# Influences of the Pretreatments of Residual Biomass on
## 5 Conclusions  
In this work, devolatilization tests of untreated and pretreated wheat straw pellets were carried out at three temperature levels (700, 800, and 900 \({}^{\circ}\)C), in a fluidized bed made up of sand. Integral-average gas yield, H\({}_{2}\)/CO molar ratio, and carbon conversion were determined from gas release data obtained by devolatilizations of individual pellets. Whatever the considered biomass, all these parameters increased as the temperature was increased, with a general improvement in syngas quality and productivity. Concerning the specific pretreatments:  
* No evident influences on the integral-average gas yield emerged;
* All pretreated wheat straw pellets showed integral-average H\({}_{2}\)/CO molar ratios higher than those of untreated wheat straw: the highest value was recorded for wheat straw pellet torrefied at 270 \({}^{\circ}\)C (the highest explored devolatilization temperature);
* Integral-average carbon conversion of untreated wheat straw pellets was significantly higher that of pretreated pellets;
* The washing pretreatment after torrefaction did not produce significant improvements in term of integral-average gas yield, H\({}_{2}\)/CO molar ratio, and carbon conversion, when compared to only-torrefied ones. Because of the intrinsically unsteady-state of devolatilizations (performed for individual pellets), a new analysis method of devolatilization data was proposed, focused on the peak in the experimental curves of released flow rates of syngas components (CO, CO\({}_{2}\), H\({}_{2}\), CH\({}_{4}\), and hydrocarbons as C\({}_{3}\)H\({}_{8,\mathrm{eq}}\)). Trends of syngas compositions as functions of devolatilization temperature were obtained by regressions with straight lines. Similarly, trends regarding the parameter \"specific maximum gas production\" were also obtained. As to fractions of gas species, the regressed trends offered some further information, which were not inferred from the previous integral-average analysis:  
* The higher the devolatilization temperature, the greater the H\({}_{2}\) fraction in the syngas, at the expenses of CO\({}_{2}\), CH\({}_{4}\), and hydrocarbons;
* All pretreatments improved the H\({}_{2}\)/CO molar ratio related to peaks, in comparison to the same ratio obtained from untreated wheat straw;
* A direct influence from torrefaction temperature emerged on H\({}_{2}\)/CO molar ratio related to peaks, corroborating the less clear indication obtained by the integral average analyses. Observations from the two kinds of analysis were in fair agreement with literature. The integral average estimations and the regression peak analysis both appeared as general and straightforward methods to investigate the thermochemical behavior of biomasses, as well as the influences from operating conditions and biomass nature. Together with the experimental procedure of devolatilization of a few pellets, they constitute a faster and simpler procedure to select the more promising biomasses and operating conditions during a preliminary screening phase, in comparison to a more complex and time-demanding experimental campaign based on a continuous gasification process. An additional outcome of this work is the provision of elaborated experimental data for further studies with modeling purposes, which also allow careful extrapolation (out of the experimentally explored temperature range) by means of linear regressed trends. As a general remark, the torrefraction pretreatment brings in several advantages (e.g., grindability, pelletability, storability, increased heating value, higher H\({}_{2}\)/CO molar ratio in devolatilized syngas), while the related operational costs may be limited--thanks to the low required temperatures--and easily compensated via heat recoveries in the intensified industrial configuration of a CLG plant. Conceptualization, A.D.G. and K.G. ; methodology, A.D.G. and K.G. ; software, S.L. and A.D.G. ; validation, A.D.G. and K.G. ; formal analysis, A.D.G. and K.G. ; investigation, S.L., A.D.G. and K.G. ; resources, K.G.