[Stoves] Jatropha and its future

Wed Aug 17 02:27:59 CDT 2011

Dear Crispin, 

            Thank you VERY much for helping me with the learning curve. The info below will help me digest better the language of stove. I know some guys who can help me put these things into action so I can better communicate with you. A gut level or instinctual answer would guesstimate a good six hour burn on these "logs" ( I think we are talking about like fuel here) with enough heat to handle the two bedroom house belonging to my pen pal in UlaanBaatar. He is the one reporting 8 tons of coal per season. I would love to get a sample of what they have there, I think I have a good chance at really cleaning up and reducing consumption. I will try the water test sometime this next week when the first stove comes up for destructive testing.....and photos. 
            Again, Thank you ! 
From: bostonnyer at gmail.com
Date: Tue, 16 Aug 2011 23:52:37 -0600
To: stoves at lists.bioenergylists.org
Subject: Re: [Stoves] Jatropha and its future

FYI: In addition to being toxic when ingested (as previously discussed), some phorbol esters can activate tumors.  Although compounds may break down during the normal cycle of the stove, they may not when it is being lit.  When testing the toxicity of emissions from J stoves, we must test at the various times during pyrolysis.  In my opinion we should be extremely cautious regarding the toxicity before promoting this stuff.  If you are interested in literature on the toxicity of Jatropha, Harrinder Makkar at the University of Hoffenheim has published a significant amount.

Boston

On Tue, Aug 16, 2011 at 10:11 PM, Crispin Pemberton-Pigott <crispinpigott at gmail.com> wrote:

Dear Roger 

>I am curious if this "log" was an extruded or pressed product. 

It is a pressed/extruded log (same thing) using no binder save the lignin in the material. The diameter is about 110 mm and the length about 250/300mm – will check.

The colour is ‘pine’ so I would say, golden.

>…The moisture content is known to be about 8%. 

It varies with storage. The production process dries the wood almost completely (hot) and it picks up some moisture after that.
>It is approx 8500 btu/lb, 

That would be 8500 x 1055 x 2.2046 (lbs/kg) = 19.8 MJ per kg which is definitely a ‘dried’ energy content.

With 8% moisture it is about 17 MJ/kg for typical hardwood.

>…and gives a burn time of up to 12 hours (in our stove) 

It is important that you express this burn time together with a kW rating (or BTU if you can work that out instead).

A couple of contributors explained this before but here is a repeat:

8500 BTU’s / lb in the 2.2 kg log.That is 8500 x 1055 x 2.2 = 43,493,000 Joules total heat content (43.4 MJ)

One Watt is 1 joule per second of energy.

12 hours = 12 x 60 minutes x 60 seconds = 43,200 seconds.43,493,000 Joules / 43,200 seconds = 1007 Watts average heat output on a continuous basis. That is the same as saying ‘the power output is 1 kW’ average.

>Funny thing is I get more smoke at a higher heat output than the medium to lower end. 

That has to do with the availability of secondary air and the combustion environment (including its physical size).

>Estimated [heat] output at 27,000 high, 5,000 btu low output. 

Per what? Per hour? Per day? It is not clear. 5000 BTU’s is 5.275 MJ. If that was per hour, it is 1.465 kW. The 27,000 = 7.9 kW. If it takes 12 hours to burn the log, (and in fact there is still some coals left) it averages 1 kW heat output average.

An earlier point I was making about Mongolian space heating is that the homes need between 4 and 12 kW on a continuous basis. We would need to burn at about your ‘medium’ power level continuously to keep the place warm. The largest stoves we work with in homes are 20 kW, equivalent to about 1.3 kg of wood per hour (depending on the moisture content).

Any stove sold there has to be able to cook a 16 inch diameter wok, and to boil 9 litres of water (in the wok) in less than 1.5 hours from ignition (or it won’t be considered at all for the programme). Some stoves can boil it in 30 minutes, but 90 is the upper limit. Mass production facilities are available. It has to retail under $150.

Good luck with the EPA testing and alla that. Please keep us informed about how it goes.

Crispin
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