UC Davis

California's residents produced approximately 40 million tons of municipal solid waste (MSW) in 2019, of which about 7 million tons was organic waste. This organic waste usually comprises food waste and food service packaging products (FPPs). In addition, California also produced about 2.5 million tons of rice in 2020, producing plentiful rice husk and straw as a part of post-harvest processing, which is termed Agricultural Residue Waste (ARW). The traditional disposal method of landfilling is not a preferred option for managing this waste as landfills release greenhouse gases and can create soil and water pollution. Thus, there is an urgent need to explore alternative treatment strategies to address these wastes in a way that significantly reduces negative environmental impacts and, where possible, provides ancillary benefits. The main goal of this research was to investigate and assess possible options to treat organic waste in MSW and ARW in California by using literature reviews, bench-scale, and field-scale experiments. The approach used in this study was to identify and prioritize the development of the best use of these MSW and ARW with global applicability. The 1st chapter provides a general introduction to the area of research. It provides an overview of the overall problem faced by California's organic waste management industry, cement industry, and rice producers. The 2nd chapter reviews and analyzes California's legislative and technical frameworks to treat food waste and FPPs. This literature survey focuses on different disposal treatment options available to treat food waste and FPPs and reviews the current existing capacity of California to treat food waste and FPPs. The study suggests that anaerobic digestion and composting are the most viable options for treating food waste, FPPs, and mixed waste. The 3rd chapter of this work focuses on finding the key parameters that influence the food waste composting process through a comprehensive literature review. The review further synthesizes different factors that can potentially affect the degradation of these FPPs in the composting environment. The 4th chapter identifies the biodegradability of the FPPs that are commercially labeled as “100% compostable” through bench-scale and commercial-scale investigations. The bench scale experiments aim to assess the impacts of varying moisture content (45% and 60%) on the degradation of the FPPs in a controlled condition using cow manure as the inoculum. The field-scale experiments aim to evaluate the biodegradability of FPPs in a commercial-scale composting facility using different inoculums (food waste and matured compost). The bench-scale studies conclude that the 60 % moisture content with cow manure as an inoculum exhibits a higher rate of degrading the tested products compared to the 45 % moisture content with cow manure as an inoculum. The commercial-scale experiments conclude that composting certain types of FPPs (Bioplastic Bags) with food waste as inoculum can facilitate higher degradation rates at a commercial-scale composting facility. The research findings also indicate that not all commercially labeled "100% compostable" FPPs achieve complete compostability. The 5th chapter of this work examines the potential of employing water leaching as a pretreatment method for rice straws. The research aims to determine the ideal soaking duration for leaching soluble salts and micronutrients from rice straws by conducting lab-scale experiments. The study also investigates the viability of utilizing the resulting ash from the rice straws as Supplementary Cementitious Material (SCM). Finally, it assesses the feasibility of using Reverse Osmosis (RO) to recover nutrients from the wastewater generated during rice straw soaking, conducting chemical analysis on the brine. The study concludes that the 3 hours of soaking was equally effective in leaching the harmful compounds from rice straws compared to other tested soaking durations, and the ash generated from the soaked rice straws has the potential to be used as an alternative to traditional SCMs. The study also reveals that RO could recover nutrients from the wastewater generated during rice straw. Furthermore, the chemical analysis of the brine suggests that it can be applied as a raw material for the fertilizer industry. Finally, the last chapter summarizes the results obtained in this study, discusses the limitations of this study, and provides some insights into the scope of future research. Overall, the study provides valuable insights into organic waste management and suggests practical solutions for policymakers and waste managers to improve waste management practices in California.