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 American English, United States and rubbish in British English, Britain, is a List of waste types, waste type consisting of everyday items that are discarded by the public. ...

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 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 Value (economics), economic value. A wast ...

sludge Sludge (possibly , or some dialect related to slush) 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. It can be produced as a settled sus ...

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 biodegrada ...

, 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 applie ...

to such an extent that loading rates to sludge anaerobic digesters 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 is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water p ...

s, such as Blue Plains in

Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...

, 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 (or waste water) 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 do ...

. 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 ; ) 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 1,064,235 in 2022 ...

, Norway installed a system for converting domestic

food waste The causes of food going uneaten are numerous and occur throughout the food system, during food production, production, food processing, processing, Food distribution, distribution, Grocery store, retail and food service sales, and Social clas ...

to fuel in 2012. A thermal hydrolysis system produces

biogas Biogas is a gaseous renewable energy source produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste, Wastewater treatment, wastewater, and food waste. Biogas is produced by anaerobic ...

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