Dear Mark Interesting thoughts, Thanks. Something that is pretty hotly debated are the health issues surrounding Black Carbon. There were divergent opinions at the Bangkok stove meeting in November - expressed as 'ultrafine BC is a health problem' and 'there is no proof' of it.
What emerged is that when a stove is cleaned up in terms of PM 2.5 (well, in terms of PM 1 because stoves produce almost no PM 2.5) the reason it looks so clear is that the usual method of looking for the particles is light scattering. This detection method has become affordable and works for particles down to 0.1 microns. What has been discovered (as ever more health problems are ascribed to fine BC particles) is that as the technology advances in the detection of much smaller particles, we find them in increasing numbers. A 'clean burning' stove with a low PM 2.5 number usually has a massive number of much smaller BC and OC particles. They are just not big enough to see with light scattering equipment. This begs the question as to whether they are better, worse, more in number and or mass than the larger ones. And as they get further into the lungs, are they more dangerous? It is hard to believe that having a clean appearing stove could be worse for you than a smoky one but I think we should be open minded while the jury is out. Modern diesel engines are remarkably clean in terms of PM 1 and 2.5. If however they still produce instead a massive cloud of invisible ultrafine particles we may still have a long way to go to a healthy environment. From what I read, all carbon containing fuels produce BC in some form. The lack (measureable with our equipment) of PM 2.5 from smouldering coke fires (like charcoal or coal) even if there is little or no flame it apparently the result of solid fuel going directly to burned gas on the surface of the fuel. I was surprised how low the CO level is in a hot version of such a fire. What I can't tell is if there are in fact a great number of BC particles instead! Yes, it is an interesting question. Regards Crispin _______________________________________________ Stoves mailing list [email protected] http://listserv.repp.org/mailman/listinfo/stoves_listserv.repp.org http://stoves.bioenergylists.org http://info.bioenergylists.org
