"Carbon removal is the closest thing we have to a time machine, if you want to not just mitigate climate change, but actually reverse it," says Shashank Samala, CEO of Heirloom, a California startup using limestone as a carbon-sucking sponge. Heirloom opted for limestone because it's available in large quantities. And there's no shortage of storage space either. Carbon capture will be a central topic of discussions at the COP28 climate talks which take place in Dubai from November 30-December 12. Many see it as necessary to get closer to a zero-emission world while others fear it is being hailed as an easy ticket to avoid making the sacrifices needed to slow climate change. IMAGES AND SOUNDBITES