The life cycle environmental performance of a new biomaterial: Wood-based nanocellulose
Conference contribution, 2014
This is a study of the environmental performance of nanocellulose, which is a bio-based nanomaterial. Being stronger than steel, biodegradable, transparent, and antibacterial, many potential applications of nanocellulose exist, including composites and films. Global production is steadily increasing, and there are three main types of nanocellulose: (1) Nano-fibrillated cellulose (NFC), which consists of long, spaghetti-like fibers, (2) nano-crystalline cellulose (NCC), which consists of rice-shaped nanoparticles, and (3) bacterial nano cellulose (BNC), which is produced by bacteria. Of these three, NFC and NCC are currently the most produced ones. Many concerns have been raised regarding the high energy use from producing NFC from wood by disintegration of the cellulose fibers. In response to this, a number of production routes involving some kind of pretreatment to facilitate disintegration have been developed. We assessed three routes for NFC production: (1) no pretreatment, (2) the enzymatic production route, where pulp is pretreated by enzymes to facilitate disintegration, and (3) the carboxymethylation production route, where the pulp is pretreated with polyelectrolytes to facilitate disintegration. The routes were assessed with regard to their cradle-to-gate life cycle energy use with a functional unit of 1 kg NFC. Preliminary results show that the enzymatic route required approximately 80-100 MJ/kg, whereas the carboxymethylation route requires approximately 1000 MJ/kg. The route without pretreatment required approximately 200-400 MJ/kg. Notably, the carboxymethylation route had a much higher life cycle energy use than the believed-to-be energy intensive no pretreatment route. This is because the carboxymethylation route requires a large amount of fossil energy in the form of fossil input materials for various purposes. The results illustrate the value of a life cycle perspective when the production of new materials is planned. Comparing these energy use results to that of other nanomaterials as reported in the literature, such as carbon nanotubes and fullerenes (~1000-100000 MJ/kg) and traditional materials such as aluminium (~200 MJ/kg) and polypropylene (~100 MJ/kg) suggest that enzymatic NFC has a very low energy use. Suggestions for improvements are provided in the presentation, and implications for further upscaling are discussed.