Beim SETAC Europe LCA Case Study Symposium 2018 in Wien wird Hans-Jürgen Garvens vom Umweltbundesamt Deutschland ein Poster zum Thema Erderwärmungspotential (GWP) durch Verbrennung von Klärschlamm präsentieren. Das Forschungsprojekt des deutschen Umweltbundesamtes zum Thema biogener Kohlenstoffanteil in Klärschlamm und Klärgas wird von der Hydroisotop geleitet.
Der Titel des Posters lautet "Global warming potential from combustion of sewage sludge - how LCA results are changing".
Part 1: Introduction to the research results on the characterisation of carbon sources in sewage sludge and gas from German municipal and industrial wastewater treatment plants (WWTP)
A brief overview of the Research on the 14C-share in sewage sludge and gas is given. Research project by German Federal Environment Agency conducted at Hydroisotope in Schweitenkirchen, Bavaria, Germany. There is a significant share of fossil carbon in sludge and gas from municipal wastewater treatment plants (also those plants without industrial sewage). Most sludge and all gas from these plants is incinerated in Germany. Flue gas from combustion of these fuels contains at least 20 % fossil CO2 and has thus an impact on Global Warming.
Part 2: Meta-Analysis of LCA studies
Based on the results on GWP some LCA studies will be highlighted, where sewage sludge and gas are playing an important role. Results: In agricultural use, carbon is fixed in the soil leading to improvement of the soil and to some sequestration if carbon content in the soil is build up. The effect of sequestration on GWP is smaller the more fossil carbon is contained in the sludge. Main use of the sewage sludge and gas is incineration as renewable fuel. The characterisation “renewable” is not associated with no impact on GWP. Sludge and gas from WWTP has to be accounted like other wastes from municipal sources. Magnitude for the effect in Germany: About 200.000 t CO2 of the total 1 Mio t of sludge in ETS annually impacts on GWP. Interpretation LCA methodology is very sensitive to the change on knowledge about source streams. Results have always carefully be interpreted, if major lack of data occurred while modelling. Even from fully biological processes, fossil carbon might be released after incineration.