Combined effect of assisted Bioaugmentation and biochar incorporation on olive mill wastewater sludge composting

The main environmental issue of the olive oil agro-industry has been the disposal of olive mill wastewater (OMW) due to its recalcitrant characteristics. This study aimed to assess the potential of co-composting combined with assisted Bioaugmentation and Biochar application (5 % f.w.) as a treatment technique for OMW. For this purpose, two different co-composting mixture with increasing amount of OMW (Mixture A 30 % f.w.- Mixture B 50 % f.w.) were prepared and composted under commercial conditions. The results showed that assisted Bioaugmentation led to a greater reduction in phenolic compounds and phytotoxicity, and improved the microbial profile. The use of biochar did not alter the evolution of the process, however, the assessment of greenhouse gas emissions revealed a reduction in N₂O (-19.4 %) and CH₄ (-25.4 %) emissions and in the overall global warming potential (GWP) of the process, although an increase in NH₃ (+9.7 %) emission were observed. Finally, the combined use of biochar and Bioaugmentation produced a synergistic effect in Mixture B leading enhanced organic matter degradation (+5 %) in this recalcitrant environment.