Sustainable construction materials are a new area of interest. Materials are needed that release no greenhouse gas emissions during manufacturing, require minimal energy to produce, and can be recycled into something of equivalent value after their design life is complete. One potential material for construction meeting these demands is biocomposites; bio-based materials that are composed of natural fibers such as hemp and a matrix material that acts as glue holding the fibers together. This matrix material may be made from many plastic-like materials including polyhydroxybutyrate (PHB). Biocomposite materials have many potential applications in construction including formwork, scaffolding, temporary shelters and wall partitions. When no longer needed, these materials will biodegrade anaerobically, without oxygen to produce carbon dioxide and methane, which can be harvested and used as fuel for heat or electricity production, or as a feedstock to produce more biopolymer.

This research explores the anaerobic biodegradation of biocomposite materials with a focus on PHB-hemp fabric composites. A novel experimental procedure is outlined to investigate the rates and properties of anaerobic biocomposite degradation. Among the variations studied are the different matrix materials and fiber orientation, the mixing and temperature effects, and the influence of copolymer content on biodegradation. Additionally, scanning electron microscopy is employed to study the microbial attack on these materials.

The acceleration of the biodegradation rate was seen for biocomposites with exposed fibrous rides, as well as PHB thin films with more exposed surface area. It was revealed that biodegradation of biocomposites is a surface phenomenon during the first two days of microbial exposure, with different morphological appearances in the microbial community on the hemp fibers and PHB thin film. The exploration of pre-exposed inoculums found that the microbes that biodegrade hemp are most likely different than those who biodegrade PHB. On day seven, the microbes have completely penetrated the biocomposite surface, dissolving the top PHB-HHx polymeric film and exposing the hemp fiber fabric. The presence of microbial anchors suggested mechanisms for attachment to the biocomposite surface. Mixing and rinsing experiments revealed that charge interactions and shear forces play a roll in microbial adherence to the sample surface. The biodegradation rates of PHB-HHx depend not only on the copolymer content, but also the processing method. Additionally, the biodegradation of the samples exposed the underlying morphological details of the polymer, which may easily be used by others to explore underlying polymer characteristics.

This work will enhance the knowledge of biocomposites and contribute to the development of green building materials, offering a comparable replacement to traditional materials of timber, engineered wood, plastic and polymer composites that are less environmentally friendly.