Evaluation of Waste Gypsum Wallboard as a Compost Additive by Christopher Richards Submitted in partial fulfilment of the requirements for the degree of Master of Science at Dalhousie University Halifax, Nova Scotia December 2013 © Copyright by Christopher Richards, 2013 DEDICATION PAGE This paper is dedicated to my wife and best friend Penny. Without her support, encouragement, understanding and occasional kick in the posterior it would never have been completed. Thank you is not enough. ii TABLE OF CONTENTS LIST OF TABLES ............................................................................................................ vii LIST OF FIGURES ............................................................................................................ x ABSTRACT ...................................................................................................................... xii LIST OF ABBREVIATIONS USED .............................................................................. xiii ACKNOWLEDGEMENTS ............................................................................................. xiv CHAPTER 1 INTRODUCTION .............................................................................. 1 1.1 Background .................................................................................................................. 1 1.2 Literature Review ......................................................................................................... 1 1.2.1 Manufacture of Wallboard .................................................................................. 1 1.2.2 Current Situation in Nova Scotia ........................................................................ 2 1.2.3 Wallboard Concerns ............................................................................................ 3 1.2.4 Flue Gas Desulfurization Gypsum (FGD) .......................................................... 3 1.2.5 Gypsum in Agriculture ........................................................................................ 4 1.2.6 Waste Gypsum Wallboard Strategies ................................................................. 4 1.2.7 Composting ......................................................................................................... 5 1.2.8 The Composting Regulatory Environment ......................................................... 7 1.2.9 Heavy Metals in Compost ................................................................................... 8 1.2.10 Composting Using Waste Gypsum Wallboard ................................................. 9 1.3 Objectives................................................................................................................... 10 CHAPTER 2 IN-VESSEL COMPOSTING STUDY ............................................. 12 2.1 Introduction ........................................................................................................................ 12 2.2 Materials and Methods ....................................................................................................... 13 2.2.1 In-Vessel Composter.................................................................................... 13 2.2.2 Compost Feedstocks .................................................................................... 14 2.2.3 Experimental Design.................................................................................... 15 2.2.4 Compost Recipe and Preparation ................................................................. 15 2.2.5 Monitoring and Sampling ............................................................................ 15 2.2.6 Analytical Methods/Analysis ....................................................................... 16 2.2.7 Statistical Analysis ....................................................................................... 19 2.3 Results ................................................................................................................................ 19 iii 2.3.1 Feedstock Analysis ........................................................................................... 19 2.3.2 Moisture Content ......................................................................................... 23 2.3.3 Total Carbon and Total Nitrogen ................................................................. 25 2.3.4 Total Heavy Metals ...................................................................................... 28 2.3.5 Bioavailable Heavy Metals .......................................................................... 30 2.4 Discussion .......................................................................................................................... 32 2.4.1 Feedstocks ......................................................................................................... 32 2.4.2 Moisture Content............................................................................................... 32 2.4.3 Carbon and Nitrogen Contents of Composts .................................................... 33 2.4.4 Total and Bioavailable Heavy Metals ............................................................... 34 2.5 Conclusion .......................................................................................................................... 35 CHAPTER 3 LYSIMETER CELL STUDY ........................................................... 36 3.1 introduction ........................................................................................................................ 36 3.2 Materials and Methods ....................................................................................................... 39 3.2.1 Study Site / Location of Feedstocks .................................................................. 39 3.2.2 Experimental Design ......................................................................................... 41 3.2.3 Composting Process and Sampling ................................................................... 41 3.2.4 Analytical Methods ........................................................................................... 44 3.2.5 Statistical Analysis ............................................................................................ 46 3.3 Results ................................................................................................................................ 47 3.3.1 Feedstocks ......................................................................................................... 47 3.3.2 Treatment Temperature Profiles ....................................................................... 50 3.3.3 Treatment Leachate Flows ................................................................................ 51 3.3.4 Compost ............................................................................................................ 52 3.3.4.1 Composting Parameters ................................................................................. 52 3.3.4.2 Total Heavy Metals ........................................................................................ 53 3.3.4.3 Bioavailable Heavy Metals ............................................................................ 54 3.3.4.4 Bioavailability Fraction of Heavy Metals ...................................................... 55 3.3.5 Soil .................................................................................................................... 58 3.3.5.1 pH ................................................................................................................... 58 3.3.5.2 Total Heavy Metals ........................................................................................ 59 3.3.5.3 Bioavailable Metals........................................................................................ 59 3.3.6 Leachate ............................................................................................................ 60 iv 3.3.6.1 pH ................................................................................................................... 60 3.3.6.2 Electrical Conductivity .................................................................................. 61 3.3.6.3 Chloride Ion Concentration ............................................................................ 62 3.3.6.4 Soluble Metals................................................................................................ 63 3.4 Discussion .......................................................................................................................... 64 3.4.1 Temperature ...................................................................................................... 64 3.4.2 Compost Parameters ......................................................................................... 65 3.4.3 Total Heavy Metals ........................................................................................... 66 3.4.4 Bioavailable Heavy Metals ............................................................................... 67 3.4.5 Bioavailability Fraction..................................................................................... 68 3.5 Conclusion .......................................................................................................................... 69 CHAPTER 4 COVERED COMPOST STUDY .................................................... 71 4.1 Introduction ........................................................................................................................ 71