[Stoves] Health protective environment and solid fuel burning devices

[Crispin Pemberton-Pigott]

Dear Friends

I will be posting, as I find it, information relating to the concept that there is a 'health protective' aspect to the lowering of stove emissions, the improvement of indoor air quality (or not) and ambient (meaning outdoor) air pollution. This is a very important argument being made presently in the funding pool and we should have a clear perspective on what works and doesn't, and what is fundable and what is not.

Individual perceptions are necessarily partial so through consultation we should be able to draw a larger picture.

Because everything cannot be put into a single message I hope readers will keep things in mind and add relevant perspectives. The first thing to establish is whether improvements in indoor air quality can be achieved with current technologies (this is first, a technology question). Here is an example of a 'desired result:

[cid:image002.png at 01D2DAB4.468F98B0]

In this region a lot of homes have inexpensive LPB (low pressure boilers, hydronic heaters, to Americans) and this is a set of measurements made by Fresh Air in comparable homes. The metric is intended to show IAQ (indoor air quality). In the control homes, the PM2.5 level was 165, 45 and 62 (24 hr average, if I read correctly).

In the homes with a higher performance and better constructed LPB (about the same price as the usual ones) there is a significant difference, 'significant' meaning a difference larger than the limit of determinability (LOD) by a factor of 3 (which is a sort of standard, accepted way of saying the difference is real which high confidence).

In order to have some way of saying, "This product delivers significant health benefits" we have to be able to prove that either the overall result (24 average PM2.5) is 'acceptable' or we have to be able to prove that the contribution to the total has been reduced a great deal. What I mean by that is if the above values of 25 for each of the improved LPB homes is only made of cooking emissions (boiled fats etc), smoking indoors, shuffling of feet, clapping of hands, combing of hair, outdoor air ingress and so on, then the contribution by the LPB is zero. So changing fuels from chopped wood to wood pellets would make no difference unless it affected the contribution from the ambient air ingress.

We should not casually mix these two reporting 'mechanisms'. There is the PM2.5 delivered into the home from the device, and there is the total. We cannot look at the total exposure (those are individual exposures, not indoor air averages - people wore personal measurement devices) and say that it was all from the appliance.  Those are two different things. If I put the LPB in a lab, pipe all the exhaust outside the lab, and measure the leakage from the appliance, I can quantify the total that comes out. If I place that in a home and measure the total in the room or the total to which someone is exposed, I do not get the same answer because now the leakage is mixed with all the other sourced materials. Are you with me? There is the contribution from the device and the total contribution.

A lab test is a good at to isolate the stove's contributions. A field test is a good way to show the difference between a home with and without the device. Obviously the test conducted in the lab should have the same typical burning conditions and fuels as the field test so the difference has meaning. There is literally no use testing in the lab and getting an emissions number and then taking it to the field to check how that impacts the total exposure, say, but operating the stove differently with a different fuel. That is nearly useless as a method of producing the information needed to inform policy.

To 'inform policy' one needs enough information to decide whether or not to support the dissemination of a particular device.

Here is another way of making a comparison of 'performance':

[cid:image008.jpg at 01D2DAB4.468F98B0]
Baseline CO (48 hrs)

[cid:image009.jpg at 01D2DAB4.468F98B0]
Improved stove installed.

This is a demonstration that the CO level can be reduced quite a lot just by changing the stove. There are very few other sources of CO other than the stove however one should not rule out that other cooking appliances may be in the home. My home has a dozen different 'appliances' from kettles to BBQ. A gas BBQ is a significant source of PM2.5 but not a big source of CO. In the second chart the average is a bit less than 10 ppm. Prior to changing the stove there were periods of several hours with a value above 50, sometimes 100 in other homes.

Important to the discussion is that all these improvements were achieved without changing the fuel. It is all coal or dung or wood or (frequently in the baseline homes) combinations. Dung burns much better in a dreadful stove if it is mixed with crop waste like cotton stalks or wood.

There is a toxin spreading through the stove community which is the claim that only gas and certain (but not all) liquid fuels can deliver the necessary 'health benefits'.  It is obviously false, based on the above, but it is easier to say it than to effectively counter a years-long campaign to demonise solid fuels in general using the invalid assumption that the above results are impossible to achieve.

If we are going to talk about 'health benefits' we have to talk about the whole package and the discussion has to be grounded on first principles. Measuring PM2.5 for IAQ purposes has to be analysed correctly.

End of rant
Crispin
-------------- next part --------------
A non-text attachment was scrubbed...
Name: winmail.dat
Type: application/ms-tnef
Size: 87801 bytes
Desc: not available
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20170602/df8a5ac8/attachment.bin>