Abstract
Responsibly managing greenhouse gas (GHG) emissions that lead to climate change is a present-day issue to address without delay. Proactively focusing on emerging and high carbon-intense sources of pollution is essential to slowing climate change. Cryptocurrencies, including bitcoin, have sharply risen in popularity in recent years and have been the center of financial and ethical debates. Bitcoin is a peer-to-peer financial transaction system that does not rely on a central entity or physical commodity to establish its value. The Bitcoin network relies on distributed nodes (or miners) to process transactions and release new pre-allocated bitcoins, in which specialized Application Specific Integrated Circuit (ASIC) mining computers solve mathematical and cryptographic problems to process these transactions. However, this process requires tremendous computing power, thus leadings to immense electricity consumption. Electricity consumption is often linked to GHG emissions but are not always directly related. The fuel mix composition of electricity, including coal, oil, natural gas, nuclear, and renewable energies, more closely dictate the carbon intensities of electricity. Previous studies have estimated electricity consumption on a global scale and subsequently attempted to estimate the associated GHG emissions of Bitcoin. While this can paint an overall picture, global electricity estimates do not accurately suffice to estimate GHG emissions because electricity fuel mixes vary vastly across the globe. This study takes a closer look at bitcoin mining within the United States (U.S.) with small mining operations of one, three, and five Bitmain S19j Pro ASIC miners. GHG emission factors were first found for a U.S. average along with the states of California, Texas, and Louisiana. Fuel mix data through the U.S. Environmental Protection Agency (EPA) and California Energy Commission (CEC) were used with the GREET Model to calculate emission rates for the four regions. For a single ASIC miner, annual GHG emissions were found to be 5,586-kgCO2e/year in California, 10,082-kgCO2e/year in Texas, 10,877-kgCO2e/year for the U.S. average, and 11,837-kgCO2e/year in Louisiana. This study also evaluated grid-tied distributed energy technologies of solar photovoltaic (PV), PV with battery storage, and PV with wind power, and battery storage in California using HOMER Pro. It was found that solar PV systems could decrease annual energy consumption and GHGs while also increase annual profit. A total of 12.6 megawatt-hours annual grid-purchase savings were observed for the single-miner case, corresponding to a savings of 2,565 kg of CO2e.