Thermodynamic feasibility of shipboard conversion of marine plastics to blue diesel for self-powered ocean cleanup

Significance Plastic waste accumulating in the world's oceans forms massive “plastic islands” in the oceanic gyres. Removing the plastic offers an opportunity to restore our oceans to a more pristine state. To clean the gyres, ships must collect and store the plastic before transporting it to port, often thousands of kilometers away. Instead, ocean plastic waste can be converted into fuel shipboard, for example, using hydrothermal liquefaction (HTL), which depolymerizes plastics at high temperature (300 °C to 550 °C) and high pressure (250 bar to 300 bar). The resulting depolymerization products, termed “blue diesel,” have the potential for self-powered cleanup. The objective of this work is evaluating the thermodynamic feasibility of this scheme and its implications on cleanup. Collecting and removing ocean plastics can mitigate their environmental impacts; however, ocean cleanup will be a complex and energy-intensive operation that has not been fully evaluated. This work examines the thermodynamic feasibility and subsequent implications of hydrothermally converting this waste into a fuel to enable self-powered cleanup. A comprehensive probabilistic exergy analysis demonstrates that hydrothermal liquefaction has potential to generate sufficient energy to power both the process and the ship performing the cleanup. Self-powered cleanup reduces the number of roundtrips to port of a waste-laden ship, eliminating the need for fossil fuel use for most plastic concentrations. Several cleanup scenarios are modeled for the Great Pacific Garbage Patch (GPGP), corresponding to 230 t to 11,500 t of plastic removed yearly; the range corresponds to uncertainty in the surface concentration of plastics in the GPGP. Estimated cleanup times depends mainly on the number of booms that can be deployed in the GPGP without sacrificing collection efficiency. Self-powered cleanup may be a viable approach for removal of plastics from the ocean, and gaps in our understanding of GPGP characteristics should be addressed to reduce uncertainty.

[1]  Q. Guo,et al.  Supercritical water co-liquefaction of LLDPE and PP into oil: properties and synergy , 2021 .

[2]  P. Savage,et al.  Oil from plastic via hydrothermal liquefaction: Production and characterization , 2020 .

[3]  Fiona L. Kearns,et al.  Characterization and engineering of a two-enzyme system for plastics depolymerization , 2020, Proceedings of the National Academy of Sciences.

[4]  Jesse F. Abrams,et al.  The long-term legacy of plastic mass production. , 2020, The Science of the total environment.

[5]  C. Reddy,et al.  Opinion: We need better data about the environmental persistence of plastic goods , 2020, Proceedings of the National Academy of Sciences.

[6]  S. Suh,et al.  Degradation Rates of Plastics in the Environment , 2020 .

[7]  Y. Kimura,et al.  Biodegradation of PET: Current Status and Application Aspects , 2019, ACS Catalysis.

[8]  Wan-Ting Chen,et al.  Use of Supercritical Water for the Liquefaction of Polypropylene into Oil , 2019, ACS Sustainable Chemistry & Engineering.

[9]  A. Hoang,et al.  A REVIEW ON FUELS USED FOR MARINE DIESEL ENGINES , 2018, Journal of Mechanical Engineering Research and Developments.

[10]  Lars-André Tokheim,et al.  Experimental Study of Thermal and Catalytic Pyrolysis of Plastic Waste Components , 2018, Sustainability.

[11]  P. King.  Fishing for Litter: A Cost-Benefit Analysis of How to Abate Ocean Pollution , 2018 .

[12]  K. Rose,et al.  Horizontal Dispersion of Buoyant Materials in the Ocean Surface Boundary Layer , 2018, Journal of Physical Oceanography.

[13]  Dorothea Hilhorst,et al.  Synthesis Report , 2018, Reshaping Decentralised Development Co-operation.

[14]  L. Lebreton,et al.  Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic , 2018, Scientific Reports.

[15]  anonymous.  In Review , 2018 .

[16]  S. Lewis,et al.  Compatibility Assessment of Fuel System Infrastructure Plastics with Bio-oil and Diesel Fuel , 2017 .

[17]  Thomas Efferth,et al.  Threats to human health by great ocean garbage patches. , 2017, The Lancet. Planetary health.

[18]  B. Sainte-Rose,et al.  Hydrodynamics and Capture Efficiency of Plastic Cleanup Booms: Part I — Experiments and Dynamic Analysis , 2017 .

[19]  T. Walker,et al.  International policies to reduce plastic marine pollution from single-use plastics (plastic bags and microbeads): A review. , 2017, Marine pollution bulletin.

[20]  Robert A. Kotchenruther.  The effects of marine vessel fuel sulfur regulations on ambient PM2.5 at coastal and near coastal monitoring sites in the U.S. , 2017 .

[21]  Qi Cheng,et al.  Sequential Monte Carlo simulation for robust optimal design of cooling water system with quantified uncertainty and reliability , 2017 .

[22]  D. Cressey.  Bottles, bags, ropes and toothbrushes: the struggle to track ocean plastics , 2016, Nature.

[23]  Andrew J. Schmidt,et al.  Hydrothermal Liquefaction and Upgrading of Municipal Wastewater Treatment Plant Sludge : A Preliminary Techno-Economic Analysis June 2016 , 2016 .

[24]  Carlos M. Duarte,et al.  Plastic debris in the open ocean , 2014, Proceedings of the National Academy of Sciences.

[25]  Hans Janssen,et al.  Monte-Carlo based uncertainty analysis: Sampling efficiency and sampling convergence , 2013, Reliab. Eng. Syst. Saf..

[26]  K. Kołwzan,et al.  Alternative Fuels for Marine Applications , 2012 .

[27]  Andrew J. Schmidt,et al.  Review and Assessment of Commercial Vendors/Options for Feeding and Pumping Biomass Slurries for Hydrothermal Liquefaction , 2012 .

[28]  William Miller,et al.  Flexibility in Engineering Design , 2012 .

[29]  Richard de Neufville,et al.  Flexibility in Engineering Design , 2011 .

[30]  Karin L. Lemkau,et al.  Composition and fate of gas and oil released to the water column during the Deepwater Horizon oil spill , 2011, Proceedings of the National Academy of Sciences.

[31]  Jay R. Lund,et al.  A Monte-Carlo game theoretic approach for Multi-Criteria Decision Making under uncertainty , 2011 .

[32]  J. Akhtar,et al.  A review on process conditions for optimum bio-oil yield in hydrothermal liquefaction of biomass , 2011 .

[33]  Martijn Gough.  Climate change , 2009, Canadian Medical Association Journal.

[34]  G. Nagarajan,et al.  Performance, emission and combustion characteristics of a DI diesel engine using waste plastic oil , 2009 .

[35]  Richard C. Thompson,et al.  Plastics, the environment and human health: current consensus and future trends , 2009, Philosophical Transactions of the Royal Society B: Biological Sciences.

[36]  Theo Notteboom,et al.  Fuel surcharge practices of container shipping lines: is it about cost recovery or revenue-making ? , 2009 .

[37]  D. Richon,et al.  Solubility of ethylbenzene and xylene in pure water and aqueous alkanolamine solutions , 2008 .

[38]  Neil Canter.  A second-generation biofuel , 2008 .

[39]  P. Williams,et al.  Analysis of products from the pyrolysis and liquefaction of single plastics and waste plastic mixtures , 2007 .

[40]  Tom N. Kalnes,et al.  Green Diesel: A Second Generation Biofuel , 2007 .

[41]  Haifeng Zhang,et al.  Investigation on degradation of polyethylene to oil in a continuous supercritical water reactor , 2007 .

[42]  M. Mohamed,et al.  Degradation of benzene, toluene ethylbenzene and p‐xylene (BTEX) in aqueous solutions using UV/H2O2 system , 2004 .

[43]  J. Drever,et al.  The solubility of toluene in aqueous salt solutions. , 1999, Talanta.

[44]  Shu‐Sing Chang.  Heat Capacity and Thermodynamic Properties of Poly(Vinyl Chloride). , 1977, Journal of research of the National Bureau of Standards.

[45]  S. S. Chang,et al.  Heat Capacities of Polyethylene from 2 to 360 K. II. Two High Density Linear Polyethylene Samples and Thermodynamic Properties of Crystalline Linear Polyethylene. , 1974, Journal of research of the National Bureau of Standards. Section A, Physics and chemistry.

[46]  I. Ward.  Molecular Weight Determination in Polyethylene Terephthalate , 1957, Nature.

[47]  D. E. Roberts,et al.  Heats of combustion and solution of liquid styrene and solid polystyrene, and the heat of polymerization of styrene , 1947 .

[48]  W. Lane.  Determination of Solubility of Styrene in Water and of Water in Styrene , 1946 .