Much less than they used to be. NFTs (non-fungible tokens) are tokens issued on blockchains, mostly Ethereum. Since Ethereum moved to Proof of Stake in September 2022, the footprint of minting or transferring an NFT has become marginal: a few grams of CO2 per transaction, compared with kilograms before. NFTs now have almost no environmental impact; what remains is the debate over their real usefulness and the risk of a speculative bubble.
Read the source article: Bitcoin carbon footprint: 33 tCO2e/year per million euros held