Plant 2 of OPTC uses ultrasound to break down the microbial cells in organic sludge, which is then returned to the wastewater treatment plant. While increasing biogas generation, this process also achieves sludge reduction. Biogas is a form of biomass fuel and an alternative to purchased fossil fuels. It also reduces carbon emissions, sludge accumulation and sludge treatment costs while cutting emissions resulting from sludge transport.

The sludge generated from the wastewater treatment system at FEDZ is considered general solid waste. To achieve zero-waste production, FEDZ collaborates with subcontractors to recycle, process and reuse the sludge. With 30% moisture content, the sludge is dried or incinerated, and mixed with the bottom ash derived from the process along with additional materials. The mixture is then made into building bricks, completing the zero-sludge/waste process.