Abstract

The management of municipal and industrial organic solid wastes has become one of the most critical environmental problems in modern societies. Nowadays, commonly used management techniques are incineration, composting, and landfilling, with the former one being the most common for hazardous organic wastes. An alternative eco-friendly method that offers a sustainable and economically viable solution for hazardous wastes management is fast pyrolysis, being one of the most important thermochemical processes in the petrochemical and biomass valorization industry. The objective of this work was to study the application of fast pyrolysis for the valorization of three types of wastes, i.e., petroleum-based sludges and sediments, residual paints left on used/scrap metal packaging, and creosote-treated wood waste, towards high-added-value fuels, chemicals, and (bio)char. Fast pyrolysis experiments were performed on a lab-scale fixed-bed reactor for the determination of product yields, i.e., pyrolysis (bio)oil, gases, and solids (char). In addition, the composition of (bio)oil was also determined by Py/GC-MS tests. The thermal pyrolysis oil from the petroleum sludge was only 15.8 wt.% due to the remarkably high content of ash (74 wt.%) of this type of waste, in contrast to the treated wood and the residual paints (also containing 30 wt.% inorganics), which provided 46.9 wt.% and 35 wt.% pyrolysis oil, respectively. The gaseous products ranged from ~7.9 wt.% (sludge) to 14.7 (wood) and 19.2 wt.% (paints), while the respective solids (ash, char, reaction coke) values were 75.1, 35, and 36.9 wt.%. The thermal (non-catalytic) pyrolysis of residual paint contained relatively high concentrations of short acrylic aliphatic ester (i.e., n-butyl methacrylate), being valuable monomers in the polymer industry. The use of an acidic zeolitic catalyst (ZSM-5) for the in situ upgrading of the pyrolysis vapors induced changes on the product yields (decreased oil due to cracking reactions and increased gases and char/coke), but mostly on the pyrolysis oil composition. The main effect of the ZSM-5 zeolite catalyst was that, for all three organic wastes, the catalytic pyrolysis oils were enriched in the value-added mono-aromatics (BTX), especially in the case of the treated wood waste and residual paints. The non-condensable gases were mostly consisting of CO, CO2, and different amounts of C1–C4 hydrocarbons, depending on initial feed and use or not of the catalyst that increased the production of ethylene and propylene.

Highlights

  • The management of municipal and industrial organic solid wastes has become one of the most crucial environmental problems in modern societies

  • It is found that the water content of the initial petroleum sludge waste (NAS-1) is ~44.5 wt.%, with the ash content being ~73.6 wt.%

  • Different hazardous organic waste materials were tested as fast pyrolysis feeds in order to investigate the potential of a possible industrial management and valorization process

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Summary

Introduction

The management of municipal and industrial organic solid wastes has become one of the most crucial environmental problems in modern societies. Commission Directive 2008/98/EC, it is mentioned that “the following waste hierarchy shall apply as a priority order in waste prevention and management legislation and policy: prevention; preparing for reuse; recycling; other recovery, e.g., energy recovery; and disposal”. Still, when the recovery of chemicals is not efficient enough, the waste to energy path is applied via combustion/incineration or gasification and subsequently via steam production or steam/electricity co-generation for improving energy recovery [2,3]. There is very little knowledge concerning hazardous organic waste management, and the method of incineration towards energy production has already been in dispute [4]. Over the last few years, Greece, in accordance with EU regulations, put forward the “National Waste Management Plan (ESDA)” in 2015 and later, in 2016, the “National Hazardous Waste Management Plan (ESDEA)”, which were formulated by the Ministry of Environment and Energy with the aim to set out the strategy, objectives, and actions for waste management at the national level

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