Valorization of Pumpkin Peels as Agro-Food Processing Waste for Sustainable Biochar and Hydrochar Production: Environmental Assessment and Structural Characterization

The valorization of agricultural wastes such as pumpkin peel generated from the food
processing industry through thermochemical conversion offers sustainable solutions for
both waste management and carbon cycling. This study aims to evaluate the physicochemical
properties and environmental impacts of charcoals produced from pumpkin peel
waste (PPW), without the use of chemicals or pre-washing. In this context, pumpkin peel
hydrochar (PPH) was produced by hydrothermal carbonization (HTC) and pumpkin peel
biochar (PPB) by pyrolysis. The systems were modeled according to a pilot-scale scenario
based on the processing of 100 kg of PPW, and the functional unit was defined as the
processing of this amount. The properties of the products were determined by various
physicochemical characterization techniques, and environmental impacts were analyzed
using Life Cycle Assessment (LCA). The results showed that PPH has a higher specific
surface area (16.35 m2 g−1) than PPB (9.80 m2 g−1), as well as a higher carbon content
(76.18% for PPH and 66.07% for PPB). Furthermore, the environmental impact of PPH
(16.42 kg CO2-equivalent/FU) is lower than that of PPB (32.33 kg CO2-equivalent/FU).
Based on the obtained physicochemical properties, the potential of both materials as soil
conditioners has been evaluated. The lower environmental impact values suggest that
PPH may be a more advantageous alternative in terms of sustainability. However, this
evaluation is not based on direct soil application experiments, and further applied studies
are needed to confirm this potential.