I am reading the biochar literature now and it is fascinating stuff. But first glance reveals that pyrolysis schemes return 20-50% of the total carbon originally in the biomass back to sequestration in the soil (ES&T Sept 1 2007, p 5932). So already there is an efficiency problem compared to CROPS which is 90% efficient. Also I am concerned about how often biochar can be done on a given soil without undesirable effects on agricultural soil ecology. And how permanent is charcoal in soil? Amazonian terra preta still contains charcoal, but how much was lost over the intervening 500 years? We would be storing biochar in soil in direct contact with the atmosphere. If it decays there is no safety factor as there would be in deep sediments. Safety factors and redundancy are important in engineering; although geoengineering doesn't seem much like any other engineering I am familiar with...
= Stuart = Stuart E. Strand 167 Wilcox Hall, Box 352700, Univ. Washington, Seattle, WA 98195 voice 206-543-5350, fax 206-685-3836 http://faculty.washington.edu/sstrand/ -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Andrew Lockley Sent: Monday, February 02, 2009 12:46 PM To: [email protected] Cc: Stuart Strand; [email protected]; [email protected] Subject: [geo] Re: Crop residue ocean permanent sequestration Isn't it more efficient to pyrolyse the waste first, recovering energy and reducing transport carbon? A 2009/2/2 David Schnare <[email protected]>: > Stuart: > > I've been studying notill agriculture that relies, in major part, on > building soil carbon to hold nutrients in the soil (reducing application > requirements and keeping it out of streams). While a 14% sequestration > (limited to only about 20 years before maxing out on sequestration > potential) seems small compared to 100% if dumped into the ocean deeps, it > seems to me that when used in places more than 150 miles from the ocean, it > is carbon reduction efficient (based on fuels needed for transport). > > As such, shouldn't we be narrowing the crop waste discussion to coastal > agriculture only, and give credit for soil sequestration where that's as > good as is available? > > David Schnare > > On Mon, Feb 2, 2009 at 11:54 AM, Stuart Strand <[email protected]> > wrote: >> >> By straw we are referring to the stalks of agricultural plants, wheat >> stalks and corn stover. The water and nutrients were expended to grow the >> grain. Straw has a low nutrient content (C/N = ca 50/1). Presently straw >> is wasted by allowing it to decay on the soil surface (only 14% or less of >> the straw carbon is incorporated into the soil). >> >> >> >> A variety of processes are available to get energy out of crop residues, >> but they are limited by the poor specific energy of biomass. Our focus is >> how to efficiently remove Pg amounts of carbon from the atmosphere and >> permanently sequester it in the least environmentally harmful manner. >> >> >> >> = 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! >> >> >> >> From: [email protected] >> [mailto:[email protected]] On Behalf Of >> [email protected] >> Sent: Wednesday, January 28, 2009 7:16 PM >> To: [email protected] >> Subject: [geo] Re: Crop residue ocean permanent sequestration >> >> >> >> Stuart, >> >> >> >> Why bundle and stash terrestrial straw. Growing straw requires >> substantial fresh water and nutrients. You could bundle and stash algae >> instead. How about sargassum or kelp? A macro-algae can be bundled in >> large mesh "tea bags" with much of the water being squeezed out during the >> bundling process. >> >> >> >> Then, as long as you've got bundles of biomass, why not separate the >> nutrients from the carbon before you stash the carbon? That way, you can >> recycle the nutrients back to the ocean surface for growing more biomass. >> High-pressure anaerobic digestion will release the carbon in two separate >> streams; one gaseous CH4, one dissolved CO2, which easily converts to liquid >> CO2 at typical ocean temperatures and pressures. >> >> >> >> Would you or others be interested in a California Energy Commission grant >> to run a few bench experiments on high-pressure anaerobic digestion? I can >> send a draft abstract. >> >> >> >> >> >> Mark E. Capron, PE >> >> Oxnard, California >> >> www.PODenergy.org >> >> >> >> >> > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
