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<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Dear Paul<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">></span>Beginning with the baseline fuelwood use of 187,800 kg of fuelwood per year per village, if we assume a 10% moisture content, the baseline fuelwood is equivalent to 170,700
kg of dry fuelwood.<span style="color:windowtext"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Correct.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Convert that to char using a pyrolytic gasifier and you get 25% of 170,700 = 42,675 kg of charcoal (not carbon).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">The carbon fraction is probably about 36,300 kg.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Of the original carbon some 170,700 x 50% = 85,350 kg of C, minus 36,300 = 49,050 kg of carbon which creates 179,850 kg of CO2.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">As pointed out here years ago, the challenge for pyrolytic stoves to have a heat transfer efficiency that more than makes up for the additional fuel requirement. If you look back
far enough I provided a formula for calculating the requirement. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">As whole-wood burning cooking stoves have reached the 33-35% efficiency range, the efficiency of a gasifier has to be high enough to compensate for the additional fuel, if the fuel
savings matters to the project, which in the case of CDM and GS it does. If the char retention is 25% of dry mass, and that fraction contains 50% of the original energy in the fuel (at least), then the stove will have to be twice as efficient as the wood burner,
i.e. 66-70% heat transfer efficiency. In theory it is possible, in practice I haven’t seen it. All pyrolytic gasifiers consume more fuel than the best wood burner available at the time.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Your stoves might compare favourably with an open fire or a declared 10 or 15% efficient baseline, but they will not be as fuel efficient as a stove that burns wood completely.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">A stove that burns wood completely paralleled with a small charcoal making operation in the same community might use less total wood and produce more total char because both technologies
can be optimised to their function. If the purpose is to create the most char and the most cooking from a given source of biomass, so at least, a pyrolytic gasifier is not the best option. It is
<i>an option</i> but it is not yet out-competing other technology combinations. The cleanest wood burning stoves are as clean-burning as an LPG stove, or there is not enough between them to find a meaningful difference.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">If one can sift through a biomass source and take out everything ideal for a wood burner, and pyrolyse the rest into char, that is a reasonable thing to do if the char has a use
or value. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">I proposed two years ago that in Hebei, which has a serious problem with air pollution caused by the in-field burning of crop residue, that they put a small price on the material
making it worth collecting it to a central point. This could be charred while making wood gas that can be piped into the local distribution network. The remaining char would go into the input line of local fertiliser factories that are making organic fertiliser,
of which char is one component. There are multiple factories making these products, almost of all of which is sold outside the province to others which subsidise organic fertiliser products (Hebei doesn’t).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">They are not so unsophisticated as to advocate randomly planting char in the soil. They make compounded fertiliser products designed for typical or particular applications. I think
it is a good use of millions of tones of agricultural wastes. So far they are not doing it.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US">Regards<br>
Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:windowtext;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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