The side-stream upcycling sector is rapidly evolving as companies seek to extract value from waste materials generated across diverse industries. A growing cluster of innovators focuses on agricultural and food processing residues, such as crop waste, fish by-products, and spent grains, transforming them into protein ingredients, bioplastics, and fertilizers. Another significant stream comes from the textile and fashion industry, where offcuts and unsold garments are being repurposed into new apparel, insulation, or composite materials. The municipal and industrial waste streams, including wastewater, sewage sludge, and packaging, are being tapped to recover nutrients, produce biogas, and manufacture construction materials. Meanwhile, forestry and wood industry residues like sawdust and lignin are fueling the development of sustainable materials and bio-based chemicals. Even CO₂ and chemical emissions are being upcycled by biotech startups into high-value inputs like surfactants or fuels. This ecosystem demonstrates the sector’s shift toward circularity, where waste is no longer an endpoint, but a resource.