Growing concerns about climate change, irreversible environmental damage and rapid depletion of non-renewable resources have made a great impact on the global construction industry. This has resulted in a search for renewable next generation construction materials. Could biofoams be a viable possibility?
Bio-based renewable construction materials are not a new concept for the construction industry. Indeed, they have been widely used as various building components all over the world for building construction for many years. However, in modern construction, the ratio of bio-based to non-renewable building materials is very low.
This is primarily due to performance requirements. Purely bio-based construction materials have performance levels that are not quite as good as those of modern construction materials. The biggest challenge for the development of bio-based construction materials is to bring environmental friendliness and performance together in a single material.
Lignin is an important constitutive component of plant or wood and some algae and it is the second most abundant organic polymer after cellulose. It is a major industrial waste product of the paper pulp and textile fibre industries. Lignin is extracted from the wood pulp before production of high quality paper or textile fibre.
Chemically, lignin is a natural polyphenol and polyol, but at the moment its industrial applications are very limited. However, a recent initiative under the National Bioproducts Programme (NBP) of the National Research Council (NRC) Canada has incorporated lignin in petroleum-derived commercial polyols for the production of polyurethane (PU) foams (See Figure 1).
The ultimate goal of this initiative is to produce bio-based PU foam that can be used as thermal insulation for building envelope construction. At present research is being conducted to partially replace petroleum-based polyol in PU foam with the ligno-polyol developed from commercially-available lignins.
However, the impact of the presence of bio-based ligno-polyol in PU foam on its performance, particularly for the application in building envelope construction, is still very much unknown. In order to investigate the effects of ligno-polyol on the hygrothermal (i.e. moisture and thermal) response of PU foam, seven ligno-polyol based PU foams with different types and concentrations (five types and two concentrations) of lignins were characterised for hygrothermal performance and compared with a reference petroleum-based PU foam prepared under the same conditions in the laboratory.
In the study, the following observations were made regarding the hygrothermal performance of ligno-polyol based PU foams: 1. Addition of ligno-polyol in polyurethane (PU) foam in the studied concentrations does not influence its short-term hygrothermal responses significantly; 2. The long-term performance of ligno-polyol based polyurethane (PU) foam under extreme weather conditions needs to be investigated further; 3. Partial replacement of petroleum-derived polyols with a biobased ligno-polyol in PU is possible but there could be a maximum limit for this replacement.
These promising findings show that there is a real possibility to use biofoam in the construction industry in the near future.
