Researcher Seeks Improved Polymer Bin Liners

By Annel K. Greene, PhD, Center Director
Clemson University Animal Co-Products Research and Education Center


Polymer plastics have long caused difficulties in rendering systems. Polyethylene readily melts in the fat in rendering cookers, but upon cooling re-solidifies causing product downgrading. In butcher shops and grocery stores, a variety of bins and containers are used to collect animal by-products. In order to keep these containers clean and presentable as well as to reduce collection labor, renderable polymer liners would be beneficial to the industry. Dr. R. Andrew Hurley, a member of the Clemson University Animal Co-Products Research and Education Center (ACREC) team, is studying new polymers that can be used in these animal by-product bins.

The project objectives include development of an economical package material that will allow safe transport of animal by-products to the rendering facility and then allow complete disposal through the rendering cooker. Hurley will begin by reviewing commercially available polymer resin characteristics such as melt temperature, rendering cooker compatibility, and safety. In selecting the polymer resins, he will look at industrial applicability, economics, as well as compatibility with the cooker.

Upon selection of potential polymer resins, Hurley will obtain the resins and extrude these into films of various calipers (thicknesses). Each caliper film will be formed into bags using a forming machine and then made in sizes needed for the three most popular sized bins used by renderers. Once the bags have been created in various thicknesses, Hurley will study the tensile strength, seal integrity, break point, and burst point of the liner bags. This data will be used to determine the optimum liner design for use in the collection bin.

Using a lab-scale rendering cooker developed at Clemson University and available in the ACREC laboratories, Hurley will test samples of the resin materials in animal by-products under typical cooker conditions to ensure the safe and effective degradation of the liner material during rendering. The goal is to ensure that the polymer will not contaminate the animal fat or protein materials.

Upon completion of the studies to determine the best polymer(s) for use in the industry, Hurley will conduct an International Safe Transit Association/ASTM International test. This test will ensure the liners meet standards and assure that the appropriate film caliper was selected. This test will be conducted to confirm the polymer liners will withstand the rigors of use in the butcher shop, grocery store, or other rendering collection point, and will fulfill the needs of transport to the cooker.

For the final part of the study, Hurley will develop full specification sheets and send these to at least three U.S.-based polymer suppliers to get full pricing and ordering information for renderers to purchase liners for their own use. Hurley will also develop a matrix that will allow ACREC members quick reference to determine: (1) the best liner design and material for each bin; (2) full specification sheets and manufacturing information; (3) three suppliers for bids; and (4) detailed cost analysis for each design.

Hurley is a lecturer in the Department of Food, Human Nutrition, and Packaging Science. He is being assisted on the project by Dr. Lauren Mitchell, research assistant from the Department of Architecture.

Hurley is a member of the Walmart Sustainable Value Network board and through this he has direct contact with suppliers of the latest state-of-the-art sustainable materials and biopolymers. Hurley also has knowledge and access to the Walmart scorecard information, which details specific product attributes such as melt temperatures, specific sustainable values, and a wide variety of marketing information that Walmart uses to approve products for use and labeling as sustainable in the company’s supply chain. This information will be of great benefit in developing polymers for the rendering industry.

Clemson University’s Packaging Science department has extensive equipment available for use in this project, including cast and blow-film extrusion lines, a full in-line bag former and sealer, and a film laminator. Full testing equipment such as an Instron tensile strength tester, gas permeability measurement equipment, seal integrity tester, vibration table, incline/impact tester, drop tester, and compression tester are available in the Clemson University Packaging Science laboratories.

The timeline for the project is proposed to be one year. The director of the Clemson University Sonoco Institute of Packaging Design and Graphics has volunteered to match funding in terms of machine time in various fabrication laboratories for this project. The director has graciously agreed to donate up to $15,000, or 100 hours of machine time for this project.

The projected benefits from this study will be improved cleanliness of collection bins, improved customer satisfaction, and ease of product collection by rendering personnel. Upon roll-out of the liners, marketing information can be included by the rendering companies to ensure the industry will be viewed favorably by customers for providing a state-of-the-art, sustainable polymer that provides them with clean collection bins.

The project can be emphasized to customers as pro-sustainable, which is especially important to many large corporations such as Walmart and will be of benefit to promoting the rendering industry’s image to these large companies. And, perhaps most importantly, this ACREC project will allow renderers a method of collecting materials without the difficulties currently encountered from “poly” in the product.


ACREC Solutions – August 2011 RENDER | back