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Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed. Detailed product analysis revealed the importance of fatty-acid oligomerization during biocrude formation, highlighting the role of acid-base catalysts in promoting condensation reactions. Economic and environmental analysis found that the new technology has the potential to reduce US greenhouse gas emissions by 2.6% while producing renewable diesel with a minimum fuel selling price of $1.06/GGE. HAP can play a role in transforming food waste from a liability to a renewable fuel.

Sunlight exposure is a control of long-term plastic fate in the environment that converts plastic into oxygenated products spanning the polymer, dissolved, and gas phases. However, our understanding of how plastic formulation influences the amount and composition of these photoproducts remains incomplete. Here, we characterized the initial formulations and resulting dissolved photoproducts of four single-use consumer polyethylene (PE) bags from major retailers and one pure PE film. Consumer PE bags contained 15-36% inorganic additives, primarily calcium carbonate (13-34%) and titanium dioxide (TiO2; 1-2%). Sunlight exposure consistently increased production of dissolved organic carbon (DOC) relative to leaching in the dark (3- to 80-fold). All consumer PE bags produced more DOC during sunlight exposure than the pure PE (1.2- to 2.0-fold). The DOC leached after sunlight exposure increasingly reflected the 13C and 14C isotopic composition of the plastic. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed that sunlight exposure substantially increased the number of DOC formulas detected (1.1- to 50-fold). TiO2-containing bags photochemically degraded into the most compositionally similar DOC, with 68-94% of photoproduced formulas in common with at least one other TiO2-containing bag. Conversely, only 28% of photoproduced formulas from the pure PE were detected in photoproduced DOC from the consumer PE. Overall, these findings suggest that plastic formulation, especially TiO2, plays a determining role in the amount and composition of DOC generated by sunlight. Consequently, studies on pure, unweathered polymers may not accurately represent the fates and impacts of the plastics entering the ocean.

Oil is a complex mixture of alkanes, cycloalkanes, aromatics, nitrogen/sulfur/oxygen (N/S/O) heterocycles, alcohols, ketones, carboxylic acids, porphyrins, and myriad possible combinations therein. Once introduced into the environment, some weathering processes reduce this complexity through evaporative losses (loss to atmosphere) as well as water washing of low ring number aromatics, N/S/O heterocycles, alcohols, ketones, and carboxylic acids (loss to seawater). However, Gulf of Mexico Research Initiative (GoMRI) supported research has revealed that the contributions of these mechanisms to the reduction of molecular complexity are dwarfed by that of oxidative weathering processes (photo- and bio-oxidation) that increase the compositional complexity of the transformed oil. Because these oxidative processes increase the complexity of an already analytically challenging organic mixture and the boiling point of transformed species is higher than that of the precursors, conventional analytical techniques yield little insight into the identification of oil spill transformation products. Despite the challenge, recent advances in analytical science now allow molecular-level insight into these complex systems irrespective of initial (unaltered) or transformed-product boiling point; these advances were largely made possible by GoMRI supported research efforts. They expose a continuum of oxidized transformation products that span oil-soluble, oil-soluble interfacially-active, and water-soluble species. The isolation and characterization of oil-soluble, interfacially-active species confirm a long-standing theory that photo-oxidation generates oil-soluble surfactant-like species, which limit the effectiveness of dispersants. Furthermore, photo-oxidation specific microcosms are shown to generate unique species that are also found in field samples. Bio-oxidation only microcosms were found to generate very different, oil-soluble species; thus, photo-oxidation is implicated in the formation of transformation products in the field. Finally, analyses of photooxidized distillate cuts as well as asphaltene samples confirm prior reports of photo-induced polymerization and photo-cracking of native petroleum molecules. Here, we summarize the advances in the molecular-level understanding of oil over the past 8 years, in the context of oil spill science, by high resolution mass spectrometry, and we highlight potential opportunities for future research, as well as knowledge gaps that must be addressed for future spills.