At all facilities, wet feedstocks are off-loaded into indoor, concrete bunkers where an extraction system collects the air and sends it on to the biofilter to help control odors. High-moisture materials are dropped onto a bed of very dry amendment or compost to absorb free liquid.
Dry feedstocks, like the woody fraction of yard waste, shredded pallets, etc., may be stored on a small, outdoor pad until needed for blending.
The off-loading bunker or “pit” is actually an extension of the blending area floor. Trucks typically tip from tan outdoor ramp into the bunker. However, at some facilities, trucks may tip under a shed-type roof or back into the building before tipping. This photo shows the indoor off-loading area at McGill’s Glenville facility near the city of Cork in Ireland where trucks can be totally enclosed behind the garage door prior to off-loading. This is an extra safeguard to mitigate odor generation in highly-sensitive areas.
Truck and trailer washdown
This photo shows the washdown area at McGill-Merry Oaks near Raleigh, NC.
Tractor-trailer rigs are pressure washed after off-loading to eliminate odors and minimize track-out. The concrete apron is sloped so wash water drains into the pit for use in the composting process. Non-toxic detergents and cleaners keep our microbes safe.
Bucket blending gets the job done
The way we blend isn’t really innovative. Tried and true would be more accurate. We have used mechanical mixers and conveyor systems, but they were never as efficient, reliable or flexible as good old bucket blending, which is now the method of choice at all facilities. The pictured blending area is also at our facility in Glenville, Ireland.
Encapsulation provides control
When we talk about controlling the process, we mean it.
Residuals and by-products, blended to prescribed ratios based on available feedstocks, are placed inside concrete-encapsulated bays designed with a special floor to accommodate our aeration system. Sensors are placed and the doors closed, totally encapsulating the admixture.
The composting mass is not touched again until the computer tells us the process is complete. Some facilities have metal doors (like McGill-Glenville, pictured in top photo on this page); others use a geotextile.
The translucent panels on the roof of this bay at the Merry Oaks plant protect the composting process from weather influences, seal the bay for air extraction/biofiltration, and improve visibility for workers.
At McGill-Glenville, the aeration system is located inside a building in the attic space above the encapsulated bays, giving each bay a concrete “roof.” For bays with translucent panels as a roof, system components are outside, along the back wall.
Aeration delivers oxygen to the microbial populations responsible for biodegradation and removes the heat generated by their feeding activity, maintaining temperatures within the specific range required for happy microbes. Air is pushed up and through the composting mass, while extraction fans pull air off the pile and away from work zones within the building. Process air is piped to a biofilter.
Computers control processing and curing
Computers at all facilities regulate the aeration system and monitor temperatures, which are continuously recorded to confirm processing goal attainment for regulatory reporting. This particular system is proprietary, designed by and for McGill.
The time:temperature ratio of our process mimics pasteurization, even though no external heat is applied. The heat generated during composting is provided by the feeding activity of the microbial populations responsible for biodegradation.
Temperature sensors embedded in the composting mass detect and report heat fluctuation, sending wireless signals to the microprocessor. The computer, in turn, adjusts air flow to the composting mass.
This holds temperatures within an ideal range and greatly accelerates the composting process, eliminating the hot-cold cycling common to uncontrolled composting systems.
Products formulated for performance
Screening equipment customized to meet McGill specifications results in a compost with even consistency batch after batch.
After screening and curing, our compost is ready for market as an EPA Exceptional Quality (EQ) product.
McGill-branded products include McGill SoilBuilder, a premium quality, 100% compost, as well as a number of derivative products and blends for specialty markets. SoilBuilder is the base for all McGill blends.
McGill SoilBuilder is U.S. Composting Council certified and tested monthly in accordance with the U.S. Composting Council’s Seal of Testing Assurance (STA) program.