[Stoves] [biochar] [biochar-stoves] A review of chronological development in cookstove assessment methods: Challenges and way forward

Lloyd Helferty lhelferty at sympatico.ca
Wed Nov 25 16:09:43 CST 2015


Ahhh, but you /can/ go wrong....

   What if one "quenches" the end-of-batch char with a sound dousing of 
H2O, and that sopping wet (DAF) carbon is found to "still have hydrogen 
and lots of oxygen left indicating not a good biochar" (due to some 
volatiles)?  This (DAF) carbon might _/not/_ be very suitable for char 
cookin' anymore, which could bring us back down to a lower "efficiency" 
-- 0% in the case where one does not "use the pyrolysis gases for 
something" (cooking, heating [CHC, CHB, CHP, CHPB]), ...or, at least to 
a value that would be something approaching the "heat transfer 
efficiency" of flame --> pot --> water/food/load due to the /use/ of the 
pyrolysis gases that were liberated during the pyrolysis process 
(expressed as a ratio of the initial total energy of the biomass fuel 
(dry weight)).

  I suppose this is where the confusion / debate comes, since not 
everyone applies a "value" to the char ~ or at least not to the Energy 
(equivalency) of the char that is produced [whether or not it could be 
considered valuable "biochar" or "fuel for producing additional 
biochar... or energy").

Regards,

   Lloyd Helferty, Engineering Technologist
   Principal, Biochar Consulting (Canada)
   www.biochar-consulting.ca
   Earth Stewardship consultant, Passive Remediation Systems Ltd. (PRSI)
   http://www.prsi.ca/
   Promotions Manager, Climate Smart Agriculture Youth Network (CSAYN)
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    www.biochar.ca

"Start loving the people in your life more unconditionally and relating to them more conditionally."
  - Wm. Paul Young

On 2015-11-25 3:49 PM, Frank Shields wrote:
> Dear Ron and Stovers,
>
> My interest is controlling the fuel. This done by 1) collecting fuel 
> like that being used in real World and 2) normalizing the energy value 
> going to the secondary by using pyrolyze gases + (CO -> CO2) values.
>
> I cannot determine any energy efficiency values because this is just 
> one side of the equation. And you do not supply me with the values of 
> this one side as I need them.
>
> The value I am proposing is only useful for energy traveling to 
> another location - secondary. Making char does not require energy, in 
> fact it waste energy. And (bio-)char does not have useful energy, in 
> fact the energy is locked up and cannot be used by soil microbes for 
> 1000 years. So what I propose is not applicatable to what you are 
> talking about and not intended to be so.
>
> Your (bio-)char (not charcoal used for cooking) is not ‘energy’ locked 
> up but should be referred to as carbon. Following the total carbon in 
> the feedstock; separating it into available carbon and non-available 
> carbon (TGA) for optimum then determining the amount actually made 
> from your char-maker is more to what you want. And that being your 
> efficiency values.
>
> But in a World that is connecting fuel energy producing non-available 
> carbon (biochar) and that biochar is made >90% carbon (DAF) I guess it 
> would be ok to assign non-available carbon with an energy value and 
> use in calculations. Lets see if we can do that:
> 1) we need total energy of the biomass fuel (dry weight)
> 2) using TGA we need energy of the total char (DAF)
> We assume the char (DAF) is 90+% carbon and assign that an energy value.
> 3) We determine energy of the pyrolysis gases (total - char)
>  4) So thats the total maximum amount of energy assigned to biochar 
> that should be produced in your devise.
> 5) You run YOUR device and produce biochar. Ash  a subsample to 
> determine the weight of biochar (DAF). Assign an energy value to it 
> based on biochar (DAF) being >90% carbon.
>
> Now you can calculate the efficiency of your device at producing biochar.
>
> Note: If you have wood (dry) and you use the pyrolysis gases for 
> something, you use the CO->CO2 gases for something and use the 
> (Bio-)char left over for something then 100% of the energy in the wood 
> is always used. You are left with efficiency determinations found 
> (compared to that determined by TGA) for making biochar. But if making 
> biochar is found less than expected so to be not very efficient then 
> the non-biochar gases (CO -> CO2) went to join the pyrolysis gases and 
> it still always = all adds up to 100%. You can’t go wrong!
>
> Where you can go wrong is if after making the biochar you test it to 
> see if it still has hydrogen and lots of oxygen left indicating not a 
> good biochar and it is then wasted. This is bad.
> But if still good for char cooking (due to some volatiles) you are now 
> back to 100% efficiency. You can’t go wrong!
>
> 100% efficiency every time!
>
> Love it!
>
> Frank
>
>
>
>> On Nov 25, 2015, at 8:52 AM, Ronal W. Larson wrote:
>>
>> Paul, Brian, and lists:
>>
>> 1.  Thanks to both Paul and Brian (their messages below).  Brian’s is 
>> a nice comparison to CHP.  The efficiency for CHP is always taken as 
>> the sum of the separate power and heat.  Using the waste heat is 
>> clearly to everyone’s advantage (save companies selling less fuel).   
>> Biochar literature has tacked on a B to discuss combined heat, power 
>> and biochar as CHPB.  There is a considerable difference from CHP in 
>> that the B = biochar competes with the H and P.  More B means less of 
>> both H and P.  But the terms are all (necessarily) measured in energy 
>> terms.  What other units could be used?
>>
>> The same seems true for what Brian is calling CHC.  No reason not to 
>> use this, but an alternative is obviously CHB.  If one was producing 
>> char only for further combustion, then CHC would certainly be 
>> preferred.  The stoves list will probably use both CHC and CHB 
>> interchangeably.   Biochar (three sites receiving this) and climate 
>> (on which this first started) lists will presumably mostly prefer CHB.
>>
>> I cannot accept Frank Shield’s arguments below.  He is trying to 
>> force a false preference between char-making or not - when such a 
>> choice is not needed.  Both are wanted by many if not most stove 
>> users.  I again ask Frank to express an opinion on which efficiency 
>> and inefficiency (presumably always inversely related exactly) is 
>> best.  His reply to me was not used by Brian - so readers will have 
>> to go back to a message close to mine on the 22nd.
>>
>> I similarly reject the arguments by Kevin Chisholm against the use of 
>> both the third and fourth efficiencies.  Like Frank, he offers no 
>> answers to my two basic ending questions, and (I find) no valid 
>> reasons for those two rejections.
>>
>> I have added Prof.  Jain again - as it was his comment (below) that I 
>> quoted in moving this climate thread to the stoves and biochar arenas:
>>
>>>>>>>>>> /t_*he energy stored in the *__*charcoal*__*should be 
>>>>>>>>>> considered *_//_*as a useful energy. *_/
>>>>>>>>>>
>>
>> I again urge readers new to this thread to read his lengthy scholarly 
>> (free) article relating climate issues to stoves in numerous ways.
>>
>> To all - I hope we can hear more on especially the inefficiency 
>> computations; forget efficiencies.  Also on what is the physics or 
>> chemistry which causes char-making stoves to be more efficient?  Is 
>> the fuel composition of either/both H2 and O2 important? Another 
>> possibility is that it is where the flame appears.  Burning char in a 
>> TLUD is obviously inefficient because the main flame and energy 
>> release is as far from the cook pot as possible - below the char, not 
>> above it.
>>
>> To Paul - I hope this is what you wanted.
>>
>> Ron
>>
>>
>>> On Nov 25, 2015, at 6:52 AM, Paul Anderson wrote:
>>>
>>> Stovers,
>>>
>>> The comment below from Brian to one Listserv merits being sent to 
>>> the Stoves Listserv and Biocharstoves Listserv. Brian's comments 
>>> make a lot of sense.   Let's discuss further and see if some 
>>> "implementation" can result.
>>>
>>> I hope that Ron will filter and coordinate any such discussions 
>>> because there are numerous listservs to which the messages need to 
>>> be circulated at least occasionally. There should be assistance from 
>>> the rest of us, especially if implementation is to occur.
>>>
>>> Paul
>>> Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
>>> Email:psanders at ilstu.edu    
>>> Skype: paultlud      Phone: +1-309-452-7072
>>> Website:www.drtlud.com
>>> On 11/24/2015 8:54 PM, 'Brian Dougherty'[biochar] wrote:
>>>>
>>>> Ron,
>>>> I don’t see a problem with reporting the higher efficiency values 
>>>> as long as it’s made clear what is included in that number. As an 
>>>> example, combined heat and power (CHP) plants typically report high 
>>>> efficiencies because they are factoring in the energy from the heat 
>>>> plus the energy from the electricity, but the name implies they are 
>>>> capturing both. A char making stove that is also heating water is 
>>>> essentially a miniature CHP plant if you think of the char as the 
>>>> “power’' output, but it would need to be labeled as such. It’s a 
>>>> matter of semantics, but if a unit is marketed as a char maker or a 
>>>> stove then the higher efficiency numbers might be misleading. If 
>>>> it’s marketed as or intended to be a combined heat and char maker 
>>>> (CHC stove?) then the higher number makes sense.
>>>> Brian
>>>> *From:*mailto:biochar at yahoogroups.com
>>>> *Sent:*Tuesday, November 24, 2015 5:38 AM
>>>> *To:*Discussion of biomass <mailto:stoves at lists.bioenergylists.org>
>>>> *Cc:*S. Jain (Env. Engg.) <mailto:sureshjiitd at gmail.com>;Entire 
>>>> Group <mailto:biocharstoves-7xpll at wiggiomail.com>;Biochar 
>>>> <mailto:biochar at yahoogroups.com>
>>>> *Subject:*Re: [Stoves] [biochar] [biochar-stoves] A review of 
>>>> chronological development in cookstove assessment methods: 
>>>> Challenges and way forward
>>>>
>>>> Frank et al
>>>> Those of us working on char-making stoves (a category bigger than 
>>>> TLUDs ) don’t have the “/don’t know what to do with” problem./Even 
>>>> better is that they seem cleaner and are apt to save time and money 
>>>> (maybe make money).  The issue is reporting -  if you feel such a 
>>>> stove (stove not char-maker) has merit.  What is your answer to my 
>>>> two questions?
>>>> Ron
>>>>> On Nov 23, 2015, at 12:36 AM, Frank Shields wrote:
>>>>> Dear Ron,
>>>>> If your task is to make char your calculations is dry weight of 
>>>>> fuel IN and weight of char (DAF) OUT. Boiling water is just 
>>>>> something to do so you can have a cup of tea while you wait.
>>>>> If your task is boiling water and you are left with char you have 
>>>>> a byproduct to add to your garden.
>>>>> If you want both I suggest you place an importance on each 
>>>>> (percentage of importance) for the span of a year or season. Then 
>>>>> with each run you keep track of the char produced and water boiled 
>>>>> and try to achieve your percentage ratio. At the end of the year 
>>>>> you may need to just boil off some water to get more char or have 
>>>>> left over char you don’t know what to do with.
>>>>> Regards
>>>>> Frank
>>>>> Frank Shields
>>>>>> On Nov 22, 2015, at 9:36 PM, Ronal W. Larson wrote:
>>>>>> Lloyd et al:  Adding “stoves - as that is where we have had a 
>>>>>> similar dialog in the past
>>>>>> I promised an example.  Use energy of wood and charcoal as 
>>>>>> measured to be 18 and 30 MJ/kg - both possible.)
>>>>>> Assume 1 kg of wood into the stove - or 18 MJ.
>>>>>> Assume water boiling away calculates to 6 MJ; Effic1 = 6/18  = 
>>>>>> 33%  (Some say stop here; this is a typical number for many 
>>>>>> stoves including TLUDs)
>>>>>> Assume (to get easy numbers) 26.7% (a little high but a possible 
>>>>>> number) by weight char production - gives .267* 30 = 8 MJ in the 
>>>>>> char.   Effic2 = 8/18 = .444 = 44%,
>>>>>> Using the pyrolysis gases in the denominator - Effic 3 = 6/(18-8) 
>>>>>> = 6/10 = 60%  (This use of the char energy in the denominator is 
>>>>>> the most common way of handling char- added (60-33 =) 27% to the 
>>>>>> reported value of the stove - )
>>>>>> But I think it more proper to add the first two efficiencies: 
>>>>>> Effic4 = Effic1+ Effic 2 = .333+.444 = .777  (17.7% bigger than 
>>>>>> the 60% value - and I think also an honest way to look at what is 
>>>>>> going on.  Last I saw,  EPA did not add these together, but they 
>>>>>> did report Effic 1 and Effic 2.  Sales people for biochar and 
>>>>>> TLUDs are apt to add them of course.   We obviously want both 
>>>>>> numbers to be as high as possible.
>>>>>> The losses are 18-6-8 = 4 MJ or 4/18= 22.2% (mostly hot gases).  
>>>>>> This is what we should be concentrating on - not 100-60 = 40%.  
>>>>>> In inefficiency terms, I claim the losses we want to reduce are 
>>>>>> nowhere near 40% - if you want both char and water boiled away.  
>>>>>> 40% is the portion of energy in the pyrolysis gases that we 
>>>>>> failed to capture.
>>>>>> If we burnt the wood (no resultant char) rather than pyrolyze it, 
>>>>>> we might expect to have a 60% efficient stove - but no-one 
>>>>>> measures any wood stove that high.  Why not? I don’t have a good 
>>>>>> answer, but suspect it might relate to how hydrogen fits in.  
>>>>>> That is - with little hydrogen in the char, the hot gases are 
>>>>>> more hydrogen rich with a pyrolysis stove.  Better heat transfer 
>>>>>> with more hydrogen?  A hotter flame? Or is the effect due to 
>>>>>> oxygen - which also is a lower percentage in char than in wood?   
>>>>>> Or both?
>>>>>> Comments appreciated when we are striving to make char in a stove:
>>>>>> Q1: are the losses 22%, 40%, or 67%?
>>>>>> Q2:  Is the efficiency 78%, 60%, or 33%?
>>>>>> Ron
<snip>
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