Humans, in both municipal and industrial settings, produce a lot of waste. Naturally, this waste must go somewhere. The obvious approach is landfilling. However, landfills produce toxic leachates, produce odors and greenhouse gases, take up land, and in doing so inevitably create concerns of environmental justice. Waste-to-energy approaches such as combustion and pyrolysis reduce space concerns and produce valuable energy, but agro-industrial and even municipal solid wastes have a high moisture content, creating massive energy losses in the process of evaporating water. Hydrothermal processing, be it carbonization, liquefaction, or gasification, leverages the water as a reaction medium, solvent, and catalyst to upcycle these wastes, and while elegant, still lacks notable market penetration.Several issues prevent hydrothermal processing from being upscaled, including low value of the products, questions about char utilization, and a waste aqueous phase produced in large quantities. There is research on all of these topics, but their presence in the literature pales in comparison to flashier, more straightforward to study topics like metal catalysts or the tried-and-true “this feedstock under these conditions makes this product” template. Solving the current issues of hydrothermal processing requires collaboration across disciplines—a look beyond the hydrothermal reactor. Starting with two wet waste studies on a cascaded wet and dry pyrolysis process, we uncover how adding inexpensive, abundant clay catalysts at different points can change biochar properties, and how secondary char extraction greatly increases adsorption capacity. The chapter ends with a discussion of secondary char derivatization helps reveal alcoholic compounds during gas chromatography-mass spectrometry while hiding others. The following chapter covers three studies of real hydrochar and biomass combustion, detailing the limitations (and uses) of thermogravimetry, the role of secondary char on burning, and a critical look at the comprehensive combustion index. The next two chapters cover aqueous phase treatment with the bacterium Gluconobacter oxydans, with the first showcasing how the aqueous phase from hydrothermal processing can surprisingly benefit G. oxydans growth. The second is a deeper dive into specific aqueous phase compounds across a wide range of concentrations, detailing how each one affects G. oxydans growth, and its many stress resistances.