© 2016 The AuthorsTrees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.rser.2016.09.10

In directly addressing the question, ‘can flax replace E-glass as a reinforcement for structural composites?’, this manuscript adopts a novel comparative case study approach to investigate the manufacture and mechanical testing of full-scale 3.5-m composite rotor blades (suitable for 11kW turbines) built from flax/polyester and E-glass/polyester.The resin transfer moulded flax blade is 10% lighter (fibre mass saving of 45%) than the identical construction E-glass blade. Static flap-bending tests, conducted in accordance to certification standards, confirm that like the E-glass blade, the flax blade satisfies the structural integrity requirements under ‘normal operation’ and ‘worst case’ loading. It is consequently claimed that flax is a potential structural replacement to E-glass for similar composite small wind turbine blade applications.The failure root bending moment and corresponding tip displacement of the flax blade are 11.6kNm and 2300mm, respectively. The blades exhibit distinctly different load–deflection curves and failure modes. The mean flexural rigidity of the flax and E-glass blades are estimated to be 24.6kNm2 and 43.4kNm2, respectively. It is interesting to find that although flax fibres and their composites are generally recognized for their stiffness, a flax blade cannot compete against an E-glass blade in terms of stiffness