Commercial & municipal composting
Challenges of Digestate Composting
Composting the digestate from anaerobic digester (AD) facilities involves similar challenges as biosolids and commercial composting facilities: facilities need to operate efficiently and produce valuable pathogen-free compost products while managing environmental factors such as stormwater, leachate and odors. GMT’s partnership with Compost Systems GmbH of Austria brings decades of experience and many successful integrations of industrial composting facility design at AD facilities, combined with GMT’s experience designing and equipping many of the largest industrial composting facilities in N. America.
Composting the digestate outputs of AD facilities presents a compelling economic and environmental opportunity. Most AD facilities in N. America do not generate significant income from the sale of the digestate materials coming out of their AD process. In many cases, disposal of digestate is a cost factor for AD facilities.
Digestate is typically a heavy liquid material that cannot be economically transported to farms for field application, and the material has low value in terms of a soil amendment. In some cases digestate is piped to sewage plants for pathogen-treatment before it ends up in our waterways, wasting valuable nutrients and causing potential nutrient-loading harm to watershed ecosystems. Some states, such as Texas, have outlawed the spreading of untreated AD digestate on farm fields.
Digestate does contain valuable but unstable nutrients that when processed in an aerobic composting facility can produce compost products with high market value.
Another compelling reason for AD facilities to co-locate composting infrastructure on-site is this enables them to accept compostable packaging and biodegradable plastics. These materials cannot be effectively processed via anaerobic digestion, however many AD facilities are processing large volumes of food waste that often come co-mingled with compostable packaging and flatware.
For more information about how anaerobic digester facilities can best integrate composting read this White Paper in Waste Advantage Magazine. This white paper explains in detail how co-location of aerobic composting infrastructure at AD facilities offers significant operational efficiencies and compelling economic and environmental upside. While composting of digestate has become a standard practice in Europe and other markets, in N. America the majority of AD facilities are not yet composting the digestate outputs.
Stormwater Management
With PFAS and groundwater concerns on the rise, it has become more pertinent to ensure contaminated runoff is contained and properly treated. Our reliable and cost-effective solutions ensure that all contact water is controlled and either treated prior to discharge, or reused in the composting process.
Pathogen Destruction
GMT’s deep understanding of aeration requirements, compost recipes, and temperature monitoring ensures outstanding pathogen destruction, with automated temperature tracking in exportable csv files.
Odor Management
The number one reason for facility closure is odor violations. We’re proud to report that none of our clients have been shut down due to odors. Our systems allow you to operate even in the most densely populated regions.
Permitting and Public Relations
Commercial and municipal composting facilities require extensive permitting. Through decades of experience, we have learned how to work with regulators to permit facilities that protect both the environment and objectives of our clients.
Our Solutions
We provide composting technology, facility design and consulting services to hundreds of commercial and municipal composting facilities of all sizes around the world. Comprehensive planning and operational consulting are core to every project.
1. Turned Aerated Pile (TAP)
The Turned Aerated Pile (TAP) process is the fastest way to make compost on a large scale. A six acre TAP site with two equipment operators can process over 300 tons per day (100,000 tons per year) from the initial grinding process to the final loadout making this the most streamlined and profitable system available today.
Low
Opex
Small
Footprint
High Quality
Compost
3+ Week
Active Process
2. Aerated Static Pile (ASP)
ASP composting eliminates the need for mechanical turning of the material, while speeding up the composting process to just 30 days, plus 4-8 weeks curing time (compared to 6+ months with turned windrow composting). Our ASP systems can reduce footprint and material handling costs by as much as 75% when compared to windrow composting.
Low
Opex
WebMACs
Controls
Low Handling Costs
4+ Week
Active Process
3. Aerated Static Pile (ASP) + Compost Covers
ASP technology combined with our PFAS-free geomembrane covers can eliminate 90%+ emissions and VOC’s from the composting process. Our Fleece cover systems offer less odor control than geomembrane covers but are much less expensive and offer higher breathability for the increased volume of moisture loss desired when composting AD digestate.
Medium
Footprint
High
Opex
Low
Odor
6+ Week
Active Process
4. Tunnel Composting System
The CompoBox Tunnel System is the most cost effective in-vessel composting system on the market. Each CompoBox is enclosed within a hoop house and accessed through hydraulic load doors. Once filled the CompoBox tunnel system processes the feedstocks in positive, negative or reversing aeration capturing and treating all exhaust air.
Low
Opex
Fully
Enclosed
Minimal
Odor
4+ Week
Active Process
Related Projects
Learn More About Digestate Composting
“Phoenix has authored one of the most remarkable sustainability turnaround stories in the country, and our new composting facility starts an important new chapter. This award is a testament to our partners and their commitment to make Phoenix one of the most sustainable and resilient cities in the world.”
Greg Stanton, Mayor, City of Phoenix
