[Stoves] Looking for stove designþ

Thu Mar 13 20:59:40 CDT 2014

My impression from visiting and friends who live there is that the place is really productive. Zambia imported something like 1000 of the 3800 white Zimbabwean farmers in one go and went from a food deficit country to an exporter in one year. The reason is that the best farmers in the world are those 3800. So it is more knowing how to farm than what to farm.

Perhaps you are aware that no tillage farming in Zimbabwe was widely practiced because the spoils are so friable and easily damaged. There are few farmers in the world that can take proper care of 5000 acres and 2000 staff, security, education, supplies and marketing. Mozambique brought in about 500 in one go. Very successful. Nigeria tried with a few hundred. Not sure how that worked out. I think a lot were from South Africa.

So the reports you sent look terrible but the reality is different. Is skill the difference?

Western farmers in Canada make a pretty go of it on some pretty lousy land.

Thoughts?
Crispin

BB10 Rocks!
From: Lloyd Helferty
Sent: Thursday, March 13, 2014 20:42
To: Discussion of biomass cooking stoves
Reply To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Looking for stove designþ

Crispin,

   I was looking up the topic of Zambia (part of a task I have been
doing recently looking at what countries might be seeking out
biochar-producing stoves), and I came across this old email, where right
at the end (bottom) you write, "The soils of Zambia are already
/*famously productive*/".
   This was _not_ the impression that I had been given about Zambia:

http://en.wikipedia.org/wiki/Ecoregions_of_Zambia#Soils

  * Red sandveld soils *cover _most of the country_*, and are generally
    *not very fertile* due to weathering and leaching; the top soil is
    *sandy*

  * Grey dambo soils contain more nutrients but are waterlogged in the
    rainy season and often *very acidic*, restricting the plants which
    can grow there to sedges and wiry grasses tolerant of marshy conditions.

  * Kalahari Sands in the south-west of the country are *infertile and
    do not retain moisture*

ONLY:

  * *Black soils of floodplains* are fertile, grasses grow on them as
    soon as the annual flood recedes and provide a rich resource for
    herbivores.*If the annual flood is _disrupted by dams_, woody shrubs
    of lower nutritional value tend to replace grasses and so reduce the
    number of herbivores and biodiversity.*

Are you referring (only) to the "Black soils of floodplains"? What about
the rest of the country?

Regards,

   Lloyd Helferty, Engineering Technologist
   Principal, Biochar Consulting (Canada)
   www.biochar-consulting.ca
   48 Suncrest Blvd, Thornhill, ON, Canada
   905-707-8754
   CELL: 647-886-8754
      Skype: lloyd.helferty
   Steering Committee coordinator
   Canadian Biochar Initiative (CBI)
   CURRENTS, A working group of Science for Peace
   http://www.scienceforpeace.ca/currents/
   President, Co-founder & CBI Liaison, Biochar-Ontario
   National Office, Canadian Carbon Farming Initiative (CCFI)
   Organizing team member, 2013 N/A Biochar Symposium:
     www.carbon-negative.us/symposium
   Member of the Don Watershed Regeneration Council (DWRC)
   Manager, Biochar Offsets Group:
            http://www.linkedin.com/groups?home=&gid=2446475
    Advisory Committee Member, IBI
   http://www.linkedin.com/groups?gid=1404717
   http://www.facebook.com/group.php?gid=42237506675
   http://groups.google.com/group/biochar-ontario
   http://www.meetup.com/biocharontario/
   http://www.biocharontario.ca
    www.biochar.ca

"Producing twice as much food with diminishing resources, without further loss of natural habitats and biodiversity and in a changing climate may be the greatest challenge facing humanity."
    - Lloyd Helferty

On 2011-11-14 3:35 PM, Crispin Pemberton-Pigott wrote:
>
> Dear Vetle
>
> This is exactly the sort of information that builds the case for a new
> stove or a new approach to fuelling and operation.
>
> Use acceptance is a major issue and the follow-up is important --
> meaning do the new stoves remain in use. When they do, it is often for
> reasons that have to do with fuel availability in my limited
> experience. Not have to go as far or spend as much for fuel is a
> strong incentive. The only thing that mitigates hard against it is if
> the stove is inconvenient to use or won't cook properly. African women
> tend to like a high heat (high firepower) to 'cook fast' so speed to
> boil is important.
>
> >The 6 liter Peko Pe stove can be filled with 600 grams of Maize cobs,
> with
> the sizes of 40-60 mm, it will burn for about 30 minutes and boil one
> liter of water within 9 minutes after ignition (6,5 minutes after the pot
> is put on the "flame").
>
> Is 1 litre large enough to interest a family? How much to people cook
> at a time? The answer might be 'a little in the morning and a lot in
> the evening'. It is quite reasonable for there to be two stove sizes
> or for one to be used only for certain tasks. If the fit is good,
> people will adopt them.
>
> If I estimate 600 g @ 15% moisture (air dry in summer) I get about 7.8
> MJ of potential energy. Subtracting for 20% char (125 g) I get 4.1 MJ
> of heat over that 30 minutes. That is 2.3 kW average (with perhaps a
> peak of 3 kW?).  Does that sound reasonable? Is the heat fairly
> constant during that time? If so, it is going to have a pretty
> constant thermal efficiency.
>
> If the fire is low for 2.5 minutes then the pot goes on, and the
> boiling is 6.5 minutes per litre, that is an overall efficiency of
> about (0.335 MJ heat absorbed / 0.975 MJ heat applied) = 34%.  If the
> power is not up to that 2.5 kW average at the time, perhaps it is
> higher. If the fire is really large at that time, perhaps the
> efficiency is In the high 20's. Does any of this sound like what you
> are seeing?
>
> 30% is pretty good.
>
> So the information I will be looking for relates to the cooking power
> in the first phase (pyrolysis), the duration of the burn and the
> heating power that is available if one wanted to continue to simmer on
> the remaining char.
>
> There is a test which would be very valuable and it is a water heating
> (not boiling) test.
>
> Put on a large pot with a lot of water, large enough that it will not
> boil for at least 40 minutes. Record the temperature every 20 seconds
> or so (be regular to make it easier to analyse) using a thermometer
> that gives 0.1 Degrees.
>
> As the thermal efficiency will probably not change a great deal during
> the cooking session, the temperature rise /rate/ is an indicator of
> power output. It can be calculated for various intervals based on time
> or temperature. I have attached a typical result of such a test for an
> old Panda paraffin stove using a heterogeneous test protocol. The top
> blue line is the mass of water remaining. You can see when the stove
> was changed from High to Medium power as the boiling rate (water mass
> loss) changes. The thermal efficiency line (green) detects a change in
> efficiency with the turn-down.
>
> If the power level changes the slope of the water heating line will
> change. This can tell you what the power change is as the stove goes
> from ignition to a fully developed fire to a late-pyrolysis burn. This
> information is very valuable for you. It would be very helpful if you
> share the result. Using this approach, you can tune the performance to
> a cooking task in a given community.
>
> If the pot boils during this type of test the result is harder to get
> because it has to be done on a scale but it can be done if you have to.
>
> >For normal cooking of Nshima and similar food
> preparing, 30 minutes would be enough for each meal in everyday use.
>
> For South Africa and vicinity it would take 45 minutes after boiling
> to cook 'pap' which is much longer.
>
> >Cooking Nshima need less than 10 minutes so usually they can prepare
> most of their additional food with one filling.
>
> That is a very good fit then, especially if adding some chopped wood
> will extend it by a few minutes if needed. Do people object to
> chipping/chopping the wood? Zimbabwe (rural) had difficult with
> splitting wood for cooking because the trees are so hard. That problem
> is avoided it no wood or little wood is involved. As the maize cobs
> collect around the house it should be used first I guess. Hopefully.
>
>
> >We do feel that 6 liter Peko Pe stove is a suitable size for unprocessed
> BIOmass wich are most available around the farms.
>
> Agreed, by the sound of it. You have a good match between the stove,
> fuel and the cooking task.
>
> >Since they already are cooking with one pot at the time, we don't think
> they need to have more than one stove,.
>
> Good point. How do they prepare the 'relish' to go with the nshima? I
> have seen it prepared in a smaller separate pot.
>
> >This is off course an investment cost up for discussion for every
> household. When less cooking time are needed they can
> just use less fuel.
>
> Exactly.
>
> >With beans, the farmers will spend more time for cooking. This can either
> be done by empty the stove and refilling it with maize or use smaller
> cobs
> (>10 - 20mm) to get more mass into the stove (800g = <40 min "flame
> time") or also by
> using other kind of denser BIOmass. Chopped wood will burn for more
> than 1
> hour.
>
> Is the burn rate (mass per minute) the same with all the fuels or do
> see a noticeable difference?
>
> So far it seems that the farmers are satisfied with both the size and
> cooking time. Time will show if adjustment of stove size are required.
>
> Agreed.
>
> >Since the farmers in this project are targeted to collect BIOchar from
> maize cobs used for household energy purpose, they will refill the
> stove when needed to get sufficient cooking/energy time.
>
> They will probably do that until they run low on fuel and there is
> nothing wrong with that.
>
> >The BIOchar will be stored for later to be used as soil improvement
> instead of using it as glowing charcoal.
>
> I understand that process. *The soils of Zambia are already famously
> productive* so any effect will be important to document.
>
> I really appreciate you taking the time to provide hard data for us
> who are disconnected from the work on the ground. I would have shown
> one to the Chinese rural energy delegation Roger Samson is bring
> around this week if I had a working sample. We are going to
> demonstrate several stoves that can burn pelletized (and chunked)
> switchgrass to try to generate interest in TLUD technologies.
>
> Thanks
>
> Crispin
>
>
> _______________________________________________
> Stoves mailing list

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