Familiarize Yourself with Common Compost Production Equipment
Compost processing equipment and infrastructure are regularly some of, if not the largest, capital expenses for a composting facility. A facility’s equipment needs depend on several factors, such as:
- Quantity of material handled and or processed on a daily, weekly, or annual basis.
- Quality and type of feedstocks.
- Type of composting operation, such as static pile, windrow, or aerated static pile.
- Types and quality of end product required to satisfy customer base.
- Financial situation of the operation
- Legislative and/or permitting considerations.
- Diesel, hydraulic, or electric operational preferences.
The stages of the composting process require different types of equipment.
Volume reduction one of the first steps to turn feedstocks into compost. An initial volume reduction is the way to take raw feedstock and reduce its volume so that it is a more manageable and compostable material. A breakdown of some this equipment can be found below:
Horizontal and Tub High-Speed Grinders:
(on left of this paragraph show Ecoverse grinder, a bit lower down in the same paragraph show Morbark tub grinder) High-speed grinders are some of the most common machines used to break down feedstock for composting. These machines use a high-speed hammermill with aggressive teeth to grind material against a screen that sizes the material to a predetermined size. The sizing of the material depends on the site-specific compost recipe. These machines offer many advantages, such as impressive material throughput up to hundreds of yards per hour. With large industrial diesel engines, they typically have high fuel and maintenance needs. The aggressive hammermill, while providing maximum throughput, can cause issues with common contamination found in typical feedstocks. These machines also have the ability to create a spec mulch product, another common product found at composting facilities.
High-speed grinders are some of the most common machines used to break down feedstock for composting. These machines use a high-speed hammermill with aggressive teeth to grind material against a screen that sizes the material to a predetermined size. The sizing of the material depends on the site-specific compost recipe. These machines offer many advantages, such as impressive material throughput up to hundreds of yards per hour. With large industrial diesel engines, they typically have high fuel and maintenance needs. The aggressive hammermill, while providing maximum throughput, can cause issues with common contamination found in typical feedstocks. These machines also have the ability to create a spec mulch product, another common product found at composting facilities.
High-Torque, Low-Speed Shredders:
Developed in Europe, high-torque, low-speed shredders are growing significantly as a volume reduction solution for composters in the North America. These machines use slow turning shafts to shred material through a comb or a screen system. While they do not offer the small sizing or mulch producing capability of a high-speed grinder, they offer other significant advantages such as low fuel consumption, superior ability to handle contamination, and general low wear and maintenance needs.
Mechanical turning is a traditional way to add oxygen, homogenize the feedstock, and distribute moisture in a compost pile. There are several types of mechanical compost turners.
Tractor pulled, or “tow-behind” turners are the lowest cost and most common type of windrow turner available in the marketplace. Typically powered by the PTO of the tractor, these machines are most used in manure composting. They generally are offered in a smaller size range, and can be a great entry-level windrow turning machine for composters. These are limited by the tractor’s speed and power.
Self-Powered “Straddle” Windrow Turners
A self-powered turner is commonly seen at a larger and industrial composting facility. These machines “straddle” the windrow and use a large hydraulic or belt driven drum to turn the pile inside-out, redistributing moisture and oxygen, and further breaking down the material. These machines can range in machine widths from 10’ to 25’, allowing for a larger composting facility to turn multiple rows per day, and keep up with the demands of high-volume operation.
Trapezoidal / Side Turners
These machines are used to turn static or aerated piles without the typical windrow shape. They drive along the side of the pile, pulling in material and discharging it to one side.
A trommel screen uses a rotating drum screen to size feedstock and separate fine material of pre-determined size to make a product. Trommel screens are some of the most common screens used for composting, as they offer an ease of changing product size, ability to handle wet material, and multiple size ranges to fit most any operation.
Specifically developed for the organics market in Europe, a star screen is a large machine that uses a screen of hundreds of rotating stars to move and separate material. A star screen is a high-end, high-volume solution for making compost. They offer very high throughput potential, and many star screens can make 2 or 3 sized products at one time.
Scalping Screens / “Shaker Decks”
Available in a very wide range of sizes and price ranges, a scalping screen uses a flat vibrating deck to shake the material over a mesh screen to create 2 or 3 sized products. These versatile screens are traditionally used in the topsoil and aggregate markets, and can be challenging for a typical wet and sticky compost product, due to buildup of material on the screens.
A true game changer in the processing of pre-and-post-consumer food waste, a depackager is a machine that separates food waste from the bags and packaging it’s contained in. Depackagers are the best solution in the market to allow for large-scale processing of food waste with minimal contamination of the organic output. These machines utilize vertical or horizontal rotating mills to shear, but not destroy the packaging, allowing for the organics to be released but not contaminated.
A newer technology applied by composters to address the growing issue of contamination in composting feedstocks. These machines are varied in concept, but use water, air, suction, magnets or some combination to agitate and separate contamination from compost or feedstocks.
In-vessel compost equipment is growing in popularity with an increased need for composting in smaller commercial and institutional settings, and with requirements in some settings to capture or reduce odors or emissions.
The process takes place in an enclosed drum or container.How Within-Vessel Composters Work. Within-vessel composting is a way of composting materials, such as food or landscape wastes, within an enclosed drum. Conditions are maximized in the drum for standard temperature and moisture.
In some cases, covered static pile systems are considered as “in-vessel” as well, but generally the term is used for mechanical units.
Not all units that call themselves “in-vessel” composters are making plant-ready compost when it exits the system. See compostingcouncil.org/food-dehydrators to learn more.
Links and Resources
US Composting Council blog post: Machine Rates: Do You Know What Your Equipment Costs You?, https://www.compostingcouncil.org/page/Blog-CompostFacilityOperation
Compost Equipment Guide, https://www.compostingcouncil.org/page/EquipmentGuide
Post-Landfill Action Network In-Vessel Equipment Guide, bit.ly/Digesters-Resource