[Stoves] [biochar-policy] Re: Edinburgh biochar

[ajheggie at gmail.com]

On Saturday 28 May 2011 20:11:56 rongretlarson at comcast.net wrote:

>
> I left one extremely important bit out, The American guy that is
> working at a Welsh University had access to some Carbon14 data from
> Rothamsted, where they have some trials running for over 100 years.
> Apparently there is no "priming" ( which I take to mean causing or
> catalysing CO2 release from soil organic carbon) of the long lived
> element of SOM, the humic fraction, when biochar is used, so biochar
> does not affect this very long lived SOM.
>
> [RWL2: It would be a help if you or any reader could report this
> fellow's name. 

Thomas DeLuca, Bangor U of Wales

Carrie A. Masiello from Rice got the accolade for clear presentation

Richard Nugent was also there from Rothamsted and made some input on the 
difficulties of replicating soil tests, this was available in one of the 
videos.


> I think you are referring to a relatively minor put-down 
> of Biochar started by a Dr. Wardle in Sweden. IBI has quite a long
> discussion of this - and this sounds like an added refutation.

In fact earlier Almuth from Biofuelwatch had posed a question about a 
trial where the net effect of adding char to a soil had been an overall 
loss of total carbon in the soil, it was not a very precise cite and as I 
missed her on the first day I wanted to meet her on the second to see if 
she was referring to the Wardle trial, but she did not re-attend.

She was answered by Lehmann and Nugent but there were further refutations 
in presentations by DeLuca and Yu Luo, who explained abiotic mechanisms 
for initial release of CO2 after additions of biochar, including a 
graphic showing an overall increase of soil carbon even after allowing 
for abiotic and biotic priming.

There was some comment about use of peat  which seemed to be generally 
frowned upon but the fact is it is a major energy source which is being 
used in Scandinavia and Eire and I believe respiration of peat is an 
issue with temperature rises. I wonder if there is a good case for using 
it before it is lost, after all warm climes don't have acid peat bogs do 
they?

>
> It looks like we are going to see a lot more results as the non-fixed
> portion of biochar degrades and then effects will only be related to
> fixed carbon char. Lehman pointed out the CEC potential of biochar has
> not been seen yet as it takes much longer to develop.
>
> [RWL2: It would be good to hear more about this - and whether anyone
> knows how to speed this CEC benefit process up. ]

I too was on the lookout for this but didn't catch anything (apart from a 
cold in the stuffy lecture theatre ;-(). There are lots of things not 
understood including why an anion like Phosphorus should be retained by 
biochar but a lot of this is beyond me.

> Anyway if humanity is here for the long game it begins to look like
> from a sequestration perspective on the 100 year plus scale a higher
> temperature char may be better, which means you forego less energy in
> the conversion in an energy recovery combined biochar plant.
>
> [RWL2: I have heard this - but also arguments for low temperatures and
> mid-temperatures. Not just impact on soil productivity - but also total
> life cycle carbon sequestration. I look forward to listening to more of
> the talks. I think the jury is still out on the right temperature. ]

Yes but we seem to be learning fast, in fact I was staggered about the 
amount of research in biochar being done, it must have attracted post 
grads and funding for so many to be interested and involved in current 
research, just look at the international spread of the speakers. 

I did qualify my statement to the sequestration perspective.

As tera preta seems to have gotten us into this for its fertility I 
imagine this was from low temperature charring or smouldering then 
quenching.

> [RWL2: I like all the above. But I wasn't clear - I was and am still
> concerned about the number 15% (which sound too low) in this phrase: "
> the fixed carbon of a
>
> > > woodchar sample is always ~15%


Well it fits with my understanding of pyrolysis, the reference I use is 
NRI's "Charcoal production a Handbook" and a graph from Pohl 1970 shows a 
drop in yield to just around 20% by 640C with the curve continuing just 
below flat to 1000C. Bearing in mind ash content will have been a near 
constant and there is still residual hydrogen  and oxygen then 15C seems 
realistic for fixed C, I'm not sure where alkali metal carbonates will 
fit in here as in incineration they would have been the metal oxides in 
the ash but with lower molecular weights than the carbonates formed in a 
reducing atmosphere.

A later graph, Beall et al 1974, shows the relative yields of pure lignin, 
cellulose and hemicellulose, though there are no grids in these 
graphicscellulose falls very steeply to 10% of its dry mass at ~375C and 
then levels off to ~5% at 600Cat which temperature hemicellulose has lost  
80% of its dry mass and  lignin 60%, extrapolating it looks like they all 
continue to fall with higher temperatures. Overall wood made of these 
compounds in mixture has fallen to below 25% of its dry mass at this 
600C. We know from experience that these are the temperatures we see in 
TLUD and 25% conversion of dry mass with pine in a TLUD stove seems to 
match claims. In fact with the simple boy scouts' method of making char 
in a tin can placed in a fire yielding about 45% of the dry mass as a 
char, from fresh (60%mc wwb), split, stem wood from young trees, 
suggesting the temperature, in the basic retort, only gets to just over 
400C.

There are also some tables relating to acacia wood that point in the same 
direction.

>
> I missed out that he seemed to imply the 385 ppm CO2 concentration
> mentioned at Newcastle two years ago had moved up a surprising number
> of parts but I forget the figure.
>
> [RWL2: I see 392 all the time - and 393 some today. We are not slowing
> down. 400 is only a few years away. We keep making it harder to get
> back to 350. Which I think cannot happen without large scale Biochar.]

At that rate it's no more than 5 years away and we haven't stored our 
first Gigatonne of biochar yet? What's the equivalent sequestrated carbon 
for 1ppm CO2 allowing for 45% in equilibrium with the oceans?

> [RWL2: I haven't yet tried listening to any 2nd day talks (and look for
> your guidance.0 We need you on the Biochar lists. I am limiting this
> return to the biochar-soils and biochar-policy folk so as to minimize
> cross-posting. ]

I'd choose DeLuca 20011/05/26 09:30 but bear in mind he is only 
considering the first 30cms of depth in his longevity in soil.
and Masiello 2011/05/26 14:35 

timings on the programme but probably later in fact.

>PAHs act by forming
> bonds between the two strands of the DNA helix. I think they are only a
> problem if digested and as they are reactive they shouldn't last long
> in the soil, I would like to learn more.
> [RWL2: This is helpful new data. Charcoal is prescribed often for
> ingestion by MDs - why I don't think we are apt to find PAHs to be a
> problem - although well worth studying.

 I think we should have juxtaposed the words ingestion and digestion, my 
take would be the stomach is better able to deal with PAHs in the course 
of digestion and that the problems are more likely from ingestion via 
mucous membranes, the lungs being the principle area of concern.

AJH