[Stoves] Chimneys, rice husks [Ovens]

[Paul Olivier]

Tom,

In the design of household stoves, I do not think that we should advocate
the direct combustion of rice hulls or any other biomass with an
appreciable amount of silica. Even in supposedly sophisticated commercial
applications in Asia, things can go seriously wrong. I believe that TLUD
technology is far better in this regard than direct combustion, but even
here, I can point to two ways in which cristobalite can end up in biochar
and fly ash in the processing of loose rice hulls. Loose rice hulls are
generally messy and dusty, and when processed in a TLUD, they emit
particulate matter that more than likely contains cristobalite. Until
someone can prove to me that this fly ash dies not contain cristobalite, I
back away from promoting the processing of loose rice hulls in a TLUD.

I am hopeful that if the rice hull is formed into a pellet, the possibility
of cristobalite formation within a TLUD can be minimized. It is hard for
air to form a channel through dense pellets, and pellets do not (should
not) contain a lot of fine dust. One big advantage of using pellets is that
the price of the TLUD drops substantially. One big disadvantage lies in the
cost of the pellets.

Therefore I call on funding organizations to step in and help create a
competitive infrastructure and supply chain that assures that pellets are
reasonably priced. They could also help out in showing farmers the benefits
of biochar. The sale of biochar might be terribly important in offsetting
the cost of pellets. If farmers in Dalat (where I live) already understand
in part the benefit of incorporating rice hull biochar into the soil, why
can't other farmers be taught the same?

Thanks.
Paul Olivier

Thanks.
Paul


On Sat, Jun 15, 2013 at 11:49 PM, Tom Miles <tmiles at trmiles.com> wrote:

> From my experience with industrial rice husk burning in Thailand I suspect
> that it is likely that a health hazard is not from the combustion process
> itself, where emissions are controlled by control devices, but from the
> management of the fuel and the ash which can create what are called
> fugitive emissions. Devices used at plants like AT Power are designed to
> remove fine particulates. If their smoke stack is in compliance then that
> is not the problem. (If it is out of compliance then the problem may be
> corruption, not technology.) We don’t have similar complaints from
> communities in the US where rice husks are burned at the same scale but
> where fugitive emissions are tightly regulated. In one case fugitive
> cristobalite silica was an issue for the ash handling system but that was
> resolved.   ****
>
> ** **
>
> Testing combustion and fugitive emissions could determine if a household
> that burns a few kg per day of husks for cooking is going to create a
> health hazard similar to an uncontrolled plant that burns 20-30 tons per
> hour. As far as I know that has not been done. ****
>
> ** **
>
> If ash or char from burning rice husks in domestic or industrial devices
> is determined to be hazardous then it should be appropriately identified,
> labeled, and handled. Since rice husk is perhaps the largest potential
> domestic fuel source in a desperate world it is likely that survival will
> be chosen over potential health risks. We can’t abandon rice husk as a
> fuel. We have to find ways to make it work. TLUDs may be part of the
> answer.  ****
>
> ** **
>
> Tom    ****
>
> ** **
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Richard Stanley
> *Sent:* Saturday, June 15, 2013 9:13 AM
>
> *To:* Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] Chimneys, rice husks [Ovens]****
>
> ** **
>
> Paul,****
>
> From the side lines,…  that appears to be solid research. Aside from a few
> bribe-oriented complaintants, most report what you are concerned about and
>  the partners and sources of funding for the  groups doing the reportage
> are good as well.  I guess then it is a question of whether or not binding
> and blending of the rice hulls with other biomass effectively retards
> cristobalite formation -- or has no effect on it--or enhances it, for that
> matter. ****
>
> Richard Stanley****
>
> www.legacyfound.org****
>
> ** **
>
> On Jun 15, 2013, at 12:20 AM, Paul Olivier wrote:****
>
> ** **
>
> Tom,****
>
> I found this news report:
>
> http://www.ipsnews.net/2009/10/thailand-renewable-energy-not-so-clean-and-green-after-all/
> ****
>
> Not such a nice story.****
>
> I do not think it's a good idea to burn rice hulls or rice straw in either
> power plants, brick kilns or household stoves.****
>
> Paul****
>
> ** **
>
> On Sat, Jun 15, 2013 at 1:10 PM, Paul Olivier <paul.olivier at esrla.com>
> wrote:****
>
> Tom,
>
> I have read in many articles that cristobalite can form at temperatures of
> about 900 C.
> http://www.jicosh.gr.jp/old/niih/en/indu_hel/2004/pdf/42-2-24.pdf
> In burning rice hulls, temperatures can easily exceed 900 C.
> If cristobalite forms and is breathed in, human health is severely
> impacted: silicosis, tuberculosis, cancer and so forth.
>
> *Silica (SiO2) is a constituent of the ash produced by the combustion
> process. Different
> types of biomass fuels contain different quantities of silica. The
> International Agency for
> Research on Cancer has classified silica as a human carcinogen. Long term
> inhalation
> of airborne silica particulates can cause lung cancer or other related
> health problems.
> As rice hull ash contains high levels of silica (~15%), its use as a
> biomass fuel
> presumably increases the risk of developing silicosis-related illnesses,
> and care should
> be used in handling the ash.*
>
> http://www.reap-canada.com/online_library/IntDev/id_eco_sugarcane/7%20Strategies%20for.pdf
>
> *Silica (SiO2) is the main mineral component of rice husk ash (RHA)
> (85-90 per cent). It carries serious health risks, particularly to the
> respiratory system.*
> http://www.dhf.uu.se/pdffiler/cc7/cc7_web_art4.pdf****
>
> Cristobalite can be present in both the ash and fly ash. If someone
> designs a stove to burn rice hulls or rice straw, he has to be sure that
> temperatures remain below the point of cristobalite formation. ****
>
> Paul****
>
> ** **
>
> On Sat, Jun 15, 2013 at 11:18 AM, Tom Miles <tmiles at trmiles.com> wrote:***
> *
>
> Paul,****
>
>  ****
>
> After discussing rice hull combustion and gasification at some length you
> are now saying this is dangerous. Why, specifically? You have discussed the
> potential to emit cristobalite but there is no evidence of the hazard it
> presents. What evidence do you have that burning rice husks or rice straw
> is a health hazard?****
>
>  ****
>
> Tom ****
>
>  ****
>
> *From:* Stoves [mailto:stoves-bounces at lists.bioenergylists.org] *On
> Behalf Of *Paul Olivier
> *Sent:* Friday, June 14, 2013 8:56 PM
> *To:* JJ Claire; Discussion of biomass cooking stoves
> *Subject:* Re: [Stoves] Chimneys, rice husks [Ovens]****
>
>  ****
>
> JJ,****
>
> I would not recommend that you burn rice hulls ir rice straw.****
>
> In many cases this is quite dangerous.****
>
> Paul****
>
>  ****
>
> On Sat, Jun 15, 2013 at 9:40 AM, JJ Claire <pugoclaire at yahoo.com> wrote:**
> **
>
> Greetings one and all,****
>
> I visit the Philippines often and usually stay about six months a year.  *
> ***
>
> I often use a rice hull stove.  I would like to get a plan to build a ****
>
> concrete stove.  I am also wondering if there is such a thing as building
> ****
>
> an 'oven' using cement and/or concrete?  I would like to build one, ****
>
> a white model if possible, [vice a black model], if such a plan is ****
>
> available and if the technology would be practical.  We have a ****
>
> lot of rice hulls and not all that much firewood.  ****
>
> I would be open to heating the oven with firewood and then ****
>
> maintaining the heat level with or by burning rice hulls.  I have****
>
> a lot of rice hulls and want to make the best use of the hulls.****
>
> I currently use the wood ashes to make lye so I can make soap, ****
>
> but I have not used any ashes from rice hulls to make lye.  I****
>
> wonder if making lye with rice hulls is possible.****
>
> The rice hull stoves we use are sort of a metal pail with a wire rack.  **
> **
>
> I am looking for a stove, hopefully one that is hot, medium and cool, ****
>
> for cooking with rice hulls over a long number or years.   ****
>
> On our island, rice hulls are still burned to 'get rid of them', and ****
>
> believe it or not, rice straw is still burned. I often ask neighboring****
>
> farmers to bring me their straw and provide them a small bit of ****
>
> cash for doing so.  We use the rice straw for making compost.****
>
> We add some rice hulls to the compost.  Most of the rice hulls****
>
> are burned for fuel to cook with.  We add the char from the cooking****
>
> process to the garden.  I am wondering if we are making the best****
>
> use of the rice hulls and if the plans I am speaking of by post ****
>
> are available.  ****
>
> Please inform, I am open to suggestions and direction.****
>
> Blessings,****
>
> JJ****
>
>  ****
>
> *From:* "ajheggie at gmail.com" <ajheggie at gmail.com>
> *To:* Discussion of biomass cooking stoves <
> stoves at lists.bioenergylists.org>
> *Sent:* Friday, June 14, 2013 5:02 PM
> *Subject:* Re: [Stoves] Chimneys, rice husks****
>
>
> [Default] On Fri, 14 Jun 2013 17:37:30 -0400,"Crispin
> Pemberton-Pigott" <crispinpigott at gmail.com> wrote:
>
> >We are experimenting in Indonesia with draft-operated buoyancy balancers
> to limit the pull to the ideal even when combustion conditions change in
> the large wood stoves. They are easy and cheap to make. They are mounted on
> the side of the stack of all oil furnaces.
>
> We have used them on pellet stoves (which have their own id fans) to
> limit draught on an insulated ss chimney that rose through 4 floors. I
> wasn't entirely happy with the idea as it raised the possibility of
> the boiler room getting combustion products if the seal wasn't good, I
> would have been happier if the air was sucked from outside. In fact
> there was subsequently a problem but this was down to poor
> maintenance.
>
> AJH
>
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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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>
> --
> 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/ ****
>
>
>
>
> --
> 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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