Waste Management, Inc., through its subsidiaries, engages in the provision of environmental solutions to residential, commercial, industrial, and municipal customers in the United States and Canada. It offers collection services, including picking up and transporting waste and recyclable materials from where it was generated to a transfer station, material recovery facility (MRF), or disposal site; and owns and operates transfer stations, as well as owns, develops, and operates landfill facilities that produce landfill gas used as renewable natural gas for generating electricity. As of December 31, 2022, the company owned or operated 254 solid waste landfills, five secure hazardous waste landfills, 97 MRFs, and 337 transfer stations. It also provides materials processing and commodities recycling services at its MRFs, where cardboard, paper, glass, metals, plastics, construction and demolition materials, and other recycling commodities are recovered for resale or redirected for other purposes; recycling brokerage services, such as managing the marketing of recyclable materials for third parties; and other strategic business solutions. In addition, the company offers construction and remediation services; services related with the disposal of fly ash, and residue generated from the combustion of coal and other fuel stocks; in-plant services comprising full-service waste management solutions and consulting services; and specialized disposal services for oil and gas exploration and production operations. The company was formerly known as USA Waste Services, Inc. and changed its name to Waste Management, Inc. in 1998. Waste Management, Inc. was incorporated in 1987 and is headquartered in Houston, Texas.

Energy Recovery, Inc., together with its subsidiaries, designs, manufactures, and sells energy efficiency technology solutions in the Americas, the Middle East, Africa, Asia, and Europe. The company operates through Water and Emerging Technologies segments. The company offers high and low pressure, and ultra pressure exchangers; AT and LPT hydraulic turbochargers; and high-pressure feed and circulation booster pumps for use in seawater and brackish desalination, and wastewater treatment. It also provides PX G1300, which reduces energy consumption and operating costs of carbon dioxide-based refrigeration systems; and spare parts, as well as repair, field, and commissioning services. It sells its products under the ERI, PX, Pressure Exchanger, PX Pressure Exchanger, Ultra PX, PX G, PX G1300, PX PowerTrain, AT, and Aquabold brands to original equipment manufacturers, supermarket chains, cold storage facilities, refrigeration system installers, and other industrial users; aftermarket customers consisting of desalination plant owners and operators; and project developers, end-users, and industry consultants, as well as engineering, procurement, and construction firms. Energy Recovery, Inc. was incorporated in 1992 and is headquartered in San Leandro, California.

Quest Resource Holding Corporation, together with its subsidiaries, provides solutions for the reuse, recycling, and disposal of various waste streams and recyclables in the United States. The company provides disposal and recycling services for motor oil and automotive lubricants, oil filters, scrap tires, oily water, goods destruction, food waste, meat renderings, cooking oil and grease trap waste, plastics, cardboard, metal, glass, mixed paper, construction debris, as well as a large variety of regulated and non-regulated solid, liquid, and gas wastes. It offers antifreeze and windshield washer fluid, dumpster and compacting equipment, and other minor ancillary services. In addition, the company offers landfill diversion services. Its services focus on the waste streams and recyclables from big box, grocers, and other retailers; automotive maintenance, quick lube, dealerships, and collision repair; transportation, logistics, and internal fleet operators; manufacturing plants; multi-family and commercial properties; restaurant chains and food operations; and construction and demolition projects. The company markets its services to automotive, manufacturing, hospitality and retail, construction and demolition, and commercial and multi-family property management industries through direct sales force and strategic partnerships. The company was formerly known as Infinity Resources Holdings Corp. and changed its name to Quest Resource Holding Corporation in October 2013. Quest Resource Holding Corporation is headquartered in The Colony, Texas.

Babcock & Wilcox Enterprises, Inc., together with its subsidiaries, provides energy and emissions control solutions to industrial, electrical utility, municipal, and other customers worldwide. The company operates through three segments: Babcock & Wilcox Renewable; Babcock & Wilcox Environmental; and Babcock & Wilcox Thermal. The Babcock & Wilcox Renewable segment offers technologies divert the waste from landfills for power generation and replacing fossil fuels and recovering metals and reducing emissions. It offers BrightLoop, a hydrogen generation technology that generates hydrogen from a range of fuels, including solid fuels, such as biomass and coal. This segment also provides technologies for power and heat generation comprising waste-to-energy; OxyBright, an oxygen-fired biomass-to-energy technology; and black liquor systems for the pulp and paper industry. The Babcock & Wilcox Environmental segment offers a range of emissions control and environmental technology solutions for utility, waste to energy, biomass, carbon black, and industrial steam generation applications. This segment provides systems for cooling, ash handling, particulate control, nitrogen oxides and sulfur dioxides removal, chemical looping for carbon control, and mercury control under the SolveBright, OxyBright, BrightLoop, and BrightGen names. The Babcock & Wilcox Thermal segment offers aftermarket parts, construction, maintenance, engineered upgrades, and field services for its installed bases, as well as the installed base of other OEMs for power generation, oil and gas, petrochemical, food and beverage, metals and mining, and others. This segment also provides steam generation systems, including package boilers, watertube and firetube waste heat boilers, and other boilers to medium and heavy industrial customers. Babcock & Wilcox Enterprises, Inc. was founded in 1867 and is based in Akron, Ohio.

ClearSign Technologies Corporation designs and develops products and technologies to enhance emission and operational performance, energy efficiency, emission reduction, safety, and overall cost-effectiveness of industrial and commercial systems in the United States, the People's Republic of China, and Hong Kong. The company's technologies include ClearSign core burner technology consists of an industrial burner body and a downstream porous ceramic or metal flame stabilizing structure; ClearSign core process burner technology that provides a direct burner replacement for traditional refinery process heaters; ClearSign core boiler burner technology; ClearSign core flaring burners that can be used individually, or in combination, to provide a flare product with extremely low nitrogen oxide emissions; and ClearSign eye flame sensor, an electrical flame sensor for industrial applications. It serves energy, institutional, commercial and industrial boiler, chemical, and petrochemical industries. The company was formerly known as ClearSign Combustion Corporation and changed its name ClearSign Technologies Corporation in November 2019. ClearSign Technologies Corporation was incorporated in 2008 and is headquartered in Tulsa, Oklahoma.

Clean Energy Technologies, Inc. designs, produces, and markets clean energy products and integrated solutions that focuses on energy efficiency and renewable energy in the United States. It operates through four segments: Clean Energy HRS and CETY Europe, CETY Renewables Waste to Energy Solutions, engineering and Manufacturing Business, and CETY HK. The company offers Clean Cycle, which generates electricity by recycling wasted heat produced in manufacturing, waste to energy, and power generation facilities. It also converts waste products created in manufacturing, agriculture, wastewater treatment plants, and other industries to electricity, renewable natural gas, hydrogen, and bio char. In addition, the company offers engineering, consulting, and project management solutions. Further, the company is involved in the sourcing and suppling of liquefied natural gas to industries and municipalities located in the southern part of Sichuan Province and portions of Yunnan Province. The company was formerly known as Probe Manufacturing, Inc. and changed its name to Clean Energy Technologies, Inc. in November 2015. Clean Energy Technologies, Inc. was founded in 1993 and is headquartered in Irvine, California. Clean Energy Technologies, Inc. is a subsidiary of MGW Investment I Ltd.

Recon Technology, Ltd. provides hardware, software, and on-site services to companies in the petroleum mining and extraction industry in the People's Republic of China. The company offers equipment, tools, and other components and parts related to oilfield production and other energy industries; and develops and sells industrial automation control and information solutions. It is also involved in designing, testing, and implementing solutions for sewage, oily sludge treatment; and produces and sells integrated equipment and project services. In addition, the company develops, upgrades, and maintains online operation platform of gas stations, marketing, and promotion related services, as well as engages in production and efficiency of exploited oil wells business and plastic chemical cycle activities. Further, it provides equipment for oil and gas production and transportation, including heating furnaces, burner, waste water and oil treatment products and services, chemical recycling plan, automation system and service; and operates platform services comprising of intelligent marketing system and digitalization solution for gas stations. Additionally, the company offers equipment and accessories. Recon Technology, Ltd. was incorporated in 2007 and is headquartered in Beijing, the People's Republic of China.

CN Energy Group. Inc., through its subsidiaries, engages in the manufacture and supply of wood-based activated carbon primarily in China. The company's activated carbon is used in pharmaceutical manufacturing, industrial manufacturing, water purification, environmental protection, and food and beverage production. It also engages in the generation and supply of biomass electricity; production of steam for heating; sale of minerals, stone, metal materials, construction materials, wood, chemical materials and products, rubber products, and paper products; management and conversion of forest and natural ecosystem; and forest acquisition, rights transfer, and nurturing, and timber harvesting and processing activities. The company was incorporated in 2018 and is based in Lishui, China.