[Stoves] Stoves Digest, Vol 147, Issue 5 - Nganga

[Ronal Larson]

Crispin and list:

	Yours is not a standard approach:  If the biochar community hears of a 20% yield, that is on the total input weight, not 20%  of the incoming carbon.   Your 858.22 (at least 3 too many digits) is at least a factor of 2 too high (since 20% yield is lower than normally reported).

Ron

> On Dec 20, 2022, at 12:42 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Nganga
>  
> I have changed the subject line to remove the chaff.
>  
> The carbon footprint is of two types: the mass of carbon emitted and the mass of carbon dioxide – you have to know which you want.  Unfortunately in the effort to demonize carbon dioxide, “carbon” has been substituted in nearly all cases, because carbon is usually black and is easily considered “dirty” by the populace.  Carbon dioxide has gained a reputation as “dirty” and “pollution” through repetition, not fact.  This is unfortunate because it makes it harder to answer your straightforward question.  Confusion persists because it is not clear from “carbon” if it is C or CO2.
>  
> Let’s assume you want to know the CO2 output from a gasifier that consumes 50 kg per month.  You ask for an annual number so I will express the consumption on an annual basis.   50 x 12 = 600 kg/annum.
>  
> If you burned the wood completely, the answer is easy:
>  
> Wood is ~50% carbon.  More likely 45%-48% but 50% is often used because wood can range up to 52%.
>  
> 600 kg x 50% = 300 kg carbon.
> 300 kg carbon emitted as CO2 is (300 / 12 * 44) = 1100 kg  CO2 / annum.
>  
> The “12” is the mole mass of carbon and the “44” is the mole mass of carbon dioxide.
>  
> This would be the case if there was no moisture in the fuel. 
>  
> I caution that some people want to know the mass of carbon and others the mass of CO2.
>  
> Suppose it was wood pellets with a 6% moisture content (on a wet weight bases ‘WWB’) .  Suppose the fuel is 94% wood and 6% moisture, by weight.
>  
> Then the CO2 emitted would be proportionally less:  1100 kg x 0.94 = 1034 kg / annum.
>  
> However, you said it was a gasifier.  What is the carbon remaining after the burn is  complete?  Often there is a deliberate attempt to create char with a gasifier. Yes? 
>  
> The carbon mass remaining should be subtracted from the total of 300 kg carbon without moisture and 300 x 0.94 = 282 kg carbon with moisture.  If the char yield is 20% and the char is 85% carbon, you get the following:
>  
> 600 kg biomass, 6% moisture
> 300 kg carbon minus 6% moisture = 282 kg carbon in the fuel fed.
> 20% char yield = 282 x 0.20 = 56.4 kg char
> (It is normal to express the char yield in terms of the dry mass input)
>  
> At 85% carbon in the char: 56.4 kg char 4 x 0.85 carbon = 47.94 kg carbon in the residue.
> That carbon not burned: (47.94 / 12 * 44) = 175.78 kg CO2 not emitted
> So the emitted mass is (1034 kg CO2 potential – 175.78 kg avoided) = 858.22 kg CO2 emitted.
>  
> All you have to do is substitute the relevant numbers into the formulas. 
>  
> Best regards
> Crispin
>  
> From: Stoves <stoves-bounces at lists.bioenergylists.org <mailto:stoves-bounces at lists.bioenergylists.org>> On Behalf Of nganga liambai
> Sent: Monday, November 21, 2022 12:16
> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>>
> Subject: Re: [Stoves] ***SPAM*** RE: ***SPAM*** Re: Stoves Digest, Vol 147, Issue 5
>  
> Greetings to all,
>  
> I am asking for assistance in respect of methodology for determining annual carbon footprint (in weight quantity) for a micro-gasfier stove consuming 50kgs of pellet fuel per month. 
>  
> Nganga Lyambai 
>  
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