Effect of new back-pressure turbine and phosphate recovery on LCA and CO2
N.V. Slibverwerking Noord-Brabant (SNB) commissioned CE Delft to perform a life cycle assessment (LCA) of sewage sludge processing. This report, which is an update of a similar study carried out in 2013, was needed because SNB has since taken additional measures that lead to significant changes in the LCA score. The main new measure is installation in 2016 of a back-pressure steam turbine to boost power generation from the heat raised. The LCA was elaborated for both the total environmental score (expressed in Points) and CO2 emissions (per tonne of sludge cake processed).
The new study shows that SNB has greatly reduced the environmental footprint of its process since 2011: in 2015 that footprint was 70% less than in 2013 and in 2017 it will be 100% less, thanks to the new back-pressure turbine. When the sludge incineration ash is used as a phosphate substitute in 2019, as scheduled, the SNB processing route will tip over to having a positive life-cycle environmental impact.