From National Review:

Josiah Neeley of R Street, meanwhile, points out that

even at the low end of the cost range, $94 a ton is still more than double the Obama administration’s estimate of the amount of damage done by a ton of carbon dioxide emissions (and is nearly 20 times the new Trump administration’s estimate). Going by the Obama numbers, using this technology on a large scale simply would not be worth the cost. And even if you thought the Obama administration had vastly underestimated the dangers of climate change, you would still only want to use a technology this costly once you had taken advantage of any cheaper ways to reduce emissions (of which thankfully there are many). This method is not even the cheapest technique for geoengineering (although some other possible methods tend to be more controversial).

To really be a breakthrough, technologies to counteract the effects of climate change need to be a lot cheaper, and the possible side effects need to be studied.