Background Sewage sludge from the chemical industry cannot be re-used as agricultural fertiliser because of its high toxicity. Nor can it be used for the production of biogas due to the fact that it slows down the chemical reactions in conventional gas plants. Since the disposal of sewage sludge in landfills is prohibited in Germany, CURRENTA has had to incinerate all its accumulated sewage sludge, which generates large amounts of CO2 emissions. Objectives A small scale demonstration project was planned at the waste water treatment site of CURRENTA in Leverkusen to test new approaches for converting sewage sludge from the chemical industry into biogas. The pilot activities aimed to transfer organic constituents from sewage sludge into a soluble form, which could then be used to produce biogas. The proposed process included removal of inhibitors, alkaline hydrolysis, ozonation and a subsequent innovative anaerobic treatment. The biogas produced would significantly reduce the amount of sewage sludge being incinerated, limit associated CO2 emissions and provide a new renewable energy source. Results The project succeeded in demonstrating new technology capable of processing problematic waste water sludge, gaining biogas and reducing the amount of sludge. However, the pilot technology requires further work before it can be considered as economically viable. A strong alkaline hydrolysis proved effective in breaking down most of the organic constituents into smaller, easily soluble (and therefore accessible) molecules. The resulting hydrolysate, including solids, was then successfully fermented and the microbe cocktail adapt over time to produce beneficial biogas yields. The originally proposed ozonation phase was abandoned during the trials since it inhibited biogas production. An additional washing process was also introduced to eliminate sulphate and further boost biogas production. Results regarding reduced sludge volumes provided encouraging outcomes with sludge dry matter being reduced by 70%. This in turn ensures that only 30% of surplus sludge requires incineration. Further findings showed that the LIFE project’s Sludge Redox process was unable to reach its projected potential in terms of the overall impact forecasts. This was primarily attributed to the conclusion that biogas could only be generated from surplus sludge created during the biological treatment stages, which amounted to approximately 30% of the total sludge. Nevertheless, the biogas generated from Redox technology contained 60% methane and this outcome was still considered an important step by the beneficiary in converting, previously unusable, organic compounds from industrial sludge into renewable energy. The pilot project’s potential, extrapolated to a commercial context at Leverkusen, was assessed to offer: • reductions in sludge organic constituents by about 81%; • generation of about 1-2 million Nm³ biogas per year if treatment of primary sludge from municipal wastewater is included; • direct savings in CO2 emissions of between 4,000 and 5,000 tonnes; and • indirect savings in CO2 emissions of up to 1,000-2,000 tonnes by substituting natural gas for biogas. Taken as a whole, the pilot project’s Redox process costs was calculated at up to €140 per metric tonne of sewage sludge and is therefore markedly more expensive than conventional sewage sludge incineration which costs between €50 and €100 per metric tonne of sludge. Savings made through the use of biogas for electricity generation or substitute for natural gas help improve the pilot project’s feasibility calculations but not enough for Redox to be considered commercially viable in its current stage of development. At the start of this project prices for sludge incineration in Germany were much higher and are expected to raise in the next few years. The beneficiary remains committed to improve the Redox process beyond LIFE funding and intends to progress the pilot work in a new larger plant. He will examine further options to reduce the costs of this process. Disclaimer : This « results » section should be considered as a draft until the Commission has completed its evaluation.