Sugar mills represent a largely underutilised opportunity for regional decarbonisation and renewable manufacturing in Australia. Their access to concentrated lignocellulosic residues, existing materials-handling infrastructure, and availability of renewable electricity provides a unique platform for distributed biorefineries. This work presents process modelling case studies assessing the technical performance, economic viability, and sustainability impacts of repurposing conventional sugar mills into integrated, multiproduct biorefinery hubs. Process modelling and techno-economic analysis were applied to emerging conversion pathways: (i) production of high-value bio-based platform molecules and (ii) renewable hydrogen generation. The results demonstrate that multi-product integration optimises resource use and reduces both market and environmental risks relative to single-product systems. These findings highlight the strategic role that sugar mills could play in enabling a circular, resilient, and low-emissions chemical manufacturing sector, while supporting regional economic diversification in Australia.