Millions of tons of compostable materials --- including cooked vegetables and other food wastes --- end up as waste in landfills instead of being converted into valuable nutrients. Composting cooked vegetables is slightly more complicated than composting yard waste like grass and leaves, but if managed properly, this type of food waste can indeed contribute to a rich soil amendment. (See References 2)
Once cooked, vegetables break down and start to rot very quickly. Rotting vegetables cause unpleasant odors, and if too many cooked vegetables are included in a compost pile, the smell may attract pests like rodents and flies. Cooked vegetables are also generally higher in nitrogen than yard waste (see References 1, page 15), so balancing the carbon-to-nitrogen ratio of the pile is vital for success.
Composting relies on a carbon-to-nitrogen ratio between 30:1 and 45:1 (see References 1, page 11). Any higher, and the pile does not heat properly. Any lower, and the pile will smell bad. (See References 1, page 8) Cooked vegetables range between 11:1 and 19:1, so without adding an additional source of carbon, they would have too much nitrogen to compost successfully. Adding an equal amount of oat straw, which has a ratio of 60:1, would result in a carbon-to-nitrogen ratio between 35.5:1 and 39.5:1, which is within the acceptable range. (See References 1, page 20)
Too much moisture in a compost pile prevents oxygen from infiltrating and leads to smelly, anaerobic decomposition. Cooked vegetables contain about 87 percent moisture by weight --- well above the ideal level of 50 percent (see References 1, page 21). Fortunately, high-carbon materials like paper, straw and sawdust tend to be low in moisture. Check the moisture of the pile after the ingredients are mixed by squeezing a handful of it. Only a single drop of liquid should emerge. (See References 1, page 8)
Rotting food is unsanitary, but allowing small amounts of cooked vegetables to decompose aerobically in a well-maintained compost pile effectively kills most of the pathogens as long as the temperature in the pile reaches temperatures between 131 degrees and 160 degrees Fahrenheit. (See References 1, page 9) Never site a compost pile in an area where runoff is a problem; if liquid leaches out of the pile, it could end up in waterways (see References 1, page 16). Keep the pile covered in areas where rain could make the pile too wet (see References 1, page 13). Don't use compost until it is crumbly and homogenous (see References 2).
Based in central Missouri, Rachel Steffan has been writing since 2005. She has contributed to several online publications, specializing in sustainable agriculture, food, health and nutrition. Steffan holds a Bachelor of Science in agriculture from Truman State University.
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