This quick guide is written to inspire designers, policy makers, company owners, employees, educators and students to change the linear economy into a circular economy by collaborating in local value chains. This guide explains the basics of circular economy, value chains and it gives practical tips for you to work with and practical examples to learn from. It is developed within the context of the Biocup project, part of the BIOCAS Interreg project supported by the North Sea Programme of the European Regional Development Fund of the European Union.
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The transition to a biobased economy necessitates utilizing renewable resources as a sustainable alternative to traditional fossil fuels. Bioconversion is a way to produce many green chemicals from renewables, e.g., biopolymers like PHAs. However, fermentation and bioconversion processes mostly rely on expensive, and highly refined pure substrates. The utilization of crude fractions from biorefineries, especially herbaceous lignocellulosic feedstocks, could significantly reduce costs. This presentation shows the microbial production of PHA from such a crude stream by a wild-type thermophilic bacterium Schlegelella thermodepolymerans [1]. Specifically, it uses crude xylose-rich fractions derived from a newly developed biorefinery process for grassy biomasses (the ALACEN process). This new stepwise mild flow-through biorefinery approach for grassy lignocellulosic biomass allows the production of various fractions: a fraction containing esterified aromatics, a monomeric xylose-rich stream, a glucose fraction, and a native-like lignin residue [2]. The crude xylose-rich fraction was free of fermentation-inhibiting compounds meaning that the bacterium S.thermodepolymerans could effectively use it for the production of one type of PHA, polyhydroxybutyrate. Almost 90% of the xylose in the refined wheat straw fraction was metabolized with simultaneous production of PHA, matching 90% of the PHA production per gram of sugars, comparable to PHA yields from commercially available xylose. In addition to xylose, S. thermodepolymerans converted oligosaccharides with a xylose backbone (xylans) into fermentable xylose, and subsequently utilized the xylose as a source for PHA production. Since the xylose-rich hydrolysates from the ALACEN process also contain some oligomeric xylose and minor hemicellulose-derived sugars, optimal valorization of the C5-fractions derived from the refinery process can be obtained using S. thermodepolymerans. This opens the way for further exploration of PHA production from C5-fractions out of a variety of herbaceous lignocellulosic biomasses using the ALACEN process combined with S. thermodepolymerans. Overall, the innovative utilization of renewable resources in fermentation technology, as shown herein, makes a solid contribution to the transition to a biobased economy.[1] W. Zhou, D.I. Colpa, H. Permentier, R.A. Offringa, L. Rohrbach, G.J.W. Euverink, J. Krooneman. Insight into polyhydroxyalkanoate (PHA) production from xylose and extracellular PHA degradation by a thermophilic Schlegelella thermodepolymerans. Resources, Conservation and Recycling 194 (2023) 107006, ISSN 0921-3449, https://doi.org/10.1016/j.resconrec.2023.107006. [2] S. Bertran-Llorens, W.Zhou. M.A.Palazzo, D.I.Colpa, G.J.W.Euverink, J.Krooneman, P.J.Deuss. ALACEN: a holistic herbaceous biomass fractionation process attaining a xylose-rich stream for direct microbial conversion to bioplastics. Submitted 2023.
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Stricter environmental policies, increased energy prices and depletion of resources are forcing industries to look for bio-based and low carbon footprint products. For industries, flax is interesting resource since it is light, strong, environmental friendly and renewable. From flax plant to fiber products involves biochemical and mechanical processes. Moreover, production and processing costs have to compete with other products, like petroleum based materials. This research focusses on sustainable process improvement from flax plant to fiber production. Flax retting is a biological process at which mainly pectin is removed. Without retting, the desired fibre remains attached to the wooden core of the flax stem. As a result, the flax fibres cannot be gained, or have a lows quality. After retting, the fibers are released from the wooden core. Furthermore, machines have been introduced in the flax production process, but the best quality fibers are still produced manually. Due to the high labor intensity the process is too expensive and the process needs to be economical optimized. Since the retting process determines all other downstream processes, retting is the first step to focus on. Lab-scale experiments were performed to investigate the retting process. Factors that were researched were low cost processing conditions like, temperature, pH, dew retting and water retting. The retting rate was low, around three weeks for complete retting. The best retting conditions were at 20°C with water and any addition of chemicals. The process could be shortened to two weeks by recycling the water phase. In a scale-up experiment, a rotating drum was used at the optimal conditions from the lab-experiment (20°C and water). First the flax did not mix with the water content in the rotating drum. The flax was too rigid and did not tumble. Therefore, bundles of flax plants were used. The inner core of the bundle seemed to be protected and the retting rate was less compared to the flax on the surface of the flax bundle. This implies that mechanical impact increased retting in the rotating drum, however heterogeneous retting should be avoided. To overcome the heterogeneous retting problem, a water column was used to improve heterogeneous retting. Retting was performed in a water column and mixing was accomplished by bubbling air. As a result of the mixing, the flax bundle was retted homogenously. And after drying, it was possible to separate the fibers from the wooden flax core. Retting with a bubble column can overcome this problem and seems to be a usable retting process step. Water samples of the lab-scale experiments, the rotating drum and the bubble column showed a chemical oxygen demand (COD) content up to 4 g/L. Overall, 1 kg Flax resulted in 40 g COD. This indicates the possibility to produce biogas that can be used for generating heat and electricity, to make the process sustainable. Around 50% of the weight consists of wooden shives. The shives can be used for pyrolysis and it was possible to produce around 30% coal and 20% oil. These compounds can be used as building blocks, but also to generate heat and electricity. Heat and electricity can be used for the flax processing. Shives were only dried for 1 day at 105°C and slow pyrolysis was used. This indicates that a higher yield can be expected at fast pyrolysis. Overall, the reported implicates that quality fiber production from flax plant can be a feasible, sustainable and a renewable production process. Feasibility of the process can be obtained by, (1) retting at low-cost process conditions of 20°C and using water without any addition of chemicals, (2) with increased flax retting rate by recycling water, (3) with increased flax retting rate by introducing mixing forces, and the ability to lower the energy consumption of the overall process, (4) producing biogas from the COD with anaerobic digestion and (5) producing pyrolysis oil and pyrolysis c
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