Pellet Production from Woody and Non-Woody Feedstocks: A Review on Biomass Quality Evaluation

Abstract

Forest and agricultural biomass are important sources of renewable and sustainable fuel for energy production. Their increasing consumption is mainly related to the increase in global energy demand and fossil fuel prices but also to the limited availability of petroleum and the lower environmental impact of these biomass compared with other non-renewable fuels. In particular, the pellet sector has seen important developments in terms of both production and the number of installed transformation plants. In addition, pellet production from non-woody biomass is increasing in importance. One of the fundamental aspects for the correct and sustainable use of a biofuel is evaluation of its quality. This is even more important when dealing with pellet production, considering the broad spectrum of possible raw materials for pelletizing. Considering the significant number of papers dealing with pellet quality evaluation and improvement in the last decade, this review aims to give the reader an overall view of the most current knowledge about this large and interesting topic. We focused on pellets of agricultural and forestry origin and analyzed papers regarding the specific topic of pellet quality evaluation and improvement from the last five years (2016–2020). In particular, the review findings are presented in the following order: the influence of different agro-forest management systems on pellet quality; analysis of pellets from pure feedstocks (no blending or binders); the influence of blending and binders on pellet quality; and the influence of pre and post treatments. Finally, a brief discussion about actual research lacks in this topic and the possibilities for future research are presented. It is important to underline that the present review is focused on the influence of the biomass characteristics on pellet quality. The effects of the process parameters (die temperature, applied pressure, holding time) on pellet features are not considered in this review, because that is another very large topic deserving a dedicated paper.

Evaluation of Urban Tree Leaf Biomass-Potential, Physico-Mechanical and Chemical Parameters of Raw Material and Solid Biofuel

“…The bulk density (603-665kg•m −3 ) and specific density (above 1100 kg•m −3 ) are similar to the level of typical wood pellets used in the power industry [51,72]. This is probably due to the increased value of mineral fractions.…”

Energy Use of Mediterranean Forest Biomass in Sustainable Public Heating Systems and its Effects on Climate Change – Case of Study

“…The aim was to turn this excess of wood biomass, which was treated as green waste, into a resource usable as energy (Kyriakopoulos et al 2013) Wood chips were the initial solid biofuel used, however issues caused by low density, low calorific power and high heterogeneity forced the change to wood pellets. Green waste mixture composition and moisture has direct consequences on the quality of the wood biofuel (IDAE 2007) obtained and its energetic use capacity (Carrillo-Parra et al 2020, Picchio et al 2020, Miranda et al 2015. In the early stages of the Project, raw material was largely composed of green waste from pruning predominant ornamental trees in the study area, such as Morus alba, Pinus pinea, Pinus halepensis, Melia azedarach, Jacaranda mimosifolia, Platanus acerifolia, Ceratonia siliqua.…”

WP3 – Innovation in Agriculture and Forestry Sector for Energetic Sustainability

“…Papers submitted and published in this Special Issue "WP3-Innovation in Agriculture and Forestry Sector for Energetic Sustainability" bring together some of the latest research results in the field of biomass valorization and the process of energy production and climate change and other items about energetic sustainability [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Moreover it is very important to evaluate the safety aspects for energy plant use [21][22][23][24].…”