Future Perspectives of Biomass Torrefaction: Review of the Current State-Of-The-Art and Research Development

Abstract

Abstract:The growing search for alternative energy sources is not only due to the present shortage of non-renewable energy sources, but also due to their negative environmental impacts. Therefore, a lot of attention is drawn to the use of biomass as a renewable energy source. However, using biomass in its natural state has not proven to be an efficient technique, giving rise to a wide range of processing treatments that enhance the properties of biomass as an energy source. Torrefaction is a thermal process that enhances the properties of biomass through its thermal decomposition at temperatures between 200 and 300 • C. The torrefaction process is defined by several parameters, which also have impacts on the final quality of the torrefied biomass. The final quality is measured by considering parameters, such as humidity, heating value (HV), and grindability. Studies have focused on maximizing the torrefied biomass' quality using the best possible combination for the different parameters. The main objective of this article is to present new information regarding the conventional torrefaction process, as well as study the innovative techniques that have been in development for the improvement of the torrefied biomass qualities. With this study, conclusions were made regarding the importance of torrefaction in the energy field, after considering the economic status of this renewable resource. The importance of the torrefaction parameters on the final properties of torrefied biomass was also highly considered, as well as the importance of the reactor scales for the definition of ideal protocols.

Fuel Properties of Torrefied Biomass from Pruning of Oxytree

“…Torrefaction is the thermochemical process (similar to 'roasting')-typically at temperatures between 200 • C and 300 • C-occurring in the absence of oxygen, resulting in biochars [17]. Torrefaction allows the conversion of raw biomass into solid fuel with energy properties similar to bitumen and lignite coal [18], depending on the initial properties of the feedstock.…”

A Review of Biochar Properties and Their Utilization in Crop Agriculture and Livestock Production

“…Typical BC pyrolysis time and temperature range from 60 to 240 min and from 300 to 700 • C; however, those parameters are determined by the desired properties of the final material [3]. Torrefaction, a low-temperature pyrolysis at a range of 200 to 300 • C, also referred to as "mild pyrolysis" or "high-temperature drying", has recently gained more interest as it allows a feedstock material with similar properties to be obtained but with simpler technology compared to regular pyrolysis for the same feedstock material, due to the lower temperature of the process [6].…”

Biomass Torrefaction as a Key Driver for the Sustainable Development and Decarbonization of Energy Production

“…Given this context, biomass torrefaction has emerged as an alternative capable of meeting the needs of a demanding energy market due to its ability to supply a final product according to the needs of coal users, as it is capable of directly replacing coal without the need for process changes, and therefore, prevents the need to invest significant amounts for the conversion of coal-fired power plants to biomass power plants [35]. Torrefaction can be defined as the thermochemical conversion process of biomass, occurring within a temperature range of 220 to 320 • C, at atmospheric pressure, in an oxygen-deficient environment, where the degradation of the constituent hemicellulose occurs with cellulose and lignin remaining [36][37][38][39]. This process eliminates volatile organic compounds and water, contributing to an increase in the fixed carbon content, and subsequently to the calorific value of the final product [40,41].…”