CLEANER Act of 2021 or the Closing Loopholes and Ending Arbitrary and Needless Evasion of Regulations Act of 2021 This bill eliminates the exemption of waste associated with the exploration, development, or production of crude oil, natural gas, or geothermal energy from regulations governing the disposal of hazardous waste. Within a year of enactment, the Environmental Protection Agency (EPA) must determine whether such waste meets the criteria for hazardous waste, promulgate regulations concerning the disposal of such waste if the EPA determines it is hazardous, and revise regulations applicable to solid waste management and disposal facilities (e.g., landfills) to address such waste that is nonhazardous.