Extrusion Processing of Biomass By-Products for Sustainable Food Production

The sustainability of the food supply chain is gaining increasing attention in the quest to balance economic, environmental, and social dimensions. A key opportunity to enhance food system sustainability is by addressing food waste through upcycling strategies to generate higher value, functional foods. Extrusion is a food manufacturing technology that is emerging as a promising option for the incorporation of various types of biomass by-products, such as fruit and vegetable pomace, brewer’s spent grain, bagasse, and oil press cake. In this chapter, we present an overview of the latest research conducted on incorporating biomass by-products into extruded food products, with an emphasis on the challenges and opportunities associated with this approach. A meta-analysis study was conducted regarding a key challenge for product quality when incorporating by-products, which is the reduction in radial expansion index of expanded snack and breakfast cereal products. To highlight future opportunities, two case studies illustrate successful examples of by-product incorporation for commercial extruded food products, while emerging protein sources from waste-consuming insects were also explored. Overcoming these challenges and leveraging opportunities can contribute to a more sustainable food system through the integration of by-products into value-added extruded foods

DataSheet1_Statistical genetics concepts in biomass-based materials engineering.docx

With the rise of biomass-based materials such as nanocellulose, there is a growing need to develop statistical methods capable of leveraging inter-dependent experimental data to improve material design, product development, and process optimisation. Statistical approaches are essential given the multifaceted nature of variability in lignocellulosic biomass, which includes a range of different biomass feedstock types, a combinative arrangement of different biomass processing routes, and an array of different product formats depending on the focal application. To account for this large degree of variability and to extract meaningful patterns from research studies, there is a requirement to generate larger datasets of biomass-derived material properties through well-designed experimental systems that enable statistical analysis. To drive this trend, this article proposes the cross-disciplinary utilisation of statistical modelling approaches commonly applied within the field of statistical genetics to evaluate data generated in the field of biomass-based material research and development. The concepts of variance partitioning, heritability, hierarchical clustering, and selection gradients have been explained in their native context of statistical genetics and subsequently applied across the disciplinary boundary to evaluate relationships within a model experimental study involving the production of sorghum-derived cellulose nanofibres and their subsequent fabrication into nanopaper material. Variance partitioning and heritability calculates the relative influence of biomass vs. processing factors on material performance, while hierarchical clustering highlights the obscured similarity between experimental samples or characterisation metrics, and selection gradients elucidate the relationships between characterisation metrics and material quality. Ultimately, these statistical modelling approaches provide more depth to the investigation of biomass-processing-structure-property-performance relationships through outlining a framework for product characterisation, quality evaluation, and data visualisation, not only applicable to nanocellulose production but for all biomass-based materials and products.</p

Sorghum as a novel biomass for the sustainable production of cellulose nanofibers

Agricultural residues are emerging as a viable biomass resource for various industries and applications due to their abundant growth, relatively low starting value, and suitability for integration into a biorefinery system, alongside their fast regeneration time. Further, their favourable biochemical composition with a relatively high hemicellulose and low lignin content enables sustainable processing into cellulose nanofibres (CNF). Sorghum (Sorghum bicolor L. Moench) is a highly adapted and widely bred agricultural crop with drought resistance, lodging tolerance, high biomass production, and excellent nitrogen usage efficiency. To introduce sorghum agricultural residues as a sustainable biomass resource for CNF production, four phenotypically diverse sorghum varieties (Sugargraze, Yemen, GreenleafBMR, Graingrass) were selected, grown, harvested, and separated into 4 different plant sections (leaf, sheath, stem(1 m)). Each sample within this biomass library underwent a mild NaOH treatment (2%, 80 °C, 2 h), followed by high pressure homogenisation at 3 subsequent energy levels (Low, Medium, High). Tracking the evolution of nanopaper material properties over this mechanical processing series, we found the average tensile strength of sorghum-derived CNF nanopaper ranged from 51 to 115 Nm/g. GreenleafBMR and Graingrass stem produced the strongest nanopaper, Yemen consistently produced tough nanopaper, and sheath sections were highly amenable to nanofibrillation at relatively low energy input. Transmission electron microscopy (TEM) analysis of sorghum-derived CNF quantified the fibre width across all samples to range from ∼6 nm – 5.4 μm. Sorghum-derived cellulose nanofibres present outstanding material performance under low chemical and energy input processing, launching sorghum as a compelling biomass resource for sustainable nanomaterial production

Facile tuning of the surface energy of cellulose nanofibers for nanocomposite reinforcement

The isolation of nanocellulose from lignocellulosic biomass, with desirable surface chemistry and morphology, has gained extensive scientific attention for various applications including polymer nanocomposite reinforcement. Additionally, environmental and economic concerns have driven researchers to explore viable alternatives to current isolation approaches, employing chemicals with reduced environmental impact. To address these issues, in this study, we have tuned the amphiphilic behavior of cellulose nanofibers (CNFs) by employing controlled alkali treatment, instead of in combination with expensive, environmentally unsustainable conventional approaches. Microscopic and spectroscopic analysis demonstrated that this approach is capable of tuning composition and interfacial tension of CNFs through a careful control of the quantity of residual lignin and hemicellulose. To elucidate the performance of CNF as an efficient reinforcing nanofiller in hydrophobic polymer matrices, prevulcanized natural rubber (NR) latex was employed as a suitable host polymer. CNF/NR nanocomposites with different CNF loading levels (0.1-1 wt % CNF) were prepared by a casting method. It was found that the incorporation of 0.1 wt % CNF treated with a 0.5 w/v % sodium hydroxide solution led to the highest latex reinforcement efficiency, with an enhancement in tensile stress and toughness of 16% to 42 MPa and 9% to 197 MJ m, respectively. This property profile offers a potential application for the high-performance medical devices such as condoms and gloves

Lignocellulosic plant cell wall variation influences the structure and properties of hard carbon derived from sorghum biomass

Agricultural by-products offer attractive renewable feedstock options for the production of carbon to be used as electrode materials for energy storage applications. Developing insights into the carbonisation behaviour of these alternative feedstocks will enable us to tune the materials and processing conditions effectively. For the first time, this study reports the influence of lignocellulosic biomass variation on the structure and properties of sorghum-derived hard carbon materials. Four primary plant sections of sorghum biomass (leaf, sheath, upper stem and bottom stem), with different lignocellulosic composition and hierarchical native plant cell wall morphology, were partitioned from the harvested biomass and subsequently carbonised. Thermal and structural analysis of these sections before and after carbonisation revealed that both the morphology and associated lignocellulosic composition were influential upon the structure and properties of the resultant carbon. The leaf section with the highest lignin and ash content yielded 23% carbon, with high crystallinity and a higher existence of graphite-like domains. It also exhibited a highly porous structure and a large specific surface area. The sheath section with the highest cellulose content yielded 26% carbon with thinner graphitic layers and a larger D-spacing compared to other sections. Stem sections with high extractives facilitated early-stage stabilisation. The upper stem, which had the lowest lignin and ash content, yielded 25% carbon with the lowest BET surface area and pore volume. In contrast, the bottom stem yielded 30% carbon with more disordered turbostratic hard carbon and a lower D-spacing compared to other sections. It is noted that a higher graphitic carbon ratio can be achieved by selecting a biomass precursor with a higher lignin content and lower crystallinity index. Additionally, the value of BET surface area and pore volume strongly correlates with starting lignin content. This research contributes to developing a more sophisticated and comprehensive understanding of how the subtle structural and compositional variations present in different plant sections of sorghum biomass can influence the properties of carbonised materials, hopefully aiding the future potential for enhanced tunability of sustainable biomass-derived carbon products.</p

Effects of the growth environment on the yield and material properties of nanocellulose derived from the Australian desert grass Triodia

Triodia, an endemic Australian grass genus of ∼70 species inhabiting arid and monsoonal regions, is an abundant and underused biomass resource. Harsh environmental conditions have driven the evolution of adaptive extremophile traits, including uniquely high aspect ratio cellulose nanofibres (CNFs) and high hemicellulose content. In this study, we advance understanding of CNFs by comparing three Triodia species (four ecotypes) grown in their natural desert habitat or cultivated in an irrigated farm setting. We evaluated biomass production, morphological and biochemical responses to these contrasting growth environments, and analysed the properties of fabricated nanopaper to assess the impact of species and growth environment on the material properties. We hypothesised that growing Triodia plants in well-watered and fertilised cultivation would relax arid environmental cues and may result in less desirable material properties. Contrary to our hypothesis, nanopaper derived from cultivated plants showed no regression in material properties compared to plants grown in their natural habitat. For instance, we found: (1) cultivated ‘soft’ species had a daily yield of greater than 2 g of dry biomass per plant; (2) three of the four ecotypes tested had higher hemicellulose contents in cultivation; (3) and with this higher hemicellulose content, the biomass proved to be more amenable to fibrillation, as cultivated plants achieved a lower average fibre diameter product. Overall, this study adds to the existing knowledge on the material properties of the Australian desert grass Triodia and the potential for production in agronomic settings. Understanding and potentially manipulating the traits of Australian desert grasses for beneficial material properties will accelerate the development of bio-based products in the future