From raw biomass to advanced solid biofuels: Pilot-Scale torrefaction and pelletization of multi-lignocellulosic feedstocks

Biomass conversion represents a sustainable alternative to fossil fuels, using renewable organic matter as a source of energy. Pelletization is one of the most efficient methods for converting biomass into biocombustibles. This step not only makes it easier to store and transport biomass, but it also increases its calorific value and combustion efficiency. Following the pelletization process, a thermal treatment called torrefaction may be employed. This step entails heating the pellets to low temperatures, typically between 250 and 300 °C, in a controlled atmosphere. Torrefaction alters the chemical structure of biomass, increasing its heat capacity and decreasing its humidity rate. Therefore, torrefied pellets have ideal combustion characteristics, which makes them very appealing for heating and energy generation applications. This study focuses on transforming various pellets based different biomass (olive pomace (B1), olive stones (B2), apricot kernels (B3), soya (B4), cannabis waste (B5), algae (saccorhiza) (B6), and de-oiled olive pomace (B7)) into torrefied pellets (T1 to T7). This process makes it possible to produce torrefied pellets with a yield that ranges from 68.50 to 81.15 %, a calorific power that increases from (12.87 - 20.38 MJ/kg) to (19.80 – 27.80 MJ/kg), These values comply with the standards EN 14961-4 and ISO 17225-4 (A1+). A fixed carbon percentage that ranges from 6.17 to 20 % for biomasses and 8.30 to 31.68 % for torrefied biomasses comply with international standards (DIN Plus, AOI, AQHP, and N-CAN/CSA-ISO 17225 Class A1 and A2).