Hacker News Reader

Comment by davidw | Hacker News Reader

> Is there any work on smaller scale, "home" or "neighborhood" carbon capture technologies that could work with some extra energy laying around?

Trees? They make efficient use of solar energy to capture carbon and have a lot of other benefits:

https://www.cnu.org/publicsquare/2020/08/31/powerful-virtuou...

View on HN

Trees are a temporary carbon store, but the issue is that they eventually die and rot, and then that carbon gets released right back into the atmosphere. A permanent solution would be to grow trees, chop them down, and then bury them.

Alternately, let new trees grow to take the place of trees that die.

This is yet another stock/flow issue, where the sequestered carbon is a function of the stock of living trees, which itself grows with the delta of trees added - trees removed. You don't need to manually manage the lifecycle of each individual plant, just focus on the increasing the living stock, or rather, letting the living stock increase all on its own in response to more carbon in the air. So this is about land zoning and habitat protection, not building little coffins for individual trees. Let forests grow and protect their habitat, they will grow all on their own if allowed to.

FYI we've added 60 million hectares of forests since 2000. That process can be even expanded.

Yes, this is true. If you can create a stable forest then that becomes a carbon sink for the lifetime of the forest. It is still hard to see how this is going to make a big difference. The biomass of the Amazon rainforest is ~120 gigatons. Annual CO2 emissions are right now around 30-36 gigatons. Growing a new forest the size of the Amazon would make up for about four years of emissions.

Of course that doesn't mean that reforestation isn't valuable. It certainly is. But even enormous growth of forest wouldn't make a big dent in atmospheric CO2 levels. The carbon came from underground and almost all of it will have to return underground to get CO2 levels down.

Those are valid points. But you don't need to add the square footage of the Amazon, what also happens is that forests become more dense per square foot. But not only forests, grassland sequesters about 343 gigatons and that rate has been growing at half a gigaton/year as the grassland gets taller/denser due to increasing carbon in the air. Biomass in topsoil itself sequestors twice as much carbon as biomass in trees, but this covers only 3% of the earth's surface. This paper has a nice overview[1]

[1] https://innovate-eco.com/storing-carbon-in-plants-and-trees-...

Mature forests are carbon neutral because new growth will take the place of growth that dies and decays.

Bacterial rot is not the only thing that trees can turn into: their carbon can enrich the soil and be consumed by insects, fungus, lichens etc that goes onto feed higher species on the food chain. On top of that, rotting trees is fantastic habitat for animals, which are also made of carbon.

“the issue is that they eventually die and rot, and then that carbon gets released right back into the atmosphere”

You make it sound like a rapid process. Univ of Arizona did a study that showed CO2 emissions of dead trees was lower than living ones due to the rotting process being very slow compared to a living trees normal respiration cycle

Well the timescale of climate change is on the order of a few decades to a century. The decomposition process is somewhat slow by human standards, but it's still fast compared to a century. In order to effectively remove CO2 from the atmosphere to prevent climate change, it needs to be removed on timescales longer than a century.

decomposition doesn’t evaporate the tree into the air, it can build the soil and become habitat for larger animals (which also count as biomass)

Grow trees, chop them down, and build houses. We still have a housing shortage.

So long as lifespan is on the order of 100 -- 1,000 years, the net gain is all but certainly worthwhile.

I still favour wetlands over trees as a first priority.

You can cut them down regularly and turn the wood to biochar and bury it. That is fairly stable in the soil. If you just bury them normally they'll decompose back to carbon dioxide much faster.

While I believe this comment is well intended, I don't believe it addresses the parent's question. The extra resource they have is electrical power, not land. They are asking if there is a way to turn electrical power into carbon capture.

I also want to say that the planting trees method is a bit more nuanced than everyone makes it out to be. But don't trust me, let's ask someone who knows better: Forrest Fleischman[0][1]. I'm not saying "don't plant trees" (do) but that this is often everyone's go to response to CCS and it is a bit naive (as explained in the threads).

[0] https://twitter.com/ForrestFleisch1/status/13062214459331297...

[1] https://twitter.com/ForrestFleisch1/status/14440088233506037...

Also interesting that grassland can in some cases like California be better co2 sinks than trees. https://www.earth.com/news/trees-grass-carbon-sink/

It is something that have to be done anyway, as the other benefits matter too. But how it is done could be the difference between a solution and a far worse problem.

Global warming is already pushing toward more frequent forest fires, or droughts in vast regions that if they have trees will end burning up as well.

Intensive tree planting in relatively small areas probably is a bad idea, or will have a big maintenance cost to try to avoid that risk.

But, in any case, it is the low hanging fruit of carbon capture. I just hope that it is done in the right way.

FYI, it takes 7-8 trees just to offset a single person's breathing if this math is right.

https://www.sciencefocus.com/planet-earth/how-many-trees-doe...

The maths may be right but the thought is wrong since it takes zero trees to offset the whole world's population of air-breathing organisms as all the CO₂ they produce started out as... CO₂. This is taken up by algae and plants, which are eaten by organisms which are eaten themselves until the target organism is reached, which will use the energy gained from consuming the previous hop in the carbon chain, breathing out CO₂ upon which the circle is complete.

Had humans consumed fossilised carbon the thought would still be wrong since trees only store the carbon temporarily, eventually it is released as CO₂ when the tree burns up or rots away.

This leaves aside the whole discussion on whether there is any need to offset CO₂ from non-fossil sources - which there is not as far as I can see.

That's ok, I've planted 920,000.

It's not how many you've planted, it's how many are still alive at age 20.

They all had good quality and trees make pine cones.

Those calculations are for oxygen required to breathe, not carbon dioxide exhaled by people. The cycle for biologically produced and consumed CO2 tends to be carbon neutral.

As far as I'm aware, the issue isn't with CO2 produced by cellular respiration, the issue is the burning of fuels dug up from the ground and the destruction of natural carbon sinks.

If I could grow the things... I struggle to get them watered properly.

Practically, though, I'm out in some fairly high desert, and I have to pump water for irrigation out of a deep well. I can certainly do it, but I'm looking for something of a bit more "geologic scale" sequestration, if it's possible.

You might consider hydroponics (ie consumer Aerogarden) as the water requirements are approximately 90% less. It does the "watering" for you.

I'm actually planning to get a backhoe for a couple years to build a large basalt greenhouse, then do aquaponics - combine growing fish and plants in something that removes most of the downsides of aquaculture and hydroponics. Done properly, it's a synthetic pond ecosystem that doesn't require flushing the water ever.

Looks like you're somewhere east of where I live in Oregon. Do Junipers grow there with maybe a little bit of water?

Reply on news.ycombinator.com