Basics Bioplastics from
Basics Bioplastics from the slaughterhouse Animal-based protein for thermoplastic products By: Johan Verbeek University of Waikato School of Engineering Biopolymers and Composites Group Hamilton, New Zealand www.waikato.ac.nz The complexity of proteins as macromolecules greatly restricts their processability as thermoplastics. Proteins may consist of up to 20 different amino acids leading to a vast variety of intermolecular interactions in this heteropolymer. In their native state proteins fold into a variety of structures, classified as primary, secondary, tertiary and quaternary structures. The primary structure is determined by the amino acid sequence while the higher order structures are determined by the way the three dimensional structure has formed. The most important structures, leading to a protein’s semicrystalline nature are alpha helices and beta sheets. The challenge to the plastics engineer is to unravel the protein’s structure to enable extrusion and injection moulding. Its properties are then determined by the final structure as it shifts between either predominantly helical or sheet-like structures and the overall degree of crystallinity. Despite the potential environmental advantages of proteinbased plastics, these materials do have some challenges. Most important of these are difficult processablility, weak mechanical properties and their water sensitivity. Many of these could be overcome by blending with other polymers or appropriate additives. However, these new bioplastics will have to be fit for purpose rather than claiming general applicability in the plastics industry. For example, using a biodegradable material where biodegradation is a requirement rather than a marketing benefit. Research at the University of Waikato’s Polymers and Composites Group have developed a thermoplastic based on bloodmeal which is a by-product of the meat industry [1]. Bloodmeal is more than 80% protein (most of which is hemoglobin) making it an ideal precursor for a thermoplastic, similar to the many plant-based sources that have been used. Waikatolink is the intellectual property commercialisation office of the University of Waikato, and it is now commercializing the technology through a spin off company called Novatein Ltd. Work is mostly supported by a local rendering company (Wallace Corporation Ltd.) and the industry body, Meat and Live Stock Australia (MLA). 42 bioplastics MAGAZINE [04/12] Vol. 7
Bioplastics from Protein Figure 1: Injection moulded plant pots Figure 2: Composting NTP over 12 weeks (from left to right). Figure 3: Conceptual weasand clip The process of making Novatein Thermoplastic Protein (NTP) is not overly complicated and is based on using an additive cocktail of protein denaturants and plasticizers, extrusion and pelletizing. NTP can be extruded and injection moulded, but its properties currently prevent film blowing. The material’s compostability makes it an attractive material for applications where rapid degradation is required, such planting pots, seedling trays, golf tees, clay targets and possibly wads for shot-gun ammunition. NTP loses about half its mass in 3 months under commercial composting conditions [2]. One of the attractive features of NTP is that the protein raw material is completely bioderived as well as being a byproduct of a different industry. It is easy to assume that such a product should be completely environmentally friendly, however, it is important to assess it’s entire life cycle. For NTP, the group has evaluated its cradle-to-gate eco-profile thereby avoiding specific product applications and allowing a comparison to some other bioplastics (although LCAs should not typically be used for that). The most appropriate way to consider NTP’s eco-profile was to consider blood as a waste with regard to farming and meat processing, but include energy consumption and gas emissions during blood drying. This takes into account the motivations for farming and meat processing, but also recognizes that there are other treatment options for blood that do not produce blood meal used in manufacturing NTP. It was shown that NTP is comparable to other bioplastics in terms of non-renewable primary energy use and greenhouse gas emissions [3, 4]. Probaby the most promising attribute of NTP is that it can be rendered with waste from meat processing. For example, slaughtering cows requires clips used for closing animals’ wind pipes (weasand clips) to prevent stomach contents from contaminating the meat. These plastic clips end of in the rendering process, contaminating products such as pet food; making these from NTP could avoid their recovery. Research in the Polymers and Composites group mainly focuses on improving mechanical properties and processability of NTP. To this extent it has been shown that it can be blended with polyethylene and some biodegradable polyesters. By using an appropriate compatibilizer, a product with exceptional ductility and strength can be produced by blending LLPE and NTP. Although its bioderivable content is reduced, the improvement in properties such as water resistance could be considered more important. More recently, structural changes during processing have been investigated using synchrotron light FTIR. It was found that different phases exist within the material that is rich or poor in different protein secondary structures; it is though that this is one of the aspects influencing it’s film blowing ability. Other work include decolouring and deodourising bloodmeal to create wider market application, recovering fibre from chicken feathers and manufacturing protein-intercalated clay using waste water from meat processing and rendering. Hopefully some products will be seen on the market within the next two years and Novatein Ltd. is actively working with its partner organizations, however the bioplastics market is interesting and new materials like these require a significant technology push. The Author would also like to acknowledge a large team of researchers that have contributed to this project; they are Mark Lay, Kim Pickering, Lisa van den berg, Jim Bier, Aaron Low, Velram Mohan, Rashid Shamsuddin, Marcel Ishak and Darren Harpur for his work on commercialization. 1. Verbeek, C.J.R., et al., Plastics material. New Zealand, NZ551531, 2. Verbeek, C., Hicks, T.; Langdon, A. Biodegradation of Bloodmeal-Based Thermoplastics in Green-Waste Composting. Journal of Polymers and the Environment. 2011, 1-10. 3. Bier, J., Verbeek, C.; Lay, M. An ecoprofile of thermoplastic protein derived from blood meal Part 2: thermoplastic processing. The International Journal of Life Cycle Assessment. 2012, 1-11. 4. Bier, J., Verbeek, C.; Lay, M. An eco-profile of thermoplastic protein derived from blood meal Part 1: allocation issues. The International Journal of Life Cycle Assessment. 2012, 17(2), 208-219. bioplastics MAGAZINE [04/12] Vol. 7 43
