**3.1 Proximate analysis**

The proximate analysis provides information on the biomass in terms of volatile matter (VM), ash content, fixed carbon (FC) and moisture (M). VM of biomass is the condensable and non-condensable gases released from the biomass during heating. The amount of VM depends on the heating rate and the final temperature to which biomass is heated. Ash is the solid residue left after the biomass is completely burned. FC shows the percentage of biomass burned in the solid states, while VM indicates the percentage of biomass burned in the gaseous state. The ash content indicates the quantity of non-combustible ash remaining on the fire grates or ash pit or entrained with flue gases. These are of fundamental importance for biomass energy use and such information for specific LCB are depicted in **Table 2**. Such data provides the furnace designer with essential information for the furnace design, including sizing and location of primary and secondary air supplies, refractory, ash removal and exhaust handling equipment etc. [49, 50].

The composition of ash depends on the type of biomass which includes mostly inorganic residues such as silica, aluminum, iron, calcium and small amounts of magnesium, titanium, sodium and potassium may also be present. Even though ash content of biomass is usually very small, it may play a significant role in biomass combustion or gasification if biomass contains alkali metals (such as potassium) or halides (such as chlorine). Straw, other agricultural residues and grasses generally contain potassium compounds and chlorides are particularly susceptible to this problem and can cause severe agglomeration, fouling and corrosion in boilers or gasifiers. The ash obtained during biomass conversion does not necessarily come from biomass itself but also from other sources such as contamination as well. Biomass can pick up a considerable amount of dirt, soil, rock and other impurities during collection and handling. These also partly contribute to ash content. FC is


### **Table 2.**

*Proximate analysis (wt%) of common LCB [35].*

*Recent Advances in Thermochemical Conversion of Biomass DOI: http://dx.doi.org/10.5772/intechopen.100060*

the solid carbon (non-volatile) in the biomass that remains in the char in the pyrolysis process after devolatilization. The amount of FC is related to VM, moisture (M) and ash by the equation: *FC VM ASH* =− − − 1 M [18, 49].

The relationship between FC and charcoal yield in biomass is positive, while VM and ash relate negatively to charcoal yield. It is expected that the greater biomass VM lead to greater gas production instead of the solid phase. Moisture content will have a significant impact on the biomass conversion process. High moisture content is a major concern in biomass. Biochemical conversion processes can use biomass with high moisture content, while thermochemical conversion processes generally require biomass with low moisture content. However, gasification processes require some moisture to produce hydrogen and the amount of hydrogen produced will increase with moisture content. The moisture content of some biomass, such as water hyacinth, can be very high (> 90%). As the energy used in evaporation is not recovered, moisture drains much of the deliverable energy during conversion [49–51].
