Small-scale Process-modeling Compost Respirometer

Oxymax-C is a personal-computer-based system that monitors and controls up to 16 compost reactors using a single set of precision O2 and CO2 gas sensors. Each insulated reactor comes with a dedicated mass-flow controller matched to the volume of compost. Differently sized reactors can be operated concurrently, with data being recorded at specified time intervals. All information is available for printing and plotting during acquisition and for post-acquisition analysis. Oxymax-C adjusts fresh-air ventilation to maintain a given compost temperature and aerate the chamber. Consumption of O2 and CO2 production are continuously calculated, based the reactor's inlet and outlet flows; cumulative values are tallied. Optional measurements of methane and hydrogen sulfide are available. As an option, water drained through the system may be captured and recycled. This prevents the compost from drying out and loss of any essential bacteria, micro-organisms, or trace elements. (Chambers without insulating water jackets are available for tests not requiring precise temperature stabilization.) Standard system specifications include: volume of compost, 1.4 cu ft (39.3 l); temperature range: 0 to 99 C +/- 0.1 C); air flow rate to the reactor: 100 ml/min to 4l/min; water-jacket volume, 11.7 gal (44.3 l); sensor range: 12 to 22 percent (optional paramagnetic sensor range 0 to 100 percent); CO2 sensor range, 0-15 percent; compost chamber dimensions: 8-in. diameter x 48-in.length; overall dimensions, 19 in. long x 36 in. wide x 64 in. high; weight: 210 lb.