Several altcoins are focused on carbon neutrality. Algorand aims to be carbon-negative, while Cardano and Tezos use energy-efficient proof-of-TG Casino mechanisms. Chia minimizes energy use with its proof of space and time approach. NEO and EOS also promote sustainability through low-energy consensus algorithms. Verge explores renewable energy partnerships, SolarCoin rewards solar producers, and Power Ledger facilitates peer-to-peer energy trading. These altcoins reflect the growing emphasis on sustainability in the crypto space.