Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Research article Untapped potential of zeolites in optimization of food waste composting M. Waqas a,∗∗ , A.S. Nizami b,∗ , A.S. Aburiazaiza c , M.A. Barakat c,d , Z.Z. Asam e , B. Khattak f , M.I. Rashid b,g a Department of Environmental Sciences, Kohat University of Science and Technology, 26000, KPK, Pakistan b Center of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah, Saudi Arabia c Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia d Central Metallurgical R & D Institute, Helwan 11421, Cairo, Egypt e Department of Environmental Sciences, University of Gujrat, Gujrat, Pakistan f Department of Microbiology, Kohat University of Science and Technology 26000, KPK, Pakistan g Department of Environmental Sciences, COMSATS Institute of Information Technology, Vehari, 61100, Pakistan ARTICLEINFO Keywords: Food waste Natural zeolite Modifed natural zeolite Organic matters Compost ABSTRACT This study aims to examine the efect of zeolites in optimizing the process of food waste composting. A novel method of sequential hydrothermal was introduced to modify the natural zeolite and apply to in-vessel compost bioreactors. Raw and modifed natural zeolites were applied at 10 and 15% (w/w) of the total waste and compared with un-amended control trial. Both raw and modifed zeolites afected the composting process, but the notable results were observed for modifed natural zeolite. The results for compost stability parameters were prominent at 15% modifed natural zeolite concentration. The rapid and long-term thermophillic temperature and moisture content reduction to the optimum range was observed for modifed natural zeolite. Furthermore, the total ammonium (NH 4 + ) and nitrate (NO 3 − ) concentration in modifed natural zeolite were increased by 11.1 and 21.5% respectively as compared to raw zeolite. Compost stability against moisture contents (MC), electrical conductivity (EC), organic matters (OM), total carbon (TC), mineral nitrogen, nitrifcation index (NI) and germination index (GI) was achieved after 60 days of composting that was in accordance with the inter- national compost quality standards. The fndings of this study suggested the suitability of modifed natural zeolite addition at 15% to the total waste as the optimum ratio for the composting of food waste in order to achieve a stable nutrient-rich compost. 1. Introduction Today the sustainable management of food waste is a stern issue in most of the developing countries including the Kingdom of Saudi Arabia (KSA) where around 8 million tons of food waste is generated every year (Chan et al., 2016; Waqas et al., 2018a). Most of this food waste is disposed to open landflls as being the easiest way. Such practice is causing several environmental issues such as emissions of greenhouse gases (GHG), odors and leachate production (Anjum et al., 2016). The key constituents of this food waste are carbohydrates (60%), proteins (20%), and lipids (10%), which make them suitable to process into a stable and nutrient-rich organic fertilizer and other value-added chemicals like enzymes (Awasthi et al., 2017). Therefore, in KSA, food waste composting has emerged as a sustainable, economical and eco- friendly approach to produce organic fertilizer while reducing the food waste problems (Waqas et al., 2017). The composting process is an aerobic degradation of complex or- ganic matters (OM) into simpler components and fnally into a mature organic compost by the action of diferent microbes including bacteria and fungi (Sadef et al., 2016). However, the poor chemical and physical structure of food waste pose several challenges during the composting process (Wang et al., 2016). During the early stages of composting, the rapid degradation of readily available OM initiates a sequence of events that result in intensive acidifcation and slowing down of composting process (Waqas et al., 2018a). Several research studies convincingly demonstrated the addition of various additives and bulking agents to overcome these limitations and modify the physical structure of the composting matrix (Wang et al., 2016). Several organic materials such as biochar, wood barks, and leaves, and inorganic materials like zeo- lites, lime and minerals were added as bulking agents to the composting https://doi.org/10.1016/j.jenvman.2019.04.014 Received 30 September 2018; Received in revised form 20 March 2019; Accepted 6 April 2019 ∗ Corresponding author. ∗∗ Corresponding author. E-mail addresses: mwaqas222@gmail.com (M. Waqas), nizami_pk@yahoo.com (A.S. Nizami). Journal of Environmental Management 241 (2019) 99–112 0301-4797/ © 2019 Elsevier Ltd. All rights reserved. T