C-Green is an innovative process engineering company with a complete solution to efficiently convert large amounts of sludge into biocoal. The process is based on hydrothermal carbonization (HTC), which copies nature’s way of breaking down complex organic compounds into coal but takes a few hours instead of millions of years.
What is sludge?
Sludge – a semi-solid byproduct of processes carried out by industry, agriculture and municipal wastewater treatment plants (MWWTPs) – is produced globally in the hundreds of millions of tonnes each year.
The more we reduce water pollution by increasing wastewater treatment, the more sludge is produced. In solving one problem we create another: sewage sludge contains hazardous substances, emits large amounts of greenhouse gases, and is increasingly expensive to handle due to stricter environmental regulations. But it also contains valuable inorganic components such as nitrogen, carbon and phosphorus – a mineral designated as a critical raw material by the European Commission.
Despite the more than €20 billion spent annually on handling sludge and other wet waste most of it still ends up in the environment. A single OxyPower HTC™ plant can convert 30,000 tons of sludge – the amount generated from the treatment of wastewater from 300,000 people – into 5,000 tons of biocoal – while at the same time eliminating pathogens, removing pollutants, increasing biogas production, eliminating greenhouse gas emissions and saving money.
At the core of the OxyPower-HTC technology is a specially designed high-temperature, high-pressure reactor that converts sludge into a carbon-based slurry containing tiny granular particles. The process mimics and accelerates the natural process that transforms organic material into coal over millions of years. Water separation and pressing of the carbon-based slurry results in the biocoal product. A dry, carbon-based material easily compressed into briquettes or pellets for transportation, biocoal has only 20-30 % of the original bulk of the sludge. The energy value of biocoal is similar to standard wood chips, making it an attractive biofuel for incineration in power plants, and its granular particle structure simplifies the recovery of phosphorus from the ash after incineration.
C-Green’s OxyPower-HTC process provides a pioneering, cyclic way of turning the current sludge disposal problem into a highly-efficient and environmentally sound recovery of energy and nutrients. The flexibility of the technology in handling almost any organic wet sludge, combined with its self-generating heat energy capability, positions it as a genuinely cost-effective and realistic solution to deal with the negative environmental impact and health risks associated with organic waste disposal.
Advantages of the C-Green OxyPower-HTC solution for sludge handling:
» Runs on the chemical energy in the sludge – no additional external heat energy necessary.
» Produces an odour-free biocoal – a high-energy, bio-based fuel.
» Thermally sterilizes the sludge – eliminating the risk of exposure to harmful pathogens.
» Instantly halts natural decomposition, significantly reducing greenhouse gas emissions (GHG) from sludge.
» Reduces the cost of and greatly simplifies phosphorus recovery.
» Onsite processing helps avoid costly transportation (and the resulting GHG emissions) of high-water content sludge to offsite disposal.
» Enables an increase of existing biogas production.