A comparative assessment of fast pyrolysis, hydrothermal liquefaction, and intermediate pyrolysis to produce value-added products from municipal solid waste

  • Author / Creator
    Rahman, Wasel-Ur
  • The increasing complexity in municipal solid waste (MSW) streams along with the growing waste-to-product market call for innovative and flexible technologies that can efficiently process MSW streams into value-added products. One of these value-added products is transportation fuels; producing them from MSW, can reduce greenhouse gas (GHG) emissions from both the transportation and waste sector. A new and emerging method that provides flexible, on-site generation of high-quality bio-oil and other value-added by-products from MSW is intermediate pyrolysis (IP). Other thermochemical conversion routes such as hydrothermal liquefaction (HTL) and fast pyrolysis (FP) are also adept at converting MSW into bio-crude or bio-oil. However, to reach compatible transportation grade fuels, it is necessary to upgrade the intermediate product (bio-crude or bio-oil) in all the processes; the extent of upgrading differs depending on the quality and quantity of the product. Unlike HTL and FP processes, the performance and economics of intermediate pyrolysis have not yet been investigated to identify areas in which investment and research can be focused on for the greatest impact. Thermo-catalytic reforming (TCR) is considered one of the intermediate pyrolysis pathways. In this study a comprehensive techno-economic assessment (TEA) of a decentralized IP plant of 500 kg h-1 (12 dry t d-1) input capacity with MSW as the preferred feedstock was conducted. From the developed process model and economic evaluation, the plant’s capital cost was estimated to be 3.9 million USD. The calculated IP bio-oil production cost was $ 2.01 L-1. It was also found that generating additional revenue by selling by-products (biochar and hydrogen) is an important means of reducing bio-oil production costs. Other financial benefits are in the form of gate fees and carbon credits from using MSW as a feedstock. The effects on bio-oil production cost of increasing the plant scale from 500 kg h-1 to 4000 kg h-1 were also investigated.
    To understand better the limitations and opportunities of HTL and FP processes versus IP, a comparative techno-economic assessment of the three technologies was performed. The organic-dominant MSW stream was considered the primary feed for each process and transportation fuels (gasoline, jet fuel, and diesel) the final products. The effects of different production frameworks were also integrated into the study by evaluating these technologies in centralized and decentralized configurations. In a centralized system, MSW is transported to the facility where an intermediate is produced and upgraded (on-site upgrading), while in a decentralized system, an intermediate is produced from MSW at distributed regions and transported to an upgrading facility (off-site upgrading). In this study, four scenarios were developed to evaluate the production cost of gasoline, jet fuel, and diesel: 1) centralized HTL plant (C-HTL) at 2000 dry t d-1 with on-site upgrading, 2) centralized FP plant (C-FP) at 2000 dry t d-1 with on-site upgrading, 3) decentralized FP plant (D-FP) at 50 dry t d-1 with off-site upgrading; and 4) decentralized IP plant (D-IP) at 12 dry t d-1 with off-site upgrading. For decentralized scenarios, multiple plants were used to have an overall processing capacity of 2000 dry t d-1. Jet fuel was considered to be the primary fuel for comparison and the production cost was calculated to be $0.71 L-1, $0.80 L-1, $1.00 L-1, and $0.78 L-1 for C-HTL, C-FP, D-FP, and D-IP, respectively. Secondary products (gasoline and diesel) could be produced for $0.96 L-1 - $1.36 L-1, and $1.01 L-1 - $1.43 L-1, respectively, through the developed scenarios.

  • Subjects / Keywords
  • Graduation date
    Fall 2020
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
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