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Glen Peters Profile picture
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22 Sep, 5 tweets, 3 min read
#ClimateTwitter Direct Air Capture (DAC)

In 2011, Rob Socolow estimated that 1MtCO₂/yr DAC would require a contact structure with height 10m & length of 5km.

Is that still the case?

1/
aps.org/policy/reports…
If I look at these pictures of Climeworks Orca via @EdgarHertwich

The height is ~3m, the length ~10m, & 4 units
Area: 120m² for 4000tCO₂/yr
Or: 30,000m² for 1MtCO₂/yr (120/4*1000)

If 10m high (Socolow), then contact structure ~3km long.



2/
This is rather crude, but is quite similar to the original Socolow estimate. If true, this is fascinating…

If contact structure is 10m high, then 1MtCO₂/yr requires 3-5km structure

1GtCO₂/yr requires 3-5000km
5GtCO₂/yr requires 15-25,000km

3/
If there is 250m space on each side, 500m total, then

1MtCO₂/yr requires 1.5-2.5km²
1GtCO₂/yr requires 1,500-2,500km²
5GtCO₂/yr requires 7,500-12,500km²

4/
Are my calculations approximately correct?

In terms of area, far less than several India's required for BECCS or afforestation (several million km²), but still DAC is often sold as having a small footprint.

I can see the NIMBYs already with these vast structures...

5/5

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More from @Peters_Glen

Glen Peters Profile picture
21 Sep
"Have you ever published a paper that *never* would have happened without twitter?" @dsquintana

Hmmm, certainly yes, & most of my papers are in some way influenced by Twitter, & five minutes on Twitter can generate lots of new paper ideas...

1/
Perhaps the most (in)famous climate paper in recent times only came about because @MLiebreich provoked 90% of #ClimateTwitter with #RCP85isBollox, laying the foundation for this paper with @hausfath & myself
nature.com/articles/d4158…
2/
I met @Oliver_Geden on Twitter, & we have written several papers together (& have many ideas that are waiting some time & resources).

I suspect the trouble paper with @KevinClimate was heavily influenced by debates on Twitter science.org/doi/abs/10.112…

3/
Read 7 tweets
Glen Peters Profile picture
16 Sep
Estimating CO₂ emissions from forests is difficult, not least because of different definitions.

CO₂ emissions come from conversion (cutting down or growing a tree).

There is also a 'sink', soaking up CO₂ we previously emitted.

What should be reported as CO₂ emissions?

1/
It is really rather complex. The reason the 'sink' is included in emission accounting, is that it is difficult to determine what is 'anthropogenic'.

It was decided to use self-defined 'managed land' & include 'indirect' (climate) effects.

carbonbrief.org/guest-post-cre…

2/
Scientific studies (eg IPCC Assessment Reports) generally consider CO₂ emissions from 'Net Conversions' as the emissions, while government reporting to the UNFCCC combines the conversions & sink (black line).

The 'sink' is not the total sink, only a part of the forest sink.

3/
Read 6 tweets
Glen Peters Profile picture
14 Sep
Carbon Capture & Storage (CCS) in Canada.

There are two facilities (capturing in 2019), but very different stories:
* Boundary Dam: Operates ~60% capacity, used for EOR
* Quest: Operates ~90% capacity, permanent storage, but the generated H₂ is used to upgrade oilsands

1/
Boundary Dam is CCS on coal power, with the goal of capturing CO₂ for Enhanced Oil Recovery.

In short, it has not lived up to expectations. How much CO₂ gets stored is unknown, & in any case, the CO₂ is used for EOR (more CO₂).

2/
en.wikipedia.org/wiki/Boundary_…
Quest produces H₂ in a steam methane reformer, the concentrated CO₂ stream is captured & permanently stored.

Though, the H₂ is used to make heavy oil marketable, & in a sense, it is a type of EOR: the CO₂ is indirectly used to generate more CO₂.

3/
en.wikipedia.org/wiki/Quest_Car…
Read 4 tweets
Glen Peters Profile picture
13 Sep
Norway is known for its Carbon Capture & Storage (CCS) & is best in class.

Even the best in class does not run at capacity. Currently ~80% of capacity is used, but Sleipner has dropped to ~65%.

But, Norwegian CCS is the easy type, removing CO₂ from extracted gas.

1/
The extracted gas at Sleipner Vest contains ~9% CO₂, but has to be reduced to ~2.5% to meet sales specifications.

The extracted gas in the Snøhvit field contains ~5-7.5% CO₂, and this has to be removed to avoid it freezing out in the downstream liquefaction process.

2/
The CO₂ has to be removed for market or technical reasons. You would therefore expect the facilities to run at a high capacity, as they have to!

The CO₂ is captured & stored, presumably to avoid paying the Norwegian CO₂ tax. This is great, but a different issue.

3/
Read 8 tweets
Glen Peters Profile picture
9 Sep
“[W]e scientists carry a big responsibility in not spreading the wrong messages” @jrockstrom

3/4 answered “yes” to this question, but Rockström said “no” in an interview with @MLiebreich

The question is ambiguous, so let’s unpack it a bit.

cleaningup.live/ep49-johan-roc…

1/
“[Y]ou're absolutely right, that nobody is suggesting that there is a planetary tipping point out there that causes runaway climate change” @jrockstrom

[I used this to make the question in the Twitter poll]

2/
That statement seems clear, but there are ambiguities:
* “a” or many?
* “planetary” or smaller scale?
* “runaway” or a new state?

These issues were common in yesterday’s discussion

3/
Read 17 tweets
Glen Peters Profile picture
8 Sep
"I accept that thanks to human activity... atmospheric CO₂ has increased from ~300ppm [to] ~400ppm, & without appropriate action, it will probably go up to 500ppm in 30-40 years, maybe sooner... I accept that that could have consequences that we would much prefer to avoid."
1/
"I absolutely accept that". For added emphasis.

"[I]t's very hard to disagree with facts, & in the end a fact is a fact is a fact. And we cannot ignore facts just because in the short term, they don't see their argument."

2/
It would seem that Tony Abbott (former Prime Minister of Australia) is quite keen on facts. And climate change is a fact, according to his own words, & action is therefore needed.

Oh, but it is China: "by far the largest source of additional emissions right now" (a fact)

3/
Read 6 tweets

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