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The relevant growth of the wood pellet market in Europe in the last decade led to an increased focus on solid biofuel as a necessary and available renewable resource for energy production. Among biofuels, wooden pellets are among the most widespread for domestic heating. Therefore, monitoring the qualitative properties of commercialized pellets is crucial in order to minimize the amount of harmful emissions in residential areas. Standard ISO 17225 sets threshold values for the chemical and physical properties that commercialized biofuels must fulfil. Specifically, ISO 17225-2 defines that pellets for residential use must be produced from virgin wood, but no method is proposed to assess the actual origin of the material, leading to the risk of the commercialization of pellets made up from chemically treated materials. This study proposes a model obtained via near infrared spectroscopy analyses and chemometrics methods, such as classification, to rapidly assess whether pellets are made up of virgin or chemically treated wood. The result suggests the effectiveness of NIRs for the detection of non-virgin pellets with an accuracy greater than 99%. Furthermore, the model appeared to be accurate in the assessment of both milled and intact pellets, making it a potential in-line instrument for assessments of pellets' quality. [ABSTRACT FROM AUTHOR]

Quality is a crucial issue for the energy use of residual biomass, especially for agricultural biomass [[20]]. The authors highlighted that local sourcing of biomass materials with an efficient logistics system presents environmental benefits and significant economic advantages regarding various logistical aspects of biomass transport and energy distribution. All the published papers deal with aspects connected with the SI's theme, such as residual biomass quality, sustainability assessment of solid biofuel production, and bioenergy sustainability assessment. Ilari et al. [[45]] analytically defined the quality of residual woody biomass produced in marginal areas and the solid biofuels obtained from that biomass material. [Extracted from the article]

Replacing fossil energy sources with renewable energy sources is a key strategic action to limit environmental issues. To achieve this goal, substitution with biomass is beneficial due to its versatility in various fields. In terms of circular economy and sustainability, the possibility of energy exploitation of residual biomass is particularly desirable in small-medium enterprises. The use of supply chain by-products can improve sustainability and create opportunities for companies. The purpose of this study is to evaluate the suitability of residual biomass of conifers and broad-leaved trees to produce quality pellets using an agri-pellet machine activated by the power take-off of a tractor. This system can be employed at the farm level. Wood biomass of four species was tested; poplar, stone pine, black locust, and oak. Wood chips samples were analyzed to determine their qualitative characteristics following the technical standard ISO 17225-4. Based on the results, different wood blends were created to produce pellets, subsequently characterized according to ISO 17225-2. The analyses carried out on wood chips and pellets were bulk density, moisture, ash content, calorific value, elemental composition, chlorine, sulfur, and heavy metals. In addition, particles size was measured only for wood chips, while the length, diameter, mechanical durability, and ash melting behaviors were determined only for pellets. Some of the analyzed mixtures show acceptable values according to the current ISO technical standards. The values related to the apparent pellet bulk density and the durability test highlight that not all the mixtures are suitable to produce quality pellets. Results also represent a good starting point for future studies. [ABSTRACT FROM AUTHOR]

This study focuses on verifying the influence of some additives in the ash melting process of herbaceous biomass, developing a pelletized biofuel from the mixture of herbaceous biomass and various inorganic substances through a series of experimental tests. Therefore, different materials were sampled, chemically characterized and combined in mixtures of low-melting biomass materials. Tests were performed with various inorganics products added directly on the relative ashes to verify the interaction between the two systems. Subsequently, herbaceous biomass pellets containing growing amounts of additive were produced, verifying their effectiveness by analyzing the ash melting temperatures and adopting the PASSA test, that investigates the size of the ashes after incinerating the biomass in a muffle. The same method was then used to evaluate the ashes of an industrial boiler. Results show that the addition of inorganic additives in the extent of 3–5% by weight determines an increase in deformation temperatures over 547 °C for several biomass materials and additives. Tests carried out on forage pellets made with alfalfa and CaO as additive brought instead to an increase in deformation temperature between 43 and 107 °C. This work could be of interest in the evaluation of the energy reuse of herbaceous materials that would otherwise be considered as waste, and also it suggests the possibility of using egg shells as inorganic additives in accordance to the circular economy approach. Furthermore, the additivation level of these pelletized biofuel is perfectly in line with the provisions of ISO 17225-6 for non-woody pellets (≤5% weight). [ABSTRACT FROM AUTHOR]