AeroThermal Group, an autoclave engineering firm based in Dorset in the United Kingdom, has been developing a comprehensive waste treatment process that maximises organic material recovery from a variety of waste streams. A research project has now shown the autoclave process significantly increases methane yield. The resultant biogas which can be upgraded to biomethane is a virtual zero-carbon renewable fuel that can be used by natural gas-powered transportation.
Last week, AeroThermal announced that pre-treating sewage sludge in an autoclave increased methane generation by 47%, according to a new research report, Effect of Autoclaving on Anaerobic Biodegradation of Sewage Sludge, by Dr. Zhengjian Wang & Dr. Nigel Baily.
Three batches of dewatered sewage sludge cakes from three different sources were separately treated by autoclaving at 160⁰C (5.2 bar gauge) for 45 minutes at the company’s Poole facility. It was concluded that stable digester operation is possible at a loading rate of 5 kg VS/m³/day, and under these conditions, an autoclaving pre-treatment for anaerobic digestion of sewage sludge cake could increase bio-energy production by over 45% and facilitate the easy co-processing of multiple ‘problematic’ streams, such as screenings and scum.
Christian Toll, AeroThermal’s CEO, said: “We are very excited that we have proven that the British designed and built, AeroThermal hydrolysis system, is an efficient way to produce a higher yield of methane gas, through autoclaving of sewage sludge cakes, to potentially be used as a source of green energy and at the same time go some way to solving the waste problem which is so damaging to our environment.”
The UK’s Biomethane website explains the greatest advantage of biomethane over fossil fuels is the fact that it does not contribute to carbon dioxide emissions despite the fact that biomethane combustion produces this greenhouse gas as well. This is due to the fact that the utilization of biomethane is basically only utilization of energy which is released during the natural decomposition of organic matter. Carbon dioxide which is released into the atmosphere during biomethane combustion equals the amount of carbon dioxide that is emitted during natural decomposition of manure for instance. Fossil fuel burning, on the other hand, increases the emissions of carbon dioxide because the gas would not be released into the atmosphere if it would not be extracted and utilized for power generation by humans.
(Source: AeroThermal Group)