1a. Objectives (from AD-416):
Characterize the amounts and rate of compostability and biodegradation of poultry feather keratin-based polymer composite formulations in soils, potting soils, composts, and composting processes using ASTM 6400, ASTM 5338, ASTM D790 protocols and particle-size reduction along with spectroscopy/microscopy protocols developed by ARS for this project; determine the short and long-term growth response of selected horticultural plants grown in biodegradable pots; and provide USDA with data generated from controlled environment and field studies, including at least quarterly, a status report and completed milestones.
1b. Approach (from AD-416):
Determine the biodegradation of the subject keratin-based thermoplastic formulations under natural soil, soil with compost amendment, and during thermophilic and backyard composting conditions over short (1-3 months) and long (6-12 month) periods using ASTM 6400, ASTM 5338, ASTM D790, particle size reduction, and advanced microscopy and Raman spectroscopy; determine the short and long-term growth response of selected horticultural plants grown in biodegradable pots; the biopolymeric items to be tested will be provided by the Horticultural Research Institute, Washington, D.C.
3. Progress Report:
The USA nursery industry is seeking to enhance eco-friendly alternatives to the current petroleum-based plastic nursery pots and horticultural containers because large numbers of pots are discarded rather than recycled after use. Estimates indicate that at least 90% of horticultural pots are sent to landfills due to the current expense of commercial recycling. Using biodegradable nursery pots could eliminate 470 million pounds of petroleum-based plastic pots or approximately 1.8 trillion individual pots from ultimate disposal in landfills in the USA. Use of biodegradable keratin-based polymer pots has the potential to resolve environmental issues resulting from current use of petroleum-plastic pots. In this study, eight keratin-based polymer resin formulated materials, produced and molded by the extrusion process for ultimate use as pots, were tested and compared to polyethylene, polyhydroxyalkanoate, and wood for rate of biodegradation in soil. Two formulations were identified with high potential for biodegradation in 120 days in moist soil. Based on these results, formulations were modified and new standard coupons were prepared of keratin-based polymer resin, produced and molded by the extrusion process, for use in ASTM biodegradation tests with composting. A system for conducting the ASTM standard method for determining compost biodegradability for the formulations was developed and constructed to allow for continuous respiratory measurement; the latter is based on a customized gas pressure monitoring system with incubations for up to 180 days at 58 C, as required by the ASTM protocol. Rate of degradation of selected keratin-based biopolymer-extruded formulations and the raw feedstock biopolymers will be calculated for the ASTM method tests and for windrow compost pile (managed according to standard good composting management practices) tests. The conversion of the biopolymers to plant available nutrients is being evaluated by Raman spectroscopy. Microbial decomposition of the different formulations is being documented by cultural and non-cultural approaches. Results from the initial studies show promise in achieving formulations that are biodegradable in soil and thus will likely also biodegrade in compost, so the emphasis is on determining the rate of degradation and conditions conducive to customizing the rate relative to specific horticultural conditions and applications.