Controlling reversing aeration

Engineered Compost Systems’ (ECS) latest automated control package includes the implementation and control of reversing aeration, which means alternating automatically between positive or negative aeration modes depending on pile conditions. “We’ve refi ned air handling and offer in one control package: reversing and recirculating aeration, control of fresh air added into the system, and control of the process exhaust air temperature headed out to the biofi lter,” explains Tim O’Neill, ECS President. The reason for reversing the aeration direction is that it keeps the compost pile much more uniform in terms of temperature and humidity. Anytime air is run in one direction (through a compost pile) the point at which air comes in is cooler than the place where it exits, (air heats as it runs through). The initial point of contact is typically close to ambient, whereas the temperature at the exit point could be upwards of 80 degrees C, although 65 to 70 degrees C is more common. It is possible to see as muchas a 60 degree differential from inlet to exit temperatures. Portions of the compost pile could be below thermophilic temperatures while others could be much hotter (and higher temperatures produce more odours). By reversing the aeration at set temperature differentials, the temperature gradient in compost piles becomes more uniform. This is especially important for facilities complying with time and temperature protocols set by regulatory agencies.ECS’s CompTroller real-time feedback system works with a wireless transmitting temperature probe and automatically adjusts fan speeds, controls the volume of air to a given compost-ing zone or vessel, controls the direction of air flow (positive or negative), and controls the percentage of recirculating process air.