SUMMARYResearch backgroundMayhaw jelly, made from mayhaw berries from the southern United States, is a popular food product that on processing produces a berry pomace waste. Little information is available in the literature about this waste or how to valorize it. This study investigated this food production waste and its possibilities for conversion to a biofuel.Experimental approachDried mayhaw berry wastes were characterized with fiber analysis using the US National Renewable Energy Laboratory methods. After drying and grinding, hydrothermal carbonization was applied to the mayhaw berry wastes, the mayhaw waste without seeds, and mayhaw waste seeds. Fourier transform infrared spectroscopy (FTIR) was performed on mayhaw berry wastes, mayhaw waste without seeds, and mayhaw waste seeds. Calorimetry revealed the fuel value of each component of the waste and of the dried mayhaw berry wastes without any component separated. Friability testing on pellets of the biomass investigated their durability.Results and conclusionsFiber analysis indicated a high proportion of lignin compared to cellulose in the dried mayhaw waste. Hydrothermal carbonization did not enhance the fuel value of the seeds due to their tough outer coat that inhibited hydrothermal carbonization’s high ionic-product water penetration. Other mayhaw berry waste samples had enhanced fuel value after treatment at 180 or 250 °C for 5 min, with a higher fuel value attained for 250 °C treatment. After hydrothermal carbonization, the wastes were easily pelletized into durable pellets. Fourier transform infrared spectroscopy characterization indicated raw seeds had high lignin content, as did the hydrothermal carbonization-treated mayhaw berry wastes.Novelty and scientific contributionHydrothermal carbonization is a process not previously applied to mayhaw berry wastes. This study fills in the gaps of this waste biomass’ potential to become a biofuel.