Submitted to: Bioresource Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2011
Publication Date: 1/22/2011
Publication URL: http://handle.nal.usda.gov/10113/49269
Citation: Ahn, H., Smith, M.C., Schmidt, W.F., Huda, M.S., Reeves III, J.B., Mulbry III, W.W. 2011. Biodegradability of injection molded bioplastics containing polylactic acid and poultry feather fiber. Bioresource Technology. 102:4930-4933. Interpretive Summary: Over four billion pounds of chicken feather waste is generated by the U.S. poultry industry each year. Although feathers are typically treated as a waste, they possess characteristics of potential interest for biopolymer production. First, feathers are composed of over 90% keratin, a fibrous and insoluble structural protein extensively cross linked by disulfide bonds that is flexible and resistant to digestion by animals, insects, and microbial proteases. Second, the mixed hydrophobic/hydrophilic surface chemistry of poultry fibers makes them at least partially compatible with both hydrophilic and hydrophobic polymers. Third, poultry feather can be extruded using typical polymer extrusion equipment similar to those used for petroleum-based polymers. Unfortunately, it is likely that the same properties that create disposal problems for feathers will negatively influence the biodegradation of feather based bioplastic materials. The objective of this work was to characterize the biodegradation of poultry feather based biomaterials that were processed into flower pots by extrusion and injection molding. We evaluated the biodegradability of these biomaterials by measuring carbon dioxide produced during laboratory controlled composting. Our results showed that pots molded from 100% polylactic acid (PLA) (a normally degradable material) degraded only 13% during 60 days of composting at 58 C (136 F). This may be due to chemical structural changes, observed in their near infrared spectra, to the PLA by extrusion and high molding temperatures and pressure. Our results also showed that feather fiber was not degraded under the conditions utilized in this study. These materials should be inoculated with keratinase producing microbes to improve biodegradability during composting.
Technical Abstract: Biodegradability of three types of bioplastic pots was evaluated by measuring carbon dioxide (CO2) produced from lab-scale compost reactors containing mixtures of pot fragments and compost inoculum held at 58 C for 60 days. Biodegradability of pot type A (composed of 100% polylactic acid (PLA)) was very low (13 ± 3%) compared to literature values for other PLA materials. Infrared spectroscopy results suggest that the PLA undergoes chemical structural changes during polymer extrusion and injection molding. These changes may be the basis of the low biodegradability value. Biodegradation of pot types B (containing 5% feather fiber, 80% PLA, 15% starch), and C (containing 50% feather fiber, 25% urea, 25% glycerol), were 53 ± 2% and 39 ± 3% after 60 days, respectively. Pot types B and C degraded linearly with time for the first 38 and 30 days of composting, respectively. More than 85% of the total biodegradation of both bioplastic pots occurred in this period. Infrared spectroscopy results revealed that in contrast to other bioplastic components, feather fiber was not readily degraded during composting.