Comment by D_Alex | Hacker News Reader

Comment by D_Alex | Hacker News Reader

This is actually a very bad idea and a complete waste of money which should have been used for other projects. It reminds me of another bad idea, which just will not die - extracting water from air by cooling it.

Right now, we have several technologies ready to go. Starting with the most cost-effective, and omitting the "use less" scenarios:

1. Replacement of fossil fuel power plants with carbon free electricity such as wind and solar power (also geothermal, where possible and nuclear, where palatable). Cost per tonne of CO2 saved: less than zero for about 30% of current generation, and "very low" for a good portion of the remainder.

2. Sequestration of concentrated CO2 streams, such as those produced in natural gas processing. Cost: $20-$40 per tonne.

3. Biosequestration, ie tree planting. Cost varies greatly, maybe $15-$50 per tonne.

The approaches above are the only ones that are actually used in the industry today, but there is plenty of room to do more. The approaches below are considered to be economically prohibitive, and AFAIK are not in use:

4. Post-combustion carbon capture: Scrubbing the CO2 from exhaust gases of power plants etc, where the CO2 concentration is 10-20%. Cost: $50-100/tonne, PLUS the cost of sequestration, as above.

5. Pre-combustion carbon capture: here, the carbon is removed from the fuel and sequestered, and only the hydrogen is burned. Cost: $80-150/tonne, but sequestration cost is low.

and then we have:

6. Removal of CO2 from the atmosphere. The article says the cost may be "under $100/tonne", but the serious estimates I have seen are circa $500/tonne. Consider that the CO2 concentration in air is around 0.04%, cf post combustion concentrations of 10-20%. Regardless of the advances in technology, this will never be as cheap as post-combustion carbon capture, which is essentially the same process but with 250 times less throughput.

I am with the people who worry that this is a cynical move by the companies to avoid urgent action to reduce CO2 emissions.EDIT: another comment calls this "moral licensing", and I completely agree.

I think the technology is needed because I don’t think we have the capacity as a culture to stop emissions fast enough.

I am concerned that they are so focused on syngas because it just creates a cycle that doesn’t reduce the CO2 we have released..... eventually we will just use a technology like this do pull CO2 out of the environment but there can’t be a financial aspect to it.

I like your point "and nuclear, where palatable".

I think that until marketers can convince Joe Public that nuclear is probably the safest and best tech now we have Gen IV reactors, and that they are the best way to remove by-products of older generations, we will continue to degrade our environment searching for energy.

How much of your valuable land would you like to convert to forest? Unless we start paying people more to keep forests than they otherwise could in real estate, agriculture, etc it is a nice argument that trees can sequester carbon but unrealistic that it can happen on a scale large enough to move the needle.

The thing I like about reforestation is that it's a positive, tangible, symbolic, easily understood concept that is likely relatively easy to get public support for. Conversely, carbon reduction campaigns feel more like being scolded. When I was young, the big environmental push was centered around saving the rainforest. I would like to see a return and expansion of this idea. It has many benefits beyond just global warming such as fighting desertification.

To be clear, I also support renewables and the other things listed by OP.

Sometimes I'm surprised how cheap land is. You can get an acre of grazing land for maybe 5 grand in the right area (if you buy in bulk), in a place conducive to rainfall and reforestation (Ireland).

I've looked at this and there are grants, but they're paltry (maybe a grand a year for 3 acres?) and you give up the right to do whatever you like with the land, like graze it.

I did some back-of-an-envelope calculations on converting beef grazing land (with its high methane emissions) to forest, specifically for Ireland

tl;dr - it's not cheap, but it's doable

A cow produces around 2.3 tonnes of CO2-equivalent emissions per year [1] You need 0.184 hectares of grazing land per cow [2] So each hectare of beef-grazing land emits around 12.5 tonnes of CO2-equivalent per year

Irish forests sequester on average 3.36 tonnes of CO2 per hectare per year [3] So converting beef-grazing land to forest offsets around 15.86 tonnes of CO2 per year per hectare. Cost of grazing land is around €25k/hectare [4]

Cost of planting a forest is around EUR3k per hectare [5]

So the cost of offsetting 1 tonne of carbon per year by converting beef-grazing land to forest is around €1750

Ireland's total emissions are around 61 million tonnes per year [6] So to offset it ALL would cost over a hundred billion euro, and a little more grazing land than actually exists in the country (and not all of that is beef anyway)

Or in other words, offsetting carbon by converting beef grazing land to forest would take around 1 billion euro per percent of our total current emissions. To put that in context - Irish govt spending is currently around EUR75 billion per year [7], and under the Paris Agreement we're committed to a 30% reduction of emissions by 2030 [8]

[1] https://timeforchange.org/are-cows-cause-of-global-warming-m... [2] https://www.teagasc.ie/animals/dairy/statistics-and-links/fr... [3] http://woodenergy.ie/media/coford/content/publications/proje... [4] https://www.agriland.ie/farming-news/2018-agricultural-land-... [5] https://www.teagasc.ie/crops/forestry/advice/establishment/r... [6] https://www.rte.ie/news/enviroment/2018/1205/1015300-greenho... [7] https://whereyourmoneygoes.gov.ie/en/2018/ [8] https://www.dccae.gov.ie/en-ie/climate-action/topics/eu-and-...

Thanks for that! Really appreciate it.

It explains why most of the forestry is on land not suited to a lot else.

Plus they just release it when they die.... that’s not a solution for petroleum and coal based carbon since it was environmentally sequestered before we dug it up.

Trees don't release CO2 when they die. They release CO2 when they rot. That might sound like an unimportant distinction, but for example buildings made of wood are a CO2 sink. The wood does not rot, and thus does not release the carbon bound in it. Basically burying trees (or generally biomass) in an oxygen-poor environment will sequester CO2.

Plus, if you do it in bulk, you are creating coal for future people, millions of years from now.

Don’t forget to throw in a few Dinos for the oil!

It might be useful for other readers to explain that on your #1, "less than zero for about 30% current generation", based on my knowledge it means that the "running cost" of building and then operating a renewable plant (e.g. financing it at current rates and then paying interest on the financed sum) is lower than the pure cost of operating existing "polluting" plants.

That's why it's "lower than zero".

Please correct me if that's not what you meant.

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