By Annel K. Greene, PhD
Center Director, Clemson University
Animal Co-Products Research and Education Center
Polymer scientist Dr. Amod Ogale, a member of the Clemson University Animal Co-Products Research and Education Center (ACREC) team, is working to find new high-value solutions for the rendering industry by making biodegradable geostructural plastics from animal co-products. His research is exploring ways to use animal co-products in non-feed, non-food with the goal of obtaining greater financial return for renderers.
While still in the early stages of testing and development, it is easy to see potential markets for Ogale’s flexible sheet polymers. These materials could be used in a variety of large-volume applications such as biodegradable geostructural sheets for reinforcing temporary roads and driveways during construction projects. Because it is permeable, water could percolate through the material, preventing pools of standing water. Another potential large-scale use of this polymer sheeting could be for silt fences during construction projects. Silt fences are required at construction sites where sediment run-off poses a pollution risk for rivers and streams. These are often difficult to remove at the end of a construction project and, consequently, are sometimes left in place to become a waste problem. Ogale’s biodegradable polymers have the potential to be left in place to biodegrade into a nitrogen-rich fertilizer material. Numerous other applications are easily imaginable with Ogale’s materials, including mulch base film, disposable paint drop cloths, and biodegradable hay and silage wrapping materials. Applying seeds to the surface of these biodegradable sheets could be used for instant gardens when placed onto prepared soils.
Ogale’s research utilizes animal co-product materials in conjunction with a softening or “plasticizer” agent. The first year of his project involved evaluating the melt-processability of feather meal protein into sheets. As with all scientific experiments, the simplest system must be first investigated and understood before more complex systems can be deduced. Thus, Ogale initiated his studies into animal protein-derived polymers by utilizing feather meal. Although an extremely complex protein matrix in its own right, feather meal is less complex in chemical composition than meat and bone meal or other rendered products. In addition, Ogale’s process requires denatured and dried proteins; therefore, it is necessary to use rendered materials for his polymers rather than raw animal by-products.
Preliminary studies were conducted using oleic acid and glycerin (also referred to as glycerol) as plasticizers. However, Ogale’s preliminary results indicated that the glycerin was significantly better at improving the ability to process the feather meal protein. In the production of biodiesel, glycerin is generated as a by-product. Because most biodiesel is currently made with methanol, there is potential for residual methanol to contaminate the by-product glycerin. The use of this biodiesel glycerin in animal feed is being examined due to purported safety concerns. Ogale can use this rapidly growing by-product glycerin as a plasticizer in the production of his polymers; thus, his research brings two by-product streams together to form a new value-added product – geostructural plastic films.
In the study, numerous rheological factors have been evaluated to determine the optimum mix conditions for the materials. The conditions used during mixing can vastly change the final product. Various permutations of a batch intensive method and a starving extrusion method using twin screw continuous processing were evaluated with commercial scale-up considerations in mind. Sheet-like samples of material were prepared using compression molding at specified temperature/pressure/time combinations. After preparation, the sheet samples were tested for tensile strength, water vapor permeability, and water absorption according to ASTM International standard procedures.
During tensile strength testing, Ogale determined that a mixture of 35 percent glycerin/65 percent feather meal resulted in the most flexible film. In addition, he determined that increased mixing and processing time also increased the flexibility of the films. Film strength was greatest when the mixture was processed at 140 degrees Celsius (C). Ogale discovered that at temperatures higher than 140 degrees C, the resultant films were less flexible, had reduced strength, and emitted strong odors. At temperatures lower than 140 degrees C, the material had poor strength and was not uniform in color or texture.
Thicker specimens were prepared for studying flexure and bending. These samples were evaluated in a three-point bending fixture. The resultant polymers were not brittle and performed well in terms of flexibility. Ogale’s extensive testing regimen revealed that permeability was not greatly affected by glycerol content, processing temperature, or aging of the material.
Ogale is a professor in the Department of Chemical and Biomolecular Engineering and also serves as the deputy director of the Clemson University Center for Advanced Engineering Fibers and Films. Equipment used in this project was provided by the Engineering Research Centers Program under National Science Foundation Award Number EEC-9731680. The Fats and Proteins Research Foundation also has provided partial funding of this work by supporting an undergraduate researcher, Eric Quin, and three months assistantship support of a doctorate student, Chavi Manocha. Clemson University and Ogale’s other grants have provided the remaining support for this graduate student including funds to pay for the tuition waiver.
The team has completed work for an upcoming publication entitled “Structural and Permeability Characteristics of Feather Meal Protein Sheets,” which will be ready for submission to a scientific journal in August. Future work will study alternative methods of processing the proteins to develop more uniform polymers. In addition, Ogale’s team will work on cross-linking the materials to improve the polymer qualities. In later studies, the research will turn to methods of scaling the melt-process to produce large sheets of materials for evaluation of these sheets for commercial use.
Clemson University’s ACREC is very proud that Dr. Amod Ogale and his team are working on solutions for using animal proteins in the manufacture of biodegradable geostructural plastics.
ACREC Solutions - June 2007 Render