Compost and Climate Change

Carbon-rich gases in the atmosphere, such as carbon dioxide and methane, absorb heat from the sun and keep it from escaping out into space. You can think of the amount and accumulation of these gases like a warm blanket—the more blankets on the bed, the more heat is kept inside. As more carbon is emitted into the atmosphere, more of these “blankets” are layered around the earth, trapping more and more heat inside.

Food production is intimately tied to the carbon cycle and therefore with climate change. For example, in 2009, emissions associated with food production, processing, transport, and disposal accounted for 13 percent of US greenhouse gas emissions. Approximately 42 percent of US greenhouse gas emissions are associated with the energy used to produce, process, transport, and dispose of the food we eat and the goods we use (Opportunities to Reduce Greenhouse Gas Emissions through Materials and Land Management Practices, 2009).

Sending organic waste to landfills results in the highest greenhouse gas emissions scenario when compared to composting and anaerobic digestion with gas or heat capture (Nordahl et al., 2020). Moreover, diversion of organic waste to compost and application of that compost to agricultural lands results in the uptake of greenhouse gases because soil health improves. In turn, healthy soil leads to healthier, more productive plants. Specifically, applying compost increases plant productivity due to improved soil structure, improved water availability, and improved nutrient availability. These improvements made through the application of compost can be long-term (Ryals et al., 2014).

Although organic material breaks down in both landfills and composting processes, the effect on the atmosphere is dramatically different. In landfills, the practice of packing in waste of all kinds—for instance, plastic bags of yard waste packed in with building refuse and food waste—leads to conditions where atmospheric oxygen can not penetrate into the pile. As a result, many areas packed with organic waste are not exposed to oxygen. These organic wastes get broken down by the kinds of microbes that generate methane as a byproduct of their activity instead of microbes that use oxygen to generate carbon dioxide. Although carbon dioxide is a harmful greenhouse gas, methane is much more potent, and thus is a thicker “blanket” than carbon dioxide. By composting these wastes instead of landfilling them, you ensure that oxygen is available to the microbes, so that they can prevent methane production while making a valuable soil amendment!

An additional benefit of composting is the reduced need for inorganic fertilizers. Nitrogen fertilizer production is an extremely energy-intensive process. Phosphorus and other minerals require mining and transport costs. By reusing the waste material in food production, the nutrients from the browns and greens stay on the land to be taken up by the next generation of plants and animals.