On-Site Composting Using Large Composting Units — California Grey Bears Food Scrap Diversion Project
California Grey Bears have completed a project to evaluate on-site composting of food scraps to reduce disposal costs. Using two Earth Tub composting units, the Grey Bears will save $2034 per year on hauling and disposal costs.
Performance of the Composting System
The Grey Bears used two Earth Tubs to compost their food scraps. Earth Tubs are small-scale, in-vessel (completely enclosed) composting units. They are designed to compost organic materials at the sites where they are generated.
The Earth Tubs processed about 3 cubic yards (1112 pounds) of food scraps per week. Earth Tubs are capable of processing as little as 50 pounds or as much as 150 pounds of organic material per day. The modular design of the system allows it to be adapted to a wide variety of applications.
Earth Tubs have been developed specifically to meet the needs of food handling businesses-food stores, colleges, hospitals, camps, restaurants, caterers and cafeterias. For more information on the Earth Tub, visit the manufacturer's website: www.gmt-organic.com and check out the Products page.
About the California Grey Bears
Grey Bears is a non-profit that distributes food to seniors and the disabled through a Brown Bag Program. Each year, Grey Bears provides over 100,000 'Brown Bags' of recovered food to seniors and people with disabilities.
Each week, approximately one ton of the food that is collected is discarded, primarily due to deterioration.
The in-vessel system was used to compost discards from the Brown Bag Program as well as food scraps and biodegradable table service from the Grey Bears' annual Holiday Dinner. Compost is sold through the Grey Bears Thrift Store. For more information on the California Grey Bears, visit their website:
http://www.steiny.com/sc/orgs/greybears/
Economics of On-Site Composting
By composting food scraps in the Earth Tubs, Grey Bears will avoid disposal of 29 tons of garbage per year. Savings on disposal and hauling will be $2034 per year. Grey Bears will sell the compost in their Thrift Store for $2 per bucket, for an annual revenue of $2102.
The warehouse supervisor spends about one hour per week overseeing the project and the balance of the labor (about 4.5 hours per week) is provided by volunteers, for a total annual labor cost of $780. Electricity cost is estimated at $100 per year. Equipment and installation cost of $17,802 included the two Earth Tubs, a cement pad, and electrical and sewer connections.
Payback time for the installation of the two Earth Tubs will be about 5.5 years.
Educational and Environmental Benefits of the Project
