Gemini-owned non-fungible token (NFT) marketplace Nifty Gateway pledged Monday to become “carbon negative” this year through a combination of offset purchases and technology improvements.

Nifty Gateway will buy offsets equivalent to double its CO2 footprint at the end of every month, said founders Duncan and Griffin Cock Foster. Site developers also plan on running Nifty’s NFT minting system through EIP-2309 to cut Ethereum gas fees by 99%.

The concession comes as environmentalists attack NFT creators for crypto’s carbon emissions, reserving particular shade for marketplaces like Nifty Gateway that drive thousands of transactions. Already, a torrent of online criticism prompted one art website to abandon its NFT plans.

Nifty Gateway said the offset program will use an open-source emissions project as its benchmark. That codebase (whose contributor did not immediately reply to CoinDesk) estimated Nifty Gateway was responsible for 13 million kg of CO2 through March 22 – the second-largest footprint among marketplaces – despite it being only the fourth-largest marketplace by transaction count.

“In theory Nifty Gateway will become a net remover of carbon,” the Cock Fosters wrote in their blog post.

Even as they touted the offsets, the twins bemoaned the “double standard” they claimed is applied to the booming crypto art scene – which relies in large part on traceable transactions on the Ethereum blockchain. Meanwhile, the “offline art world” goes unchecked, they said.

“Because there is no blockchain to account for the carbon footprint of the traditional art world,” they wrote, “such criticism has not been leveled against” it, pointing to museum-goers who drive cars as one example.

Indeed, CoinDesk could not find public estimates on the global carbon impact of patrons of the arts by press time. This reporter estimated that driving to the Philadelphia Museum of Art’s gift shop for the purpose of buying a Claude Monet print (a 6.7-mile drive, his nearest available marketplace) would emit 4 kg of CO2. Meanwhile, acquiring a GIF of a 1,239-run gummy bear mugshot on Nifty Gateway would produce nearly 31 kg of CO2, according to Digiconomist.

A representative for Gemini did not immediately tell CoinDesk when Nifty Gateway would begin purchasing offsets.