Hagel Sebastian, Lüssenhop Phillipp, Walk Steffen, Kirjoranta Satu, Ritter Annalena, Bastidas Jurado Carla Gabriela, Mikkonen Kirsi S, Tenkanen Maija, Körner Ina, Saake Bodo
Institute of Wood Science, Chemical Wood Technology, Universität Hamburg, Hamburg, Germany.
Institute of Wastewater Management and Water Protection, Bioresource Management Group, Technische Universität Hamburg, Hamburg, Germany.
Front Chem. 2021 Nov 15;9:779609. doi: 10.3389/fchem.2021.779609. eCollection 2021.
Street tree pruning residues are a widely available and currently undervalorized bioresource. Their utilization could help alleviate an increasing biomass shortage and offset costs of the pruning process for the municipalities. In this work, a holistic valorization pathway of pruning residues leading to fibers, oligosaccharides, biogas, and compost is presented. For this, representative mixtures of tree pruning materials from the most prevalent street tree genera (oak, linden, maple) found in Hamburg (Germany) were prepared by shredding and cleaning procedures. Collection of sample material was performed in summer and winter to account for seasonality. A steam-based fractionation was conducted using treatment severities ranging from log R = 2.5 to 4.0. At the highest severity, a fiber yield of around 66%, and liquor yield of 26-30% was determined. The fibers were evaluated with respect to their properties for paper product applications, with higher treatment severities leading to higher paper strengths. From the oligosaccharide-rich liquor, emulsions were created, which showed promising stability properties over 8 weeks of storage. The liquors and the rejects from the material preparation also displayed good potential for biomethane production. Overall, the differences between material collected in summer and winter were found to be small, indicating the possibility for a year-round utilization of pruning residues. For the presented utilization pathway, high severity treatments were the most promising, featuring a high liquor yield, good biomethane potential, and the highest paper strengths.
街道树木修剪残余物是一种广泛可得且目前未得到充分重视的生物资源。其利用有助于缓解日益严重的生物质短缺问题，并抵消市政当局修剪过程的成本。在这项工作中，提出了一条将修剪残余物转化为纤维、低聚糖、沼气和堆肥的整体增值途径。为此，通过粉碎和清理程序，制备了来自德国汉堡最常见街道树种（橡树、椴树、枫树）的具有代表性的树木修剪材料混合物。在夏季和冬季采集样本材料，以考虑季节性因素。使用从对数R = 2.5到4.0的处理强度进行基于蒸汽的分馏。在最高强度下，测定的纤维产率约为66%，液体产率为26 - 30%。对纤维在纸制品应用方面的性能进行了评估，处理强度越高，纸张强度越高。从富含低聚糖的液体中制备了乳液，其在储存8周期间表现出良好的稳定性。液体和材料制备过程中的废料在生物甲烷生产方面也显示出良好的潜力。总体而言，发现夏季和冬季收集的材料之间差异很小，这表明修剪残余物全年利用的可能性。对于所提出的利用途径，高强度处理最具前景，具有高液体产率、良好的生物甲烷潜力和最高的纸张强度。
