Composting and Food Safety
By: Allison Howell
In 2011, the FAO released a report with a startling statistic: nearly 1/3 of food produced in the world is wasted or lost. Since then, reducing food waste has become a hot topic 1. One popular method of reducing the amount of food waste sent to landfills at the consumer level is composting. Composting is a process of converting organic waste, such as fruits, vegetables and yard waste like leaves and grass clippings into a mixture for promoting plant growth, a “natural” fertilizer. This fertilizer can then be used to provide fuel for your plants, vegetable gardens, or window boxes. While commercially produced and distributed compost is subject to regulation by the Ohio EPA, compost created at a home residence is not subject to regulation or inspection. Without any sort of regulation into the safety of home-generated compost, risk arises in using the compost for vegetable or herb gardens, where the plant grown is intended to be consumed.
Today, there are lots of options for individuals to start composting. A quick search for “home composting” reveals a plethora of articles and guides for individuals to start composting. Some require the use of compost bins which can cost anywhere from $60 to upwards of $200, but you can also find DIY guides that require only space, time, and lots of browns (carbon-rich materials like leaves, newspapers, and twigs) and greens ( nitrogen or protein rich materials like grass clippings, fruit and veggie scraps, or egg shells).2 The EPA provides guidance on which waste items can be composted at home and which should not. While most yard and food scraps can be composted, some should be avoided for food safety and feasibility reasons. Dairy and meat may be hosts for harmful bacteria like Salmonella or E. coli. Composting contaminated foods would lead to the spread of pathogens onto the crops that is fertilized. Moreover, composting these items can attract pests or insects to the compost, which could again lead to transmission of pathogens.
However, for those low on space or time, but rich in browns and greens, community composting groups have begun to pop up in some neighborhoods. The mechanics of composting are the same, but the logistics make composting much easier (and possibly less stinky) for consumers. Composting programs such as the Compost Exchange in Columbus, Ohio provide subscribers with a plastic bucket and compostable liners to collect compostable materials and then collect the contents of the bucket to be composted at their own facility. Programs like this are becoming quite popular. A 2019 report from US Public Interest Research Group revealed that the number of communities offering composting programs like Columbus’ Compost Exchange has grown by 65 percent over the last five years3.
So what exactly happens to the compost generated by at-home composters or community composting groups?
- If you compost at home, you can reap the benefits of your hard work and use the compost as you wish to fertilize plants. Most composting groups also make the final compost product available to those that helped contribute the browns and greens necessary, sometimes free and sometimes for a small fee.
The final piece of this composting puzzle is where the food safety questions begin to arise. Here are some common questions about composting and food safety.
- Is it safe to use homemade compost as a fertilizer for home-grown fruits and vegetables?
- Probably. If you composted the correct materials and incorporated an appropriate amount of air and water to your compost.
- What if I accidentally composted something that I shouldn’t have? Can I still use my compost as fertilizer for plants that will be eaten?
- It depends. There are various reasons why certain items should not be composted and the resulting risk of incorrectly composting an item may vary based on that reason. To be safe, it would be best to not use for growing food, though you could use it for flowers or decorative plants.
- How do I know that my compost is ready to be used as fertilizer? If I use it before it’s ready, am I going to get sick?
- Compost is ready to use after it no longer resembles the starting materials, but looks like potting soil. It should feel cool and crumbly when touched4. It’s unlikely that compost contains pathogenic bacteria that could make you sick, but it could happen. There is always chance food could make us sick, and it is possible that harmful bacteria may be present in a compost heap at some time or another.
The rise of composting as a mechanism for reducing food loss (see the important distinction between food loss and food waste here), is a great advancement towards creating a more sustainable food system. But this excitement must be balanced with a conservative approach to and consideration of how composting might affect the safety of food, which it is used to fertilize down the line. To quote a 2018 review article on the topic “Understanding the mechanisms of pathogen survival during the composting process and mechanisms that reduce pathogen populations can minimize the risk of pathogen contamination in the cultivation of fruits and vegetables”5. An aptly-titled 2020 article from Food Safety News “Cook your compost to the same temperature as your burgers” provided several important calls to action for individuals looking to start composting. However, the first action item cited by Brian Bonner is to “educate yourself on composting’s benefits and risks” is perhaps the most important6. The act of composting is positioned uniquely between two major areas of food studies: food safety and food loss and waste. To make responsible decisions and minimize food safety risk while maximizing the benefit of reducing food waste and loss, education is an imperative first step. Learning about and incorporating an understanding of food safety risk in your approach to composting can help ensure that the compost generated by your efforts best nourishes plants without introducing additional food safety risks to the friends, family, or even strangers that may end up consuming compost-fertilized produce.
1. Food Loss and Food Waste. Food and Agriculture Organization of the United Nations
2. Vanderlinden, C. Which Items Are ‘Greens’ and Which Are ‘Browns’ for Composting? The Spruce
3. Composting in America | U.S. PIRG.
4. Composting | NRCS.
5. Gurtler, J. B. et al. Composting To Inactivate Foodborne Pathogens for Crop Soil Application: A Review. J Food Prot 81, 1821–1837 (2018).
6. Bonner, Brian. Cook your compost to the same temperature as your burgers. Food Safety News
Graduate Research Associate