Thermal hydrolysis is a process used for treating

industrial waste Industrial waste is the waste produced by industrial activity which includes any material that is rendered useless during a manufacturing process such as that of factories, mills, and mining operations. Types of industrial waste include dirt and ...

municipal solid waste Municipal solid waste (MSW), commonly known as trash or garbage in the United States and rubbish in Britain, is a waste type consisting of everyday items that are discarded by the public. "Garbage" can also refer specifically to food waste, ...

and

sewage sludge Sewage sludge is the residual, semi-solid material that is produced as a by-product during sewage treatment of industrial or municipal wastewater. The term "septage" also refers to sludge from simple wastewater treatment but is connected to si ...

Description

Thermal hydrolysis is a two-stage process combining high-pressure boiling of

waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor economic value. A waste prod ...

sludge Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems. For example, it can be produced as a settled suspension obtained from conventiona ...

followed by a rapid decompression. This combined action sterilizes the sludge and makes it more

biodegradable Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

, which improves digestion performance. Sterilization destroys pathogens in the sludge resulting in it exceeding the stringent requirements for land application (agriculture). In addition, the treatment adjusts the

rheology Rheology (; ) is the study of the flow of matter, primarily in a fluid ( liquid or gas) state, but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an appl ...

to such an extent that loading rates to sludge

anaerobic digesters Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the ferm ...

can be doubled, and also dewaterability of the sludge is significantly improved. The first full-scale application of this process for sewage sludge was installed in

Hamar Hamar is a List of cities in Norway, town in Hamar Municipality in Innlandet Counties of Norway, county, Norway. Hamar is the administrative centre of Hamar Municipality. It is located in the Districts of Norway, traditional region of Hedmarken. ...

, Norway in 1996. Since then, there have been over 30 additional installations globally. Blue Plains - Thermal hydrolysis sludge treatment 2016a

Commercial application at a sewage treatment plant

Sewage treatment plant Sewage treatment (or domestic wastewater treatment, municipal wastewater treatment) is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable for discharge to the surrounding envir ...

s, such as Blue Plains in

Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...

, USA, have adopted thermal hydrolysis of sewage sludge in order to produce commercially valuable products (such as electricity and high quality biosolid fertilizers) out of the

wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industr ...

. The full-scale commercial application of thermal hydrolysis enables the plant to utilize the solids portion of the wastewater to make power and fine fertilizer directly from sewage waste.

Municipal waste-to-fuel application

The city of

Oslo Oslo ( , , or ; sma, Oslove) is the capital and most populous city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of in 2022, while the city's greater urban area had a population of ...

, Norway installed a system for converting domestic

food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...

to fuel in 2012. A thermal hydrolysis system produces

biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...

from the food waste, which provides fuel for the city bus system and is also used for agricultural fertilizer.

30 largest thermal hydrolysis plants

References

External links

*{{Commons category-inline Biodegradable waste management Biofuels technology Chemical reactions Equilibrium chemistry Sewerage