[Stoves] Burning homes, children, and spewing smokes from stoves (Was Biochar Proposal - Lloyd Helferty)

[Crispin Pemberton-Pigott]

Dear Anil and All

Those floundering in a sea of conceptual error are clinging to the lifebuoy of ‘clean fuels’. It will not save them. Ethanol is frequently listed as a ‘clean fuel’ when as you point out, it can be anything but.

I was measuring CO emissions with a couple of trainees developing an ethanol stove (in California). By making very small changes to the ring of metal surrounding the fire, the CO level could be raised or lowered at will.

The ethanol gel fires under a bain marie which is the hot food serving tub seen at buffet lunches are not ‘clean’ at all. The CO/CO2 ratio is about 6% which is triple the limit for indoor cooking fires in most countries with regulations on such things (Germany, South Africa). Bains marie are not a regulated cooking appliance in any country I know of.

The pretty well-known CleanCook stove appeared at the ETHOS meeting and after demonstrating that the CO was far too high, it was shown that after raising the pot 40mm to give the flame some breathing space, it fell to a low level. This change was incorporated into the design and that is what you can buy today. It is another example of ETHOS contributing to the development of good cooking products.

There are no clean fuels and there are no clean stoves. There are only clean stove-fuel-operating context combinations which is why I am a big supporter of contextual testing as evinced by the CSI test method, with all that that entails.

At present some dozens of stoves are being tested for rollout in Hebei Province in China. The pilot project will distribute 800,000 of them.  They are being tested (rated) burning raw coal from Shanxi Province because that is what something like 85% of the users burn in them, even though they are nominally ‘semi-coke briquette burning stoves’ only. So why are we testing them using a fuel that is not recommended? Because that is the local context and we want to reduce the emissions in the whole province, not claim to reduce the emissions.

It is illegal to burn raw coal in Hebei; that is the legal context. Most of the people living in rural areas do exactly that. That is the actual context. We want actual results, not ‘legal’ results.

What the testing shows (fortunately) is that some of the product can burn raw coal really well (low PM2.5), even though they were ostensibly ‘designed’ to burn semi-coked briquettes. So, obviously we will support the distribution of those which burn both really well and meet a certain fuel efficiency which is assessed using the National Standard.

To answer Nikhil’s question about who’s problem it is, it is Beijing’s problem. Having done really well cleaning up their own air, they are suffering from the emissions of their neighbouring province.

As for ‘what is smoke’, it is unburned fuel. PM2.5 can be much more than unburned fuel as it could be ash or road dust or any other fine particles including droplets of condensed liquids. Breathing unburned fuel is a bad idea. How bad? That is the $64,000 question. After a decade of being told that it causes childhood pneumonia and that reducing it at least 90% was necessary to get a meaningful change in the hazard, a major study in Malawi shows that such a reduction in emissions from the stove had no statistically detectable effect at all.

There are several possible reasons for this:

-        The exposure was much less that supposed and/or reducing the emissions didn’t change it

-        The emissions from the claimed >90% reducing stoves were in fact not >90%

-        The test method employed to assess the emissions was irrelevant to the context in the field (i.e. WBT)

-        The test method reported the emissions rate using a metric that was poorly chosen/irrelevant

-        Childhood pneumonia is not caused or aggravated by stove smoke

-        Children are not exposed to stove smoke in the same way adults are

-        Children are not exposed to stove smoke in proportion to its emission from the stove

-        While children are theoretically exposed to stove smoked when modelled using a single box, instantaneous distribution, equal exposure model, the model grossly over-predicts their actual exposure

This last point is so silly, and the usefulness of the WHO’s (Berkeley’s) single box model contradicted by the WHO committee’s own discussion notes, that it bears receiving special emphasis. If stove smoke has a real effect on children, defined as incidence of pneumonia, and the model of exposure is as facile as that used by the WHO, then one can expect field results to contradict model results. The single box model, discarded as long ago as 1982 by the Eindhoven Stoves Group, over-estimates the exposure of adults to stove smoke by at a factor of more than 2, at least, and children live near the floor where exposure is even lower. That figure of 2 is compared with a three box model, which is itself not a very good representation of exposure.  We cannot be too surprised that there is no detectable effect on children’s health when ‘90% reduction’ stoves are used in the home.

Burns, on the other hand, are easily reduced by enclosing the fire, whether there are reduced emissions or not. Reducing emissions of smoke can easily increase emissions of CO if there is also a fuel change. Ethanol burned badly is a toxic fuel, particularly because it makes very little smoke (or none) when it generates high CO, which has no smell or colour.

It would not surprise me at all that people using a poor ethanol stove in enclosed surroundings get a headache. There are lots of organic compounds that can be produced from hot, evaporated ethanol.

Context is everything. Rate accordingly.
Crispin



Anil:

Let me throw some questions at you. I hope you reply, because then I will respond accordingly.

1. What is "smoke"?

2. What is the proper measure of "clean"? Who decides, why and how? Why does it matter if some stove is "clean", to whom and traded off against what other criteria to choose to purchase or use?

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As for ethanol stoves, why aren't ethanol stoves "clean enough"? Because they have high 15-minute emission rates for CO?

It's exposures that matter, not emissions. Or emission rates. This is why the ISO IWA exercise is "fundamental folly" without a context. I do agree with the principle of testing and ranking stoves in terms of desired qualities. I just don't believe that by itself, boiling water does anything but feed the researchers.

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I hope someone else tells me what "smoke" means. There is too much of blowing rings about stoves and smoke.


Nikhil



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