Total worldwide carbon production is 38.2 billion tons per year. Cost to sequester a ton of carbon is between $30 and $150, depending on who you ask and how you do it. Let's assume a middle of the road price of $90/ton. That's $3.438 trillion a year, or about $478 per person. This is roughly equal to the US yearly federal spending, or 3% of the world GDP.
If you somehow pooled together all the world's billionaires and got them to contribute their annual income (roughly $600 billion a year, averaging the past 7 years) to the effort, you could eliminate roughly 20% of carbon produced in the world every year.
Suddenly, it becomes crystal clear why finding new sequestration methods is incredibly important: if you can get the cost from $160 to $10 per ton, then suddenly all you'd need would be a coalition of half the world's billionaires to stop the main cause of global warming.
Additionally, it's important that people realize that CO2 production is in tons of CO2 per year. Tree offsets are a one-time deal, since when trees die they release CO2, and when new ones are born they absorb that CO2 again. After they've been planted, forests are generally carbon neutral. That's why we can't "just plant trees": we'd have to be continuously planting new trees. The Earth is only 8% arable land, much of which already has stuff on it, or is undesirable for one reason or another. We'd run out of space pretty fast. Trees are good for other reasons: preventing climate change (different from global warming), preserving species diversity, being nice to look at, etc etc.
Mostly off-topic: when I was looking at estimates of land size, apparently the amount the US has shrunk from 2007 to 2015 (14,000 km2; went from 9,161,120 km2 to 9,147,420 km2)  is roughly equivalent to half the area of the Netherlands. Wow.
OTOH, the total cost (not just for sequestration) is about $100, maybe a bit more, in most estimates.
For reference, a gallon of gas produces 20 pounds of CO2, so $100/ton equals $1/gallon of gasoline. That's roughly what you'd have to increase gasoline price by to fund CO2 capture, transport and storage. (This neglects that the capture part is neigh-on impossible.)
For electricity, to compensate for the average US CO2 emissions per kWh (~1.2 lbs/kWh), you'd have to increase the price by about 6 cents per kWh.
To do CCS for both gasoline and electricity consumption, the average US family would have to pay (order of magnitude) 1000 x $1 + 12000 x $0.06 = $1720. That would compensate for about half the family's CO2 emissions. The remaining half is dominated by emissions from the food we eat, the stuff we buy and from having fun.
You misunderstand the purpose of trees. They're basically solar powered, organic carbon sequestration devices that happen to run for free. If we ever run out of space to plant trees, we can just cut some down, reduce it down to charcoal and bury it back into the ground which conveniently leaves a readily accessible fossil fuel source for our ancestors in the case of civilizational collapse.
But we're still a long way away from running out of room to plant trees. We're still desperately trying to plant enough trees to stop the encroaching of the Sahara and there's vague, futuristic plans to try and turn the entire Sahara into a forest. Similarly, China is desperately planting trees to stop the encroachment of the Gobi.
If you're removing carbon from the air by burying trees then you'll only be able to sustain the energy intensity of civilization in the Britain of 1800, plus what we can get with renewables. What this new form of capture gives us is the ability to get rid of excess carbon without using huge amounts of arable land to do it.
There are plenty of high-power ways to make energy without carbon. The question is if enough of the population can accept it.
Yes, that's the point. Plant trees, cut them down when mature and plant new ones. Use the harvested trees to make cross laminated timber and other engineered wood products and use these to replace concrete and steel (which also release CO2 during production). As long as the timber doesn't burn or rot the carbon is stored permanently.
They will just release their carbon content back when they are burned or transformed in any other way that only the mineral content is left. Otherwise, paper still contains carbon. Coal (buried, not burned) contains carbon. Furniture, houses, anything you make with wood will be a way of storing carbon.
You just also need to supply water and solar light. They will grow. Simple and efficient.
The implication being that we have one good shot at solving civilisation. It just gets more difficult when we start to run out of fossil fuels.
One of the reasons we don't see anything going on out there when we look up could very well be that most civilisations never properly make it off their planets.
Can anyone else comment on this that might have better information than me?
The global potential of energy from hydroelectricity is only a small fraction of our current fossil-based consumption, though. And while wind and solar have potential resources far past fossil power, they can't expand as fast as fossils did historically. So the Fermi Paradox aspect might be that civilizations without fossils and without the self-control to limit reproduction are hobbled by cycles of Malthusian collapse. Or perhaps space-capable civilizations that didn't fall into the Malthusian boom-bust trap while still confined to one planet also don't go crazy with growth once they escape their gravity well, so they're out there but not leaving evidence dramatic enough to be seen by our current telescopes.
If you just mean that it's impractical to build the electrical grid out to a remote mining site, that's true. In the present day remote mining sites typically use diesel fueled generators, now being supplemented with photovoltaic arrays in sunny regions. If you imagine a world with approximately-1940-level technology (so PV is not yet an option) and no fossil fuel, then you'd need to use something like biodiesel or ethanol instead of fossil-derived diesel.
Yes, that was the general issue. We do a lot of mining in remote sites that don't have hydro power or any realistic way to get it there. You could use biofuels, but it's hard to imagine bootstrapping a technical society to the point that that becomes feasible without prior use of fossil fuels.
Well, we are busy recycling that one. All that carbon in the atmosphere will likely eventually precipitate out. On a geological timescale oil is renewable; it's simply that humans don't live that long. I suppose the cockroach civilization 60 megayears hence will be able to power their vehicles that way.
Or, you could be one of the few who believes the abiotic theory of oil production. I'm not one of them!
Why not just let nature do it's job? If too much CO2 will kill us, then it's a self regulating system. It happened before with the Azolla event. You get fewer humans, more plants, everything else gets a chance to die off or recover, maybe a new species takes over.
Why bother with carbon sequestration?
Jesus, grow some empathy.
Rather than store carbon in solid form, which in fact plants (rainforest and such) already do anyway without the unecessary expense, why not close coal fired power stations and build nuclear? They're safer and the waste is negligible compared to coal and can be further reduced (breeder reactors, thorium cycle etc.). Burning coal also throws heavy metals (Mercury and Arsenic to name a few) and SO2/SO3 into the air. Carbon dioxide is the least of coal's problems because it can be fixed by plants or turn into bricks with additional expense.
is that really true? If a tree died, i would assume the carbon is either buried, or otherwise remain solid, unless it's burnt.
"Based on a genetic analysis of mushroom fungi, it was proposed that large quantities of wood were buried during [the Carboniferous] period because animals and decomposing bacteria had not yet evolved enzymes that could effectively digest the resistant phenolic lignin polymers and waxy suberin polymers. They suggest that fungi that could break those substances down effectively only became dominant towards the end of the period, making subsequent coal formation much rarer."
https://en.m.wikipedia.org/wiki/Carboniferous See Rocks and Coal
Moral of the story: you should start regular forest/grass fires to turn the stored carbon into charcoal. A biologist can give you a number of other reasons why this is good for the forest as well: common knowledge about forest fires is almost completely false.
By default about half of a tree's absorbed carbon is injected into the ground to build soil, as root mass and root exudates. Plus trees drop mulch -- mainly leaves. Soil carbon is only released when the soil is destroyed or eroded away. So... don't do that. :)