Polyhydroxyalkanoate (PHA) biopolymers are emerging as attractive new sustainable polymers due to their true biodegradability and highly tuneable mechanical properties. However, despite significant investments, commercialisation barriers are hindering the capacity growth of PHA. In this work, we investigated the market potential for wood plastic composites (WPCs) based on PHAs. We considered the latest global production capacity of PHAs, estimated at 66,000 tonnes/year, and examined the implications of using PHAs for WPC production on the WPC market. Results indicate that a hypothetical usage of the current global PHA production for WPC manufacture would only represent the equivalent of 4.4% of the global WPC market, which is currently experiencing a 10.5% compounded annual growth rate. An economic assessment revealed that a wood-PHA composite as a drop-in alternative WPC product could cost as little as 37% of the cost of its neat PHA counterpart. Thus, WPCs with PHA offer a means to access benefits of PHA in engineering applications at reduced costs; however, further developments are required to improve strain at failure. The successful adoption of wood-PHA composites into the market is furthermore reliant on support from public sector to encourage biodegradable products where recycling is not a ready solution.

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The paper describes a simple, inexpensive method for evaluating settling properties of granular sludges. Test conditions, sample recovery, reproducibility, interpretation of results and applications are discussed.

Toxicity of chemi-thermomechanical pulping (CTMP) wastewaters was tested in batch assays and in anaerobic sludge blanket reactors. In batch serum bottle tests particulate constituents were responsible for 80-90% of the inhibition of acetoclastic activity, and the soluble (fines-free) fraction accounted for 10-20%. Performance of two 2-stage anaerobic sludge blanket reactor systems was compared, one receiving fines-free (NF) and the other unaltered (F) CTMP waste for 140 days. Both reactors became acclimatized to CTMP and developed a tolerance to resin acid concentrations as high as 300-1500 mg·1−1 in the sludge bed. The fines-free reactor was superior throughout, but the differences in performance did not reflect the batch test results. At the organic loading rate of 17-22 g soluble COD.g VSS−1·d−1 NF treated 100% CTMP waste with 42% and F with 38% removal efficiency. Fines accumulation in the sludge bed of F reactor caused a 70% increase in bed volume, resulted in deterioration of sludge settleability, and led to an increased likelihood of biomass loss.

Extrusion of wood fibre reinforced Poly(hydroxybutyrate-cohydroxyvalerate) (PHBV) biocomposites: statistical analysis of the effect of processing conditions on mechanical performance