C-Green‘s OxyPower HTC process
C-Green has developed and patented OxyPower HTC™, converting sewage sludge, manure, and food digestate into solid hydrochar by a combination of hydrothermal carbonisation (HTC) and wet oxidation of the separated water. HTC or wet pyrolysis was invented in 1913 by the Nobel prize-winning German chemist Friedrich Bergius. Wet oxidation produces heat, which is used to heat the incoming sludge and to convert the nitrogen in the separated water into ammonium ions.
OxyPower HTC™ simplifies both nitrogen and phosphorus recovery. Nitrogen is extracted from the separated nitrogen-rich wet oxidized process water by ammonia stripping. Up to 60% of the nitrogen in the sludge is separated as ammonium sulphate.
The hydrochar can be used as a biofuel or for soil improvement depending on local regulations. Mono-incineration of the hydrochar makes it possible recover phosphorus from the ash. NOx emissions are significantly lower compared to sludge incineration. In addition, more than 50% of the nitrogen in the sludge can be recovered as fertiliser.
If the hydrochar is used for soil improvement, virtually all phosphorus and up 90% of the nitrogen in the sludge (60% ammonia water and 30% in the hydrochar) is used.
C-Green is confident that membership in ESPP will help us contribute to developing sustainable carbon and nutrient recycling through information, monitoring, networking and contacts with decision makers.