[Stoves] Re looking for a stove design for large amounts of biochar

Sat Nov 12 10:56:18 CST 2011

Dear Paul

>Each household produces about 1/3 kg of biochar each day.  If the biochar
yield by weight of the raw fuel is 20%, the biomass needed is 1.66 kg per
day.  If 25%, then the biomass is only 1.33 kg/day.

I am not completely clear on your calculation. Are you showing the amount of
biomass input needed for a yield of 20 and 25%?

>Less than 2 kg/day represents fuel savings compared with the inefficient
3-stone and other fires.  AND they are getting the biochar.  This correctly
contradicts the people who say that making biochar leads to increased
cutting of the forests.  

I am not sure who says it leads to an increase, I do read a number of people
asking the question about that possibility which is perfectly legitimate.  I
have, myself, asked this question and did not get clear answers for a long
time. It may be that it was assumed the answer 'was obvious' and therefore
unnecessary to be quantified. Well, that is not how science works. If we
step up to a programme manager and announce we can reduce the cutting of
biomass by 15%, or 30%, we have better have the reliable numbers to back it
up.

For that reason I would appreciate it if you could clarify the % numbers
above. 

How many times have we been told that such and such a cooking technology
'saves fuel' or 'reduces emissions' but when examined closely the savings
are not there, not obvious, or are only obtained under special, not general
circumstances. It would be unfortunate of we did not ask basic questions and
agree that the answers are realistic and reproducible before running to
market.

I agree with your analysis about why the savings are there:

>1.  The Peko Pe and most other TLUDs keep the fire focused onto the cooking
task.

>2.  These micro-gasifier stoves can use many types of biomass, so any
energy-equivalents of cut trees that can be replaced with maize cobs or
ag-waste briquettes also means LESS deforestation.

The first point is where the fuel savings are made because nothing is free -
if you are saving fuel it can only be by burning the fuel more efficiently
or by increasing the heat transfer efficiency, or by being able to control
the fire to only give the heat you want at the time (so no heat is wasted
with an over-large fire).

The second point is where fuel switching makes its mark. If you can burn
something that is plentiful and free, like papyrus near Kampala, you have
effectively broadened the resource base. If you are burning fertilizer there
may be unintended consequences.

That said, it is not magical or eternal. Pellets are becoming more popular
and it is just these sorts of 'wastes' that can be made into top quality
(relatively expensive) fuel so there is already in some places, competition
for the resource. This pressure (competition) will not go away. In other
words, always remain sober when analysing the new proposal.

There are certainly some happy moments ahead where there is such huge waste
of biomass like Zambia. 

>The Wendelbo project in Zambia with 200,000 rural households is a major
effort that should help the world realize that the TLUD micro-gasification
is a truly significant part of the solution we all are seeking.

It certainly can be and I congratulate Paal for getting the attention he
deserved years ago. When the next wave of innovation comes, it will compete
against a different baseline.

>I did NOT say that TLUDs are THE solution.  But it is major.  This  

needs to be recognized and implemented in so many more locations.   

Paul, as I have said in other communications, there is more than one way to
burn as a gasifier or a pyrolyser and I am always a little surprised that
you mention TLUD's without leaving room for other approaches. I will point
to two other ways to burn the same materials in the same
gasifying/pyrolysing manner that are not TLUD's. One is the downdraft stove
which has been well discussed here. At this time I feel it is not as
efficient for cooking but I don't want to arbitrarily limit its potential -
people are clever, they may invent something. The other is a crossdraft
stove which, like the downdraft, has the added advantage of being easily
refuelled. Rok's side-feed achieves this with briquettes.  It could easily
make char if secondary air ports were added.  Both of these alternative
layouts can, like the TLUD, make char, or not. I agree completely with Dean
Still on this point: one should be able to choose what mode to use depending
on user preference, or the time of year, or any other reason such as
seasonal demand for char.

>Stovers, the TLUDs are not a bandwagon.  

Yeah, well, let's not beat around the bush. The bandwagons are lining up to
jump to the front of whatever wave is arriving. People are very attached to
their ideas or technologies or fuels or approaches to burning. It is a stew
of possibilities to be eaten with a pinch of salt.

Here is what we have to explain to funders:

1.       Baseline fuel consumption per day, per week and per year (seasonal
variation is significant and one cannot cheat by comparing the high-use
baseline moments with low-use improved stove moments).

2.       The improved stove fuel consumption documented on the same bases.

3.       An explanation of how the savings are achieved. It has to be
scientifically valid. A simple check of the savings should correlate the
heat transfer efficiency and the fuel savings, for example. In the case of
the current crop of TLUD's it will be because of improved heat transfer
efficiency as fuelled and operated over an open fire as operated in that
community. Remember that Tami Bond achieved an thermal efficiency of more
than 30% and long before her, Piet Visser did the same thing in Eindhoven.
Few improved biomass stoves are much more than 30% efficient so there are
open fires and there are open fires. Depends on who is running it.

4.       The range of cooking that can be addressed by the proposed stove
should be described. Breakfast? Saturday night supper? Weddings? Funerals?
Baking? Where is the best fit? That sort of thing. Propose limitations so
you are confident in which cooking sector you are going to be able to
deliver verifiable results.

5.       Describe the fuel switching possibilities including what is
available and what this means to the user. I will give an example. There is
a programme to give Vesto stoves to child-headed households in Swaziland.
There are four main selling points: rapid, simple lighting, lower emissions
(esp low PM), fuel saving whatever the fuel, and the most important for
children: it is usually no longer necessary to walk far to find something to
burn. This last point is a fuel-switching argument. Children struggle to
gather enough 'real' firewood and bring it home.  Once they can burn any
sort of biomass lying around (unless everyone else is already doing it)
there is plenty to collect without having to get wood. The Peko Pe can
easily make the same four arguments.

6.       Opportunity cost. An opportunity cost is what it costs you to give
up one thing then do or accept another. In the case of an open fire, it is
said the cost is nothing. In Ethiopia they make open fires with artificial
clay 'stones' that are just the right shape to be able to support the pot,
different ones, and to move the stones in and out to create a sheltered fire
of different sizes. It has a small cost and is better than a fire on open
ground. In short, there are different open fire baselines. Next explain what
will your stove cost in money, time, attention and maintenance. Give up
this, get that. When the value proposition is greater than the opportunity
cost most people will switch/buy the alternative.  Stove cost is usually the
most important of these, even if the fuel saving is total. In other words,
even if a stove cost nothing to run, but it costs too much to acquire,
people will not be able to get their hands on one. A big 'access' advantage
of the Peko Pe is that it is cheap to make. The market for stoves in Zambia
has been well studied by social anthropologist Cecil Cook and the prices
people are able (not just 'willing') to pay have been characterised. This
forms part of the opportunity cost analysis. Make your case showing the
argument for economic access and impact. If you need a subsidy, give reasons
for it and why it is worth it.

My last point is speaks to the issue of stove subsidies. Lately much has
been said here and elsewhere about charcoal (now titled 'biochar' but it is
still just charcoal, in English) and how it can have agricultural benefit.
Ron Larson has presented an argument that it is worth, if necessary,
subsidising stoves (increasing access to them) because of the benefits of
better agriculture and or a value assigned to the amount of carbon that can
be buried in the ground (sequestered). If you introduce an economic argument
that has nothing to do with the stove and fuel, you must show separately why
that argument(s) is valid on its own. The discussion on this List has
focussed on the agricultural benefit and whether they are real. The
conclusion in my view is still ambiguous, certainly nothing like as solid as
promoting TLUDs as improved stoves. The economic argument based on
sequestered carbon is very weak because the value of the trade is unreliable
and has been falling. The Chicago-based CCX dropped to 5 cents a ton and
then closed. The application of the same money to improving, on a most
marginal basis, the management of a power station will have far greater
carbon emission savings than even a stove programme, and is much easier to
monitor, verify and collect on. This is said without also raising the moral
issue of who is benefitting from the (current) carbon trading system.

On the plus side of morality, the Peko Pe project in Zambia based on what we
have read looks like it will be a huge success. That is really good news.
Zambia has not been a big stove success story for anyone so far. Let's hope
this time we have a big breath of fresh air!

Thanks

Crispin

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