15
combust in engines, boilers and other power and heat plants [86]. The upgraded
intermediate pyrolysis bio-oil can be blended with diesel and gasoline and used as a
transportation fuel in engines [87]. The gas phase showed a low ash content and a
suitable calorific value, which can be utilized in combined heat and power (CHP)
processes [85].
5.2 Pyrolysis Products
The three main products from the pyrolytic process of biomass are biochar, bio-oil
and permanent gas fraction. Their properties and yields are influenced mainly by
biomass composition and pyrolysis conditions.
5.2.1 Biochar
Biochar is an aromatic polycyclic carbon and solid residue formed after the pyrolysis conversion of carbonaceous biomass characterized by a high proportion of carbon, low volatility and small amounts of hydrogen and oxygen [81]. However,
thermo-catalytic reforming (TCR) biochar is free of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), and it contains a low level of
dioxins, hence a reliable and valid carbon source in terms of safety, health and
environmental concerns [88]. TCR technology is discussed in details in the next
section (Sect. 6).
Usually, char is extracted from the gas fraction in the cyclone step, and it contains most of the inorganic material existing in the original feed. The physical and
chemical features of the biochar are affected by the pyrolysis parameters and feedstock composition. Process conditions can vary, and thus the higher heating value
(HHV) can be between 20 and 36 MJ/kg and the carbon amount between 53 and
96 wt% [89]. Additionally, during pyrolysis, the biochar production may range from
10 to 40 wt% depending on the conditions of the process. In terms of physical properties, the temperature can increase the surface area between 100 and 500 m
2
/g due
to the formation of a microporous structure [90]. Below 400 °C, there is an incomplete elimination of biomass volatiles, and consequently, the alteration of the char
surface area is insignificant. From 400 to 900 °C, the surface area of the biochar
starts to increase gradually [89].
Biochar has the capacity to retain water in different soils (up to 25% in comparison with no added biochar) and to provide carbon, nitrogen and inorganics for agricultural fields, improving the quality of the crops [91]. Moreover, it is extremely
stable when introduced in the soil environment, and it can perform carbon sequestration due to its rounded structures [92]. For those reasons, biochar is considered to
be an optimum fertilizer and soil amendment being utilized for hundreds of years as
an eco-friendly solution to improve and remediate the quality of the soils [93].
Thermochemical Conversion of Biomass and Upgrading of Bio-Products to Produce…
combust in engines, boilers and other power and heat plants [86]. The upgraded
intermediate pyrolysis bio-oil can be blended with diesel and gasoline and used as a
transportation fuel in engines [87]. The gas phase showed a low ash content and a
suitable calorific value, which can be utilized in combined heat and power (CHP)
processes [85].
5.2 Pyrolysis Products
The three main products from the pyrolytic process of biomass are biochar, bio-oil
and permanent gas fraction. Their properties and yields are influenced mainly by
biomass composition and pyrolysis conditions.
5.2.1 Biochar
Biochar is an aromatic polycyclic carbon and solid residue formed after the pyrolysis conversion of carbonaceous biomass characterized by a high proportion of carbon, low volatility and small amounts of hydrogen and oxygen [81]. However,
thermo-catalytic reforming (TCR) biochar is free of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), and it contains a low level of
dioxins, hence a reliable and valid carbon source in terms of safety, health and
environmental concerns [88]. TCR technology is discussed in details in the next
section (Sect. 6).
Usually, char is extracted from the gas fraction in the cyclone step, and it contains most of the inorganic material existing in the original feed. The physical and
chemical features of the biochar are affected by the pyrolysis parameters and feedstock composition. Process conditions can vary, and thus the higher heating value
(HHV) can be between 20 and 36 MJ/kg and the carbon amount between 53 and
96 wt% [89]. Additionally, during pyrolysis, the biochar production may range from
10 to 40 wt% depending on the conditions of the process. In terms of physical properties, the temperature can increase the surface area between 100 and 500 m
2
/g due
to the formation of a microporous structure [90]. Below 400 °C, there is an incomplete elimination of biomass volatiles, and consequently, the alteration of the char
surface area is insignificant. From 400 to 900 °C, the surface area of the biochar
starts to increase gradually [89].
Biochar has the capacity to retain water in different soils (up to 25% in comparison with no added biochar) and to provide carbon, nitrogen and inorganics for agricultural fields, improving the quality of the crops [91]. Moreover, it is extremely
stable when introduced in the soil environment, and it can perform carbon sequestration due to its rounded structures [92]. For those reasons, biochar is considered to
be an optimum fertilizer and soil amendment being utilized for hundreds of years as
an eco-friendly solution to improve and remediate the quality of the soils [93].
Thermochemical Conversion of Biomass and Upgrading of Bio-Products to Produce…