Technical news (January 17th 2017)

With overall higher use of wood and wooden materials in the future, the importance of recycled wood will increase. Recycled wood is currently used for the production of wood based composites and for combustion. In the future, the use of recycled wood will also be important as feedstock for biorefineries for the production of bio-based chemicals and biofuels. ReWoBioRef project exploits the technological, economic and ecological prospects for recycling wood in a steam explosion and organosolv pre-treatment process. The presence of inorganic pollutants and non-wooden material in recycled wood material was investigated. Economic analysis of lignocellulosic feedstock for a biorefinery was calculated with various price scenarios and various proportions of recycled wood instead of fresh beech chips.

The results of ReWoBioRef project gained in the first 24 project month show that chips of recycled wood A I had higher concentrations of inorganic pollutants than softwood chips, and also some pieces of non-wood material. All measured concentrations were lower than prescribed in the industrial EPF standard (2002) or by the European Commission for eco-labelling for wooden furniture (2009/894/EC, 2009). Preliminary results on steam explosion and ethanol based organosolv cooking without an acid catalyst showed typical softwood behaviour for A I quality of recycling wood with respect to hydrolysability, thus being a potential future raw material for the sugar production. The recycled wood was processable unmilled, and milling pre-treatment was not necessary prior to steam explosion in a batch reactor. Organosolv treatment under optimal cooking conditions produced slightly better hydrolysable material than steam explosion. The economic model described in the literature for a lignocellulosic biorefinery with organosolv-pre-treatment of beech wood chips for the production of lignin has been adapted in this paper to varying ratios of A I recycling wood as alternative feedstock. Mainly because of the high operating costs, the relatively low income for the considered output products and lignin revenues  around of 600 €/t  (2015), the scale effect for the organosolv pre-treatment currently classifies it as not economically viable when 100% beech wood chips are used as feedstock. The uncertainty in revenues, especially for the by-products glucose and xylose, is the major reason. However, if A I recycling wood is used, the economics improve significantly since lignin can be produced with profits of between 180 and 270 €/t. These assumptions are based on the data sets used for the referenced model calculation basically by varying the feedstock mix input. The major financial risk factors thus remain with the reference model but are significantly reduced. For A IV or D recycling wood quality the ENERKEM process is technically best suited and economics are sound depending on the output product and the raw material revenues.