Proceedings

Methane emissions from sludge treatment make up 75% of the diffuse CO2-equivalent emissions from
wastewater treatment plants (Gärtner 2017). A vacuum degassing technology developed by ELIQUO
uses a vacuum pump to extract methane from the digested sludge reducing greenhouse gas
emissions while providing additional gas yield to the CHP. This technology has been demonstrated on
a full scale, in combination with thermal pressure hydrolysis and phosphor reduction by means of
struvite precipitation. The effect of vacuum degassing is equivalent to 3 kg of avoided CO2-
equivalents per cubic metre of sludge or a 25% reduction of the total diffuse CO2-equivalent
emissions of the treatment plant. Furthermore, vacuum degassing can provide up to 3%-points
improvement in dewatering, which can reduce total sludge disposal by up to 15%. Vacuum degassing
can be installed as a stand-alone system without disruption of existing treatment processes. This
paper details the data and findings from the full-scale implementation.

Keywords
Biogas yield, biosolids treatment, carbon footprint, methane emissions, sludge dewatering, struvite
precipitation, thermal hydrolysis, vacuum degassing