Finding a better way to use bagasse, a byproduct of sugarcane production in Louisiana, is a key research interest of the LSU AgCenter. Disposal of this byproduct is so far inefficient. About 85 percent is used in-house as fuel in mill processes and for other low-value applications such as mulch and inexpensive ceiling tiles. The remaining 15 percent is waste that is allowed to decay or is landfilled.
Transforming bagasse into high-quality panel products provides a prospective solution. Bagasse-based composites offer potential as the core material for laminated floors, replacing high-density and expensive wood fiberboard. Dimensional stability of the panel is critical for this use. Otherwise, internal stresses and out-of-plane distortion to a floor will develop when the panels are exposed to high humidity.
LSU AgCenter researchers conducted studies to develop technical information for manufacturing bagasse particleboard with desired properties as a potential raw material for laminated floor applications. The objective was to investigate effects of panel density, resin content and wax level on dimensional stability and mechanical properties of the bagasse particleboard.
Producing Bagasse Panel
Bagasse was collected from a sugar mill in New Iberia, La. The fibers had been open-field stored and naturally dried for several months. Before panel manufacturing, bagasse was hammermilled to pass through a 6-mm screen. The particles were further screened to separate most pith material and then dried to about 3 percent moisture content before use. During panel manufacturing, dry bagasse particles were blended with various levels of polymeric Methylene Diphenyl diisocyanate (pMDI) resin and wax emulsion with a laboratory blending system. The mats were then manually formed and hot-pressed into solid panels with target density levels. All boards were conditioned at 68 degrees F and 65 percent relative humidity for two weeks before cutting test samples. Tests including basic mechanical and physical properties were conducted according to the American Society for Testing and Materials standard. Test results were analyzed and compared with the corresponding values of wood-based particleboards.
Panel density and resin content levels were important in controlling the strength properties of the particleboard. Bending modulus, bending strength, internal bond strength and surface hardness values all increased with increases in panel density and resin level. The strength values well exceeded the minimum specifications for wood-based particleboard at the target manufacturing conditions. The use of wax had no significantly negative effects on the mechanical properties of pMDI-bonded bagasse particleboards. All bagasse particleboards showed decreased tendency of in-plane swelling (linear expansion) and out-plane swelling (thickness swelling) with increase of wax contents. All linear expansion values from wax-sized panels were successfully controlled under the maximum allowed values for wood particleboard. Wax-sizing also showed its positive effect on the long-term thickness swelling properties of the particleboard. Water adsorption and thickness swelling increased as water soaking time increased for all boards. However, boards treated with high levels of wax showed significantly less water absorption, thickness swelling and thickness swelling rates compared with the control panels. The long-term water-soaking test also showed that boards made of pure rind particles (after removing pith from the bagasse) further improved the dimensional stability of the bagasse particleboard with reduced resin content and panel density levels.
This study shows that it is technically possible to make bagasse particleboard with pMDI resin as a bonding agent and wax as dimensional stabilizer for targeted laminated floor and furniture applications. The particleboard developed in this study had mechanical properties that well exceeded the standard requirements for wood particleboards. Panel linear expansion and thickness swelling values from water soaking tests were also in the range of the values for wood particleboards. The study demonstrated an efficient way of transforming bagasse into high quality industrial panel products, providing a prospective solution for value-added bagasse use. Further development of the technology includes rind-based structural composite for building construction.
Successful commercialization of bagasse-based panel products depends on development of a cost-effective manufacturing process on a commercial scale and establishment of a market base for the products. Panel product manufacturers are considering adding handling facilities for materials, such as bagasse fibers, to the existing wood-based composite plants. This would allow them to produce pure and mixed wood-bagasse panel products and to market them together.
(This article appeared in the summer 2003 issue of Louisiana Agriculture.)