Nowadays, air ducts components for ventilation used in offices, hospitals and schools are made from non-renewable materials mainly sheet metal and plastics. Continuing to feed the high demand of metals is a challenge and could result of depletion of natural resources. This raises the importance to look into renewable resources with a lower environmental impact and contribute to the transition towards a circular economy. By rethinking the material usage for the duct components, solutions should be found in bio-based materials such as agricultural waste, cardboard, bio-composites or bio-plastics.

This research aims to explore the potential and limitations of bio-based materials for the applicability of air duct components. Therefore the following research question is formulated: What are the potential and limitations of bio-based materials to replace sheet metal for the construction of air ducts by maintaining the same quality?

Relevant literature reviews are conducted to give an understand of the construction and relevant requirements of sheet metal ducts. As well the circularity approaches and the categorization of bio-based materials and related manufacturing methods. A method is developed to classify the bio-based materials according their manufacturing efficiency per type of duct component: linear component, joint, bend and t-component. In addition, an assessment is described based on key criteria to select a suitable material per duct component in which the carbon footprint assessment and comparison is crucial.

In conclusion, the potential for linear bio-based components made from Tetra Pak is more advanced than complex components including joints, bends and t-components. This relates to the production efficiency and the LCA of the analyzed materials. Bio-plastics and composites as potential materials for complex components resulted in a relative high carbon footprint which made recycled plastic as non-renewable material a more realistic alternative.
The limitations lie by achieving a similar quality as sheet metal in terms of moisture resistance and chemical emission. Due to the porous character of most bio-based materials they are sensitive for humidity, increasing the risk of mold growth overtime making the use of bio-based materials and the design of the connections between components challenging. Furthermore, the lifespan of the bio-based materials is unknown which is crucial for an accurate LCA in terms of carbon footprint. Low lifespan indicates more replacements leading to potentially a higher carbon footprint overtime compared to sheet metal.