green monster question, page-2

With regard to CO2 there's a couple of points here.

First the efficiency of the UCG process will determine how much CO2 is produced. Metex will use oxygen blown gasification with directionally drilled wells with moveable injection/production points. So I expect this is more efficient than using vertical wells with air gasification. Why? Air gasification requires more compression energy to get the oxygen into the coal seam, energy is used to heat up nitrogen which is wasted and the downstream plants all have to be bigger. Oxygen gasification will require less compression and smaller surface facilities, but it does require an air separation plant. The moveable wells allow the gasification process to be much better controlled than a vertical well method and I expect will be cheaper as well. Control of the process will bring efficiency benefits as well. So all up the Metex process should be much more efficient at converting the coal into syngas.

Second, in future users will consider removing the CO2 in the syngas prior to or after use (combustion, conversion to liquid fuels etc). This is not something that is done yet, but will for example be tested by Zerogen. Now the efficiency of removing the CO2 is directly related to the partial pressure of the CO2 in the syngas. So having the syngas at high pressure and without any other inerts, like nitrogen is a benefit here. Again, the Metex process will have high pressure syngas without nitrogen making this CO2 removal step much more efficient than what can be achieved with air blown generated syngas that will be produced by LNC and CXY. So overall there are a couple of potential areas where this process will be more efficient than other doing UCG.

However separation of the CO2 is just the first step as you'll need somewhere to put it. There's a couple of options but basically you can inject it into existing oilfields to enhance the recovery of oil or you could sequester it in deep rock formations or in the ocean. All methods are being studied at the moment and there are bit uncertainties around this.

So, while the efficiency benefits of the UCG process will be realised quickly, we may have to wait for removal of CO2 from the produced syngas for a while.