Wood without Trees

The building industry needs renewable materials positively impacting the CO2 footprint. The use of wood and timber as renewable construction materials has potentials, but also drawbacks because trees need long time to grow; producing timber generates considerable waste; and the process from trees to applications in buildings requires transportation and CO2 emission. “Wood Without Trees” investigated a new wood-like bio-material made of cellulose and lignin from residual biomass, to be primarily used as a feedstock for additive manufacturing processes potentially applicable in the building industry. The work was structured in three main phases: material and fabrication studies; mechanical properties investigation; preliminary prototyping. The material and fabrication studies focused on cold extrusion and hot extrusion distinctively. Experiments were performed by combining cellulose and lignin with binders, additives and natural fibres. For the cold extrusion, the studies focused on the use of nanocellulose as the main binder, combined with four selected additives, namely corn starch, bentonite, alginate and methylcellulose. Based on observations and basic measurements, the different mixtures were compared regarding properties relevant for extrusion processes, such as homogeneity, viscosity, adhesion, shrinkage, brittleness, curing time. With the methylcellulose-based mix, basic prototypes were produced, consisting of successfully 3D printed cylinders up to an height of 200 mm. For the hot extrusion, the selected binder was a natural deep eutectic solvent based on urea. Lignin’s thermoplastic, which is key for the extrusion, was analysed by performing basic thermogravimetric analysis. Overall the experiments related to hot extrusion highlighted challenges due to lignin’s degradation, for which a roadmap of future studies was defined. Finally, some studies on hot pressing were performed, potentially also in view of pellets production. As a whole, the project identified successful directions for cold extrusion promising for further scaling-up; and defined a preliminary roadmap of studies for hot extrusion and hot press.

The building industry is a major target for resource-efficiency developments, which are crucial in European Union’s roadmaps. Using renewable materials impacts the sustainability of buildings and is set as urgent target in current architectural practice. The building industry needs renewable materials positively impacting the CO2 footprint without drawbacks. The use of wood and timber as renewable construction materials has potentials, but also drawbacks because trees need long time to grow; producing timber generates considerable waste; and the process from trees to applications in buildings requires transportation and CO2 emission. This research generates new scientific knowledge and a feasibility study for a new wood-like bio-material - made of cellulose and lignin from (local) residual biomass via i.e. 3D printing - suitable for applications in the building industry. It contributes to a sustainable built environment as it transforms waste from different sectors into a local resource to produce a low carbon-footprint bio-material for the construction sector. Through testing, the project will study the material properties of samples of raw and 3D printed material, correlating different material recipes that combine lignin and cellulose and different 3D printing production parameters. It will map the material properties with the requirements of the construction industry for different building products, indicating potentials and limits of the proposed bio-material. The project will produce new knowledge on the material properties, a preliminary production concept and an overview of potentials and limits for application in the built environment. The outcome will be used by industry to achieve a marketable new bio-material; as well as in further scientific academic research.