Carbon sequestration

[fivemack]

It is reasonably clear that, having decarbonised world energy production, it will also be necessary to take CO2 out of the air; indeed, if the Siberian permafrost starts to thaw and turn into an efficient methane factory, it will be essential at the hang-the-cost mobilise-now level.

The straw-man carbon sequestration process is to grow plants, cut them down, put them in a sealed box, and throw it in the sea in a subduction zone. Let's see if this is cheap enough to do on a personal level:

The convenient subduction zones are just east of the Caribbean, just south of the Java-Sumatra island chain and just east of the Philippines - there are also ones just west of British Columbia, just west of Chile and along the Aleutian islands, but those aren't on shipping routes from Britain to anywhere that ships normally go, and I suspect the 'just' means they're within territorial waters.

It looks as if a used twenty-foot shipping container costs about its weight in scrap iron, which is a few hundred pounds, is reasonably sealed for these purposes and holds eighteen tons (ah, bother, it's 30 cubic metres, so it would float, and if you make holes in it then creatures will come in and eat the compost which defeats the point of the sequestration.

I have the strong impression that the compost made from collected domestic compostable waste in Cambridge is essentially free; use of small bulldozer for a couple of hours to load eighteen tons of it into the container, use of lorry to transport container to Harwich. Container shipping is currently extraordinarily cheap (though maybe that's only to Shanghai via the Malacca Strait, and to get over a subduction zone you'd need to ship to Bali, Manila or Caracas).

The show-stopper is convincing the crew of the ship to load your container on the outside and to push it over the edge somewhere just south of the southern edge of Indonesian territorial waters; container ships don't have the cranes on them to move the containers.

What have I missed? Aside that it looks as if it would cost about a thousand pounds to transfer twenty tons of compost to the bottom of the Philippine Sea, whilst www.puretrust.org.uk will buy and retire ETS carbon at £13 the ton.

Maybe if you bought an exceedingly rust-bucket container ship and a medium-sized escape boat, and sunk the whole ship and five hundred containers as a unit ... claiming it on the insurance afterwards would be wrong.

Comments

[papersky.livejournal.com]

I pricked it off where she sank...

You'd probably get about $20 for a poem about doing it. Or you could make a documentary.

[hsenag.livejournal.com]

How will the prices you looked at change once they are based on decarbonised energy?

[vicarage.livejournal.com]

Why not leave the containers outside Cambridge? You can be confident that they won't leak for 200+ years, by which another solution would be found.

In fact, why not look up the prices for building barns, or wrapping straw bales? For the latter I found
a quote of $1.85 for a 1.4 ton bale (www.agmrc.org/media/cms/bio98paper_CA9EFF13F9159.pdf). Make the plastic a bit thicker and cover in a tarpaulin, job done.

[fivemack.livejournal.com]

Land in Cambridge is really quite a lot more expensive than subducting land at the bottom of the Philippines Sea, and subduction has the tempting advantage of getting the carbon out of the carbon cycle on the million-year timeframe.

[vicarage.livejournal.com]

Have you accounted for the extra energy costs smelting the iron you are taking out of the economy?

[pseudomonas.livejournal.com]

If it's 2 tonnes of steel at about 26 GJ/tonne that's about 50GJ of energy.
If that came from burning coal, as at present, it'd be about 25kg/GJ * 50 =~ about 1.2 extra tonnes of carbon.

OTOH, fivemack specified that world energy has already been decarbonised, so *that's* OK.

On the third hand, world iron production of 2 billion tonnes/year would have to be stepped up quite a lot if everyone were to do this...

[vicarage.livejournal.com]

I think that estimate is low because Wikipedia (http://en.wikipedia.org/wiki/Steel#Steel_production)

quotes

Recycling one ton of steel saves 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone.

700kg of coal and limestone roughly equates to 2000kg of CO2 per ton.

One problem with this back of envelope stuff is that its so easy to get a factor of 3-4 out, and that can condemn any technological solution in an area where cost is key.

[fivemack.livejournal.com]

An excellent point. Whilst spare containers are spare, it's stupid to waste the iron; sufficiently impenetrable plastic is the way to go.

[tigerfort.livejournal.com]

Provided that you can spare the petrochemicals to make those, of course.

getting the carbon out of the carbon cycle on the million-year timeframe

[ewx.livejournal.com]

...which we might regret come the next ice age...

[beamjockey.livejournal.com]

1. Pump the container full of sea water, then seal it, just before you toss it overboard. (Assuming you find a way to toss it overboard.)

2. What's the timescale for this thing to disappear via subduction?

3. What's the timescale over which a cheap container is truly sealed?

[cultureofdoubt.livejournal.com]

It's not clear to me that simply dropping something on subducting stuff will make the thing you drop subduct too.

[fivemack.livejournal.com]

Ah yes, I suppose there's a lot of scraping off of the top layer as things subduct. And I can't argue that the waste will get covered up by enough sediment not to get scraped off, since sediment deposition rates are apparently no more than tens of metres per million years, and the subduction rate is ten centimetres a year.

Let's try plan B.

[aldabra]

You're not just getting rid of carbon there; you're getting rid of lots of useful soil nutrients and minerals.

We're running up against declining (and oil-dependent) agriculture, topsoil loss, and expanding population, which suggests food shortages on the horizon. We're going to need the non-carbon ingredients of compost here. It's not going to be politically popular to ship it to Indonesia.

How many trees do you need to grow per ton of carbon?

[pjc50.livejournal.com]

Good point. We're already importing phosphorous and potassium.

[fivemack.livejournal.com]

A hectare of trees produces eight tons of woodchips a year, but I don't know how much of that is water and how much of it is stuff you'd rather not throw away; it sounds as if you want to turn it into charcoal first. Though people selling charcoal charge $200 per ton for it.

I think you're right: using complicated disposable machinery to get carbon out of the atmosphere is silly even if the machinery happens to grow on trees.

[ewx.livejournal.com]

What happened to the portion of those minerals from the plants that became coal and oil?

[fivemack.livejournal.com]

Crude oil is really remarkably phosphorus-free, it turns out - parts per million, with nitrogen compounds at <0.1%, sulphur up to a few percent in the sour crude oils.

(on the other hand it turns out that crude oil contains measurable quantities of porphyrin-bound metals - not just haem, but also the vanadium analogue!)

So I haven't a clue.

[tigerfort.livejournal.com]

They've mostly diffused out over a few hundred million years, IIRC. But that will mostly have happened while the pre-fossil-fuel was dead organic matter in a fairly open environment, rather than sealed in an impenetrable box on the sea-bed :)

[rwl.livejournal.com]

You should check out the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter (http://en.wikipedia.org/wiki/Convention_on_the_Prevention_of_Marine_Pollution_by_Dumping_of_Wastes_and_Other_Matter), a.k.a. the London Convention (http://www.imo.org/Conventions/contents.asp?topic_id=258&doc_id=681).

[beamjockey.livejournal.com]

Aren't you worried about filling up the subduction-zone real estate?


PUBLIC SERVICE ANNOUNCEMENT

BOB: We have been asked by the National Parks Association to make the following announcement.

RAY: Will tourists and campers please stop throwing things into the Grand Canyon. It is the deepest canyon we have.

BOB: But it will cease to BE the deepest canyon we have if tourists and campers keep throwing things into it. And now a word from Ranger Horace Liversidge of the Parks Service.

LIVERSIDGE: Folks, I'm just a grizzled old forest ranger who's grown gray in the
National Parks Service. The Grand Canyon is my baby... I love it like a son. I've growed up with it. At night I walk the top of the canyon and look down into it. Can't see nothin', but I know what's there.

Now, folks, if you keep on throwin' things into it, pretty soon it's goin' to get all choked up. T'wont be a mile deep no more. T'wont be a hole no more. So, folks, don't throw things in the Grand Canyon no more. This is grizzled old Ranger Horace Liversidge thankin' you from the bottom of his canyon — heart.

BOB: That was grizzled old Ranger Horace Liversidge of the National Parks Service. Thank you, Grizzled.

RAY: If you want to help in this great campaign to preserve our natural wonders, use the litter cans on your city's sidewalks, don't throw things in the Grand Canyon.

(Music: "Grand Canyon Suite")

(See also the 2:30 point in this clip.)

[peristaltor.livejournal.com]

Wouldn't that subducted cargo eventually be forced to the magma layer below the crust? If so, wouldn't it eventually reach a nearby volcano, say, Anak Krakatoa?

Best, I think, to just pump the stuff in liquid or gas form back into a depleted oil well in a techtonicly stable area. The lines are already plumbed. Heck, grow it out of algae, shove it back down. In a few centuries, it should be oil again!

[aldabra]

Don't make it into compost, make it into charcoal...

http://www.guardian.co.uk/environment/2009/mar/13/charcoal-carbon

But if you do make it into compost I don't think you have to sail it halfway round the world and dump it overboard in a large steel box; I think you could simply spread it on farmland. Isn't the American midwest losing two inches of topsoil a year? How much carbon in two inches of compost spread across the American midwest? Then do it again next year...

[jiggery-pokery.livejournal.com]

Someone recently posted a link to Sandbag (http://sandbag.org.uk/) who will retire carbon emission permits on your behalf, and I thought "Aha, fivemack has been after just that for years". However, they charge a flat rate of £25 per permit, no matter what the carbon price is, but they're clear on what they'll do with the difference (http://sandbag.org.uk/node/142). Can you see a reason to use Sandbag rather than the PURE Trust unless you prefer their campaigning stance?

[jiggery-pokery.livejournal.com]

On further reflection, I can see a difference: the PURE Trust are carbon offsetters, and I think that (while they use non-technical language) they buy CERs rather than EUAs. CERs are cheaper, though if I understand correctly then the two are currently fungible with each other in the ETS. See also Carbon Retirement (http://www.carbonretirement.com/pages/how_we_work) who discuss why they actually buy and retire EUAs rather than buying CERs for offesetting.