The depletion of natural resources, escalating climate change, and environmental degradation underscore the urgent need to adopt circular economy models in biomaterial production and utilization. These models aim to reduce waste from conventional sources, minimize reliance on petrochemical feedstocks, and promote the recycling of materials, which is crucial for a sustainable transition. Bio-based materials, including those derived from agricultural waste, exemplify the innovative recycling strategies central to circular economies, offering environmentally friendly alternatives to traditional petrochemical-based products. In this context, terahertz (THz) technology, widely employed in non-destructive testing, detection, imaging, and quality control in various industries, holds considerable potential for enhancing the production and quality of biopolymers. Although THz characterization techniques do not directly improve biopolymer performance, they can optimize production processes by providing detailed insights into material properties, thus contributing to the enhancement of biopolymer quality and, in turn, indirectly extending their lifecycle. This review consolidates recent research on the application of THz technology in the biopolymer sector, emphasizing its role in improving material analysis and supporting the development of closed-loop processes, thereby advancing sustainability and resource efficiency in biotechnological applications.