http://www.newscientist.com/article/mg19826542.400-burying-trees-to-fight-climate-change.html?feedId=climate-change_rss20
discusses the idea of burying biomass extensively. I don't like the
tradition of 'cut and paste' content, as I know how to follow a link.
But when in Rome.....
A few years ago, Ning Zeng began to wonder about the hidden potential
of landfill sites. He had been discussing a mystery with his students:
for some reason, North America's carbon dioxide emissions are not
quite as high as they "should" be. Perhaps, one student suggested,
America's huge landfill sites were acting as carbon sinks. After all,
a lot of what is thrown away does not decompose: even 50-year-old
newspapers can be perfectly legible.
Zeng, an atmospheric scientist at the University of Maryland in
College Park, later calculated that the amount of carbon sequestered
in this way is actually tiny, but it gave him an idea. What if we
could sequester the carbon locked up in trees in such a way that it
doesn't get released back into the atmosphere? Could we store enough
of it to offset a meaningful amount of emissions?
It sounds like a long shot, but Zeng is convinced it could work. In a
recent paper in the journal Carbon Balance and Management (vol 3, p
1), he calculated that if we buried half of the wood that grows each
year, in such a way that it didn't decay, enough CO2 would be removed
from the atmosphere to offset all of our fossil-fuel emissions. It
wouldn't be easy, but Zeng believes it could be done.
Zeng's is not the only proposal of its kind. Other researchers are
totting up the amount of carbon that could be sequestered in various
kinds of biomass and are finding that it is a surprisingly large
amount. Not enough to halt climate change on its own, perhaps, but
enough to make a sizeable dent in atmospheric carbon and to buy us the
time we need to sort out the mess we've made.
The idea of burying carbon in biomass makes sense: plants remove CO2
from the air to produce carbohydrates by photosynthesis. The carbon is
returned to the atmosphere when the plant dies and decays. Planting
trees to sequester carbon is approved under the Kyoto protocol, but
critics of this approach point out that the carbon locked up in
forests is only kept out of the atmosphere for as long as the tree is
alive, and that older trees start emitting more carbon than they take
up as they reach old age. Recent studies have also suggested that
warmer temperatures and higher atmospheric CO2 may eventually kill
trees, casting doubt on the use of forests as long term carbon sinks
(New Scientist, 27 October, 2007, p 42).
There is a lot of interest in the possibility of sequestering CO2 in
disused gas and oil wells or porous rocks, or even in ocean beds.
Trouble is, finding viable sites for this kind of project is tricky
and the technology needed is far from ready. Burying biomass, say
enthusiasts, has none of these problems.
Wood burial is perhaps the simplest of the ideas. Zeng's proposal is
to thin forests regularly, and to bury excess wood, forestry waste and
even trees that have been grown specifically to be buried in trenches
between the remaining trees. To prevent the wood decomposing and the
carbon being released, it would need to be buried deep enough to avoid
being broken down by soil fauna and fungi, or stored above ground in
watertight shelters. Zeng gives an example of a plot of 1 square
kilometre (100 hectares), with the excess wood from 1 hectare of
woodland buried deeper than 5 metres and down to 20 metres. He
calculates that this could sequester 1 tonne of carbon per hectare -
using that land to grow trees would sequester 1 to 5 tonnes, depending
on the age of the forest and the type of tree. Burying wood sounds
like a lot of trouble for a small gain, but Zeng insists that, unlike
simple growing, this is a long-lasting and perhaps permanent carbon
sink. He estimates that offsetting all of the world's current
emissions would be achievable with a workforce of one million people -
substantially fewer than those already employed in the forestry
industry in the US alone. Even so, to offset all our emissions, most
of the world's forests would have to run a wood burial scheme.
Zeng's idea may be the new kid on the block, but another approach to
carbon burial has a much longer history. More than 500 years ago
Amazonian people were creating almost pure carbon by smouldering their
domestic waste and letting it work its way into the soil. This earth,
known as terra preta ("black earth") remains to this day, in some
areas half a metre deep.
Such charred organic matter, or "biochar", can be made when organic
matter is heated in the absence of air to around 350 °C - the kinds of
temperatures reached in the Amazonians' smouldering waste piles. "The
lack of air means the organic matter does not combust, but most
constituents other than carbon are driven off as gases or liquids,"
says Malcolm Fowles at the Open University in Milton Keynes, UK, who
studies the process. The leftovers are charcoal-like chunks of nearly
pure carbon. Ancient farmers had no idea that they were sequestering
carbon, of course, but they did know that adding biochar to the soil
hugely increased its quality.
The Amazonian method can reduce pretty much any organic material to
char, given enough time, but it works best with dry materials like
dead wood. A modern alternative is called hydrothermal carbonisation -
which steams organic material under pressure until it is reduced to
char. This process also works with wet material like green wood and
household waste. Until recently, hydrothermal carbonisation was a slow
process, taking days to complete. But Markus Antonietti of the Max
Planck Institute of Colloids and Interfaces in Potsdam, Germany, has
found a way to speed it up to between 5 and 12 hours. His technique
uses citric acid as a catalyst at a relatively low temperature of 180
°C. It's a very simple process, "really nothing more than a pressure
cooker", says Fowles.
Once the reaction has got going both these processes readily produce
heat, which could be used to generate electricity or heat water. But
there is a trade-off: the more heat the process produces, the more CO2
it gives off and the less carbon you have left at the end. Perhaps
unsurprisingly, low-temperature hydrothermal carbonisation produces
less energy than high-temperature pyrolysis, but it still gives off a
worthwhile amount. "It readily gives off heat," Fowles says.
"[Antonietti's group] has had some rather entertaining laboratory
explosions." Once the process is explosion-proofed, Fowles says, it
might be possible to sell household water-heating units that need only
trash, food scraps and garden debris for fuel. Such units would make a
small quantity of biochar on the side. "You'd be looking at it as a
way in which people who are suffering angst over global warming could
make a contribution," he says.
Once the process is explosion- proofed, people could make carbon and
bury it at home
Jim Amonette, a soil geochemist at the US Department of Energy's
Pacific Northwest National Laboratory in Richland, Washington, sees
biochar working as an industrial-scale technology too, with economic
benefits as well as environmental ones. "My vision is that every
municipal landfill is going to have a pyrolysis unit," he says.
Logging companies may start using it as a way to obtain carbon credits
for disposing of the debris left over from logging. "There's a company
in Washington state that is starting to head that way," he says.
Re-filling the sinks
Another idea to sequester carbon as biomass is to let nature bury its
own by restoring natural carbon sinks. One such project is already
under way on Twitchell Island, on the delta of the San Joaquin and
Sacramento rivers, east of San Francisco. Researchers are replanting
marsh grasses and bulrushes (cattails) in the hope that when they die
they will accumulate beneath the surface and gradually transform into
peat. It's the same process that created the marshes after the last
ice age, but this huge carbon sink, covering nearly 1300 square
kilometres, was drained for farming more than a century ago, leaving
the peat to dry out and rot away at a rate of about 2.5 centimetres
per year. Since draining, the land has dropped by up to 6 metres.
Eight years ago, Roger Fujii of the US Geological Survey undertook a
study to see how quickly it might be possible to rebuild the peat. The
answer appears to be even faster than it was lost: up to 10
centimetres per year once a marsh has had a few years to mature. That
offers the prospect of a substantial amount of carbon sequestration.
Fujii and Bergamaschi calculate that reflooding the whole delta and
converting it back to tules - a form of bulrush - would be equivalent
to swapping all of California's SUVs for high-efficiency hybrids.
Part of the benefit of reverting to peat marshes comes from shutting
down ongoing peat oxidation which, according to Fujii's colleague
Brian Bergamaschi, causes emissions of about 17 tonnes of carbon per
hectare per year. On a delta of over 130,000 hectares, that really
adds up. Since building up new peat takes about 60 tonnes of carbon
per hectare per year out of the atmosphere, the net benefit is
something like 77 tonnes per hectare, Bergamaschi says. That is
substantially more carbon sequestration than you would get from
planting forests (see Diagram). Even so, all of these approaches bump
into the question of how far they can be scaled up to sequester
meaningful quantities of carbon. Tules may be highly efficient carbon
accumulators, but there are only so many areas that can be converted
to marshland. Based on Bergamaschi's preliminary estimates from
Twitchell Island, it would take a tule marsh more than double the size
of California to offset most of our current carbon emissions.
The production of biochar could also be used on a massive scale, in
theory. In a paper presented at the American Geophysical Union last
December, Amonette estimated that biochar production could halt the
rise in atmospheric CO2, but we would have to pyrolyse and bury at
least 8 per cent of the Earth's annual biomass production to do it.
Conservationists might have a thing or two to say about that.
None of these approaches need stand alone, of course. Zeng does not
envision a globally or even nationally coordinated wood burial scheme
- he sees small-scale activities by individual owners of wooded land,
paid in carbon credits. This is the key to many of these schemes: to
get off the ground they will ultimately need to be approved for
inclusion in carbon trading schemes - and the price of carbon will
have to be right.
Bergamaschi is confident that investing in tule marsh would be an
attractive prospect. With carbon priced at ¬23 ($36) per tonne on the
European market right now, he adds, it is beginning to look like
farmers could earn about ¬1400 to ¬1700 per hectare. At that level, "I
think you're going to see widespread interest." Amonette estimates
that biochar processes could also become a highly sought-after
investment - as long as the price of carbon credits is in the region
of $20 per tonne or more. Zeng sees wood burial becoming viable at
around $50 per tonne.
There are a few hurdles to get over before any of these projects will
be ready for launch onto a global carbon market, if and when such a
thing gets going. One key issue is how long the carbon will stay
sequestered. Ideally, the carbon would stay captured indefinitely or
at the very least for thousands of years. Some Amazonian terra preta
has already persisted for more than 2500 years, Amonette notes.
Elsewhere, a carbon-14 study by Amonette's colleague, Johannes Lehmann
of Cornell University, has found that charcoal residue near abandoned
kilns in America's Appalachian mountains indicates that charcoal has
persisted for a century or more. Restored peat marshes will continue
to gather carbon for as long as the marsh is maintained, or until it
is completely submerged in rising waters. Zeng says that carbon buried
in wood could only stay sequestered permanently if it could be buried
under perfect, unchanging conditions so the wood would never rot. Zeng
isn't clear exactly what those conditions would be, and offers perhaps
a more realistic estimate of 100 to 1000 years.
None of these solutions offer sequestration on the timescale promised
by geological solutions such as injecting CO2 into abandoned gas
fields, but even the lower end of the range is long enough, Amonette
reckons, to buy time for a smoother transition to energy sources with
lower greenhouse gas emissions.
Another big problem for all biomass sequestration schemes is methane,
because it tends to be generated when biomass is broken down by
methane-producing bacteria in the soil. As a greenhouse gas, methane
is about 20 times as potent as CO2. Its saving grace, to the extent it
has one, is that it is short-lived in the atmosphere. It persists for
about 10 years, so transient burps, as one area of buried biomass
breaks down, for example, will not warm the planet for long. Despite
that, it would not take much methane to wreck a carbon-sequestration
scheme. Fujii's team is looking into methane generation in their tule
marsh, and their preliminary results look promising. Methane doesn't
look to be a showstopper, Bergamaschi says.
Burying wood in the wrong types of soils might also generate methane.
"It would depend crucially on where and how you bury it," Zeng says.
Termites, in the regions where they live, would be another problem.
They could eat the buried wood, converting its sequestered carbon back
into CO2 through respiration. Zeng also admits that removing dead wood
on a large scale could destroy the habitats of woodland species that
specialise in breaking down wood, and have the knock-on effect of
depriving plants of the nutrients that these species release.
Despite its long history, much about biochar remains unknown too. The
Amazonian's terra preta, Fowles says, was made by a quite different
process from that being considered today. They smouldered organic
waste directly on the land and covered the char with more waste in an
ongoing cycle. "The mulch protects the char, and animals churn up the
soil, taking the carbon down with it," Fowles says. "The assumption
that you can just plough it in [and have it stay there] is completely
untested."
So can we be sure that sequestering carbon in biomass will truly help
to stave off global warming? It's a pressing question because, as
Amonette points out, scientists keep finding that climate change is
occurring more and more rapidly than anyone previously anticipated.
"We don't have much time," he says. "We have to implement something
fairly quickly. It may not be the perfect solution, but it's better
than the disaster of waiting 40 or 50 years for the perfect solution
to be found."
2009/2/4 Albert Kallio <albert_kal...@hotmail.com>:
> In the long run, I think the only reliable way to store carbon is to set up
> carbon sequestration forests and then plant and cut these and place the wood
> mass in old mines, coal or gravel pits. Though, I can't see how coal-fired
> power stations could sequester economically carbon this way. I think it is
> very efficient in locking carbon away, but costly.
>
> Wood can be also stored almost indefinitely in deep waters and there are
> many areas in Arctic where some lakes could be made to act as carbon
> sequestration log warehouses
>
> I think crop residue and hay harvesting is 'too easy way out' here, although
> water logged peat bogs do store carbon, something similar would have to take
> place. On the other hand, melting permafrost (i.e. warmer future
> climate) will intensify decay and placing hay or crop residue to
> water-logged, or burying hay in permafrost, do not work in future if the
> climate is much warmer. Otherwise, hay-burial in permafrost would be an
> attractive option.
>
> In my mind this leaves good storages for carbon-sequestration logging such
> as the sea, lakes and man made coal and gravel pits where the logged wood
> can be put safely to salt carbon dioxide away from the athmosphere.
>
> Someone should make estimates how much this kind of forestry would cost by
> doing it where it could be done cheapest. May be initially, by just cutting
> off trees and planting new ones. Later when best sites have been done away,
> sites that require planting and fertilisation would be looked at.
>
> Initially, the idea of carbon sequestration logging would be just to get as
> much carbon salted away as cheaply as possible, perhaps also making this as
> some sort of employment generation social programme.
>
> So, lets go boys for the old gravel pits and seasides...
>
> Rgs,
>
> Albert
>
>> Date: Wed, 4 Feb 2009 15:57:35 +0000
>> Subject: [geo] Re: CROPS paper
>> From: andrew.lock...@gmail.com
>> To: agask...@nc.rr.com
>> CC: sstr...@u.washington.edu; xbenf...@aol.com;
>> geoengineering@googlegroups.com
>>
>>
>> I already suggested methane recovery. Methane from landfills is a
>> rather unreliable technology, and involves significant leakage. You
>> can accelerate production with a 'flushing bioreactor' design, where
>> water is pumped through. However, bearing in mind the fill would be
>> 100pc crop residue, the landfill (plus all the complex layering and
>> piping) would just collapse in a big wet mess - belching out huge
>> amounts of methane into the air as it did.
>>
>> Far better to use anaerobic digestion if you wish to recover methane.
>> You can then use this methane for grid gas. I don't know if you use
>> natural gas (methane) in the US but in Europe it's piped to most
>> buildings for heating and cooking.
>>
>> A
>>
>> 2009/2/4 Alvia Gaskill <agask...@nc.rr.com>:
>> > Stuart and I also discussed the possibility of disposing of the crop
>> > residue
>> > in abandoned coal mines. At the time you said you were concerned about
>> > oxidation there and if the environment were anoxic, conversion to
>> > methane.
>> > KABOOM! I proposed coal mines, since they would not involve ocean
>> > disposal
>> > (obvious) and might be closer to the fields.
>> >
>> > The issue of oxidation time is, I believe, not trivial. While it would
>> > be
>> > desirable to have the carbon gone forever, as in the case of deep ocean
>> > disposal, a storage time of 100 years would be attractive as well. If
>> > one
>> > believes that major technological advances are going to be made in the
>> > areas
>> > of renewable energy and also in air capture of carbon dioxide within the
>> > next 100 years, then placing the residue in an environment where it
>> > would
>> > slowly decay might be acceptable also. The carbon credits could then be
>> > priced and prorated to reflect storage lifetimes.
>> >
>> > Example: a ton of unbaled wheat straw will completely oxidize to CO2 in
>> > a
>> > field in 3 months (my estimate). The same ton baled up next to the field
>> > will last for 5 years (another made up estimate just for the purpose of
>> > comparison). Storage in an arid environment might extend the lifetime to
>> > 25
>> > years. As for the methane issue, why not cover some of the crop residue
>> > and
>> > collect the methane for use as fuel for transportation of the residue to
>> > deep ocean or other disposal locations? This would not require any
>> > complex
>> > technology as this is how methane is collected from municipal waste
>> > landfills. Methane from landfills is a proven use of stranded energy and
>> > could be applied to crop residue disposal as well. If the methane cannot
>> > be
>> > directly used to provide fuel for transportation of the crop residue, it
>> > could be sold and the funds generated used to purchase diesel fuel. The
>> > cost of diesel fuel appears to be the single greatest cost of the CROPS
>> > strategy and reducing that cost with stranded energy generated by the
>> > process seems like a win win plan.
>> >
>> >
>> > ----- Original Message ----- From: "Stuart Strand"
>> > <sstr...@u.washington.edu>
>> > To: "Andrew Lockley" <andrew.lock...@gmail.com>
>> > Cc: <xbenf...@aol.com>; "geoengineering"
>> > <geoengineering@googlegroups.com>
>> > Sent: Tuesday, February 03, 2009 7:22 PM
>> > Subject: [geo] Re: CROPS paper
>> >
>> >
>> >
>> > I thought I explained the methanogenesis issue pretty well previously
>> > and I
>> > don't understand your reasoning in the first paragraph below. The
>> > oceanographers I have talked to agree generally with my analysis, so I
>> > think
>> > I'll leave it at that.
>> >
>> > Temporary storage of crop residues in the river basin is a good idea.
>> > Probably at local depots, away from flood prone areas.
>> >
>> > = Stuart =
>> >
>> >
>> > It methanogenesis starts, it can fairly quickly undo a lot of your
>> > work. Even if it doesn't directly reach the atmos. any effect on
>> > partial pressure may affect exchange with the atmos and thus raise
>> > methane concentrations in the atmos. Even if the methane is oxidised,
>> > all that CO2 is eventually going to cause you problems.
>> >
>> > Open storage in the desert should be possible. Here in England we
>> > have massive warehouse-sized towers of straw bales. They take ages to
>> > rot, even in our rainy weather. Fire is the biggest problem.
>> >
>> > As regards carbon content, it's not readily available for various
>> > different kinds of straw, husk, cob etc that you might be dumping. I
>> > assume it varies between plants?
>> >
>> > The purpose of pyrolysing to char is to reduce bulk, enhance
>> > consistency and reduce bioavailability. I wasn't intending to use it
>> > as an energy recovery process. Surely a few hundred kgs of char
>> > powder is easier to handle and sequester than a ton of damp straw?
>> >
>> > A
>> >
>> > 2009/2/3 Stuart Strand <sstr...@u.washington.edu>:
>> >>
>> >> 1. Significant methane production seems unlikely, but it may be
>> >> possible
>> >> in deep deposition sites. Anaerobic metabolism in ocean sediments is
>> >> dominated by sulfate as the electron acceptor, not CO2, as in
>> >> freshwaters.
>> >> We expect crop residue mineralization under anaerobic conditions inside
>> >> the
>> >> bale to be slow, so sulfate in surrounding waters would have time to
>> >> diffuse
>> >> into the bales. But if the bales are stacked too deep sulfate will be
>> >> exhausted and methanogenesis will start. If methane is produced it will
>> >> not
>> >> be as bubbles (which could penetrate the thermocline), but as dissolved
>> >> methane, due to the pressure. Dissolved methane will be oxidized as it
>> >> diffuses up through the sediment and the water column where aerobic and
>> >> anaerobic methane oxidation occurs (the latter coupled with sulfate
>> >> reduction). So methane from the crop residues is unlikely to reach the
>> >> atmosphere.
>> >>
>> >> The above is our working hypothesis, but this is a question that must
>> >> be
>> >> answered with experiments in situ, which would also provide data to
>> >> estimate
>> >> parameters needed for modeling and design.
>> >>
>> >> 2 and 3. I am working on comparisons to pyrolysis now and I have
>> >> discussed first impressions previously on this group.
>> >>
>> >> 4. readily available info, Andrew
>> >>
>> >> 5. see above
>> >>
>> >> 6. C Lossy. Andrew, biomass is a poor energy source, whether you make
>> >> methane, ethanol or biochar from it.
>> >>
>> >> 7. Not as safe as the ocean I would judge. But it is something we could
>> >> do temporarily, while ocean research and the expected political
>> >> wrangling on
>> >> CROPS is done. But transportation costs to and from deserts and the
>> >> landfilling operations to try to keep moisture would be costly and CO2
>> >> productive.
>> >>
>> >>
>> >>
>> >> = Stuart =
>> >>
>> >> Stuart E. Strand
>> >> 167 Wilcox Hall, Box 352700, Univ. Washington, Seattle, WA 98195
>> >> voice 206-543-5350, fax 206-685-3836
>> >> skype: stuartestrand
>> >> http://faculty.washington.edu/sstrand/
>> >>
>> >> Using only muscle power, who is the fastest person in the world?
>> >> Flying start, 200 m 82.3 mph!
>> >> http://en.wikipedia.org/wiki/Sam_Whittingham
>> >> Hour http://en.wikipedia.org/wiki/Hour_record
>> >> 55 miles, upside down, backwards, and head first!
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: geoengineering@googlegroups.com
>> >> [mailto:geoengineer...@googlegroups.com] On Behalf Of Andrew Lockley
>> >> Sent: Tuesday, February 03, 2009 3:05 AM
>> >> To: xbenf...@aol.com; geoengineering
>> >> Subject: [geo] CROPS paper
>> >>
>> >>
>> >> I've read through your paper in detail and I note the following. (I
>> >> may have missed some things of course)
>> >>
>> >> 1) You don't discuss anaerobic decomposition to methane in the ocean.
>> >> Is it a risk? Outgassing may be immediate or by clathrate
>> >> destabilisation.
>> >> 2) You don't discuss pyrolysing the waste to char before sequestration.
>> >> 3) You consider burying the waste, but you do not consider creating
>> >> biochar and burying that to create terra preta
>> >> 4) You reject the idea of burning crop residues and using CCS, but do
>> >> not provide a quantitative analysis of the carbon content of biomass
>> >> by % compared to other fuels, so it cannot be determined whether
>> >> burning is relatively more efficient than for other fuels.
>> >> 5) You do not directly consider the production of char by pyrolysis
>> >> then onward transport of the fuel to be burned in sites suitable for
>> >> CCS. It may be that thermal and industrial inefficiencies preclude
>> >> this, but this cannot be assumed. Further, char is likely to be
>> >> compatible with existing coal plant, when raw crop waste is not.
>> >> 6) You do not consider anaerobic digestion of the crop waste to make
>> >> methane gas for power generation or large-vehicle transport fuel.
>> >> This technology is used extensively in the UK for food waste, albeit
>> >> on an emergent scale.
>> >> 7) You do not consider the alternative of storage of waste in the
>> >> desert. If transported by rail to the desert, crop waste could dry
>> >> naturally and then be sealed with plastic in bales. This is an
>> >> obvious alternative destination for the waste.
>> >>
>> >> A
>> >>
>> >> >
>> >>
>> >
>> > >
>> >
>>
>> >
>
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