Miscanthus is resistant to dry, frosty winters in Poland and most European Union countries. Miscanthus gives higher yields compared to native species. Farmers can produce Miscanthus pellets after drying it for their own heating purposes. From the third year, the most efficient plant development begins, resulting in a yield of 25–30 tons of dry matter from an area of 1 hectare. Laboratory scale tests were carried out on the processes of drying, compacting, and torrefaction of this biomass type. The analysis of the drying process was conducted at three temperature levels of the drying agent (60, 100, and 140 °C). Compaction on a hydraulic press was carried out in the pressure range characteristic of a pressure agglomeration (130.8–457.8 MPa) at different moisture contents of the raw material (0.5% and 10%). The main interest in this part was to assess the influence of drying temperature, moisture content, and compaction pressure on the specific densities (DE) and the mechanical durability of the pellets (DU). In the next step, laboratory analyses of the torrefaction process were carried out, initially using the Thermogravimetric Analysis TGA and Differential Scaning Calorimeter DSC techniques (to assess activation energy (EA)), followed by a flow reactor operating at five temperature levels (225, 250, 275, 300, and 525 °C). A SEM analysis of Miscanthus after torrefaction processes at three different temperatures was performed. Both the parameters of biochar (proximate and ultimate analysis) and the quality of the torgas (volatile organic content (VOC)) were analyzed. The results show that both drying temperature and moisture level will affect the quality of the pellets. Analysis of the torrefaction process shows clearly that the optimum process temperature would be around 300–340 °C from a mass loss ratio and economical perspective.

In Poland the use of solid biomass obtained from intentional plantations of energy plants is increasing. This biomass is most often processed into solid fuels. There are growing indications that renewable energy sources, in particular biomass production, will continue to develop, so the better we know the raw material, the more effectively we will be able to use it. The results of tests that determine the impact of compaction pressure on selected quality parameters of pellets made from selected biomass types are presented. Material from plants such as Giant miscanthus (Miscanthus × giganteus Greef et Deu), Cup plant (Silphium perfoliatum L.), Virginia mallow (Sida hermaphrodita (L.) Rusby) was studied. The compaction process was carried out using the SIRIO P400 hydraulic press with a closed chamber with a diameter of 12 mm. Samples were made in four pressures: 131; 196; 262; 327 MPa and three moisture levels: 8%, 11%, 14%. It was found that with increasing compaction pressure and moisture content up to a certain point, the density and durability of the pellets also increased. Each of the materials is characterized by a specific course of changes in the parameters tested.

The biomass is regarded as a part of renewable energy sources (RES), which can satisfy energy demands. Biomass obtained from plantations is characterized by low bulk density, which increases transport and storage costs. Briquetting is a technology that relies on pressing biomass with the aim of obtaining a denser product (briquettes). In the production of solid biofuels, the technological as well as material variables significantly influence the densification process, and as a result influence the end quality of briquette. This process progresses differently for different materials. Therefore, the optimal selection of process’ parameters is very difficult. It is necessary to use a decision support tool—decision support system (DSS). The purpose of the work was to develop a decision support system that would indicate the optimal parameters for conducting the process of producing Miscanthus and willow briquettes (pre-comminution, milling and briquetting), briquette parameters (durability and specific density) and total energy consumption based on process simulation. Artificial neural networks (ANNs) were used to describe the relationship between individual parameters of the briquette production process. DSS has the form of a web application and is opened from a web browser (it is possible to open it on various types of devices). The modular design allows the modification and expansion the application in the future.

Solid biofuels can be defined as processed and unprocessed biomass. By definition it can be divided into: natural fuels (as obtained) and synthetic fuels (after mechanical and chemical treatment). Raw materials for the production of solid biofuels may include: wood, stalk plants, peat, sewage sludge and grains of cereals. These raw materials can be used directly as fuel or as a half-finished product for further production. The aim of the work was to analyze trends and research topics in the production of solid biofuels. This analysis was made using bibliometric techniques. Bibliometric analyzes allow to indicate the research topics, authors, as well as research institutions that significantly influence a given discipline. The research and analysis were carried out on scientific articles taken from the Scopus database in 2014-2018. The downloaded data have been cleaned and processed in the VOSviewer program. This program allows to analyze the frequency of occurrence of keywords in years and to present results in graphic form. Next, a detailed analysis of the content of the publications and classification according to selected criteria was carried out. The main countries that carry out research in this area are: Spain, Italy, Brazil, the Czech Republic and China. The main research areas were: Energy, Environmental Science, Agricultural and Biological Sciences, Chemical Engineering and Engineering. The most popular research topics throughout the research period were: biomass (raw materials, properties), biomass agglomeration processes (briquetting, pelleting), energy properties research, thermal biomass treatment (torrefaction, gasification and others), research on production and biochar properties and other.

For biomass compaction, it is important to determine all aspects of the process that will affect the quality of pellets and briquettes. The low bulk density of biomass leads to many problems in transportation and storage, necessitating the use of a compaction process to ensure a solid density of at least 1000 kg·m−3 and bulk density of at least 600 kg·m−3. These parameters should be achieved at a relatively low compaction pressure that can be achieved through the proper preparation of the raw material. As the compaction process includes a drying stage, the aim of this work is to determine the influence of the drying temperature of pine biomass in the range of 60–140 °C on the compaction process. To determine whether this effect is compensated by the moisture, compaction was carried out on the material in a dry state and on the materials with moisture contents of 5% and 10% and for compacting pressures in the 130.8–457.8 MPa range. It was shown that drying temperature affects the specific density and mechanical durability of the pellets obtained from the raw material in the dry state, while an increase in the moisture content of the raw material neutralizes this effect.