Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: mscott on 04/04/2007 03:33:02
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I have just joined this forum and am interested for the same reasons as Erich et al. One possibility that appeals to me is that in Australia we regularly have to perform "hazard reduction burning" around the urban/bushland interface to minimise the risk of burning people and houses through bushfires. I would like to think that part of the carbon in the fuel removed could be sequestered and Terra Preta sounds like an admirable application to economically support this labour-intensive clearing operation.
If anybody is worried by the removal of nutrients from these interface zones, don't be; Australian East Coast sandstone country in particular is very infertile and its flora is well adapted to nutrient paucity. Indeed the primary problem in maintaining biodiversity here is nutrient contamination from urban runoff which promotes choking weed infestation. Already some mechanical clearing is used for fire hazard reduction and the resultant vegetable matter (woody shrubs, branches, leaves) is chipped for garden mulch. To do so on a much larger scale instead of control burning would require an economic base.
I would like to raise a few scientific questions which I hope somebody can help with:
1) Elemental carbon is apparently very stable at ambient temperature and bushfires have been shaping the Australian landscape for 40000 years or more. Although traces of charcoal do appear in alluvial sediments, would we not expect massive deposits of charcoal in stream beds etc? Where has it all gone? Surely not all of it was burned in subsequent bushfires?
2) Is the terra preta carbon actually charcoal or a partially-charred matrix of polyaromatic tar or creosote compounds? Would these not be as toxic to soil organisms as thery are to humans?
3)Am I on the right track in visualising terra preta char as simply slowing down the release of "ash bed" nutrients over several years? How would the nutrients have been refreshed for sustainable agriculture?
4)It appears from my reading that the oxidation of elemental carbon (char, graphite, diamond etc.) is inhibited, as in metals, by a tenacious film of oxide preventing further oxygen ingress. For carbon of course, that oxide is gasseous CO and CO2 in the free state but is adsorbed strongly to any clean carbon surface at ambient temperature. At temperatures above about 300°C however it is desorbed, leading to the familiar exothermic oxidation chain reaction. The question is whether any ambient temperature biological agents such as enzymes can strip away these oxides to slowly oxidise charcoal?
5)Elsewhere I have read of terra preta as being self-propagating, presumably through bacterial or fungal migration and presumably at ambient temperature. What is the evidence for this and what mechanism is postulated?
6)One feasible mechanism for propagating terra preta might be to bury dense piles of fresh vegetation at its edge, covering with earth to insulate and exclude excess air. Through bio-heating due to innoculation with microorganisms and moisture, this deposit might spontaneously combust in the manner disasterously familiar to farmers storing hay or silage. Is there any archaelogical evidence for this process in precolumbian Amazon settlements, or any reported fertiliser effect around extinguished but once-smouldering modern silage pits?
Lots of questions, any answers?
Murray.
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Sorry can't help much but in answer to Question 1: The charcoal probably fragments as it mixes with other sediments before it is finally deposited.
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I woudl have thought that Austrailian soils are going to be quite different to amazonian ones because they are so much drier. This could lead to a completely different kind of microbial community in them. Also burning things doesn't always produce charcoal - if there is lots of oxygen it will just burn to ash, austrailian forests are very dry and I think quite open so you wouldn't expect much organic matter to stop at charcoal..
I would have thought that the charcoal will add structure to the soil, improve water absorbancy, release nutrients slowly and probably affect they kind of soil fungi that are growing there - what fungi you have growing in your soil can make a huge difference to fertility.
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NASA’s Space Archaeology; $364K Terra Preta Program
http://archaeologyexcavations.blogspot.com/2010/08/time-traveling-via-satellite.html
This is the finest explanation I have read on the process of biochar testing. Hugh lays it out like medical triage to extract the data most needed for soil carbon sequestration. A triage for all levels of competence, the Para-Medic Gardener to the Surgeon Chem-Engineer.
http://terrapreta.bioenergylists.org/Characterizing_Biochars
The Ozzie's for 6 years now in field studies; Soil GHG emissions down 80%
The future of biochar - Project Rainbow Bee Eater
http://www.sciencealert.com.au/features/20090211-20142.html
Phosphorous Solution;
http://terrapreta.bioenergylists.org/nishio
The Japanese have been at it dacades:
Japan Biochar Association ;
http://www.geocities.jp/yasizato/pioneer.htm
For those looking for an overview of biochar and its benefits, These authors have done a very nice job of distilling a great deal of information about biochar and applying it to the US context:
US Focused Biochar report:
Assessment of Biochar's Benefits for the USA
http://www.biochar-us.org/pdf%20files/biochar_report_lowres.pdf
Murray, hope I can help;
"1) Elemental carbon is apparently very stable at ambient temperature and bushfires have been shaping the Australian landscape for 40000 years or more. Although traces of charcoal do appear in alluvial sediments, would we not expect massive deposits of charcoal in stream beds etc? Where has it all gone? Surely not all of it was burned in subsequent bushfires?"
Wild & forest fires produce less than 1% and 3% respectively
"2) Is the terra preta carbon actually charcoal or a partially-charred matrix of polyaromatic tar or creosote compounds? Would these not be as toxic to soil organisms as thery are to humans?"
The PAHs are food in the soil food web. Work by U. of H show that high VM% chars feed a bloom of microbes that deprive plants of Nitrogen the first year.
"3)Am I on the right track in visualising terra preta char as simply slowing down the release of "ash bed" nutrients over several years? How would the nutrients have been refreshed for sustainable agriculture?"
char for soil need good adsorption characteristics for high CEC, (look at Dr. McLaughlin's work above)
"4)It appears from my reading that the oxidation of elemental carbon (char, graphite, diamond etc.) is inhibited, as in metals, by a tenacious film of oxide preventing further oxygen ingress. For carbon of course, that oxide is gasseous CO and CO2 in the free state but is adsorbed strongly to any clean carbon surface at ambient temperature. At temperatures above about 300°C however it is desorbed, leading to the familiar exothermic oxidation chain reaction. The question is whether any ambient temperature biological agents such as enzymes can strip away these oxides to slowly oxidise charcoal?"
These oxidised surface charges; carbonyl. hydroxyl, carboxylic acids, and lactones or quinones, have as well a role as signaling substances towards bacteria, fungi and plants.
"5)Elsewhere I have read of terra preta as being self-propagating, presumably through bacterial or fungal migration and presumably at ambient temperature. What is the evidence for this and what mechanism is postulated?"
Bioturbation by soil wee-beasties bring up old chars to mix with new litter, the TP grows back with no char additions, but lower char%
6)One feasible mechanism for propagating terra preta might be to bury dense piles of fresh vegetation at its edge, covering with earth to insulate and exclude excess air. Through bio-heating due to innoculation with microorganisms and moisture, this deposit might spontaneously combust in the manner disasterously familiar to farmers storing hay or silage. Is there any archaelogical evidence for this process in precolumbian Amazon settlements, or any reported fertiliser effect around extinguished but once-smouldering modern silage pits?
Lots of questions, any answers?
Murray.
Recent NATURE STUDY;
Sustainable biochar to mitigate global climate change
http://www.nature.com/ncomms/journal/v1/n5/full/ncomms1053.html
Not talked about in this otherwise comprehensive study are the climate and whole ecological implications of new , higher value, applications of chars.
First,
the in situ remediation of a vast variety of toxic agents in soils and sediments.
Biochar Sorption of Contaminants;
http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview/breakout-session-5/agriculture-forestry-soil-science-and-environment.html
Dr. Lima's work; Specialized Characterization Methods for Biochar http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview/breakout-session-4/production-and-characterization.html
And at USDA;
The Ultimate Trash To Treasure: *ARS Research Turns Poultry Waste into Toxin-grabbing Char
http://www.ars.usda.gov/IS/AR/archive/jul05/char0705.htm
Second,
the uses as a feed ration for livestock to reduce GHG emissions and increase disease resistance.
Third,
Recent work by C. Steiner showing a 52% reduction of NH3 loss when char is used as a composting accelerator. This will have profound value added consequences for the commercial composting industry by reduction of their GHG emissions and the sale of compost as a nitrogen fertilizer.
Since we have filled the air , filling the seas to full, Soil is the Only Beneficial place left.
Carbon to the Soil, the only ubiquitous and economic place to put it.
WorldStoves in Haiti ; http://www.charcoalproject.org/2010/05/a-man-a-stove-a-mission/ and
The Biochar Fund http://biocharfund.org/
deserves your attention and support.
Exceptional results from biochar experiment in Cameroon
NSF Awards $1.6 million in grants;
BREAD: Biochar Inoculants for Enabling Smallholder Agriculture
http://iapnews.wordpress.com/2010/09/03/cornell-university-wins-biocharstove-research-grants/
Thanks for your efforts.
Erich
Erich J. Knight
Chairman; Markets and Business Review Committee
US Biochar Conference, at Iowa State University, June 27-30
http://www.biorenew.iastate.edu/events/biochar2010/conference-agenda/agenda-overview.html