This past week the composting team constructed an aerator to test the feasibility of utilizing an aerated windrow system for composting at Clemson. Adequate oxygen levels are necessary for the microbes, responsible for the composting process, to thrive. If oxygen levels are insufficient, the process becomes anaerobic and methane is released into the atmosphere. An easy way to determine if the appropriate levels of oxygen are present in the windrow are by monitoring temperature and checking for ash in the pile. Immature compost should be above 131 degrees if oxygen levels are sufficient. The presence of ash in the pile, even when temperatures are high, indicate that the process has gone anaerobic.
Currently, we turn the windrows with either a front loader or skid-steer to get oxygen in the pile. This requires significant labor time and fuel, and is a major component of operating costs. The aerated system should cut down on these costs.
Our pilot system utilizes a DeWalt air compressor with a Utili-Tech Outdoor Timer, PVC pipes and fittings, a tarp, control valves, and an air hose. The air compressor runs for 30 minutes, pumping air into the windrow, once every 3 hours. The timer will control when the unit pumps air. The Kill A Watt EZ will monitor energy consumption to determine the cost of electricity. Three 10′ long, 1.5″ diameter, pvc pipes run down the windrow. Holes were drilled every foot to allow air to pass into the windrows.
The windrow still needs to be turned to ensure the compost is mixed thoroughly. However, rather than being turned on a daily basis, turning only occurs every other week. A tarp is placed over the pile to maintain appropriate moisture levels.
After preprocessing, a blend of food and yard waste was applied to the pilot system for aeration last Thursday. So far the temperature readings and absence of ash indicate that the system is supplying the windrow with sufficient oxygen levels to support microbial activity.
Pictures of the system can be seen in the previous post.
Be sure to check back in with us soon to get more updates on the pilot aerated system and composting at Clemson, and remember to reduce, reuse, and recycle!