Valorisation of Forest Waste into Natural Textile Dyes—Case Study of Pine Cones

Abstract

The pine cone is an important forest product for the Portuguese economy. However, it is associated with environmental impacts, such as the generation of waste and the increased risk of forest fires. The objective of this research is to valorise waste from the production of Pinus pinaster Aiton in the form of natural dyes. The pine cone extracts were characterised in different alkaline solutions (1%, 5% and 10% NaOH) in order to evaluate the dyeing process on cotton knitwear, using the CIELab coordinates. The dyed samples were also subjected to light and water fastness tests. The extracts showed an increase in solids content with increasing alkalinity and a reduction in antioxidant content. The phenol content increased in the extract with 5% but decreased with the 10% concentration. All the dyes expressed a pink colour but with different shades. About the L* coordinate (luminosity), the colours became lighter as the NaOH increased. In the a* coordinate, all the samples had a reddish colour, and, in the b* coordinate, all the samples had a yellowish colour. About light and water fastness, all the samples lost colour, but in the water test, it was not noticeable.