Abstract
Pyrolysis of anaerobically digested sludge can serve as an efficient biomass for biofuel production. Pyrolysis produces products like char, bio-oil, and combustible gases by thermochemical conversion process. It can be used for sludge treatment that decreases sludge disposal problems. Sludge produced from anaerobic co-digestion (microalgae, cow dung, and paper) waste has high carbon and hydrogen content. We investigated the candidacy of the anaerobic sludge having high heating value (HHV) of 20.53 MJ/kg as a reliable biomass for biofuels production. The process of pyrolysis was optimized with different temperatures (400, 500, and 600 °C) to produce high quantity and improved quality of the products, mainly bio-oil, char, and gas. The results revealed that with the increase in pyrolysis temperature the quantity of char decreased (81% to 55%), bio-oil increased (3% to 7%), and gas increased (2% to 5%). The HHV of char (19.2 MJ/kg), bio-oil (28.1 MJ/kg), and gas (18.1 MJ/kg) were predominantly affected by the amount of fixed carbon, hydrocarbons, and volatile substance, respectively. The study confirmed that the anaerobic sludge is a promising biomass for biofuel production and pyrolysis is an efficient method for its safe disposal.
Highlights
Global increase in population, urbanization, and industrialization has increased pressure on natural resources and resulted in generation of a higher quantity of waste and sludge than ever
The high heating value (HHV) of anaerobic sludge is same as wood, highlighting its applicability as an efficient biomass for energy production
Temperature played an important role in product yields with an improved quality
Summary
Urbanization, and industrialization has increased pressure on natural resources and resulted in generation of a higher quantity of waste and sludge than ever. As sludge disposal needs to be done in accordance with strict environmental regulations. Safe sludge disposal has become an important concern in urban areas [1]. The sludge treatment and disposal usually involves incineration, landfilling, and composting techniques. Sludge is a heterogeneous mixture of both organic and inorganic matter, whose composition is further defined by feedstock, digestion method, reaction time, and reaction conditions [2].
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