The most frequent route for sludge management in Italy, and throughout Europe, is reuse by spreading on agricultural land, either directly or after composting. This method is regulated by the Sewage Sludge Directive (SSD) (86/278/EEC), originally developed to discourage uncontrolled spreading of polluted sewage sludge on agricultural land. However, the contamination of sewage sludge, by chemicals, medicines, heavy metals, residual organic oils, etc., has been continuously growing at a fast rate. The target of lowering pollutant limits in agriculture reuse of sewage sludge has led the European Commission to reconsider the SSD, which will presumably result in more stringent limits in the coming years, in particular for cadmium (Cd), mercury (Hg), lead (Pb) and chromium (Cr). The complete ban of untreated sludge is expected as well. Sewage sludge management and pollutant limits in agriculture are currently problems of concern in Italy.
The LIFE AUGIA project aims at demonstrating an innovative oxy-gasification technology to carry out the thermo-chemical conversion of sewage sludge, together with virgin chipped biomass, into a gas mixture called syngas. The syngas will be composed of basic chemicals (i.e. artificial hydrocarbons), suitable for subsequent industrial production of very high added-value products, such as methanol and methane.
The specific objectives of the project are to: Demonstrate, up to Technology Readiness Level (TRL) 7, the operability and reliability of the sewage sludge oxy-gasification plant for the production ofchemicals using a safe, efficient, environmentally-friendly and profitable approach. The plant will be operational for 2 000 hours and have a cold gas efficiency gasification higher than 75%. Finally, the carbon content of the ash will be lower than 8% and the emission limits of an equivalent fully biomass fired thermal power plant will be respected; Optimise the process parameters of the oxy-gasification plant, keeping in mind the various possible compositions of the sewage sludge and biomass. The aim is to convert at least 30% of sewage sludge (by mass with biomass) out of the overall mixture.
Expected results: The processing of a target quantity of at least 120 tonne/year of dry sewage sludge; The conversion of about 90% by weight of the annual feedstock of sewage sludge into a syngas with a nitrogen contribution as low as 3%;/li> A composition of the produced syngas suitable for the production of chemicals, with an average volume content of hydrogen and carbon monoxide of about 40% and 36%, respectively. Other compounds present in the gas to be produced are carbon dioxide (15%) and methane (3%); Carbon-free ash of about 8% (around 9 tonne/year), mainly consisting of alkaline metals. The composition will also stabilise phosphorus and sulphur, preventing the contamination of the produced syngas; and Reduction of landfill disposal to zero.