Red Mud Catalyzed Pyrolysis of Olive Mill Wastewater Sludge

Olive mill wastewater sludge (OMWS) is one of the major environmental pollutants in olive oil industry using traditional or three-phase process.  The major problem stems from the poor biodegradability of the OMWS because of its high phenolic compounds content.  In most Mediterranean countries, olive mill wastewater are stored in ponds where the major part of water evaporates and the sludge dries up and is then landfilled for disposal.  To address this serious environmental pollution problem, we developed fluidized bed catalytic pyrolysis of OMWS to produce pyrolysis liquids that are very stable, low viscosity (5-7 cP), neutral pH (6-7), and very high higher heating value (41 MJ/kg).  The pyrolysis was conducted at 400-500 ^oC in a red mud catalyst bed.  The yields of the organic fraction ranged from 28-35 mass% which is much higher than what obtains for other lignocellulosic biomass feedstocks.  The char/coke yield ranged from 20-29 mass% while the gas yield ranged from 24-37 mass%. The ¹³C NMR analysis of the liquid product showed predominance of aliphatic hydrocarbons and a small fraction of aromatic hydrocarbons.  In the absence of the catalyst, the liquid product contained acidic groups and was more viscous.