Richard (cc two lists) See some questions/notes below on your message today. You said:
" I would buy the one that burned some form of densified non wood biomass "cleanly" ...... [RWL1: Those of us who are promoting char-producing stoves believe that they are much cleaner than those that only combust . The usual low-cost stoves in developing countries almost universally use only wood (with some still-minor use of your briquettes of course). For those new to the subject, the difference is whether there is a single air supply or two. Does anyone reading this think that char-making stoves are not inherently cleaner? But I especially want to support your use of the term "densified non-wood" - which I think is also much needed in char-making stoves. Nat Mulcahy of World Stoves always emphasizes the use of "densified non-wood" as one of the main advantage of his Lucia stove (which could combust or gasify - but he chooses to operate in only a pyrolysis mode). See his website for his rationales - which are (in part) similar to yours. Several questions to you (as the person who probably knows the most on this densified non-wood cooking issue): 1a. What are the relative advantages of making (not using) pellets vs briquettes? It would seem that it should be much easier to "press" (I like your closing below) pellets than briquettes (especially the "holey" type). Do you have any data on the relative power or energy and/ or cost requirements for production of pellets vs briquettes? 1b. For those wanting char and not ash, the charred pellet is already in a wonderful form for application to soils. Pellets mean some extra costs for the fuel supply in the front end of cooking - but could be a wonderful boon both in burning more cleanly and evenly and in later application of Biochar to the soil. The same is possibly/probably true for briquettes - which I presume break up easily after being pyrolyzed. Do you have any reason to think briquettes would be better than pellets in either pyrolysis or char-application terms? You concluded:] ".... and would avoid both the wood supply and the char producing problems in one go ." [RWL: 2a. Re the first issue of supply (with which I agree), I have recently read an article (author's name forgotten - I will try to find it) that showed a breakdown of the well known global net primary productivity (NPP) number of about 60 Gt C/yr. They had about half going into wood and half into leaves - a ratio I had not previously seen. Since you are promoting the former (leaves) over the latter (wood) - and because almost all rural stove users are now using only wood (and even many briquettes and pellets seem to be made up of ground-up or chipped wood), have you seen this relative photosynthesis production ratio - which would seem to imply a huge wasted resource all over the world? 2b. But I don't understand your term "char producing problems". To me there are only benefits and advantages (at least with kitchen stoves). If you meant the horrible production of most charcoal out in the boondocks - with global warming and carcinogenic gases much worse than CO2 being produced - then I agree. To prove that it is better for society to promote household production of Biochar (char placed in the ground) will be the subject of my next message. Briefly it is that we need to make the economic argument that Biochar's two main advantages (carbon sequestration and soil improvements) outweigh the further combustion of the char for its energy value. Two main reasons that I think we can make this argument (which I do not contend has already been proven). First is the 2:1 advantage in the three-flows of money (which seem in the same ballpark). But more important is that the first two monetary flows (climate and soils) are both investments - with good payback over long time periods. The energy application of the char is only a single use - no out-year advantages at all. More coming on the many out-year advantages of Biochar. This is not to suggest that you do not believe in all this already - but others could interpret your sentence to favor burning of "densified non-woody biomass" rather than pyrolysis of the same. Ron] pressing on, Richard Stanley www.legacyfound.org On Nov 29, 2010, at 4:12 PM, Crispin Pemberton-Pigott wrote: [RWL: I have snipped this to keep the responses separate - being different issues.] Dear Friends I agree with Ron that $10 is a believable figure for an improved stove with a dramatic (90%) reduction in emissions of PM. For the +$50 stove <snipped>
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