A review of Willow (Salix spp.) as an integrated biorefinery feedstock

Publication history: Accepted - 13 October 2022; Published online - 22 October 2022Throughout history, the genus Salix (willow) has been an incredibly useful temperate plant for humans, with widespread global distribution and species indigenous to all continents except Antarctica. Estimations of the number of species range from 450 to 520 worldwide, and there are still more natural hybrids and multi-hybrid combinations. Several biomass willow breeding programmes have been established across the globe. All of these attempt to produce fast-growing, high-yielding stems with a straight habit and minimal side branching that are highly adaptable to different sites and are also disease and pest resistant. Short rotation coppice (SRC) cultivation involves growing willow at close spacings with a stocking rate of around 15,000 per hectare with harvests every 2–4 years. The crop is mechanically harvested, typically using a forager, and material has recently been used for bioenergy applications. Trial plots have achieved yields of up to 20 odt/ha/yr, whilst well-tended commercial crops have yielded up to 14 odt/ha/yr. Global willow breeding programmes have produced a wide variety of commercial genotypes that have suitable properties for easy planting and harvesting and have the added benefit of elevated levels of bioactive compounds, including salicin, present in the bark, which can be used in medical and veterinary applications. These high-yielding willow varieties grow well in the wetter regions of the globe, including NW Europe, and afford multiple harvests before re-planting. Salix's versatility and adaptability and the SRC cultivation process make them an ideal candidate feedstock for use in an integrated biorefinery to produce a range of biobased materials, including pharmaceuticals, and biocomposites, fuels, energy and fertiliser.The authors would like to thank the European Union's Interreg North West Europe programme, financed by the European Regional Development Fund (Biowill; project number 964) and also the Welsh Government (Environmental Evidence Programme) for support and to Micaela Cosgrove (European Landowners Organisation) for final proof reading

Developing an olive biorefinery in Slovenia bElektronski vir

The valorization of olive pomace through the extraction of phenolic compounds at an industrial scale is influenced by several factors that can have a significant impact on the feasibility of this approach. These include the types and levels of phenolic compounds that are present, the impact that seasonal variation and cultivar type have on the phenolic compound content in both olive pomace and mill effluents and the technological approach used to process the olive crop. Chemical analysis of phenolic compounds was performed using an HPLC-diode-array detector (DAD)-qTOF system, resulting in the identification of 45 compounds in olive mill wastewater and pomace, where secoiridoids comprised 50–60% of the total phenolic content. This study examined three different factors that could impact the phenolic compound content of these processing streams, including cultivar types typically grown on local farms in Slovenia, the type of downstream processing used and seasonality effects. Olive crop varieties sourced from local farms showed high variability, and the highest phenolic content was associated with the local variety “Istrska Belica”. During processing, the phenolic content was on average approximately 50% higher during two-phase decanting compared to three-phase decanting and the type of compound present significantly different. An investigation into the seasonal effects revealed that the phenolic content was 20% higher during the 2019 growing season compared to 2018. A larger sample size over additional growing seasons is required to fully understand the annual variation in phenolic compound content. The methods and results used in this study provide a basis for further analysis of phenolic compounds present in the European Union’s olive crop processing residues and will inform techno-economic modelling for the development of olive biorefineries in Slovenia