Surface Enhanced Smart Preprocessing of Municipal Solid Wastes for Year-Round Supply of Conversion-Ready Feedstocks

1. Overall Goals and Objectives The overall goal of this project is to develop advanced municipal solid waste (MSW) feedstock preprocessing technologies through surface enhancement and formulation to enable year-round supply of high-quality conversion-ready feedstocks for thermochemical conversion. To achieve this goal, four specific objectives will be pursued: 1) define and characterize key feedstock characteristics in various sources of MSW collected from materials recovery facilities (MRFs); 2) develop a temperature variant extrusion process for the preparation of MSW blends with enhanced surface properties; 3) test the stability and convertibility of the prepared feedstocks; and 4) conduct feedstock logistics analysis and evaluate the techno-economic feasibility and environmental impacts of the strategies developed. We will use the outcomes to develop a predictive model that guides the preprocessing and formulation strategies adaptable to MSW feedstocks with varying composition profiles. 2. Current State-of-the-Art, Challenges and Technical Relevance The generation of MSW has been steadily climbing in the past decades. Despite continuous efforts on reuse and recycling, more than 50% of MSW has ended in landfills as non-recycled MSW. MSW has been considered as a promising low-cost feedstock for biofuels (e.g., sustainable aviation fuels - SAF) and bioproducts while diverting it from landfills. The heterogeneity and large temporal and geographical variability, however, hinder the integration of MSW feedstocks into the existing bioenergy conversion platforms, given that the fundamental impact of such factors on MSW utilization remains unclear. Surface properties of the biomass feedstock affect not only the stability of the materials during long-term storage but also the flowability and convertibility of the prepared feedstocks through different conversion platforms. Significant knowledge gaps exist in the fundamental understanding of surface properties of the mixed MSW streams, how to blend and preprocess the feedstocks for desirable surface characteristics and their impact on thermochemical biomass conversion routes. For commercial projects, this knowledge gap precludes the development of a preprocessing strategy for yearround supply of high-quality conversion-ready feedstocks. Our team had worked on blending different types of waste plastics with woody biomass. Preliminary results demonstrate the feasibility to obtain hydrophobic or hydrophilic surfaces through tuning the blending ratio and extrusion temperature. Extending this knowledge to various sources of MSW collected from materials recovery facilities, we expect to develop advanced MSW feedstock preprocessing technologies through surface enhancement and formulation that will help to improve feedstock stability, homogeneity, flowability and convertibility for thermochemical conversion to SAF. 3. Proposed Technical Approach/Work Plan and Overcoming Challenges To achieve the proposed objectives, a multidisciplinary team has been formed to fulfill tasks on MSW characterization, MSW preprocessing, MSW quality validation, and TEA/LCA. Task 1. Define and characterize key feedstock characteristics. The team will take MSW samples seasonally (i.e., 4 sampling per year per site) from selected MSW facilities representing different regions in the U.S. The selection of site locations and sampling time represents the geographical and temporal variability of MSW samples. The samples will be mechanically separated into various anatomical fractions and systematically characterized following standard ASTM protocols using ion chromatography and/or ICP-OES. The surface properties (hydrophobicity, functional groups, and porosity) of MSW fractions will be measured and documented. Multivariate analysis will be performed across the established library to understand the causes and/or correlation Applicant Name: University of Kentucky Control Number: 2636-1515 3 factors for the variability in key feedstock characteristics. Task 2. Prepare MSW blends with enhanced surface properties. The MSW fractions will be separated into “clean” and “contaminant” streams by a density-based separation method. The “clean” stream will be blended at different ratios and extruded at set temperatures. The extruded shape, structural integrity, density, hydrophobicity, water uptake, and grindability will be measured. A novel high-speed, high-resolution hyperspectral 4D imaging method will be used to capture comprehensive surface features of the MSW (e.g., textures, surface roughness, composition) and correlate to the conventional wet chemistry methods. The end goal is to create an identification (ID) system recording the key parameters and catching the batch variability and multidomain properties of the prepared MSW feedstocks. Task 3. Test the stability and convertibility of the prepared feedstocks. We will conduct stability test of the raw and prepared feedstocks in a temperature and moisture-controlled incubator. The effectiveness of surface property enhancement on the feedstock flowability and convertibility will be evaluated at both benchtop reactor and 1-ton/day gasification unit. We will further analyze chemical composition, thermal decomposition, morphology, and surface species of the prepared materials and correlate to the stability and convertibility results. The information will be fed to task 2 and task 4 to investigate the impact of surface enhancement on thermochemical conversion performance and overall process cost. Task 4. Feedstock logistics and techno-economic (TEA) and life cycle analysis (LCA). Combined TEA and LCA will be conducted using data from preliminary studies and process development. We will develop process models and simulations of commercial-scale MSW facilities based on industrial data using software such as SuperProDesigner and/or python-based BioSTEAM. The analysis results will further inform process development and optimization toward the final fuel cost goal and minimized environmental impacts. Two key technical risks associated with this project would be the effectiveness of preprocessing strategies from raw materials and the overall process cost. Surface enhancement preprocessing will require integrated process design and testing to achieve desired characteristics in meeting the conversion performance and cost target. Potential Impact: The successful completion of this project will provide a thorough understanding on surface properties in relation to the biomass feedstocks characteristics and the impact on feedstock stability and convertibility during thermochemical conversion and will improve the process efficiency for gasification by creating a more homogeneous and flowable feeding stream. Consequently, this will lead to sustainable domestic SAF production, increased national energy security, and reduced greenhouse gas emission. Key Technical Risks/Issues: No major technical risks are expected in this project. The team has reached out to a few MSW industrial partners that are interested in this collaboration and will supply MSW samples. SAF production company will also join us and provide information about feedstock specifications for thermochemical conversion to help us develop MSW preprocessing technologies and TEA/LCA. Impact of EERE Funding on the Proposed Project: EERE funding would advance biofuels and bioproducts research, help leverage resources and expertise across institutes and enable industry collaborators to address the technical risks inherent in developing and scaling up thermochemical conversion of nonrecycled MSW to SAF.