While cryptocurrency and blockchain technology has the potential to improve online security and enhance medical record-keeping, it does have its drawbacks. Miners use a series of complex computer systems to produce cryptocurrency tokens, and this, combined with the energy associated with processing trading transactions, has had a negative impact on the environment. According to a report produced by the UK-based financial site MoneySuperMarket, every Bitcoin transaction consumes 1,173 kilowatt-hours of electricity, or enough to power the average home in the United States for six weeks. Some analysts suggest annual cryptocurrency energy consumption is similar to that of a small country. 

However, some cryptocurrencies are far more eco-friendly than others. Those that rely on a proof of storage or proof of stake system are inherently more energy efficient, as they involve less processing power. Other creators have taken additional measures to lower the carbon footprint of their cryptocurrencies. The following are four of the most sustainable cryptocurrencies. 

SolarCoin 

SolarCoin was designed to incentivize solar energy installations. The global decentralized platform creates a new SolarCoin token for every megawatt-hour of energy generated via solar technology. Like other cryptocurrencies, tokens can be traded and spent where accepted. Users can upload supporting energy generation documentation to the SolarCoin platform to receive new tokens. 

Powerledger 

Established in 2016 and powered by Ethereum, Powerledger is a trading platform for energy and environmental commodities. Its token, POWR, debuted on Coinbase in November 2021 and was among the few cryptocurrencies to experience a rapid price increase during the market-wide crash around that time. It was trading on Coinbase at $0.63 on January 3, 2022. 

Nano 

Unlike most traditional cryptocurrencies, Nano doesn't rely on mining to generate new coins. Instead, it employs energy-efficient block-lattice technology, which creates individual user account-chains capable of managing up to 125 transactions per second. Nano is also a scalable and lightweight platform that allows users to add blocks asynchronously. For comparison's sake, it would take more than 60 million Nano transactions to equal the energy consumption of 2 seconds of Bitcoin transactions. 

Algorand 

A rapidly rising proof-of-stake blockchain that supports smart contracts, Algorand was launched in 2019 and recorded nearly 1 million daily transactions by December 2020. It maintains a partnership with ClimateTrade and, as of April 22, 2021, became completely carbon neutral. Founder Silvio Micali and the Algorand leadership team are hoping to take things a step further by creating a carbon-negative network.