Composting is an endpoint that currently handles roughly 9% of generated MSW(1) and is viewed as a critical part of waste diversion. However, information and data regarding composting operations has historically been lacking. The newly released Composting State of Practice, a collaborative report by the Environmental Research & Education Foundation (EREF), the United States Composting Council (USCC), and the Desert Research Institute (DRI), provides details on the current landscape of composting across the United States.
- Windrow composting stands out as the most widespread method among facilities, with 60% adoption. This technique involves organizing organic waste into elongated heaps known as windrows. These rows are systematically turned to blend the materials and introduce air, creating an ideal setting for aerobic decomposition.
- Following windrow composting in popularity is the Aerated Static Pile (ASP) method, utilized by 31% of facilities. ASP composting enhances the decomposition process by actively aerating the organic matter. This is often achieved through a network of pipes that ensure the maintenance of essential oxygen levels for effective breakdown.
- Static pile composting is another method employed by 24% of facilities, bearing similarity to windrow composting but with less frequent turning. This technique depends on passive aeration, leveraging natural air flow to assist in the composting process. It’s particularly suited for materials that necessitate extended periods for decomposition.
- In-vessel composting, although less common at 8.6% usage, offers a more regulated composting approach. This method involves processing organic materials within enclosed containers, such as drums or silos. While it supports a wide variety of waste types, the requirement for advanced infrastructure often translates into higher initial costs.
In addition to the detailed composting practices outlined, the report unveils significant growth and evolution within the composting industry. Between 2016 and 2021, the number of composting facilities surged by 55%, while the tonnage of organics processed saw an 83% increase. It also highlights notable regional variations, with the Pacific and Southeast regions managing a substantial portion of organics, despite having fewer facilities compared to the densely populated Northeast.