Final report TKI toeslag project Sludge to Power and Products (S2PP)

The Dutch Water Authorities produce 1.3 million ton sewage sludge per year and the sludge disposal/treatment cost are between 115 – 250 M€ per year. There are opportunities under development to produce more renewable energy and raw materials from the sludges, lowering the sludge disposal/treatment cost. By doing so, the water authorities want to contribute to the renewable energy goals and agreements of the ‘Meerjarenafspraken Energie-Efficientie (MJA3)’, the Climate Agreement and Green Deals. In the Netherlands, sewage sludge is being digested (approximately 50 vol.%), thermally dried and subsequently incinerated in various types of installations. Drying of sewage sludge requires approximately the same amount of energy as what it will produce when the sludge is combusted. In lab-scale tests, treatment of sewage sludge using TORWASH®, dewatering the remaining fraction has been proven to result in 60 – 70% dry matter, significantly increasing the chain efficiency. For thermal conversion processes, potassium and chlorine are known precursors of fouling, slagging/agglomeration and corrosion as well as contribute greatly to fine particulate matter formation and emission. TORWASH® followed by dewatering results in a reduction of more than 90% of the potassium and sodium in the sludge. Hence, the Regional Water Authority Waterschap Zuiderzeeland (ZZL) and Wetterskip Fryslân (WSF) decided to join in this project in order to facilitate the transition of waste water treatment towards reuse of energy and raw materials from waste water. Other partners in this project include utility company RWE Essent (RWE), MILENA gasifier and OLGA gas cleaning technology provider Dahlman Renewable Technology (DRT) and technology developer ECN part of TNO. With this consortium, the complete chain for sewage sludge, from production (ZZL, WSF) to upgrading (ECN part of TNO) to sewage sludge end-use (DRT, RWE) is present.