[Stoves] pellets in an urban setting

Mon Jul 29 19:21:13 CDT 2013

See comments below.

On Tue, Jul 30, 2013 at 12:24 AM, <rongretlarson at comcast.net> wrote:

> Paul and cc list  (but the questions below pertinent to any and all)
>
>     This is to hope that you can perform a few more experiments re
> fuels.   I am sure all your comments are correct comparing loose husks to
> pellets, but wonder if you could try and report on several other fuel
> options as well - especially telling us about prices in Vietnam.
>

In Vietnam we have four major sources of TLUD fuel: from rice (lowland),
from coconut (lowland), from coffee (highland) and from pine trees
(highland).

> Your comment about running stoves for free because char produced in your
> stove is worth more than the pellets going in is very important.  Can you
> give more cost (per kilo) detail on that?
>

Rice hull biochar is commonly used in Vietnam as part of a potting soil
mix. I have not seen applications where it is applied to the soil. Rice
hull biochar is made in crude retorts where all of the gas is wasted. It is
totally lacking in uniformity: some of it is burned to ash, whole some is
barely torrefied. In spite of its lack of uniformity, it still commands a
significant price.

But this price is hard to pinpoint because it is sold by volume, not by
weight. A relatively small sack of rice hull biochar retails for about
$1.20. Sacks of biochar are often stored outdoors, and they contain a lot
of water. So a measurement by weight is not possible. I estimate a sack of
biochar to contain no more than 3 kgs of dry biochar. This equates to about
$400 US per ton for rice hull biochar. Loose rice hulls in this area sell
for about $17 US per ton (in tropical areas they are often free). It takes
about 3 kgs of rice hulls to produce one kg of biochar. So it takes $51 of
rice hulls ($17x3) to produce $400 of rice hull biochar.

One ton of rice hull pellets sells for $76 per ton. So $228 of pellets
($76x3) will produce about $400 in biochar. A sack of raw pellets of a
given size will produce a sack of biochar pellets of the same size. The raw
pellet and the biochar pellet are easy to transport due to their high bulk
density and low volume. So the biochar merchant brings a sack of raw
pellets to the household, and receives in exchange a sack of biochar
pellets of roughly the same volume.

> The next three (are there more?) items are extensions - both on technical
> results and on economics.
>
>     First is wood chips.  The stove camp activity was all based on this
> product because of a request from a South American (?) company wanting to
> harvest a large older forest,  I think specifically planted decades ago to
> save nearby old growth forests.   I presume chips are being preferred over
> pellets for cost reasons  (I have heard a 3:1 price difference).  Hopefully
> you can find a chip supply and tell us on their performance and economics
> in any of your stoves as well.
>

Wood chips can be dried thermophilically outdoors under a compost fleece
down to a 23% moisture content. To be used as TLUD fuel, they would then
have to be further dried to about 12%, preferably sun-dried. The chips
would have to be graded into several sizes to assure uniformity. The fines
would have to run through a pellet machine to achieve uniformity. I think
that uniform wood chips should work fine in a TLUD.

>
>    Second is any fuel made by hand from paper, leaves, grasses, rice husks
> (?),   etc - as promoted by Richard Stanley, etal.  Presumably you saw my
> recent report on making something specifically for TLUDs.  The advantages
> here are making productive use of materials having no other possible use
> and supplying jobs for low-income people.   I am about also to respond to
> recent message from Richard along these lines (re using only hand muscles).
>

In Vietnam I do not know of fuels made by hand. If TLUD fuels are made by
hand, ideally the fuel here should be as small and as dense as possible. If
primary air does not flow uniformly up through the fuel, CO2 is generated.
If CO2 is generated the biochar is not uniform, heat is generated far below
the pot, and the combustion of syngas is compromised.

>
>    Third is use of small twigs, ag residues, straws, reeds, grasses,  etc
> (similar to rice husks, but denser and available where husks are not) that
> can be used without any processing..
>

There is a company near Hanoi that prepares tobacco leaves. This process
leaves behind a tobacco stem  residue that is quite uniform and performs
well in a TLUD. But most other raw biomass such as twigs, grasses and pine
needles have to be rendered uniform. Pelleting is the best way that I know
of to render biomass uniform.

> Again, maybe a job creator - with hope that the char value exceeds the
> fuel cost   This presently is the fuel of choice for backpackers as it can
> be found everywhere.  Can this approach be expanded, again as a way for
> fuel preparers and cooks to make money rather than only expend it?
>
>    Fourth (and last) is the supply of larger wood  (maybe only branches?)
> cut into small pieces (I saw a lot from board lumber cut to about 6-12 inch
> length almost all less than 1 square inch cross-section (NOT the standard
> fuel in the field).  This was the main fuel alternative to chips at the
> stove camp for those not using TLUDs.  Presumably this is also possible in
> Vietnam for vertical stacking in your device with optimum heights and
> packing densities.
>

I have tried vertical stacking. But immediately I see on my burner (with 80
holes along the periphery), burner holes that do not support a flame. The
culprit here is CO2 formation, and once again, if CO2 is generated, the
biochar is not uniform, excess heat is generated far below the pot, and the
combustion of syngas is compromised. If the combustion of syngas is
compromised, I am sure that some CO will not get properly combusted.

> Again emphasis to be on economics  - still hoping to find lower fuel costs
> than pellets, but less bulky than husks,  if possible.
>

In general, the safest route is to make a pellet of irregular biomass.
Preferably this should be a pellet of a 6 mm diameter. This brings me back
to a point that I have made so often: funding organizations are not
focusing enough on fuel preparation and biochar research. Once farmers in a
given area understand the value of biochar (as many of them do here in
Dalat where I live), then biochar merchants can make a lot of money
exchanging raw pellets for biochar pellets.

Thanks.
Paul Olivier

>
>    I pick on you as probably having some local labor available to try
> these alternatives with a chance of selling more stoves where costs can be
> an important factor - and you knowing of the importance of either getting
> more char in the ground or of making char with use of the pyrolysis
> gases.   I'll be glad to split the costs of trying these other
> quite-different fuel options in your stove.
>
>    Somewhat along these lines, this is also to alert all to an EPA-GACC
> webinar on 20 August on batch stoves (10:00 AM Eastern).  This  received a
> few days ago:
> *The online registration form (
> https://unfoundation.conferencinghub.com/attendee/RegisterLogin.aspx?hubconfID=1632144&qtID=1&act=reg&cp=2861)
> includes a place to enter comments or questions you would like addressed
> during the webinar.
> *
>
>
>    So Paul, thanks in advance for anything new you can report on the
> economics of these six fuel options.
>
> Ron
>
> ------------------------------
> *From: *"Paul Olivier" <paul.olivier at esrla.com>
> *To: *"Discussion of biomass cooking stoves" <
> stoves at lists.bioenergylists.org>
> *Sent: *Sunday, July 28, 2013 9:06:32 PM
> *Subject: *[Stoves] pellets in an urban setting
>
>
> I am getting excited about the use of pellets. In an urban setting in a
> developing country such as Vietnam, a pellet gasifier should be a lot more
> socially acceptable than a loose biomass gasifier.
>
> Since pellets can be as much as 8 to 10 times more dense than loose
> biomass, the reactor can be much smaller. A net reactor height of only 8
> inches is all that is needed to give a burn time of up to 90 minutes. Since
> the unit is small, it is  lightweight. The reactor weight is but 1.2 kg. It
> is easy to handle. With such a small reactor, the manufacturing cost drops
> considerably. This means that the most heat-resistant and non-corrosive
> stainless steels become affordable. This adds years to the life of the
> unit. This also means that the unit looks good and takes on the appearance
> of a high-end kitchen utensil. If the unit does not look good, it will be
> hard to sell.
>
>
> https://dl.dropboxusercontent.com/u/22013094/150%20Gasifier/Short/Photos/IMG_1571.JPG
>
> Pellets can be more cheaply transported into urban areas than loose
> biomass. Dealing with loose biomass can often be dusty and messy. The
> storage of pellets in a kitchen takes up much less space than the storage
> of loose biomass. With pellets there should be a lot less emissions of
> particulates.
>
> Biochar pellets are easier to quantify than loose biochar. A measurement
> of biochar volume is all that is needed. There is only a small reduction in
> volume as when a pellet is transformed into biochar.
>
> The flame put out by a pellet gasifier is rich and intense throughout the
> burn:
> http://www.youtube.com/watch?v=84qDsbBO9p8
> The flame does not turn ethereal.
>
> It is true that pellets cost more than loose biomass. But pellets are
> cheaper to transport into a city than loose biomass, and the biochar
> produced from pellets has a higher value in Vietnam than the original
> pellets. I foresee the possibility of an exchange program where pellets are
> supplied free-of-charge in exchange for the biochar produced from these
> pellets.
>
> Thanks.
> Paul Olivier
>
> --
> Paul A. Olivier PhD
> 26/5 Phu Dong Thien Vuong
> Dalat
> Vietnam
>
> Louisiana telephone: 1-337-447-4124 (rings Vietnam)
> Mobile: 090-694-1573 (in Vietnam)
> Skype address: Xpolivier
> http://www.esrla.com/
>
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-- 
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

Louisiana telephone: 1-337-447-4124 (rings Vietnam)
Mobile: 090-694-1573 (in Vietnam)
Skype address: Xpolivier
http://www.esrla.com/
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