Chia (Salvia hispanica L.) is a small seed that comes from an annual herbaceous plant, Salvia hispanica L. In recent years, usage of Chia seeds has tremendously grown due to their high nutritional and medicinal values. Chia was cultivated by Mesopotamian cultures, but then disappeared for centuries until the middle of the 20th century, when it was rediscovered. Chia seeds contain healthy ω-3 fatty acids, polyunsaturated fatty acids, dietary fiber, proteins, vitamins, and some minerals. Besides this, the seeds are an excellent source of polyphenols and antioxidants, such as caffeic acid, rosmarinic acid, myricetin, quercetin, and others. Today, chia has been analyzed in different areas of research. Researches around the world have been investigating the benefits of chia seeds in the medicinal, pharmaceutical, and food industry. Chia oil is today one of the most valuable oils on the market. Different extraction methods have been used to produce the oil. In the present study, an extensive overview of the chemical composition, nutritional properties, and antioxidant and antimicrobial activities, along with extraction methods used to produce chia oil, will be discussed.

The torrefaction process upgrades biomass characteristics and produces solid biofuels that are coal-like in their properties. Kinetics analysis is important for the determination of the appropriate torrefaction condition to obtain the best utilization possible. In this study, the kinetics (Friedman (FR) and Kissinger–Akahira–Sunose (KAS) isoconversional methods) of two final products of lignocellulosic feedstocks, miscanthus (Miscanthus x giganteus) and hops waste (Humulus Lupulus), were studied under different heating rates (10, 15, and 20 °C/min) using thermogravimetry (TGA) under air atmosphere as the main method to investigate. The results of proximate and ultimate analysis showed an increase in HHV values, carbon content, and fixed carbon content, followed by a decrease in the VM and O/C ratios for both torrefied biomasses, respectively. FTIR spectra confirmed the chemical changes during the torrefaction process, and they corresponded to the TGA results. The average E_α for torrefied miscanthus increased with the conversion degree for both models (25–254 kJ/mol for FR and 47–239 kJ/mol for the KAS model). The same trend was noticed for the torrefied hops waste samples; the values were within the range of 14–224 kJ/mol and 60–221 kJ/mol for the FR and KAS models, respectively. Overall, the E_a values for the torrefied biomass were much higher than for raw biomass, which was due to the different compositions of the torrefied material. Therefore, it can be concluded that both torrefied products can be used as a potential biofuel source.

The main objective of this review is to present the latest research results regarding the importance of the torrefaction process for different biomass materials in the last 12-year period. Despite the fact that the potential of renewable energy sources has been analyzed, research regarding that of energy derived from waste biomass still remains in the infancy state. Torrefaction is known to be one of the most effective methods for enhancing the energy efficiency of biomass. Among different types of torrefactions, the focus in this study is mostly on dry torrefaction. The influential factors, like temperature and residence time, and physico-chemical properties of torrefied products, and the prospective of torrefaction due to its reduced impact on environment, are discussed in-depth. This review provides valuable insights into the torrefaction process, which is conducive to upgrading biomass for achieving net zero carbon emissions, as it has been stated in several works that torrefied biomass can be used instead of coal.

In this study, three locally available biomasses, namely miscanthus, hops, sewage sludge, and additionally, their mixtures, were subjected to the torrefaction process to improve their fuel properties. The torrefaction process was conducted at 250–350 °C and 10–60 min in a nitrogen (N₂) environment. The torrefaction temperature and time were studied to evaluate the selected biomass materials; furthermore, heating values, mass and energy yields, enhancement factors, torrefaction severity indexes (TSI), and energy-mass co-benefit indexes (EMCI) were calculated. In addition, thermogravimetric (TGA) and Fourier transform infrared analyses (FTIR) were performed to characterize raw and torrefied biomass under the most stringent conditions (350 °C and 60 min). The results showed that with increasing torrefaction temperature and duration, mass and energy yields decreased, and heating values (HHVs) increased for all studied biomasses. The results of the TSI and EMCI indexes showed that the optimum torrefaction conditions were as follows: 260 °C and 10 min for pure miscanthus and hops, whilst this could not be confirmed for the sewage sludge. Furthermore, the combination of sewage sludge and the above-mentioned types of lignocellulosic biomass exhibited better fuel properties than sewage sludge alone.

The paper presents the results of research aimed at evaluating the possibility of using selected biomass wastes to produce solid biofuels. In this work, the thermochemical properties of two lignocellulosic biomasses, namely, miscantshus (Miscanthus × Giganteus) and hops (Humulus lupulus), and non-lignocellulosic biomass, namely, municipal solid waste, and their mixtures (micanthus + municipal solid waste and hops + municipal solid waste) were studied using the torrefaction process as the main method for investigation. The effects of various torrefaction temperatures (250, 300, and 350 °C) and times (30 and 60 min) were evaluated. Proximate and ultimate analyses were performed on the torrefied samples. The following can be stated: as the torrefaction temperature and time increased, mass and energy yields decreased while the higher heating values (HHVs) and fuel ratios (FRs) increased, together with carbon contents (C). In addition, energy on return investment (EROI) was studied; the maximum EROI of 28 was achieved for MSW biochar at 250 °C for 30 min. The results of studying greenhouse gas emissions (GHGs) showed a reduction of around 88% when using torrefied biochar as a substitute for coal. In sum, this study shows that torrefaction pre-treatment can improve the physicochemical properties of raw biomasses to a level comparable with coal, and could be helpful in better understanding the conversion of those biomasses into a valuable, solid biofuel.

In this work, the thermochemical properties of municipal solid waste (MSW) are studied using the torrefaction process as the main method for investigation. Torrefaction experiments were carried out using an electric laboratory furnace, at temperatures of 200, 250, and 300 °C. The residence time was set to 90 min. Proximate and ultimate analysis were performed on the torrefied MSW samples and compared with the properties of the raw MSW samples. In addition, the thermal properties of the obtained torrefied MSW samples were evaluated by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The following could be stated: the obtained results showed that mass and energy yields (MY and EY, respectively) decrease with increasing when torrefaction temperature, while the heating values (HHV) increased under the same conditions (from 24.3 to 25.1 MJ/kg). Elemental analysis showed an increase in carbon content (C), from 45.7 ± 0.9 to 52.8 ± 1.05 wt.%, and decrease in oxygen content (O), from 45.6 ± 0.9 to 39.5 ± 0.8 wt.%, when torrefaction temperature is increased, which is consistent with the general definition of the torrefaction process. In addition, enhancement factors (EFs) and fuel ratios (FRs) were calculated, which ranged from 1.00 to 1.02 and 0.16 to 0.23, respectively. Some anomalies were observed during the thermal analysis, which are assumed to be related to the composition of the selected MSW. This study therefore shows that torrefaction pretreatment can improve the physicochemical properties of raw MSW to a level comparable to coal, and could contribute to a better understanding of the conversion of MSW into a valuable, solid biofuel.