Research Article pubs.acs.org/journal/ascecg
Hydrothermal Carbonization of Autoclaved Municipal Solid Waste Pulp and Anaerobically Treated Pulp Digestate M. Toufiq Reza,*,† Charles Coronella,‡ Kevin M. Holtman,§ Diana Franqui-Villanueva,§ and Simon R. Poulson∥ †
Department of Mechanical Engineering, Ohio University, 1 Ohio University, Athens, Ohio 45701, United States Department of Chemical and Materials Engineering, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States § USDA-PWA, ARS, WRRC, BCE, 800 Buchanan Street, Albany, California 94710, United States ∥ Department of Geological Sciences & Engineering, University of Nevada, Reno, 1664 N. Virginia Street, Reno, Nevada 89557, United States
ACS Sustainable Chem. Eng. 2016.4:3649-3658. Downloaded from pubs.acs.org by UNIV OF SOUTH DAKOTA on 12/23/18. For personal use only.
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S Supporting Information *
ABSTRACT: In this study, the autoclaved organic fraction of municipal solid waste pulp (OFMSW) and the digestate from OFMSW pulp after anaerobic digestion (AD) were processed by hydrothermal carbonization (HTC) at 200, 250, and 300 °C for 30 min and 2 h. The focus of this work was to evaluate the potential for producing an energy-dense solid hydrochar from either OFMSW or digestate by HTC. The fate of inorganics, especially the heavy metals in hydrochar is discussed. In addition, the aqueous products were analyzed to identify the chemicals produced and the chemical changes during HTC. A carbon balance was performed from the solid and liquid phase analyses. Moreover, two conceptual MSW treatments consisting of autoclaving with or without AD, but including HTC, were proposed and mass and energy balances were performed. From the proximate, ultimate, FTIR, and fiber analyses, the hydrochar becomes increasingly energy and inorganic dense with the increase of HTC temperature. KEYWORDS: Municipal solid waste, Autoclave, Digestate, Hydrothermal carbonization, Hydrochar, Solid fuel
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INTRODUCTION In 2013, the U.S. generated 254 million tons of municipal solid waste (MSW) and recycled and composted about 87 million tons of this material, equivalent to a 34.3% recycling rate.1 Paper products and yard wastes comprise the majority of recovery (>60% for each), yet these components represent nearly a quarter of the discarded waste. In all, even with diversion programs the biogenic content (renewable organic content) of discarded MSW remains >50% by weight. Food waste comprises 21% of the discarded stream; urban recovery programs will help to reduce the volume of food waste in the future to landfill. However, data shows that even with advanced diversion programs including high degree of source separated food waste recovery, the biogenic content of MSW changes very little because equal amounts of nonbiogenic materials of value are also recovered from the waste stream.2 Further recovery of biogenic materials by traditional waste handling methods and source separation becomes economically increasingly difficult with further diversion. The goal of zero organic waste to landfill through methods of nonincineration requires consideration of new technologies. Steam autoclaving is a technology that has been around since the 80s3,4 and can efficiently divide the biogenic and nonbiogenic fractions of MSW for best reuse.5,6 Autoclaving © 2016 American Chemical Society
eliminates hazardous hand sorting of raw garbage and in the process of separating the pulp fibers, sterilizes the output and allows for sequestration of pollutants that could otherwise leach into the groundwater or the atmosphere over time.7 The organic fraction is recovered by trommel screen (accepts
