An article doesn't need to be written about the challenges of replacing single-use dinner ware. Plastics and hard-to-compost waxed paper options are clogging water ways and landfills. Purdue University's School of Industrial Engineering is home to a team of engineers working to make a difference and is led by Professor Chandrasekar. They found a breakthrough in a technology you've likely seen before: compostable dinnerware. These products are typically plates or utensils made from pulped wood fiber or bagasse, a by-product from sugar cane fibers.

Current methods of manufacturing these products come with a high cost in energy-intensive methods to pre-treat, pulp, and dry sustainable materials. These products are made of almost 30% fillers and chemicals added to the fibrous pulp.

There are two challenges to sustainable dinner ware manufacturing processes: 1. Discovering sustainable materials that functionally and aesthetically match plastics and 2. Developing scalable, energy-efficient manufacturing processes to help the product complete for the plasticware consumer dollars. 

The Purdue team, partnering with research groups in India and M4 Sciences Corporation, a Purdue-based start-up, focused on an opportunity to improve the process with plant-leaf material from areca catechu, a palm widely cultivated in South and Southeast Asia. The palm is grown for nut crops, and the sheath has been considered “waste material” that can now be given new purpose. The sheaths can be pressed into dinner ware products using manufacturing processes widely used to form sheet metal. The direct forming method allows the elimination of additives and fillers, and does not require the break down into pulp, thus saving energy and water currently used in manufacturing the compostable products.

"This is fundamentally a different class of material processing from the standpoint of embodied energy and various sustainability attributes. The palm tree sheds leaf sheaths naturally in seasonal growth cycles. Not only is the plant not sacrificed in harvesting the sheaths, but the sheaths are then formed directly without the energy-intensive pulping process necessary for production of paper (wood or bagasse). In this regard, the primary form of the material literally “falls from the tree,” states Debapriya Pinaki Mohanty, a Ph.D. student with the Center for Materials Processing and Tribology and lead author on the study.

In addition, the sheath material biodegrades in 100 days compared to hundreds of years for plastics and may be used in cups and tumblers based on the team's work of characterizing the properties and limitations of the materials.

"Perhaps the most intriguing aspect of the areca palm sheath is its capacity for shape change, that is, formability, which resembles properties seen in metals such as aluminum and copper. Strength and formability are the two key property attributes of a structural material for product design and manufacturing."

Mohanty continues to state the opportunities after characterizing the material, "The high formability, together with other intriguing aspects of the mechanical response of areca sheath, suggest wide-ranging opportunities for use of palm tree materials in eco-friendly food packaging, and for unlocking the sustainable manufacturing potential of various plant-based materials."

Writer: Julia M. Sibley

Sources: Srinivasan Chandrasekar and Debapriya Pinaki Mohanty

"Mechanical Behavior and High Formability of Palm Leaf Materials"

Debapriya Pinaki Mohanty, Anirudh Udupa, Anil Chandra A R, Koushik Viswanathan, James B. Mann, Kevin P. Trumble, Srinivasan Chandrasekar

ABSTRACT

The proliferation of single-use plastics has stimulated interest in sustainable material substitutes with sufficient ductility and structural integrity. Herein, the mechanical behavior and high formability of the leaf sheath from a representative palm species—Areca catechu—and its immense potential for manufacturing of eco-friendly food packaging are reported on. Using microstructural analyses, such as X-ray micro-computed tomography (μCT), electron microscopy, and optical profilometry, under different loading conditions, it is shown that this leaf can accommodate forming strains as large as 200%, similar to ductile metals. The sheath deformation response is highly sensitive to hydration, with up to 400% increase in forming strain. The embodied energy for leaf products is four to five orders smaller than for plastic or paper products. The results establish the microstructure basis for the high formability and the contours of a forming limit diagram that delineates product shapes that can be formed in a single step from this plant material.

Advanced Energy and Sustainability Research, Volume 2, Issue 4, April 2021. Wiley Online Library, doi: 10.1002/aesr.202000080