Aerothermal Group has announced that pre-treating sewage sludge in an autoclave increased methane generation by 47 percent, according to report, Effect of Autoclaving on Anaerobic Biodegradation of Sewage Sludge, by Dr. Zhengjian Wang and Dr. Nigel Baily.
The company says this shows that the AeroThermal hydrolysis system, efficiently produces a higher yield of methane gas, through autoclaving of sewage sludge cakes, to potentially be used as a source of clean energy and also reduce waste.
For the study, three batches of dewatered sewage sludge cakes from three different sources were separately treated by autoclaving at 160 degrees C (5.2 bar gauge) for 45 minutes at the company’s Poole facility in the UK. A biochemical methane potential (BMP) test was carried out on both autoclaved and un-autoclaved sewage sludge samples.
A semi-continuous anaerobic digestion experiment was also conducted on both autoclaved and un-autoclaved sewage sludge samples using organic loading rates of 5 kg VS/m³/day with a hydraulic retention time of 15 days.
Stable conditions for digesters treating the autoclaved and the un-autoclaved sludges were achieved at this loading rate. Also at this loading rate, bio-methane production from digesting the autoclaved sludge was up to 47 percent more than that from treating the un-autoclaved sludge.
Research published earlier this year by AeroThermal Group found pretreating food waste in an autoclave machine will double the throughput of an anaerobic digester and significantly reduce the amount of ammonia concentrations by denaturing proteins.