Post by Chris Uhlik on May 12, 2012 12:04:57 GMT 9.5
The very best test plots have best-year yields as much as 5 times the average numbers I used. However, the average yields over years and plots are only about 30% better than the 0.7 kg/m2/yr that I assumed. When talking about areas several times the size of Kansas, surely you'd agree that average yields rather than best-case yields apply. Also, the test plots do not include roads and many test plots are irrigated and fertilized. When you talk about using marginal lands, the yields will be reduced further still. I stand by my large-area-average-estimate of about 300 grams of carbon captured per square meter per year using sustainable biological processes based on grasses.
Post by Roger Clifton on May 13, 2012 19:25:58 GMT 9.5
A hefty carbon price would be needed before the world turns away from liquid hydrocarbons to favour the alternatives. However, evidence of the potential punishments by a wounded climate may yet wake the complacent and make make fossil carbon too expensive to use.
As a step towards elimination of fossil carbon, we could replace the 20% of crude that is burnt off in a refinery to create heat, electricity and hydrogen. Considering how cheap crude oil, tar shales and coal are today compared to nuclear energy, a hefty carbon price would have to be applied before we will see nukes in fuel refineries.
Carbon source for synthetic fuel should not compete with food for land. It should be agricultural wastes (generally burnt), forest undergrowth and dried leaves (fuel of wildfires) municipal waste (stuff of landfills) and coal rejects/high ash seams/ deeper seams which can be gasified. A controlled water addition to coal seam fires could also produce a fuel gas. The result will be small and dispersed production but also reduce the transport of raw materials. Nuclear power could feed the energy for endothermic chemical reactions if and when feasible. Synthetic fuels should be used only where electricity or hot gases/steam cannot be used as in transport, particularly air transport.