Abstract: Municipal solid waste landfills contain substantial amounts of recalcitrant polymeric materials, such as waste plastics, rubber, and textiles, which possess considerable energy recovery potential. Using Shanghai as a case study, this study applies life cycle assessment and techno-economic analysis to evaluate resource recovery pathways for light fractions derived from landfill-mined waste of different ages from 1990 to 2024. Four scenarios were comparatively assessed, including mixed incineration, mixed pyrolysis, integrated chemical conversion and incineration, and integrated pyrolysis and incineration, in terms of their environmental and economic performance. The results indicate that the accumulated stock of light fractions in Shanghai’s landfills reached 21.015 million tons during the study period. Although the composition of light fractions varied with landfill age, the chemical conversion–incineration pathway exhibited the best overall environmental and economic performance, followed by the mixed pyrolysis and pyrolysis–incineration pathways, all of which outperformed conventional mixed incineration. Compared with conventional incineration, the optimal pathway reduced carbon footprints by approximately 55%–66% and increased the internal rate of return by 60%–67%. These findings provide a scientific basis for the high-value utilization of light fractions during landfill mining operations.