1. Significant methane production seems unlikely, but it may be possible in deep deposition sites. Anaerobic metabolism in ocean sediments is dominated by sulfate as the electron acceptor, not CO2, as in freshwaters. We expect crop residue mineralization under anaerobic conditions inside the bale to be slow, so sulfate in surrounding waters would have time to diffuse into the bales. But if the bales are stacked too deep sulfate will be exhausted and methanogenesis will start. If methane is produced it will not be as bubbles (which could penetrate the thermocline), but as dissolved methane, due to the pressure. Dissolved methane will be oxidized as it diffuses up through the sediment and the water column where aerobic and anaerobic methane oxidation occurs (the latter coupled with sulfate reduction). So methane from the crop residues is unlikely to reach the atmosphere.
The above is our working hypothesis, but this is a question that must be answered with experiments in situ, which would also provide data to estimate parameters needed for modeling and design. 2 and 3. I am working on comparisons to pyrolysis now and I have discussed first impressions previously on this group. 4. readily available info, Andrew 5. see above 6. C Lossy. Andrew, biomass is a poor energy source, whether you make methane, ethanol or biochar from it. 7. Not as safe as the ocean I would judge. But it is something we could do temporarily, while ocean research and the expected political wrangling on CROPS is done. But transportation costs to and from deserts and the landfilling operations to try to keep moisture would be costly and CO2 productive. = Stuart = Stuart E. Strand 167 Wilcox Hall, Box 352700, Univ. Washington, Seattle, WA 98195 voice 206-543-5350, fax 206-685-3836 skype: stuartestrand http://faculty.washington.edu/sstrand/ Using only muscle power, who is the fastest person in the world? Flying start, 200 m 82.3 mph! http://en.wikipedia.org/wiki/Sam_Whittingham Hour http://en.wikipedia.org/wiki/Hour_record 55 miles, upside down, backwards, and head first! -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andrew Lockley Sent: Tuesday, February 03, 2009 3:05 AM To: [email protected]; geoengineering Subject: [geo] CROPS paper I've read through your paper in detail and I note the following. (I may have missed some things of course) 1) You don't discuss anaerobic decomposition to methane in the ocean. Is it a risk? Outgassing may be immediate or by clathrate destabilisation. 2) You don't discuss pyrolysing the waste to char before sequestration. 3) You consider burying the waste, but you do not consider creating biochar and burying that to create terra preta 4) You reject the idea of burning crop residues and using CCS, but do not provide a quantitative analysis of the carbon content of biomass by % compared to other fuels, so it cannot be determined whether burning is relatively more efficient than for other fuels. 5) You do not directly consider the production of char by pyrolysis then onward transport of the fuel to be burned in sites suitable for CCS. It may be that thermal and industrial inefficiencies preclude this, but this cannot be assumed. Further, char is likely to be compatible with existing coal plant, when raw crop waste is not. 6) You do not consider anaerobic digestion of the crop waste to make methane gas for power generation or large-vehicle transport fuel. This technology is used extensively in the UK for food waste, albeit on an emergent scale. 7) You do not consider the alternative of storage of waste in the desert. If transported by rail to the desert, crop waste could dry naturally and then be sealed with plastic in bales. This is an obvious alternative destination for the waste. A --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
