List , cc Crispin and Kevin Whew - I am getting tired of this. But my name is below, inaccurately expressing my views. Much of this has been explained earlier today, so I will keep this as short as possible, using terminology from my exchange today with Jim Jetter. Crispin and Kevin below have done a perfect job of explaining why this topic should be important to all char-making stove people.
----- Original Message ----- From: "Crispin Pemberton-Pigott" <[email protected]> To: "Discussion of biomass cooking stoves" <[email protected]> Sent: Wednesday, April 24, 2013 8:49:30 AM Subject: Re: [Stoves] FW: REQUEST for complete sets of raw data of cookstove tests. Dear Kevin You analysis is correct. When rating the performance of a stove from a fuel use perspective, the chart is correct: [RWL1: Yup - correct if you leave out several lines proposed by Jim Jetter. The right two columns seem to be un-necessary - if you you are trying to downplay the importance of non-woody fuels vs forest-derived - but that is a different story (that Paul Anderson is focused on today). All of the data in the table is for E2. Needed and I have no complaints. But to say it is the full story would be mandatory if you wanted to knock char-making stoves.] [RWL2: The first missing row is one for E1, which would give 5/(10-5) - 5/(15-5) = 50% for all columns. So, no change in the E1 definition of efficiency between any of the columns. Why was this not shown in this table? Hmm.] [RWL3: The second missing row that Jim will be reporting is for the char energy value: E3= 5/15 = 33%. for the char columns B and D. Again - why not shown? Hmm. [RWL4: Now Jim won't be reporting (with my concurrence) E4 = E2 + E3. But columns B and D, with 50% increased input energy (15 rather than 10) has an increased E4 "efficiency" of 1/3 + 1/3 = 2/3 = 67%.! Hmm again. An improvement of 1/3 over the 50% in columns A and C, and the uniform E1 efficiencies of 50%. Importantly, the user puts 50% more fuel through the stove and the fuel cost can go from positive to negative! The detailed argument on this big shift in annual $ flows I assert is in the very recent ppt authored by Paul Olivier (which Kevin and I both lauded). ] RWL5. How badly hurt has been the stove user by using 50% more fuel? How badly hurt is the forest? You have to ask compared to what. Not at all if ag residues were used. But that was too easy. Certainly if the alternative to the column B/D stove is a charcoal-using stove with char made in the boondocks (probably illegally), there is again a huge favorable comparison for making char in this assumed stove. I am too short of time to make that computation. See the work recently of Paul Means on that topic. [RWL6: Crispin presumably (see below) argues we are using 50% more forest in this Column D vs Column C example (the ratio of 15/10 in input energy). Two responses depending on whether the char is combusted (case I) or placed in the ground, (case: II) . case I. If the 5 MJ of char is used in a 50% efficient char-using stove (as was used by Jim J. in his example), the new efficiency E2 is increased up to 7.5/15 = 50%. The new corresponding E1 changes to 7.5/(15-0). Also = 50%. E2 is the same (7.5/15). The new E3 is zero and E4 is (7.5 +0)/15 = 50%. These equal numbers are coincidental, based on the assumed (by Kevin?) initial energy split. He placed the char output energy at 1/3. If the char weight ratio had been 25% then the energy ratio could be above 40% (not 33%).and some differences would start showing up. The amount of $ savings for option I could be important for the cook depending on the ratio of char/wood prices, but getting to negative annual fuel costs will require selling the 5 MJ of char in this example for combustion by some one else. My view is that most users of such a stove would prefer to sell over using the (inferior) charcoal -using device [RWL7. case II. The remaining (II) option (important for forest size savings) is that the produced char goes into the ground as biochar. I don't see an easy way (help requested) to show that increased out-year biomass growth will save more forest. Getting further into this is way beyond the scope of this short response. The important point is that for all scenarios with enough time elapsing, less forest is used when the char is placed in the ground. For the terra preta soils in the Amazon, the annual growth (NPP) guarantees a payback in less than a year, and Paul Olivier gave some similar examples for Viet Nam. The char-making stoves won't be as popular if the stove sales-people can't make a good case for improved growth somewhere - or for a sufficiently high price on the produced char. Of course my hope is also that taxes on fossil fuels in the US will provide a sufficient credit for a huge biochar-stove industry.- all justified on the "polluter-pays" principle. [RWL8 - almost done. Few more below. Two stoves are being compared for "Efficiency". Given facts from Tests: STOVE A STOVE B STOVE C STOVE D Nature of Fuel Ag. Waste Ag.Waste Stickwood Stickwood Fuel Energy Supplied, MJ 10 15 10 15 Energy to Cooking Pot, MJ 5 5 5 5 Energy in Char, MJ 0 5 0 5 Stove Efficiency, % 50.00% 33.33% 50.00% 33.33% If someone is interested in the char, it can be reported. What Ron is proposing, to add that heat energy available in the char back into the mix, is akin to considering the energy efficiency to be the fuel efficiency which is precisely what created for us a problem in the first place. [RWL9: Must be a different "Ron". I hope it is clear I want all char to become biochar. If it is only possible for some reason to use it in a char-using stove, we are still ahead - as shown above. I am using the same factor of 2 loss assumption for the charcoal-using stove. I am not adding (unaltered) " heat energy available in the char back into the mix". I cannot see how I am "... considering the energy efficiency to be the fuel efficiency." But I await being enlightened .] <blockquote> The energy value of the char came from somewhere. Consider a stove that takes 2 tons of forest per year. If it produces ¼ of a ton of forest’s worth of energy in the form of char, fine. Say so. But saying so does not reduce the two tons of forest it takes. If you have (as you pointed out) a second stove that can utilise the charcoal, then that can be viewed as a ‘system’ by all and sundry, but is still does not change the fact that Stove 1 takes two tons of forest each year which is what the reported fuel consumption should be. No smoke and mirrors. </blockquote> [RWL10: The number "1/4" doesn't compute for me, even if the 2 tons of forest are green tons (not the usual way of reporting forest productivity). This new Crispin example is different than the entries in the above table, so I ask for some computations to justify this 2 ton/(0.25 ton) = 8 weight ratio for a char-making stove. The table's energy ratio of (15/5), would be multiplied by an energy ratio of about 5/3 to get a weight ratio of 5, not 8. Also in this factor of 8 sentence, Crispin seems to have given no credit for the equal cooking energy The next important point is that in the boondocks, the char production ratio is rarely as good as in the stove. Details would be helpful to further this dialog of what needs to be coming out of Jim's testing of char-making stoves . <blockquote> Burying the char as a soil amendment instead of burning it merely takes us back to the two tons of forest per year draw-down and returns it to the environment in an (apparently) inert, solid form. What has been happening that is wrong, in my view, is that stoves that take off 3 tons of forest per year have been getting credit for taking only one ton and proclaimed to be ‘better’ and ‘more fuel efficient’ than a two-ton stove. Plainly this is not the case and the test method has to report the fuel consumption correctly. It is a problem that the UNFCCC methodology does not handle this well because it is being used for CDM trades. [RWL11: These two paragraphs need more explanation. I have no idea where 1 or 3 tons comes from; I understand 2 to be some sort of an average stove. It sounds like no credit again being given to either the char-making or the cooking (fuel avoidance) as char was being made. Lastly - what are the details behind saying: </blockquote> ".. stoves that take off 3 tons of forest per year have been getting credit for taking only one ton and proclaimed to be ‘better’ and ‘more fuel efficient’ than a two-ton stove" I doubt that Jim Jetter is releasing anything related to these numbers, whatever they mean. Which stove? A UNFCCC document please? This is a serious allegation - especially if it relates to char-making stoves. Does it? <blockquote> </blockquote> Ron <blockquote> Regards Crispin </blockquote>
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