Hengelo, Netherlands

HoSt and Twence started a cooperation in 2010 with the aim to develop and build a combi-digester. The combi-digester is a pilot projects and fits into the “waste to energy” objectives pursued by Twence. The concept aims to digest organic waste material in a primair and after-digester combination (wet digestion line) in combination with a parallel-connected container digester.

In the combi-digester, organic waste like flotation sludge and contaminated organic waste/ verge cuttings are processed seperately, wherein the polluted streams will be processed into the container digester. In particular, the digestion of verge cuttings in a separate parallel container digester can be classified as innovative. The pilot focusses on the container digester and integrating the system into the wet digestion line.

The advantage of the container digester is that the different streams can be digested without pre-treatment. The combination with a wet digester is interesting, because this makes it possible to  inoculate the solid digester and to startup quickly. Furthermore, it is possible to directly feed the wet digester with liquid streams. The combination of organic waste with wet input streams is also interesting because fluctuations in the organic waste quality over the season can be accommodated.