Composting, Worms, and the Climate Crisis

Reducing food waste is one of the most important things we can do as individuals to fight the release of greenhouse gases (GHG) into the environment. The food supply chain accounts for nearly a third of worldwide GHG emissions. These gases contribute to climate change, which disproportionately burdens developing countries. The Food and Agriculture Organization (FAO) of the United Nations estimates that, if the world’s food waste was a country, it would be the third-highest emitter of GHGs, behind only the U.S. and China. While the majority of food waste is the result of food rejected for imperfections even before it reaches consumers, consumer-generated food waste in the U.S. contributes 2% of yearly GHG emissions nationally. Reducing such consumer food waste can make a meaningful contribution toward the reduction of GHG emissions, including through simple measures such as buying only what is needed, using every bit of it, and accepting imperfect fruits and vegetables. However, one measure that remains underutilized is composting of food waste. Empowering consumers to engage in composting can help mitigate GHG emissions as well as produce valuable environmental co-benefits.

It is estimated that a worldwide effort to implement composting could reduce GHG emissions by 2.3 billion tons over the next 30 years. Composting converts organic waste into soil carbon, reducing the methane produced by decomposing food waste in landfills. Compost made from food waste can be put back into the agricultural system, improving soil quality and increasing productivity. Adding compost to the soil also aids in long-term carbon sequestration, because composted material provides the carbon and nutrients necessary for the soil microbes that create stabilized forms of carbon in soil. On a large scale, composting provides the interconnected benefits of increased soil health, reduction of GHGs, and improved agricultural productivity. On a smaller scale, composting makes it easier to produce food at home. Sourcing food locally can help reduce the GHG emissions from fossil fuel combustion in the agricultural supply chain.

Vermiculture, or composting with worms, provides an efficient, odorless, and space-conscious alternative to bin composting. Worm bins can easily be kept in small spaces, such as under the sink, or outdoors (with sufficient insulation). While many species of worms can be used in vermiculture, red wigglers (Eisenia foetida) and European nightcrawlers (Eisenia hortensis) are the most commonly used. These worms can eat a combination of food waste and paper products. Red wigglers eat about half their weight in food waste every day—that means 1,000 worms (the most common number to start with) can eat about half a pound of food per day. European nightcrawlers are commonly used in combination with red wigglers because they grow much larger and feed in the lower layers of the bin. As they eat, composting worms excrete castings, a nutrient-rich humus that can be used as a safe, organic fertilizer. Worm casting fertilizer is especially valuable because it contains beneficial soil microbes, has a neutral pH, and, unlike other fertilizers, will not burn plants because its nitrogen is released slowly. Vermicompost has also been shown to reduce plant disease—beneficial microbes from worm castings can colonize the surface of a seed, protecting it from infection. Using compost and worm castings as natural fertilizers also provides an opportunity to reduce water pollution and greenhouse gas production. Excess fertilizer pollutes waterways and can be converted by microbes to nitrous oxide, a greenhouse gas that is 300 times more potent than carbon dioxide.

Bin composting can be time-consuming, and takes up more space and effort than many can dedicate to it. However, vermicomposting is a concrete step that individuals can use to take on climate change, especially if they feel helpless in the face of the climate crisis and would like to take responsibility for their food waste. It is easy, fun, and can be done almost anywhere. I began worm farming in July, and already have a colony that consumes the weekly waste of a family that shops in bulk at Costco. While the benefits worm castings have provided to my garden are hard to measure, my anecdotal evidence is that there was an explosion of growth in the weeks following the first introduction of vermicompost. My worms keep pounds of food scraps and paper products from landfills monthly, and, as the colony grows, they will eat more.

As the climate crisis worsens, contributing to droughts and food shortages, we should take advantage of every opportunity to reduce GHGs and increase agricultural efficiency. Municipal governments should reduce GHG emissions from food waste by incorporating vermicompost into waste removal. Governments should also provide vermicompost education to citizens, like this instructional video from the City of Sydney. Governments could also encourage vermicomposting with tax incentives for restaurants and grocery stores, which are perfect candidates for vermicomposting because of their high volume of organic waste. Vermicomposting is just one of the ways in which we can reduce waste, increase the availability of locally grown food, and take responsibility for our emissions in high-income countries.

Katherine Pond

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