Technologies: Within-Vessel Composting

Commercial vendors are promoting within-vessel (also known as in-vessel) composters to California businesses and institutions, such as restaurants, hotels, grocery stores, universities, prisons, and dairies, as a solution to managing that generate large quantities of food waste generated on-site. The following information may be helpful when evaluating whether this type of technology is suitable for your facility.

CalRecycle strongly recommends that food waste generators contact local government’s environmental/public health agencies for assistance in meeting local program requirements based on the type of technology and proposed end use for the products created.

How Within-Vessel Composters Work

Within-vessel composting is a way of composting materials, such as food or landscape wastes, within an enclosed drum, silo, bin, container, etc. to control emissions and maintain uniform conditions of temperature and moisture,. There are a wide variety of products and manufacturers on the market, and a significant variation among the technologies available. Before purchasing any technology, extensive research is recommended.

Things to Consider

• Conduct a waste audit to understand the type and amount of organic waste you generate. This will help as you research and find a properly sized composter.
• Composters can handle anywhere from 50 lbs. to thousands of pounds of materials per day.
• The composter may require electricity or water connections. They are typically installed in commercial or industrial settings where food waste or other organic waste are close by. The goal is to manage the wastes on-site.
• Most composters need bulking agents such as wood pellets, almond hulls, sawdust, leaves or wood chips.
• Most have a rotation device to turn the materials and some monitor temperature, moisture, oxygen, and odor.
• While materials may break down quickly, the material that comes out of the composter (output material) is not mature compost. Compost is the result of complex chemical and biological changes that take weeks or months, not hours or days. Mature compost has reached a stage of reduced biological activity as indicated by reduced temperature and rate of respiration below that of active compost. Most output material requires additional curing outside of the composter to finish the composting process.
• Know how much space is available on-site to store the composter, equipment, and finished compost.
• Removing food from the waste stream can lead to reduced hauling and disposal costs.
• Lab analysis may be required to determine if the finished material meets state and local laws for land application or compost.