[Stoves] [biochar] [biochar-stoves] A review of chronological development in cookstove assessment methods: Challenges and way forward
Crispin Pemberton-Pigott
crispinpigott at outlook.com
Wed Nov 25 18:08:25 CST 2015
Dear Lloyd
Your point may be too subtle for some. How about this: the 'remains' may or may not have 'value' depending on the intended use. What you can track, as you noted at the end of your message, is to track the total energy going into the primary combustor and the work it accomplishes. That is its energy efficiency as a cooker.
I have not yet seen any justification for tracking the energy in the recoverable portion of the unburned remaining fuel. I mean, why not track the energy in the unrecoverable fuel as well? Who decides what is a recoverable or unrecoverable particle of fuel? Are partially burned gases (CO and H2) unrecoverable remnant fuel? What the heck is the point of all the machinations?
People ask what the fuel efficiency is. It is an imperfect question because there is more than one fuel type. It is best answered as an energy efficiency question.
Where energy costs money you can make a monetary calculation of input and char values, no problem. That answers an economic question, but not a fuel consumption question.
The core reason for funding CDM biomass projects is to reduce the off-take of unsustainably harvested biomass. A 'more fuel efficient' stove can do that. Some are better than others so a measurement must be made. The obvious metric is the need for raw fuel.
That doesn't preclude the combination of multiple stoves in a system, analysed as a cooking system. What is not going to fly as an argument, is that a stove which uses the same amount of unsustainably harvested biomass and puts 20% of it into the ground in the form of inert carbon, is "more efficient" than the baseline stove.
If someone pays me to bury the carbon while continuing to use the same amount of unsustainably harvested fuel, that is a deal that exists outside the purpose of the Clean Development Mechanism. As Uganda is finding out right now, some advanced stoves with 'additional features' are leading to an increase in overall fuel consumption: electricity generating stoves are being run all day to keep the power on. This was predicted right here in Stoves, remember?
Now what? We are subsidising the destruction of the forest! That is as crazy as burning the Indonesian jungle to plant oil palms to subsidise the making of 'biofuel' to sell in Europe to 'offset carbon emissions'. All these ideas need a sanity check before being implemented.
Regards
Crispin
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)
http://csayouthnetwork.wordpress.com/
http://www.fao.org/climate-smart-agriculture/
https://www.linkedin.com/grp/home?gid=6756248
48 Suncrest Blvd, Thornhill, ON, Canada
905-707-8754
CELL: 647-886-8754
Skype: lloyd.helferty
Co-manager, Sustainable Agriculture Group
http://www.linkedin.com/groups/Sustainable-Agriculture-3866458
Steering Committee coordinator
Canadian Biochar Initiative (CBI)
Community Sustainability (CoSWoG), A working group of Science for Peace
was: http://www.scienceforpeace.ca/currents/
President, Co-founder & CBI Liaison, Biochar-Ontario
Manager, Biochar Offsets Group:
http://www.linkedin.com/groups?home=&gid=2446475
Advisory Committee Member, IBI
http://www.linkedin.com/groups?gid=1404717
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http://www.biocharontario.ca
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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