A bathhouse in Brooklyn, New York, is heating its spa pools with waste heat from Bitcoin mining rigs - and sparked a social media controversy.

Bathhouse explained in an Instagram post on Wednesday that it is running mining rigs at its N 10th Street address in Brooklyn, which generate heat as a byproduct. The heat is taken by heat exchangers and used to heat the venue's pools, via a circulating system.

– Bathhouse

"Enjoy a hot pool while supporting the Bitcoin network," said Bathhouse's post. "The pools absorb the heat and circulate cool liquid back to the miners. The process repeats forever."

The process is strikingly similar to Deep Green's campaign to heat swimming pools in the UK with heat generated by Edge data centers, which launched in March. However, Deep Green is offering its compute resources to AI and Machine Learning users via cloud workload aggregators. Bathhouse's support for Bitcoin mining has proven more controversial.

Some readers complained that Bitcoin is inherently wasting energy, while others appeared to object to cryptocurrency on fashion grounds.

New York is increasingly hostile to cryptocurrencies. Following the failure of crypto exchange FTX, banks have backpedaled on moves to integrate cryptocurrencies into the financial systems, while the state passed a bill to ban crypto mining with fossil-derived electricity in June 2022.

In October 2022 a Federal report found that crypto mining uses 0.9 percent of the world's electricity, and as much energy as conventional data centers in the US.

Fans of the Bathhouse have pointed out that it would take exactly the same amount of electricity to heat the pools, whether or not the electricity also generated Bitcoin. In their view, the scheme is attacking the problem of Bitcoin's waste of energy.

"Someone needs to teach people an emergency thermodynamics class," commented Jalil Farid on Twitter, while others mocked the users for their lack of understanding.

"They want pure, unadulterated heat for their salt baths, not that dirty byproduct heat," said Phil Geiger.

Some critics perhaps wanted the computing to be used for more valuable functions: "I’m concerned about who is mining this cryptocurrency, who is profiting from it, and whether I support that. We’re gonna need some transparency,” said one.

Batthouse explains that it describes itself as a bathhouse, not a spa, because: "Bathhouses offer functionality over fluff, while spas provide an experience that we like to call 'performative relaxation'."