**2.2 Pyrolysis products**

Products of the pyrolytic reaction are biochar and hot volatile that need to be separated and cooled down quickly. The residence time of char and volatile in direct contact should be less than 2–3 seconds [5, 15, 52]. Char is greatly porous and has a catalytic effect on volatile cracking to non-condensable gases, more char and also non-desirable volatiles [1]. The main product of fast pyrolysis is liquid bio-oil that is obtained by condensation of volatiles, yielding up to 75 wt.% based on a dry feed


**63**

**Table 3.**

*Woody Feedstock Pretreatments to Enhance Pyrolysis Bio-oil Quality and Produce…*

basis [15]. **Table 3** lists a few key properties of bio-oil and the properties of petroleum grade fuel (Fuel No. 6). Bio-oil has a heating value of about half of conventional fossil fuel oil, 17–19 MJ/kg for bio-oil versus 35–40 MJ/kg for petroleum fossil

The final application of produced bio-oil depends on its quality and properties such as solid content, stability during storage and transportation, oxygen and water contents and its pH value [54]. High oxygen and water content make the bio-oil less stable and less competitive with conventional fossil fuels. Low stabilization, including phase separation and polymerization, and acidic and corrosive properties of bio-oil make its storage and transportation difficult [39, 55]. Based on National Renewable Energy Laboratory's (NREL) recommendation, Multi-Year Program Plan (MYPP 2011), the bio-oil must maintain its consistency for at least 6 months of storage. Based on the published studies, a drastic reduction in water content of biooil, insoluble solids and oxygen content and a substantial increase in the calorific

Gas and biochar are generated as by-products of the pyrolysis process. Optimizing their properties helps to find an application for by-products to make the overall process more economically feasible. They have the potential to provide the heat required for the pyrolysis process. The non-condensable gases of the pyrolysis process have a substantial amount of CO2 and CH4. Combustion of these permanent gases makes heat for the pyrolysis process. Biochar has various interesting properties. First one is that the biochar also has a high calorific value.

with carbon that is a good soil amendment. In addition, adding char to soil moves the carbon from atmosphere to soil [56]. Third but not last, pyrolysis biochar has promising adsorption properties for heavy metals [57], dyes [58, 59] and aromatics [60] in agricultural and industrial effluents. The biomass properties influence the biochar properties to be used for adsorption purposes. For example, woody biomass contains more lignin content than agricultural biomass and its biochar has higher surface area than other biomass-derived biochars. Then, it is speculated to

**Characteristics Fast pyrolysis bio-oil Heavy petroleum fuel**

Water content (wt.%) 15–25 0.1 Insoluble solids (%) 0.5–0.8 0.01 Carbon (%) 39.5 55.8 85.2 Hydrogen (%) 7.5 6.1 11.1 Oxygen (%) 52.6 37.9 1.0 Nitrogen (%) <0.1 0.3 Sulfur (%) <0.05 2.3 Ash (%) 0.2–0.3 <0.1 Heating value (MJ/kg) 17 40 Density (g/ml) 1.23 0.94 Viscosity (cp) @ 50°C 10–150 180

**Wet Dry**

, while energy density for wood

, respectively [1]. Second, biochar is enriched

*DOI: http://dx.doi.org/10.5772/intechopen.81818*

value of bio-oil are needed for upgrading to fuel grade.

The energy density for charcoal is 9–11 GJ/m3

and coal are 8–10 and 25–40 GJ/m3

have better adsorptivity properties [61].

*Properties of wood-derived bio-oil and heavy petroleum fuel [53].*

fuel [52].

#### **Table 2.**

*Bio-oil yield in fast pyrolysis of different biomass feedstocks.*

*Woody Feedstock Pretreatments to Enhance Pyrolysis Bio-oil Quality and Produce… DOI: http://dx.doi.org/10.5772/intechopen.81818*

basis [15]. **Table 3** lists a few key properties of bio-oil and the properties of petroleum grade fuel (Fuel No. 6). Bio-oil has a heating value of about half of conventional fossil fuel oil, 17–19 MJ/kg for bio-oil versus 35–40 MJ/kg for petroleum fossil fuel [52].

The final application of produced bio-oil depends on its quality and properties such as solid content, stability during storage and transportation, oxygen and water contents and its pH value [54]. High oxygen and water content make the bio-oil less stable and less competitive with conventional fossil fuels. Low stabilization, including phase separation and polymerization, and acidic and corrosive properties of bio-oil make its storage and transportation difficult [39, 55]. Based on National Renewable Energy Laboratory's (NREL) recommendation, Multi-Year Program Plan (MYPP 2011), the bio-oil must maintain its consistency for at least 6 months of storage. Based on the published studies, a drastic reduction in water content of biooil, insoluble solids and oxygen content and a substantial increase in the calorific value of bio-oil are needed for upgrading to fuel grade.

Gas and biochar are generated as by-products of the pyrolysis process. Optimizing their properties helps to find an application for by-products to make the overall process more economically feasible. They have the potential to provide the heat required for the pyrolysis process. The non-condensable gases of the pyrolysis process have a substantial amount of CO2 and CH4. Combustion of these permanent gases makes heat for the pyrolysis process. Biochar has various interesting properties. First one is that the biochar also has a high calorific value. The energy density for charcoal is 9–11 GJ/m3 , while energy density for wood and coal are 8–10 and 25–40 GJ/m3 , respectively [1]. Second, biochar is enriched with carbon that is a good soil amendment. In addition, adding char to soil moves the carbon from atmosphere to soil [56]. Third but not last, pyrolysis biochar has promising adsorption properties for heavy metals [57], dyes [58, 59] and aromatics [60] in agricultural and industrial effluents. The biomass properties influence the biochar properties to be used for adsorption purposes. For example, woody biomass contains more lignin content than agricultural biomass and its biochar has higher surface area than other biomass-derived biochars. Then, it is speculated to have better adsorptivity properties [61].


#### **Table 3.**

*Properties of wood-derived bio-oil and heavy petroleum fuel [53].*

*Biomass for Bioenergy - Recent Trends and Future Challenges*

lytic effect on the rate of secondary reactions [51].

**Biomass type Pyrolysis temperature** 

*Bio-oil yield in fast pyrolysis of different biomass feedstocks.*

with the reaction temperature.

and storage [16].

**2.2 Pyrolysis products**

180–600°C [35]. This specification directly influences the temperature range at which the material thermally decomposes and consequently the optimum pyrolysis temperature at which the maximum bio-oil yield is obtained. **Table 2** lists pyrolysis liquid yield of various biomass species at tested temperatures and depicts the variability of produced bio-oil yield among the pyrolysis of different feedstocks. Apart from variability in conversion rate among species, the conversion rate increases

In addition to the chemical composition, the elemental and proximate analysis of the biomass feedstock changes the properties of the produced fuel. From the elemental point of view, the biomass is mainly contained of carbon, hydrogen and oxygen (**Table 1**). The composition of elements affects the storage properties of the liquid fuel. Compared to conventional fossil fuels, biomass has a high amount of ~40–50% oxygen content. High oxygen content makes the produced liquid fuel unstable, corrosive and consequently not qualified for transportation

The minor elements present in the biomass material are minerals such as potassium, chlorine, sulfur, silicon, calcium and magnesium [45]. Minerals are present in all biomass species, in a much lower amount than carbon, hydrogen and oxygen elements. Agricultural biomass has much more mineral contents than woody biomass. In a thermal process, minerals turn to ash (**Table 1**). The pyrolysis biochar typically contains up to 90% of the biomass minerals [46]. Ash shifts the size distribution of the char to smaller sizes that make their recovery from the gas stream challenging. An incomplete separation of char and volatiles causes continuous secondary reactions in the liquid phase [16, 47, 48] that accelerates the aging phenomenon and contribute to its instability [49, 50]. Aging phenomena is defined as a slow increase in viscosity bio-oil resulting from secondary reactions [16]. Minerals have a cata-

Products of the pyrolytic reaction are biochar and hot volatile that need to be separated and cooled down quickly. The residence time of char and volatile in direct contact should be less than 2–3 seconds [5, 15, 52]. Char is greatly porous and has a catalytic effect on volatile cracking to non-condensable gases, more char and also non-desirable volatiles [1]. The main product of fast pyrolysis is liquid bio-oil that is obtained by condensation of volatiles, yielding up to 75 wt.% based on a dry feed

**(°C)**

Pine wood 450 55.0 [36] Waste furniture sawdust 450 65.0 [37] Wood sawdust 650 74.0 [38] Corncob 550 56.8 [39] Municipal, livestock and wood waste 500 39.7 [40] Pine wood 450 50 [41] Rice husks 450 60 [42] Corn cobs and corn stover 650 61.6 [43] Sugar cane waste 470 56.5 [44]

**Bio-oil yield (wt.%)**

**Refs.**

**62**

**Table 2.**
