Backgrounder: Methane Emissions from Waste

Methane emissions from landfills and wastewater represent a much larger portion of the world’s methane problem than is typically understood.

In landfills, these emissions are created by the uncontrolled anaerobic decomposition of food, yard clippings, and paper/cardboard. In wastewater treatment plants, methane is often flared rather than used for energy.

Methane emissions from waste have been shown to be a larger problem than those from oil and gas operations in many areas that using enhanced measurement tools.

  • In California, satellite readings indicate landfills are the #1 source of methane emissions (41%)—more than the state’s significant oil and gas operations.
  • In Maryland, landfills were also found to be the largest source of methane in the state, not the natural gas industry as was previously thought. The 51,500 tons of methane released each year from Maryland’s landfills is four times the GHG emissions from the state’s average coal-fired power plant.

More than 43% of what gets landfilled in the U.S. is material that creates fugitive methane—food, yard clippings or paper/cardboard. U.S. landfills produce at least 888 billion cubic feet of methane every year.

  • If that methane were eliminated by diverting organic waste from U.S. landfills, it would have the effect of eliminating more than 695 million tons of CO2e/year (based on a 20-year time horizon), which is more than 13% of total annual U.S. carbon dioxide emissions.

Conservative estimates put global methane emissions from landfills and wastewater at 67 million metric tons of methane per year —20% of total methane emissions. This is based on estimates collected before aerial and satellite surveys, which have frequently shown far greater methane emissions from landfills than previously estimated.

The United States has just 230 anaerobic digestion facilities to upcycle organic waste into biomethane (also called renewable natural gas or RNG). By comparison, Europe has 738 such facilities.

Soluzioni

When organic waste is diverted from landfills, digesters can convert it to methane in a controlled environment, allowing it to be captured and used to displace natural gas in pipeline systems or to create renewable power. (While some landfills have gas collection systems in place to capture methane as it emits from the ground, this process is inefficient and allows most of the methane to escape to atmosphere.)

  • Today’s technologies can extract 90% of organics from mixed municipal solid waste at transfer stations and materials recovery facilities (MRFs). This has been found to more efficiently recover organics from landfilled waste streams than requiring people to separate food waste at their homes.
  • Wastewater treatment plants, which often have anaerobic digesters in place, can be used to co-digest food waste and wastewater biosolids, taking advantage of existing infrastructure to avoid landfills emissions, create biomethane, and displace fossil gas in the natural gas pipeline system. Currently, there are fewer than three dozen wastewater treatment plants producing biomethane in the U.S, suggesting a vastly under-tapped resource for managing landfill-diverted food waste.
  • Following digestion to maximize energy extraction, organics diverted from landfills can also be converted to nutrient-rich PFAS-free fertilizers through a cost-effective technology called pyrolysis. The carbon in digested and pyrolyzed organic material is effectively captured in soil—unlike the carbon in chemical fertilizers. Thus, anaerobic digestion of waste enables soils to serve as carbon sinks.

A Carbon-Negative Fuel Essential for Reaching Net Zero

Anaerobic digestion of food waste, sewage solids, paper and other organic material creates biomethane (renewable natural gas), a fuel that is carbon-neutral or even carbon-negative. While biomethane does emit carbon dioxide when combusted, the CO2 is a far less potent greenhouse gas than the methane that would have emitted from the landfilled organic waste, reducing overall emissions.

In addition, the carbon dioxide produced when biomethane is combusted comes from plant matter that already fixed this carbon from atmospheric CO2. In other words, the formerly living material from which biomethane is made took carbon dioxide from the air while growing. Therefore, the combustion of biomethane does not increase the amount of CO2 present in the atmosphere but it makes it circulate in short carbon cycles. Thus, anytime biomethane replaces fossil fuel, CO2 emissions are prevented. When fuel cell technology is used to convert biomethane to energy, emissions are reduced even further.

In addition, use of biomethane displaces the use of fossil natural gas and the greenhouse gas emissions associated with its extraction and combustion.

Even with ongoing electrification efforts in residential and commercial sectors, fuels are required for high-heat industrial processes, as well as for power grid reliability, for the foreseeable future. As such, carbon-negative fuels are necessary to reach net zero emissions.

Drivers of Reducing Methane Emission from Waste

To date, just eight states have enacted legislation to stop at least a portion of their food waste from going to landfills.

California’s legislation is the most sweeping, in that every municipality must divert 75% of organic material from landfills by 2025.

In addition to such mandates, biomethane production from food waste diversion is incentivized by the Federal Renewable Fuel Standard, Low Carbon Fuel Standards in California, and Oregon’s Clean Fuels Program, which have created markets for renewable fuel credits.

In addition, anaerobic digestion facilities (including wastewater treatment plants) can collect tipping fees for food waste, in the same way that landfills do.

In two states, biomethane production is also being incentivized through renewable gas standards—requirements that utilities acquire a portion of their natural gas in renewable form, similar to renewable portfolio standards (RPS) for electricity. Oregon was the first state to introduce a renewable gas standard, and in February 2022, California’s Public Utilities Commission also set biomethane targets for utilities, with a 2030 target of 12% of the state’s residential and commercial natural gas consumption in 2020

Who is Anaergia?

Anaergia was founded by an academic and environmentalist who became an entrepreneur to solve environmental problems. He initially founded Zenon in the wake of severe water pollution in the 1960s and 70s. After selling that company to GE in 2006, he eschewed retirement to address the climate crisis.

Anaergia’s leaders hold expertise in many arenas and are passionate about informing the public through journalists. We want reporters to bring light to the issue of methane emissions from waste and share accurate facts about the benefits of diverting waste from landfills and using it to make renewable fuel and organic fertilizer.

Beyond our own team we have many connections in the waste management, wastewater, and renewable fuels spaces.

Please feel free to reach out for an interview or simply for potential sources outside our company. We are happy to help.

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