Did I miss some zeroes? Is that under 4,000 $ per capita? Sounds too cheap to be true, even if it is a lot of money for half of the world population, it seems like peanuts compared to the damage I see.
Well, observation over time has revealed to me that “projects” invariably turn out to be longer and more expensive than proposed, so you’re probably right.
CCS has a lot of overlap with, but isn’t exactly, what the OP is asking about. For one thing, it tends to include capturing CO2 out of the waste stream of power plants, not just Direct Air Capture. It also excludes things like enhanced weathering.
The right buzzword is NETs, or Negative Emissions Technologies. Generally, these fall into a few buckets:
- Direct Air Capture. This is all stuff like the Orca plan discussed up-thread. Very energy intensive, and likely expensive, but if it works, it probably scales really well!
- Tree Planting. Pretty easy, but it has major challenges with scalability (there isn’t really enough land), and the albedo effects also mentioned up-thread mean that this might end up increasing warming to some degree.
- BECCS (Bioenergy with Carbon Capture and Storage). Similar to tree planting, but instead of storing the carbon in living trees, burn it, but then capture/isolate the resulting CO2 and store it geologically. Proposals are generally with fast-growing annuals, rather than trees, but it still runs into issues with the amount of land area you’d need, competition with food/natural forests/etc, as well as water use. Probably not going to significantly scale.
- Soil Sequestration. Pay farmers to use better soil conservation practices. Has the benefit of probably being (relatively) cheap, but there are huge unknowns around scalability and permanence. Niche solutions like biochar soil amendments also go in this category.
- Ocean fertilization. Major concerns around permanence and scalability.
- Enhanced weathering. As mentioned upthread, over the long-term, this is the major driver of Earth’s carbon cycle: volcanos belch out potentially vast amounts of CO2 (read up on the Deccan Traps if you’re interested!), and over millions of years, basalts and other natural rocks weather away, which chemically removes that CO2. The trick here is to mine something like olivine, grind it up into something like a sand to increase the surface area, and then distribute it widely to weather over years instead of millennia. A ton of olivine can ultimately draw down roughly a ton of CO2, so at ~40 GT of CO2 emissions annually, that’s a whole lot of hard-rock mining just to break even.
There doesn’t have to be one magic bullet, and probably won’t be. The future will probably have to consist of significant reduction of emissions, and a little bit from several of these NET buckets to get to negative net emissions. James Hansen, the hockey stick guy, and a very respected scientist who’s been working on climate change for decades, estimates you’d need to remove rough 700 gigatons of carbon (which is 2500 GT of CO2) by 2100, if we keep emissions constant and want to get the atmosphere back to 350 ppm of CO2 (which is his estimate for a safe level. This is more aggressive than the 1.5 degrees celsius number that the UN is optimistically targeting.)
That’s a lot, but even if we don’t hit scale until 2050, its 50 GT / year. If the average ton would cost $100 to remove, we’re looking at $5 trillion a year for the second half of the century. I don’t know what global GDP will be then, but it’s $87 trillion now, so it’s probably fair to assume we’re talking about a couple percent of world GDP.
Here’s the Hansen paper. It’s really good if you want a deep dive!
Kelp-based sequestration is an emerging idea that seems like it could be enormously beneficial.
Basically, it’s the “plant a trillion trees” idea, with a twist. It’s kelp, and when it’s mature, we cut it loose and let it sink to the ocean floor. It just stays there forever because the deep ocean temperature and pressure prevent it from decomposing to CO2. Some of the product may be diverted for cattle feed, which supposedly helps limits emissions of methane.
I have no idea what the scaling numbers are, but apparently it’s solid enough for a couple of startups to take a run at it:
There are many locations where solar and wind power could be very productive, but aren’t near enough to power grids for efficient transmission to consumers. If the geology of the area is conducive to carbon burial, then this might be a good way to situate a powered sequestration farm.
I think this depends on what you mean by “bigger bang for the buck” - to me, that term refers to cost efficiency, for which planting trees is generally pretty good compared to a lot of alternatives (according to this report, pasture afforestation and degraded forest reforestation come in at <10 euros/tonne CO2e, which is lower than many GHG reduction opportunities including pretty much any type of renewable energy production). If I had a limited pool of money to spend, I’d put it towards planting trees first before, say, putting it towards building a carbon capture and storage plant.
I think you might have been more alluding to the fact that the overall amount of reforestation that can be done is limited, therefore it can only be a small part of the solution. A square of 110km per side is pretty reasonable when you look at the amount of land available for reforestation - that’s ~1.2 million hectares, or close to 3 million acres, while there is ~133 million acres of reforestation potential in the US, according to this site. According to that site, that would result in ~333 MT/yr of CO2 abatement, which is not insignificant (~5% of the US’s overall annual GHG emissions). Now, much of that is private land, so if you were to just take the Federal, US Forest Service and Bureau of Land Management lands, it would be around 22 million acres with ~32 MT/yr CO2e abatement potential - down to just 0.5%. If we were to look globally, however, there are estimates that ~3GT/yr of CO2e could be removed through forest restoration.
There have been some proposals to accelerate this process, such as Project Vesta. We’ll see if it ever becomes economically viable to do at scale, but as far as planetary-scale carbon removal processes go, enhanced weathering of minerals must be up there (with several GT/yr carbon removal potentially possible).
I missed your post originally when I posted, but I agree with this - it’s going to take a combination of both emissions reductions and negative emissions technologies to get us to where we need to be - even though massive emissions reductions are absolutely critical, I think we absolutely have to be looking at our options for negative emissions because it’s likely inevitable that we will need them IMO (the alternative being to spend money on adapting to a severely warmed climate…).
That’s real progress - I seem to recall that fusion was always just 10 years away, and now we’ve got it down to 4 or 5!
This is the biggest in the world - and yet it can only remove the equivalent of 870 vehicles’ worth of carbon per year.
In other words, we’re going to need about 1 million of them.
I would say that the best way to sequester carbon might be to encourage and ‘harvest’ algae blooms.
These things can be massive, and a single bloom can contain as much carbon as the US emits in a year. Here’s a large freshwater bloom on lake Erie:
The problem is that not all of their carbon is sequestered. Some of it makes its way into large mammals and fish that eventually die. Some of them sink into the deep ocean and their carbon is sequestered for a long time. Some of the algae just sinks to the bottom on its own. But most of the algae goes into feeding the marine food chain amd is recycled.
However, algae is able to be proccessed into bio-fuel, or it could be simply filtered out of the water, processed in some way and stored. I believe this would be much more effective than planting trees, but still almost certainly won’t happen at a scale that could seriously dent the amount of CO2 in the air.
Algae blooms, btw, are an example of a climate change negative feedback. Algae grows faster in warmer water, and rising sea levels and increased storms increase the amount of nutrients that get pulled into the ocean from land. Both of these stimulate algae blooms, which sequester some of the excess carbon.
Not that the difference would be enough to substantially change the climate on human timescales, But it’s an example of how evolved ecosystems derive stability from negative feedback.
Haven’t you noticed what is happening in the West? The trees in the forests die and a massive amount of fuel builds up. There is lightning (or another cause of fire) and a fire starts and now there is a massive forest fire–and all this carbon which was stored up is converted back to carbon dioxide and dumped back into the atmosphere.
A portion, not all. And the aftermath is increased fertility and carbon in forms that are protected from decomposition (e.g. char.) And forests store carbon underground. No, we can’t just look at inputs and call it a day, but it’s not like the people building emission inventories are unaware of the outputs.
Western US forests are not expected to return to fully recover from fire damage not withstanding the long term drought conditions in the US Southwest (and now extending up to the Pacific Northwest), and at any rate trees are neither the most effective or fastest natural carbon sinks. There are other good reasons for reforestation campaigns to preserve natural habitats, but as a solution for removing excess carbon dioxide they aren’t even a rounding error in terms of the impact they would make.
Stranger
3% of net domestic emissions for CONUS reforestation, per the earlier PNAS paper. Which I posted to point out that forests do not solve the problem. But neither because “when they rot, the carbon is returned to the air”, nor because “there is a massive forest fire–and all this carbon which was stored up is converted back to carbon dioxide and dumped back into the atmosphere”. Countering a bad suggestion with flawed objections doesn’t help. US forests, on average, are a net carbon sink after accounting for both decomposition and fires.
The reason forestation doesn’t solve the problem is because the net sink per area times the limited land that is both available and suitable for forestation is only one 30th of our net emissions.
Hey, at least it’s harmless.
If it is used as an excuse not to take actual action, it causes harm.
Respectfully disagreeing, because even if it may not be useful for this, it’s useful in other ways, UNLESS they’re using non-native, invasive species (which has happened).
The people claiming that this is the answer are, for the most part, not the ones planting the trees. The ones actually planting the trees know that this is only a very temporary stopgap and that much more needs to be done.
Also, quit destroying grasslands to plan trees - they are quite possibly more effective at storing carbon long term.
There’s also more to environmentalism than the issue of atmospheric carbon. There’s a number of benefits to soil health, ecological diversity etc that come from mass tree planting campaigns. At the end of the day there’s virtually no man-made initiative we’re likely to scale up in our lifetimes that is going to move the needle anything as close to reducing carbon emissions from power generation, transportation, and heavy industry.
Only if you assume “our lifetimes” are very short, like we all have something terminal. The fact is that we’re already well on the way to electrifying automobiles. And here in Ontario we got rid of the last coal-fired plant years ago, and more than half our power is nuclear, and most of the rest is from renewable sources. Today.
It may take a long time if there is political obstructionism, but there’s no reason that technically we could not meet the goal of the UNFCCC COP21 agreement (“Paris Accord”) to limit temperature rise to no more than 2°C by 2100, and maybe even as little as 1.5°C. But we need to take pragmatic and innovative approaches to do it, not fancifully count on planting a zillion trees, which is neither possible nor effective. Nor can we count on magical carbon-removal schemes or dangerous geo-engineering fantasies. The core of the solution, well documented by the IPCC WG3, is drastically curtailing emissions, and yes, there will be up-front costs involved in doing it.