[Stoves] WBT emissions for coals v. woods [Was Re: TLUD stoves and tests]

Nikhil Desai pienergy2008 at gmail.com
Fri Jul 27 09:12:33 CDT 2018


Crispin:

Let me be precise. Are you saying that  "Under identical cycles of
temperature/power, many cookstoves with coals and charcoals had lower
emission rates than any of the stoves tested with primary biomass (wood)"?

That is a shocker. And a fact worth discussing in the context of that paper
by Quinn, et al. (2018) you provided the link to earlier today (and I
commented on).

It does not surprise me that coal burnt "cleanest". Coal is a complex
chemical, and its physical and chemical properties vary, even within the
same seam.

But the lower density of wood, and I suspect presence of a higher share of
hydrocarbons, means even oven-dry, relatively high-density wood, just
cannot burn as well as coal, and PICs ratio would be high.

This was my hunch some 30 years ago as I learned coal chemistry and
combustion basics. I would have hesitated making any general comment
because coal combustion may be designed differently.

Cooking is a special case, and fuel efficiencies are different for coal and
charcoal versus wood. (In my childhood, one of my grandmothers could get
anthracite coal for free. It was sometimes used for space heating - slow,
steady burn - perhaps ten days a year, and sometimes for special dishes.)

Still, I am not impressed by the fact that coal and charcoal stoves were
determined to burn the cleanest for merely boiling water.  They are
probably better for some uses than for something else. When it comes to
cooking, stacking rules, and no amount of hysterical screaming and banging,
or publishing journal articles, is going to change that. Even fuel bans are
not terribly effective.

1. The Jetter paper Ron cited is familiar to me. Jim allowed me to use that
picture in a paper I was working on at the time.

Controlled laboratory measurements of cookstove emissions *sometimes poorly
predict field-based emissions*.26−28,40 Some studies combine data from WBT
phases for benchmarking purposes16 or for comparing intrastudy laboratory
and field data,28 but these data are based on cookstove usage patterns that
may not be reflective of actual field use. *To improve the ability to
compare laboratory and field measurements, WBT phase-specific emissions
data are reported in this study, because each WBT phase simulates, to some
extent, different cookstove use*. (emphasis added)


>From a lay person's perspective, this is not a ringing endorsement of WBT
and Tier-making rigmarole using WBT in total, rather than by phase.

2. The authors clearly say, " Thus, *cookstove emissions data by WBT phase*
are likely to be useful in developing international standards."  (emphasis
added)

I don't remember seeing anything in 19867-1 for emissions testing by phase.
Nor in the WHO cookbook on HFC Guidelines. Nor in any of WBT-related
discussions in the last two years.

3. I am also impressed by the statement " Since these cookstoves consume
less fuel, *they generally produce lower emissions per given cooking task
(as discussed below) but have little or no reductions in emissions per unit
fuel*. "

Again, from a lay person's perspective, it is critical to acknowledge
that *emission
rate in MJd is not the same as emission rate per cooking task *(WBT phase
or any other characterization of "cooking task")

In which case, *why bother with the IWA Tiers of emission rate per MJd?
Simply because that is what EPA has in 40 CFR 60*? (Note: That 40 CFR 60 is
the source of much mischief in the IWA; seems to have been used to bulldoze
everybody into thinking that it is applicable to cookstoves. It is not. EPA
hoodwinked you all.)

4. Also note, "Development of test protocols is needed for stoves
performing *tasks substantially different from boiling water, such as the
griddle stoves* discussed above." (emphasis added)

We don't know how much cooking in poor countries' households is done on the
griddle - injeras and rotis, tortillas, dosas, pancakes seem to qualify -
but then there is wok frying, fire roasting, deep frying, pan roasting (of
flours, seeds). Since we don't know how much corresponds to heating and
boiling water, nor do we know what kind of cooking produces the highest
emission rates, *why do we bother with boiling water at all*, whether or
not it is WBT or other tests for comparable tasks?

5. Finally, see their caution: "*Despite a lack of correlation with
emissions of some other pollutants that also affect health*48 and
climate,40 CO and PM emission measurements continue to be widely acquired
for cookstoves due to their relative simplicity and availability

That is, *PM emission measurements DO NOT CORRELATE with some other
pollutants that also affect health!! If that is the case, then, what good
are mass measurements of PM per MJd or per WBT phase? *

I had heard recently that PM2.5 is merely an indicator of pollutants that
affect health. There has been discussion on this list about particle size;
this paper also discusses UFP which may be of greater value from health
perspective (not that any IER has yet been cooked up for UFP, but let's
follow science, not scientists.)

In sum,

a) I think Ron is implying this paper suggested something different from
what he does; it is by no means a defense of WBT or WHO/ISO rigmarole. At
least from emissions and health perspective, this proves conclusively that
WBT is not worth the bother, except perhaps for different phases, which is
not what I see in 19867-1 (public comments version).

b) Let's have data on coal stoves emission rates and efficiencies if they
can be compared to Figures 2 and 5.

Another nail in the coffin for "clean" definition of WHO and ISO Tiers
using WBT or modifications of boiling water.

Not that these tastes make any showing of clean "breathing space" - i.e.,
concentrations and exposures that can be realistically achieved, not just
modeled with a Single Box a la 40 CFR 60.

Nikhil

PS: Take note, that as of this paper in 2012, Kirk Smith was not taking the
position that the best of wood stoves were not good enough. If at all, the
Protos stove based on plant oil had worse performance than the Phillips or
Stove-Tec TLUD.





------------------------------------------------------------------------
Nikhil Desai
(US +1) 202 568 5831
*Skype: nikhildesai888*


On Thu, Jul 26, 2018 at 6:40 PM, Crispin Pemberton-Pigott <
crispinpigott at outlook.com> wrote:

> Dear Ron
>
> >I gave a cite yesterday to a paper by Jetter et al, that is on testing.
> Clearly the best performing stoves there were TLUDs and fan-powered (also
> TLUD principles).
>
> The cleanest burning stoves were, at the time, coal stoves, and they were
> not reported. Tests available at the time, and far more available now
> (perhaps 1000) clearly show that advanced combustor designs for coal and
> charcoal outperform biomass stoves in general.
>
> Regards
> Crispin
>
>
>
> List, Xavier and Kirk
>
>                 The main item not being discussed below is the recently
> approved (with a huge majority by a lot of stove experts - after years of
> debate) new ISO test procedures.  To me this proves conclusively that the
> WBT is fine.  Giving cites for inadequacy that are very old is no proof of
> anything.
>
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