The waste-management industry in the United States has become a favourite among environmentally conscious investors due to its efforts to recycle trash and to harvest landfill gas for use as an alternative source of energy.

As a benchmark for socially aware investing, the Dow Jones Sustainability Index Index features major firms such as Waste Management Inc and Republic Services Inc. (RSG.N). Both Bill Gates and Larry Fink, founder of BlackRock Inc. (BLK.N), who are leading advocates for corporate climate action, are among the firms’ major investors.

According to an aerial study conducted by California air-quality regulators, the waste industry may be causing far more harm to the environment than investors believe. Landfills identified as “super-emitters” accounted for 43% of total methane emissions, far outpacing both fossil fuel and agricultural sources.

Since 2016, the flyovers have been carried out by NASA’s Lawrence Berkeley National laboratory in Pasadena and the leak detection firm Scientific Aviation. Republic Services as well as Waste Management, two of the largest U.S. landfill operators, were found to be leaking methane at rates up to six times higher than the EPA’s facility-level estimates (EPA). “Super-emitter” waste disposal facilities are located in California.

Federal estimates for methane emissions from landfills were found to be 2.27 times higher than those from waste companies, which use EPA methodology.

According to the findings of a California study, the waste management sector is playing a much larger role in stimulating climate change than previously thought. It’s possible that the surveys will uncover flaws in United Nations guidance for estimating methane emissions, which are followed by major governments, including the United States.

The Los Angeles Times reports that the city’s mayor, Antonio Villaraigosa, has been Recycling trash as well as harvesting landfill gas as an alternative energy source has made the U.S. waste management industry a favourite of investors who care about the environment.

“Waste management is one of the biggest emitting industries,” he said.

Gates, who recently wrote a book titled, “How to Eliminate a Climate Disaster,” owns and over a 1/3 of Republic Services, which provides waste management services. On the basis of his individual investment vehicle and the Bill and Melinda Gates Foundation Trust, he has an estimated 8 percent stake in Waste Management, according to financing disclosures. Republic Services and Waste Management each have a 4.6 percent and a 5.0 percent stake in BlackRock, respectively, primarily through funds which track third-party indices.

Gates and BlackRock representatives did not respond to requests for comment for this storey.

The inclusion with in Dow Jones sustainability indexes is based on S&p scores for a host of environmental, social, and governance criteria. Waste Management has the best environmental score in the commercial services industry and a climate change strategy score that is very close to perfect. Waste Management does have the highest environmental score. Republic Services was also praised for its climate strategy.

In a statement, Republic Services as well as Waste Management said that they were working with California flyover questionnaires in good faith.

Waste Management has announced that it is stepping up its efforts to reduce landfill methane leaks, such as better monitoring, the addition of more soil, and the capture and repurposing of the gas.

For Republic Services, aerial survey data symbolises a snapshot of its facility’s emissions, which may not accurately reflect the company’s daily operations. It claimed to be a pioneer in environmentally friendly landfill management. ‘