All bin types can successfully produce compost conditions that effectively break down certified home compostable products, so the choice of type and size comes down to individual preference, space, and management style. Personal composting habits can be adjusted to make any bin work well, but closed bins and open stationary bins usually create conditions that are closer to ideal for composting certified products. Small tumblers and insulated bins may require higher levels of management to produce the biological conditions that foster optimal breakdown of compostable products. Generally, the larger the bin size, the easier it is to create and maintain ideal composting conditions.
Feedstocks are the materials that are put into a compost bin. The materials, size of materials, and amount of each material type added to the compost bin all impact the composting process.
These practices will ensure that the microorganisms and fungi that are needed to break down compostable products are able to thrive. Not maintaining these recommended conditions will prolong, and could even prevent, product breakdown. While BPI has certified products for home compostability, composting results are not guaranteed, as they are reliant on proper composting conditions and practices in order to break down. Read below for BPI's recommendations.
Reducing the size of feedstocks increases the surface area available to microbes and accelerates product disintegration. Larger materials—including certified home compostable products—should be torn, shredded, or chopped before putting them into the bin.
Dry leaves, fresh green yard waste, and food waste are common feedstocks for compost. “Browns”, such as dry leaves, wood chips, and compostable products, are sources of carbon. “Greens”, such as fresh yard waste and food scraps, are sources of nitrogen. The optimal ratio of carbon to nitrogen feedstocks is 25-30 parts carbon to 1 part nitrogen, but an acceptable compost recipe may vary from 10:1 to 30:1 carbon to nitrogen.
Some compostable products may come into contact with meats, fats, or dairy products. While these items can be safely composted, they have greater potential to introduce complicating factors such as odor, pests, and pathogens. Home composters should think carefully about adding these feedstocks or compostable products that have come into contact with them.
Each composter is responsible for educating themselves on the risks and benefits of including these types of feedstocks, as optimal conditions and high management levels are necessary for compost to reach temperatures sufficient to mitigate pathogenic risk. The composter will need to make sure their home composting system will meet the special conditions required to kill the pathogens. This can be time and management intensive.
The moisture level in the compost pile should ideally be maintained at a constant 50% or greater. Piles can be watered or covered to control the moisture content. Moisture levels below 30% will slow down the biological activity needed to breakdown products.
Thoroughly mixing the compost materials at least monthly is recommended in order to add oxygen, distribute materials and moisture, and maintain porosity throughout the pile. Mixing the pile will reinvigorate microbial activity inside the pile, causing the compost temperature to rise. Piles can be mixed more frequently than once per month, such as when fresh feedstocks are added.
Maintaining the proper balance between moisture and oxygen is key to successful composting. Utilizing a bin with air holes or an aeration tube(s) can passively add oxygen, while regularly turning the material in the bin will actively introduce oxygen. A pile that’s too wet will likely not have enough oxygen, which would cause the decomposition to change from aerobic (with oxygen) to anaerobic (without oxygen) and become foul-smelling.
The biological activity of microbes consuming feedstocks creates heat, so an active compost pile will be warm. Adding fresh feedstocks, turning the pile, or adding water will reinvigorate microbial activity, causing a rise in temperatures. Ideal compost temperatures are between 113-150°F. While the outside ambient temperature will affect heat retention of the compost pile, management practices can help mitigate the effects of colder weather.
Certified home compostable products will fragment into increasingly smaller pieces as they break down into carbon, water, and organic matter in a home compost pile. Maintaining optimal conditions will accelerate this decomposition of compostable products. However, the timeframe required for compostable products to fully integrate into compost will vary widely, depending on the composting conditions, and may take up to 12 months or longer to fully break down. This is similar to how different types of food scraps break down at different rate; for instance, a banana peel will typically degrade faster than an avocado pit.
Following these recommended practices will help to ensure that the microorganisms and fungi that are needed to break down compostable products are able to thrive. Not maintaining these recommended conditions will prolong, and could even prevent, successful product breakdown. While BPI has certified products for home compostability, composting results are not guaranteed, as they are reliant on proper composting conditions and practices in order to break down.
The following organizations provide additional online information on how to compost at home:
Institute for Local Self-Reliance: https://ilsr.org/composting/home-composting/
Cornell Waste Management Institute: https://cwmi.css.cornell.edu/smallscale.htm
Ohio State University Extension: https://ohioline.osu.edu/factsheet/hyg-1189-99
Penn State Extension: https://extension.psu.edu/home-composting-a-guide-for-home-gardeners
Rutgers University Extension Service: https://njaes.rutgers.edu/fs811/
University of Minnesota Extension: https://extension.umn.edu/managing-soil-and-nutrients/composting-home-gardens#compostable-materials-882312
U.S. Department of Agriculture: https://www.usda.gov/about-usda/general-information/initiatives-and-highlighted-programs/peoples-garden/food-access-food-waste/composting#:~:text=Get%20composting.,add%20water%20to%20keep%20moist.
Composting classes are also often available through state extension services’ master gardener or master composter programs and through local governments. Check locally for programs near you.
