I am by no means an expert here, but a couple thoughts back from my limited knowledge:
1) I don't think all carbon capture necessarily requires a lot of energy input. Planting trees is a more obvious example of this - of course, the trees rely on the sun's energy so it's not "low energy" in that sense, but we weren't going to harvest that energy any other way anyways. It's possible there are other solutions that are like that.
2) If we have an abundance of zero or low-carbon energy in the future that doesn't exist now, it might not matter that taking carbon out of the atmosphere uses more energy than the energy we got from putting carbon into the atmosphere to begin with.
To be clear, I really wish we'd just spend the money and take the sacrifice to use a lot less carbon right now. It certainly seems like a much easier problem to solve than trying to suck it back out later, and relying on it to work seems like a dumb risk. Even if we're confident that we'll inevitably need some amount of carbon capture and that the R&D will happen to develop it at scale, there's a good chance that it'd be easier and cheaper to put less carbon in the air now than to do more capture later.
I don't even think you need "a lot of sacrifice" to stop emitting so much carbon. The EPA estimates that energy efficiency could cut emissions by up to 20%.
The trick is that most energy inefficient buildings and appliances are used by poor people who can't afford to upgrade or maintain to the latest and greatest standards, and massive funding for poor people is a giant lightning rod at least in the US. I know that in a previous house my utility was literally paying me to replace my fridge and air conditioner to reduce peak power demand, but I have no idea how widespread such programs are.
The problem with efficiency is that it's usually not tied to reduction. We need people to have more efficient buildings and to heat and cool them less. We need LED lighting with no more lighting. So, https://www.treehugger.com/energy-efficiency/are-we-using-le...
Put simply: INDUCED DEMAND
Just like roads or computer hardware (every improvement in hardware can get eaten up by people no longer caring about optimizing software efficiency or modest file sizes: nobody needs their cute family videos to be 4k HD etc)… we can easily use up ALL the gains if we are let to just do that.
We use more efficient building technology to support homes being larger and more luxurious than we need. Defeats the whole purpose.
We need to internalize the costs. Heavy taxes on the source of pollution rather than subsidizing the clean-up or the use.
If energy gets MUCH MUCH more expensive, people WILL upgrade to efficient tech and keep minimizing their use of it.
Trees are not a great solution. Their CO2 storage is basically static in terms of the amount, once the forest is grown it won't have a huge net capture anymore. We'd have to raze them and keep re-planting to do that. Which has obvious nature impact.
But I agree with your comment. Preventing is better at this point, especially while we're still emitting (and will be for a long time). I view Carbon Capture at this stage basically as a decoy from big oil to keep doing what they're doing.
1) I don't think all carbon capture necessarily requires a lot of energy input. Planting trees is a more obvious example of this - of course, the trees rely on the sun's energy so it's not "low energy" in that sense, but we weren't going to harvest that energy any other way anyways. It's possible there are other solutions that are like that.
2) If we have an abundance of zero or low-carbon energy in the future that doesn't exist now, it might not matter that taking carbon out of the atmosphere uses more energy than the energy we got from putting carbon into the atmosphere to begin with.
To be clear, I really wish we'd just spend the money and take the sacrifice to use a lot less carbon right now. It certainly seems like a much easier problem to solve than trying to suck it back out later, and relying on it to work seems like a dumb risk. Even if we're confident that we'll inevitably need some amount of carbon capture and that the R&D will happen to develop it at scale, there's a good chance that it'd be easier and cheaper to put less carbon in the air now than to do more capture later.