# Review on Fast Pyrolysis of Biomass for Biofuel Production from [PERSON]
## 3 Biomass Generalities
### Influence of the Parameters on the Products Used during Fast Pyrolysis  
#### 3.5.1 When the Temperature Increases  
As we have seen previously, the biomass decomposes into three phases under the action of heat:  
* Condensable phase with oils composed of H\({}_{2}\)O, a number of organic substances and a number of inorganic substances. The inorganic substances are present in several forms. They include Ca, Si, K, Fe, Na, S, N, P, Mg and heavy metals [25]. The organic substances, frequently referred to as \"tars\", are mostly polyaromatic hydrocarbons (molar mass between 78 and 300 g/mol) and aromatics [25,26]. The gaseous phase mainly includes H\({}_{2}\)O, CO, CH\({}_{4}\), CO\({}_{2}\), C\({}_{2}\)H\({}_{4}\), H\({}_{2}\), C\({}_{2}\)H\({}_{2}\), and other heavier hydrocarbons, and the solid (char) phase mainly contains carbon with small amounts of hydrogen and oxygen. It also contains inorganic species.  
With an increase in temperature, the quantity of gas produced by the various technologies increases [27], the amount of CO trained increases [28], the amount of hydrogen formed in the reaction increases with increasing temperature due to the gas phase cracking of the hydrocarbons, the amount of hydrocarbons formed diminishes in the temperature range 1873-2073 K [28], the amount of CH\({}_{4}\) produced diminishes, and the amount of CO\({}_{2}\) generated during the reaction increases.  
**Effect of residence time.**  
In the literature, the effect of residence time is found to be related to the temperature parameter in biomass pyrolysis technology [29]. The interactive effect of the residence time and temperature is the not necessarily well-accepted reduction caused by biomass pyrolysis for biomethanation. [PERSON] et al. [30] observed that as temperature and residence time increase, secondary reactions increase and tar molar mass decreases. A long residence time favors tar cracking and reforming [31]. On the contrary, a low residence time leads to a partial depolymerization of the lignin and encourages the production of bio-oils [32].  
Figure 2: (**a**) Diagram showing the different categories of pyrolysis products [20]. (**b**) Influence of heating rate (for the two temperatures of 773 K and 1273 K) on pyrolysis products as a function of temperature [20].  
[PERSON] et al. [33] discovered that when the vapor residence time is long, H\({}_{2}\), CH\({}_{4}\) and CO\({}_{2}\) concentrations increase.  
The C\({}_{2}\)H\({}_{4}\) and C\({}_{2}\)H\({}_{6}\) concentrations remained weakly influenced. [PERSON] et al. [34] described that a syngas produced via the pyrogasification of biomass for biomethanation favors the production of H\({}_{2}\) with long residence times and high temperature [25; 35; 36].  
**Effect of pressure.**  
The work of [PERSON] et al. [37] showed that pyrolysis of biomass is generally performed at high pressures compared to coal. Unlike temperature, the effect of partial pressure, as well as total pressure, is not a well-studied parameter in the literature.  
The total pressure is fixed, on the one hand, in order to keep the system in the liquid state (light products, aqueous phase) at the reaction temperature and, on the other hand, in order to ensure solubility of hydrogen in the bio-oil [38]. The yield of CO\({}_{2}\) increases with pyrolysis pressure, while the yield of high molecular weight gases like C\({}_{2}\)H\({}_{4}\) and C\({}_{2}\)H\({}_{6}\) decreases with increasing pyrolysis pressure up to 30 bar [38].