Abstract
Olive mill wastewater sludge (OMWS) is an environmental pollutant in olive oil industry. The problem stems from the strong odor and poor biodegradability of OMWS because of its high phenolic compounds. In most Mediterranean countries, olive mill wastewater is stored in evaporation ponds and the residual sludge is landfilled for disposal. To address this environmental pollution problem, fluidized bed catalytic pyrolysis of OMWS was developed to produce pyrolysis liquids that are stable, low viscosity (5-7 cP), neutral pH (6-7), and high higher heating value (41 MJ/kg). The pyrolysis was conducted at 400-500°C in a red mud catalyst bed. The yields of the organic fraction were 29-35 mass%; char/coke yield was 20-29 mass%; and gas yield was 24-37 mass%. The 13C NMR and GC/MS analyses of the liquid products showed predominance of aliphatic hydrocarbons and small fractions of aromatic hydrocarbons and ketones. The composition of these liquid products is in sharp contrast with most lignocellulosic biomass pyrolysis products which are normally rich in aromatic compounds and have very low aliphatic product content. In the absence of the red mud catalyst, the liquid product was viscous and contained acidic compounds.
Highlights
Olive oil production is a major industry in Mediterranean countries and it is a growing industry in South Africa, Australia, and California in the USA
In this paper we report the investigation of red mud as a catalyst for conversion of Olive mill wastewater sludge (OMWS) into pyrolysis oils for fuel applications
About 74 mass% of the OMWS was extractable with hexanes, ethanol, and water (Table 1) which indicate that the structural biopolymers content of the feedstock was very low
Summary
Olive oil production is a major industry in Mediterranean countries and it is a growing industry in South Africa, Australia, and California in the USA. The most important disposal methods include storage ponds where most of the water is evaporated and the residual sludge (olive mill wastewater sludge (OMWS)) is sent to landfills [3, 4]. The storage pond method needs large land areas, produces bad odor, causes soil infiltration, and insect infestation [2]. Olive mill wastewater (OMW) is disposed by direct application to agricultural lands as fertilizer [5,6,7] because of its high potassium, phosphorous, and other micronutrient content. The land application has some disadvantages because of the high salt content and its use has been cautioned by some researchers [5] The chemical compositional analysis of OMW showed large fractions of organic acids, lipids, alcohols, carbohydrates, polyphenolic compounds, and many others [3]. It is conceivable to apply pyrolysis technology to such feedstock to convert it to biofuels, which will simultaneously solve waste disposal problem and produce green energy
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