In-Vessel Composting
Organic materials are fed into a drum, silo, concrete-lined trench, or similar equipment where the environmental conditionsincluding temperature, moisture, and aerationare closely controlled. The apparatus usually has a mechanism to turn or agitate the material for proper aeration. In-vessel composters vary in size and capacity.
Types of Waste and Waste Generators
In-vessel composting can process large amounts of waste without taking up as much space as the windrow method. In addition, it can accommodate virtually any type of organic waste (e.g., meat, animal manure, biosolids, food scraps). Some in-vessel composters can fit into a school or restaurant kitchen while others can be as large as a school bus to accommodate large food processing plants.
Climate or Seasonal Considerations
In-vessel composting can be used year-round in virtually any climate because the environment is carefully controlled, often by electronic means. This method can even be used in extremely cold weather if the equipment is insulated or the processing takes place indoors.
Environmental Concerns
In-vessel composting produces very little odor and minimal leachate.
Requirements
In-vessel composters are expensive and might require technical assistance to operate properly, but this method uses much less land and manual labor than windrow composting.
Results
Conversion of organic material to compost can take as little as a few weeks. Once the compost comes out of the vessel, however, it still requires a few more weeks or months for the microbial activity to stabilize and the pile to cool.
For more information on in-vessel and other methods of composting, please see:
- Biosolids Technology Fact Sheet In-Vessel Composting of Biosolids (PDF) (9 pp, 100K, about PDF)
- California Department of Resources Recycling and Recoverys (CalRecycles) In-Vessel Compost Technologies for Food Scrap Management

- Cornell Universitys Composting Resources

- King County, Washingtons Biosolids Recycling

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