Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Biotransformation of bakery industry sludge into valuable product using vermicomposting Anoop Yadav a , V.K. Garg b, ⁎ a Department of Environmental Science, School of Engineering and Technology, Central University of Haryana, Mahendergarh, Haryana, India b Department of Environmental Science and Technology, Centre for Environmental Sciences and Technology, Central University of Punjab, Bathinda, Punjab, India ARTICLE INFO Keywords: Bakery industry sludge Vermicompost Eisenia fetida Heavy metal C:N ratio ABSTRACT The aim of present work was to evaluate periodic changes in bakery industry sludge during vermicomposting. Six different blends of cow dung (CD) and bakery industry sludge (BIS) containing 10 to 50% of BIS were assessed in this study. Changes in physico-chemical parameters were evaluated at 21 days interval up to 105 days. Earthworms significantly increased NPK content and EC, while decreased pH, TOC and C: N ratio of BIS. After vermicomposting, TKN, TAP and TK contents increased 2.0–3.5, 1.2–1.9 and 1.2–1.4 times, respec- tively as compared to initial blends. A significant reduction (65.4–83.5%) in C: N ratio was observed in all blends. The concentrations of metals were found to be higher in the vermicomposts as compared initial blends. It was inferred that bakery industry sludge spiked with cow dung can be biotransformed into valuable manure employing earthworms. 1. Introduction In the present era, population explosion, haphazard industrializa- tion and unplanned urbanization have caused an enormous upsurge in solid waste generation. Waste production is directly proportional to the technological advancement, population, urbanization and in- dustrialization. Disposal of solid waste is a foremost environmental issue all over the world. Developing nations facing this problem in a serious manner due to gap in the availability and requirement of ap- propriate disposal technologies. In India, about 1,88,500 tonnes of municipal solid waste are produced per day (Arumugam et al., 2018) from various human, industrial and domestic activities. Furthermore, industrialization at its pace and day by day increasing number of in- dustries generate millions of tons of industrial waste every day (Bhat et al., 2018). Industrial sludges are produced in large quantities during efflunet treatment by various industries. This is a solid/semi-solid stuff that sometimes contain noxious compounds and heterogeneous in nature (Lee et al., 2018). Therefore, management and disposal of sludges is a challenging task. Various industries such as pulp and paper, sugar, cement, tanneries, pharmaceutical and food processing produce sludge and sometimes dispose it in irrational manner. Effluent treatment plants at Bakery industries produce non-toxic and biodegradable sludge (Yadav et al., 2015). Improper and poor management of bakery industry sludge may have adverse environmental impacts, including wind-blown litter, attraction to ver- mins, generation of liquid leachate, soil pollution, water pollution and health hazards. Therefore, safe technologies to manage industrial sludge are desired that are ecologically sound, economically viable and acceptable to community. Now-a-days biological processes are suggested to process, and treat non-toxic wastes with a paradigm to convert them into energy and organic manure (Sharma and Garg, 2018). Vermicomposting is one such biological technology that can be used for the biotransformation of the bakery industry sludge into manure (Yadav et al., 2015). It is a sustainable and economical process, by which worms convert organic waste materials into a nutrient rich, well stabilized and aesthetically pleasent material, i.e., vermicompost. Vermicompost is a peat-like material with excellent structure, porosity, aeration, drainage and en- hanced moisture holding capacity with the capability of enhancing plant growth (Sharma and Garg, 2017a). Several studies have been conducted in the past to investigate the potential of vermicomposting to stabilize various industrial wastes including Paper-pulp mill sludge (Elvira et al., 1998; Kaur et al., 2010), Tannery industry wastes (Ravindran et al., 2016), Textile industry sludge (Garg and Kaushik, 2005), Distillery industry sludge (Mahaly et al., 2018), Sago industry waste (Subramanian et al., 2010), Food industry waste (Yadav and Garg, 2013), Dairy industry sludge (Desai et al., 2016; Singh et al., 2017); Petrochemical industry sludge (Banu et al., 2005) and https://doi.org/10.1016/j.biortech.2018.12.023 Received 28 October 2018; Received in revised form 7 December 2018; Accepted 8 December 2018 ⁎ Corresponding author. E-mail addresses: vinodkgarg@yahoo.com, vinodkgarg@cupb.edu.in (V.K. Garg). Bioresource Technology 274 (2019) 512–517 Available online 10 December 2018 0960-8524/ © 2018 Elsevier Ltd. All rights reserved. T