Sludge handling is a global problem – hundreds of millions of tons are produced each year by industry, agriculture and sewage treatment. C-Green offers a patented, sustainable sludge-handling solution that turns sludge into bio-coal.
Sludge – a global problem
Handling wet sludge is a problem all over the world. Globally, hundreds of millions of tons of sludge requiring treatment or disposal are produced each year – a problem that is expected to increase as society and industry expand, therefore increasing the need for viable treatment methods.
Since sludge often contains both hazardous substances and harmful microbes, it is difficult to handle in a sustainable way. However, sludge also contains nitrogen, carbon and phosphorous which are valuable and should be recycled.
The solution
C-Green has developed a patented solution – OxyPower HTC – which makes use of hydrothermal-carbonisation (HTC) to convert sludge to bio-coal in just a few hours. OxyPower HTC solves several problems at the same time. Not only does it provide a sustainable sludge-handling solution, but it also reduces environmental impact by halting natural decomposition, which emits large amounts of greenhouse gases. No external heat energy is necessary, since the plant runs on the chemical energy in the sludge, making it energy efficient.
One of OxyPower HTC plant can convert 30 000 tons of sludge into 5 000 tons of bio-coal per year, on a site the size of 10 parking spaces. A capacity equivalent to the amount of sludge generated from 300 000 people.
OxyPower HTC™ plant (to the right) at the Stora Enso fluting mill in Heinola, Finland
How it works
C-Green’s process includes a high-temperature and high-pressure reactor that carbonises the sludge into a carbon-based slurry. The process is inspired by nature, where the transformation of organic material into coal occurs naturally but takes millions of years. By separating the water and pressing the carbon-based slurry, bio-coal in the form of a filter cake is produced. From that briquettes or pellets can be made. The bio-coal is dry and lightweight which makes it easier to transport than wet sludge. Phosphorous and other valuable nutrients are concentrated in the bio-coal which makes them easier to recover. C-Green’s technology can handle almost any organic wet sludge: from agriculture, industry or sewage treatment.
Funding to build the first OxyPower HTC plant
In 2018, C-Green received funding from the European Institute of Innovation and Technology and the Swedish Energy Agency to build the first OxyPower HTC plant. In 2019, an industrial-scale demonstration plant was completed and commissioned. The plant is located at Stora Enso’s packaging paper mill in Heinola, Finland. It has been tested and the first batch of bio-coal has been produced. Due to the covid-19 situation, continuous operation of the plant has been delayed and the goal is to begin by summer 2020.
