The current global greenhouse gas emissions have increased by over 90% since 1860 primarily due to our overreliance on fossil fuels, petrochemicals and their derivatives. Production of petrochemical plastics is also reaching 400 million metric tons in 2023. The lack of effective thermochemical processes for converting wet feedstocks and complex residues such as plastics is calling for hydrothermal gasification as an efficient approach to producing syngas. The demand for hydrogen production through greener approaches is also rising to compete with the commercial steam reforming of natural gas. Here, we review the conversion of biomass and plastics by hydrothermal gasification into hydrogen-rich syngas with a focus on the process parameters influencing the conversion of a variety of feedstock types. Parameters influencing hydrothermal gasification of biomass and plastics include temperature, pressure, reaction time, feedstock concentration, catalysts and reactor types. Several synergetic effects also influence product distribution during the co-processing of biomass and plastics during hydrothermal gasification. Processes that impact biomass conversion to syngas are hydrolysis, water–gas shift, methanation, hydrogenation, steam reforming and polymerization.

自 1860 年以来，目前全球温室气体排放量增加了 90% 以上，这主要是由于我们过度依赖化石燃料、石化产品及其衍生物。到 2023 年，石化塑料的产量也将达到 4 亿公吨。由于缺乏有效的热化学工艺来转化湿原料和塑料等复杂残留物，因此需要将水热气化作为生产合成气的有效方法。通过更环保的方法生产氢气的需求也在上升，以与天然气的商业蒸汽重整竞争。在这里，我们回顾了通过水热气化将生物质和塑料转化为富氢合成气的过程，重点关注影响各种原料类型转化的工艺参数。影响生物质和塑料水热气化的参数包括温度、压力、反应时间、原料浓度、催化剂和反应器类型。在水热气化过程中，生物质和塑料的共加工过程中，一些协同效应也会影响产品分布。影响生物质转化为合成气的过程是水解、水-气变换、甲烷化、加氢、蒸汽重整和聚合。