A 2018 study published in Nature Climate Change estimated that if Bitcoin were broadly adopted for cashless transactions, its associated energy consumption could alone produce enough carbon dioxide emissions to push global mean temperatures past 2°C within 30 years. Critics challenged the methodology immediately, arguing the projections excluded unprofitable hardware, failed to account for shifts in the electricity generation fuel mix, and assumed adoption trajectories that outpaced historical precedent for any payment technology. The methodological dispute was legitimate. What it obscured was the underlying direction of the data.

Decentralized finance — defi — is not a single product or platform. It is a collection of financial goods and services that operate through automated software programs called smart contracts, running on public blockchains, accessible in principle to anyone with the requisite technical knowledge and some quantity of cryptocurrency. The Congressional Research Service, in an April 2026 overview of the sector, defines it as a system characterized by “highly automated financial networks that have no single point of failure, do not rely on a single source of information, and are not governed by a central authority.”