[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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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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