to drive this transformation is heat.

Disadvantages: Not initially carbon neutral due to use of natural gas. I have considered, once the system is up and running a biomass gasifier could take the place of the NG supply.

sheps, Nov 21 2008


       A good idea, and as far as I understand being investigated and in some instances implemented, but the law of diminishing returns says it will not hold. This has been somewhat mitigated by the introduction of carbon credits as a tradeable entity. How far this credit crunch and its effect on derivative trading goes, i don't know. I would like to see carbon credits being traded with the same voracity as CDOs, as was the intention, but I don't know if we will see that in the current trading environment.
4whom, Nov 21 2008


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