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The Agricultural and Food Waste Methane Problem

Mark McDaniel and Thomas Parker Redick

The Agricultural and Food Waste Methane Problem
Bloomberg Creative via Getty Images

Methane (CH4) is a potent greenhouse gas, and it plays a significant role in contributing to global warming. In the United States, methane emissions primarily originate from three sources: agriculture, energy production, and landfills. This article explores the options for mitigating methane emissions from organics waste, with a particular focus on the potential for converting food waste into energy or compost, along with increasing efforts exploring emissions reduction innovations. The health of our planet, and future generations, depend on sensible management of these methane sources. What we do not manage today will surely damage the lives of future generations.

Methane emissions represent a crucial challenge in the battle against climate change. This is because “methane is more than 25 times as potent as carbon dioxide at trapping heat in the atmosphere.” In the United States, three primary sources contribute to methane emissions: agriculture, energy production, and landfills.

In comparison to the energy production issues facing the world, the methane emissions from wasted food are very manageable with existing technology. As a result, stakeholders in agriculture and landfill management should move quickly to develop optimized strategies for managing the methane-producing waste they generate. This is as simple as taking a potentially harmful food waste stream and making money from it by converting it to energy or into productive soil.

U.S. Methane Emission Sources

U.S. Environmental Protection Agency (2023). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021

U.S. Environmental Protection Agency (2023). Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2021

This chart will change over time, as the landfill and agriculture side (fully 54 percent of the total) solves its food waste problem. Unfortunately, the energy sector may greatly expand its current share under the natural gas share of 29 percent, probably becoming the largest source by far of methane.

Methane in Agriculture

  1. Livestock. Livestock farming is a significant source of methane emissions. Livestock naturally produce methane by enteric fermentation (natural part of the digestive process in ruminant animals such as cattle, sheep, goats, and buffalo) and the breakdown of waste manure. The question arises whether it is more beneficial to manage livestock waste through composting or as a source of bioenergy. This section discusses the potential benefits and drawbacks of both approaches.
    1. Enteric fermentation. While enteric fermentation is currently uncontrolled, there are potential paths for mitigation, including genetic selection, nutritional intervention, food additives, and source modeling to help better plan and mitigate methane emissions. The U.S. Environmental Protection Agency (EPA) can incentivize these technologies by subsidizing technology and forcing implementation via regulation.
    2. Composting. While many studies rank bioenergy above compost due to initial carbon dioxide (CO2) loss to the atmosphere, they fail to include the benefits of compost application as fertilizer. Compost as fertilizer is a carbon-negative process that can have long-lasting effects. “A series of experiments done in Northern California shows that one application of compost started a chain reaction of carbon sequestration that will last decades. Therefore, compost and mulch applied to many types of land may be the single greatest weapon in the fight to reduce the effects of climate change.”
    3. Bioenergy. Some experts have recommended that the current livestock model be abandoned in favor of a more sustainable agriculture––e.g., using its manure for soil amendment, not energy. Peter H. Lehner & Nathan A. Rosenberg, Farming for Our Future: The Science, Law, and Policy of Climate-Neutral Agriculture, Environmental Law Institute (2021):

      This article addresses the political reality that our love of cheap meat and abundant energy will drive the current EPA effort to reduce livestock net emissions using bioenergy, while moving landfills and composters to a new level of food waste management that cuts its methane emissions considerably.

  2. Organics and food waste. The management of organic and food waste is crucial for reducing methane emissions. This section explores the merits of landfill bioenergy versus compost sequestration and emphasizes the need for efficient and sustainable waste management practices in agriculture.
    1. Landfill bioenergy. The EPA has promoted use of bioenergy in landfills with states joining in, providing regulatory oversight to reduce methane emissions from landfills. This is a complex area of state and federal law, as the optimum approach to capturing methane from landfills develops.

      A 2021 review found that the EPA lists three types of bioreactor landfills: aerobic, anaerobic, and hybrid aerobic-anaerobic. Since many traditional municipal solid waste landfills are operated with leachate and condensation recirculation, they are “partial bioreactor landfills” and late to the program. All involve the addition of water to the landfill to promote biological decomposition. Largely considered experimental systems, the body of knowledge governing bioreactor landfill operations continues to grow.

      The EPA is moving forward to create more bioreactor landfills such as the Buncombe County Bioreactor, but it might never be able to convert all the “dry tomb” (no water added) landfills into a more sustainable energy-producing landfills. Since landfills have limits, composting will be required for some of the food waste we create.

    2. Composting. Food scraps and yard waste currently make up 20 to 30 percent of what we throw away. Both the EPA and U.S. Department of Agriculture (USDA) have programs to reduce methane emissions from food waste, with various activities and partnerships helping to reduce food loss and waste. Interagency efforts are also underway with EPA, U.S. Food and Drug Administration (FDA), and USDA support. The EPA is working on the industrial side of food waste to reduce, recover, or reuse food waste and has developed a hierarchy of preference for solutions—the most recent, published in October 2023, is the Wasted Food Scale, which moves composting up the ladder from previous versions.

Wasted Food Scale

U.S. Environmental Protection Agency (2023). Industrial Uses for Wasted Food

U.S. Environmental Protection Agency (2023). Industrial Uses for Wasted Food

Composting helps sequester carbon in soil, so keeping some food waste out of landfills will reduce methane greenhouse gas emissions. The USDA announced new investments in June to support urban agriculture, including $10.2 million in new cooperative agreements to expand community composting and food waste reduction, and $14.2 million in new grants to support the development of urban agriculture and innovative production projects.

While many sustainability studies rank bioenergy above compost due to initial CO2 loss to atmosphere, they fail to include the benefits of compost application as fertilizer that sequesters carbon, creating sinks with plants. Compost as fertilizer is a carbon-negative process that can have long-lasting effects. “A series of experiments done in Northern California shows that one application of compost started a chain reaction of carbon sequestration that will last decades. Therefore, compost and mulch applied to many types of land may be the single greatest weapon in the fight to reduce the effects of climate change.”

Several states are seeing the benefits of compost versus bioenergy, and are likely to lead the way, as other states move to follow California. A recently passed law there will soon stop all organic waste––food and greenery––from going to California landfills. This will greatly reduce emissions of methane gas where implemented. This change will likely not only change the way residents sort trash, but it will also stop food waste from going from restaurants to landfills. From food scraps to fruit trees, all organic trash will have a new use: beneficial compost.

Conclusions

The EPA is taking steps to incorporate bioenergy solutions into landfill management, while supporting efforts to control industrial food waste better. These efforts will reduce food and agriculture sector waste that ends up in landfills, and anything organic in landfills will increasingly create bioenergy. EPA envisions the convergence of these two sectors, with landfills efficiently converting the majority of available feedstocks into bioenergy, and farms utilizing wasted food through composting practices.

Moreover, homeowners and communities engaging in composting can make a significant contribution to reducing methane emissions at the local level. In conclusion, addressing methane emissions requires a multifaceted approach that combines policy, legislation, technology, and sustainable practices in agriculture, energy production, and landfill management to mitigate the impact of this potent greenhouse gas on our climate and environment. Many of these solutions are financially beneficial, producing fertilizer and/or energy. We owe to the planet that created us to take better care of this methane emitted from our waste food.

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