Natural fibres are becoming more and more important in our everyday lives and are experiencing an impressive renaissance as insulating materials and bio-composites in the automotive sector. In view of the social and economic challenges of the 21st century, it is important to analyse their environmental impact and ultimately ensure the sustainability of this revival. In fact, over the last twenty years, more and more natural fibres have been used in composites, especially in the automotive sector and more generally as insulating materials in other sectors.
Bio-composites consist of a polymer and natural fibres, the latter of which guarantee stability. Bio-composites with natural fibres can have similar functionality to other composites and are comparable to many end products.
The trend has been emerging for years: In 2012, 30,000 tonnes of natural fibres were used in the European automotive industry, mainly in moulded parts, an increase of around 19,000 tonnes of natural fibres in 2005. Current analyses from 2019 also clearly confirm this trend. When using such materials, it is important not only to consider their service life but also to compare it with the CO2 footprint.
The natural fibres normally used are hemp, flax, jute and kenaf. Results from 2015 show that the CO2 footprint of all four fibres is significantly lower than that of conventional glass and mineral fibres. Besides, researchers at the Nova Institute in Hürth have found that the CO2 footprints of the various natural fibres are very similar.
Initially Outstanding Comparative Values For Natural Fibres
The values are indeed impressively positive: the production of one tonne of glass fibres means a CO2 footprint of about 1.7 to 2.2 tonnes of CO2, while natural fibres only have a CO2 footprint of about 0.5 to 0.7 tonnes of CO2 per tonne of natural fibre (excluding transport to the customer). This is only one-third of the CO2 footprint of glass fibres. Even if the initial advantage in further processing decreases, natural fibre composites have a 20 to 50 per cent lower footprint compared to glass fibre composites.
When transporting the various natural fibres, carbon dioxide emissions to the factory gate of a European nonwoven manufacturer in the automotive or insulation sector amount to around 750 kg CO2 per tonne of natural fibre for all four natural fibres. Due to manual processing, jute and kenaf have lower emissions during cultivation, harvesting and decontamination, but long transport to Europe compensates for this advantage.
Is The CO2 Footprint The Right Measure?
Although the CO2 footprint is in itself a very useful tool for assessing the climate impact of products, a comprehensive ecological assessment needs to consider other environmental categories, according to Nova Institute researchers. Only the consideration of greenhouse gas emissions can lead to insufficient product testing and recommendations for action, especially if other environmental impacts have not been considered at all. One task of further studies is therefore to consider other impact categories. Sustainability also includes social and economic aspects. Since natural fibres are used in many industries, certification is a suitable instrument for demonstrating sustainability.