Greg and list:
There are many messages (and a few papers) of the advantages of
combining rock dust and biochar. Inoculants are already commonplace. Sharing
distribution costs would be a plus. The biochar community would welcome joint
efforts at combining the two forms of CDR - especially if the specific olivines
or other minerals can supply needed micro nutrients.
Re this from below: "In theory, one kilogram of olivine sequesters
about one kilogram of CO2”. The corresponding number for biochar is three
kgs CO2. So one kg of a fifty-fifty product could sequester 2 kgs of CO2.
I am not sure of this, but think most soil is built up from microbes
“digesting” rocks, so a productive (made more productive by biochar) soil
repository could speed up the “weathering”.
Also all chars are looking looking for a way to utilize the pyrolysis
gases productively. Grinding up rocks when you are not sending the electrons
to back up wind and solar can further speed up a transition to a carbon neutral
energy economy.
Ron
On Jan 23, 2014, at 11:17 AM, Rau, Greg <[email protected]> wrote:
> http://www.nature.com/news/rock-s-power-to-mop-up-carbon-revisited-1.14560
>
> Rock’s power to mop up carbon revisited
> Experts push for more research into olivine weathering.
>
> Daniel Cressey
> 21 January 2014
>
> Estimates suggest that olivine could be used to sequester a significant
> proportion of carbon emissions.
> Last week, a group of geoengineers met in Hamburg to discuss what on the face
> of it sounds like a very attractive idea: to soak up anthropogenic carbon
> emissions using only rocks and water. In particular, they want to help to
> mitigate climate change by crushing rocks and dropping them into the sea or
> spreading them on land. The meeting was hailed a success, but the idea is
> still far from fruition.
>
> The ‘weathering’, or breaking down, of rocks is a hugely important but very
> slow part of the carbon cycle. Natural weathering locks up atmospheric carbon
> dioxide by means of chemical reactions between common silicate minerals and
> air. For example, when magnesium-rich olivine, a rock of particular interest
> to geoengineers, is brought together with CO2 and water under natural
> conditions, the resulting reaction forms magnesium carbonate and silicic
> acid, thereby removing and storing carbon.
>
> But some scientists think that this natural process could be exploited to
> offset at least some of the carbon emitted by human activities. Rather than
> waiting for rocks to be slowly weathered away, olivine could be mined on an
> industrial scale, ground up, and spread over land or in the sea, speeding up
> these chemical reactions and sucking vast quantities of CO2 out of the
> atmosphere. But this presents practical problems: according to one estimate,
> you would need to spread 5 gigatonnes of olivine on beaches annually to
> offset 30% of global CO2 emissions (assuming 1990 levels of emissions; S. J.
> T. Hangx & C. J. Spiers Int. J. Greenhouse Gas Contr. 3, 757–767; 2009).
>
> At the informal meeting, about 20 enhanced-weathering experts discussed
> recent research in the area and tried to summarize and coordinate future
> work, for example by agreeing to standardize experiments. Until now, there
> has been no organized research agenda for the fledgling field, says meeting
> convener Jens Hartmann, who works on geological cycles and carbon
> sequestration at the University of Hamburg in Germany. “It was very positive;
> we know we are now a community,” he says.
>
>
> Hartmann points out that humans have been exploiting rock weathering for
> decades — for example, by spreading minerals such as olivine, pyroxenes and
> serpentines as fertilizers. “The question is, can we optimize it and can we
> do it in areas we are not doing it?” he says.
>
> As with its use as a fertilizer, olivine would have to be finely crushed to
> maximize its exposure to carbon. Olaf Schuiling, a geochemist at Utrecht
> University in the Netherlands and a passionate advocate of enhanced
> weathering, proposes spreading coarse olivine grains on beaches that
> experience heavy seas. “There the grains are tumbling around in the surf and
> the waves, they collide, they abrade each other, and produce very rapidly a
> lot of tiny olivine slivers that weather quickly,” he says.
>
> However, there is little evidence for the practical rates of weathering that
> could be expected if large amounts of olivine or other rocks were mined and
> spread on fields or dumped into the sea. This, in turn, means it is not clear
> how much would be needed to significantly mitigate carbon emissions, how long
> it would take to work or whether it would be cost and energy efficient.
>
> In theory, one kilogram of olivine sequesters about one kilogram of CO2, but
> the rate at which this happens can be slow. And the actual efficiency of
> sequestration will be much lower than 100%, because of the energy used — and
> emissions released — in grinding and transporting the rock. In some cases,
> this could emit more carbon than would be sequestered.
>
> “We have good and very promising results, but there are still a lot of
> unknowns.”
> Francesc Montserrat, a marine benthic ecologist at the Royal Netherlands
> Institute for Sea Research in Yerseke, is trying to pin down the figures. He
> is using small tanks to measure the weathering of olivine in various
> conditions — including the impact of worms that live in and eat the sandy
> sediment. Montserrat’s experiments will test the idea that when these worms
> eat tiny grains of olivine they also help to break down the crust that can
> form on olivine’s surface, which slows down the weathering effect.
>
> “You need to have some hard numbers to go to the authorities to say whether
> it will be safe enough to try it out,” he says. “We have good and very
> promising results, but there are still a lot of unknowns.”
>
> Even advocates of this method of geoengineering admit that large-scale
> enhanced weathering is not without risk. Olivine can contain toxic heavy
> metals such as nickel that could accumulate in the environment. Grinding
> rocks would produce dust, which might harm human health. And putting olivine
> into the sea could change the pH of the water, helping to combat ocean
> acidification driven by climate change but also potentially harming marine
> organisms by altering their environment.
>
> Phil Renforth studies carbon sequestration and minerals at the University of
> Oxford, UK, and attended the Hamburg meeting. He says that there is a
> pressing need to conduct more work on enhanced weathering given that carbon
> emissions are likely to continue to rise, and because of the current focus on
> dealing with emissions by capturing them from power stations and storing them
> underground.
>
> “We’re putting all our eggs in one basket if we’re only looking at one
> method,” he says. There’s a real need to diversify the portfolio.”
>
> Nature 505, 464 (23 January 2014) doi:10.1038/505464a
>
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