Solid olive mill residue (SOMR), a lignocellulosic material obtained from olive oil extraction, is a potential attractive source of biomass for energy generation. Although SOMR can be directly combusted, a pretreatment can reduce the oxygen and moisture contents of raw SOMR for efficient energy generation. Torrefaction is a promising thermal pretreatment method for improving fuel characteristics of raw SOMR. In this study, torrefaction characteristics of SOMR were investigated at three different torrefaction temperatures and holding times. Ultimate and proximate analysis results of torrefied SOMR were compared with dried SOMR. Results indicate that an increased torrefaction temperature and holding time can lead to a more qualified solid fuel with higher carbon content, increased higher heating value (HHV), and reduced oxygen content. Further, increased HHV and removal of volatiles are indicators of more energy-dense solid fuel obtained from SOMR. Experimental results revealed that moderately severe torrefaction conditions with holding times not exceeding 30 minutes are suitable for torrefaction of SOMR.

Torrefaction is a thermochemical pretreatment method for improving fuel characteristics of biomass. The process is conducted between 200 and 300 °C under inert atmosphere. The relatively low process temperature of torrefaction makes the use of solar energy suitable with low costs. In this study, solid olive mill residue (SOMR) was used to test the feasibility of using solar energy in the torrefaction process. SOMR is an agricultural waste obtained from olive oil extraction, and it is mainly produced in the Mediterranean region, which has high solar energy potential. In this study, the torrefaction of SOMR was conducted by concentrating solar energy with a parabolic dish concentrator, at 250 °C for 10 min. The fuel properties of solar torrefaction products were compared with raw SOMR. Solar torrefaction yielded a deoxygenated solid fuel with increased carbon content and higher heating value (HHV), similar to torrefaction.

Torrefaction is an important biomass pretreatment method that impacts fuel characteristics of biomass, specifically during the torrefaction process. Besides improving the fuel characteristics of biomass, torrefaction also contributes to increased quality of liquid and gaseous energy carriers obtained from fast pyrolysis and gasification. In this study, the effect of torrefaction on the solid energy carrier biochar, produced by carbonization, was studied by using solid olive mill residue (SOMR) as raw biomass. The carbonization characteristics of SOMR and torrefied SOMR (tSOMR) were compared by using ultimate and proximate analysis results. The higher heating value (HHV) and energy yields of biochars produced from SOMR and tSOMR were compared. The results showed that torrefaction contributed to the reduction of energy given to the biomass during the carbonization process by decreasing the holding time.