Picchio Rodolfo, Di Marzio Nicolò, Cozzolino Luca, Venanzi Rachele, Stefanoni Walter, Bianchini Leonardo, Pari Luigi, Latterini Francesco
Department of Agriculture and Forest Sciences, DAFNE, Tuscia University, Via San Camillo de Lellis, 01100 Viterbo, Italy.
Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria (CREA), Centro di Ricerca, Ingegneria e Trasformazioni Agroalimentari, Via della Pascolare 16, 00015 Monterotondo, Italy.
Materials (Basel). 2023 Jun 29;16(13):4689. doi: 10.3390/ma16134689.
Typically, coniferous sawdust from debarked stems is used to make pellets. Given the high lignin content, which ensures strong binding and high calorific values, this feedstock provides the best quality available. However, finding alternative feedstocks for pellet production is crucial if small-scale pellet production is to be developed and used to support the economy and energy independence of rural communities. These communities have to be able to create pellets devoid of additives and without biomass pre-processing so that the feedstock price remains low. The features of pellets made from other sources of forest biomass, such as different types of waste, broadleaf species, and pruning biomass, have attracted some attention in this context. This review sought to provide an overview of the most recent (2019-2023) knowledge on the subject and to bring into consideration potential feedstocks for the growth of small-scale pellet production. Findings from the literature show that poor bulk density and mechanical durability are the most frequent issues when making pellets from different feedstocks. All of the tested alternative biomass typologies have these shortcomings, which are also a result of the use of low-performance pelletizers in small-scale production, preventing the achievement of adequate mechanical qualities. Pellets made from pruning biomass, coniferous residues, and wood from short-rotation coppice plants all have significant flaws in terms of ash content and, in some cases, nitrogen, sulfur, and chlorine content as well. All things considered, research suggests that broadleaf wood from beech and oak trees, collected through routine forest management activities, makes the best feasible feedstock for small-scale pellet production. Despite having poor mechanical qualities, these feedstocks can provide pellets with a low ash level. High ash content is a significant disadvantage when considering pellet manufacture and use on a small scale since it can significantly raise maintenance costs, compromising the supply chain's ability to operate cost-effectively. Pellets with low bulk density and low mechanical durability can be successfully used in a small-scale supply chain with the advantages of reducing travel distance from the production site and storage time.
通常，去皮树干的针叶木屑被用于制作颗粒。鉴于其高木质素含量能确保强粘结性和高热值，这种原料能提供现有最佳质量。然而，若要发展小规模颗粒生产并用于支持农村社区的经济和能源独立，寻找颗粒生产的替代原料至关重要。这些社区必须能够生产不含添加剂且无需生物质预处理的颗粒，以使原料价格保持低廉。在此背景下，由其他森林生物质来源制成的颗粒的特性，如不同类型的废料、阔叶树种和修剪生物质，已引起了一些关注。本综述旨在概述该主题的最新（2019 - 2023年）知识，并考虑小规模颗粒生产增长的潜在原料。文献研究结果表明，使用不同原料制作颗粒时，最常见的问题是堆积密度低和机械耐久性差。所有测试的替代生物质类型都存在这些缺点，这也是小规模生产中使用低性能制粒机的结果，导致无法达到足够的机械性能。由修剪生物质、针叶树残余物和短轮伐期萌生林植物的木材制成的颗粒在灰分含量方面都有显著缺陷，在某些情况下，氮、硫和氯含量也存在问题。综合考虑，研究表明，通过常规森林管理活动收集的山毛榉和橡树的阔叶木材是小规模颗粒生产的最佳可行原料。尽管这些原料的机械性能较差，但能提供低灰分的颗粒。考虑小规模颗粒制造和使用时，高灰分含量是一个显著缺点，因为它会大幅增加维护成本，损害供应链的成本效益运营能力。堆积密度低和机械耐久性低的颗粒可成功用于小规模供应链，其优点是减少从生产地的运输距离和储存时间。
