As mentioned above, there are four main types of biomass used for liquid biofuels production: oleaginous (triglyceride source), sugary (sucrose to convert into a glu­cose source), starchy (natural polymer to convert into a glucose source), and cellu — losic (a natural polymer converted into a glucose source). Due to the varying nature of these materials and the processes for converting them to different liquid fuels, they all require different analytical profiles and techniques, each one is considered individually below.

1.1 Oleaginous Biomass

The oleaginous biomass has high contents of triglycerides or lipids, esters derived from glycerol and three fatty acids, within their seeds or grains (Fig. 1). Some free fatty acids may also be present. The chemical composition of the fatty acids within the triglycerides can vary, both with respect to the length of the alkyl chains and the degree of unsaturation depending on the biomass sources (Table 1). This composi­tion can also vary due to soil type, tillage, and climate conditions. The free fatty acids and triglycerides are converted to biodiesel by means of a transesterification reac­tion in the presence of a basic or acidic catalyst and an alcohol (Oh et al. 2012). The chemical composition of the oil along with the free fatty acid content affects both the

transesterification process and the properties of the biodiesel formed, and therefore, analysis of these properties are vital for different oleaginous biomass sources.

Triglycerides can represent 10-25 % m/m in vegetable oils (Gunstone 2004). Table 2 shows values of physicochemical properties from some agricultural species used for biodiesel production.

Some methylic and ethylic esters, observed in biodiesel after transesterification process, are as follows:

• Laurate, derived from lauric acid, C12:0, from palm oil;

• Myristate, derived from myristic acid, C16:0, from tallow;

• Palmitate, derived from palmitic acid, C16:0, cottonseed and palm oils;

• Estereate, derived from estearic acid, C18:0, from tallow;

• Linoleate, derived from linoleic acid, C18:2, C18:2, from cottonseed oil.

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Fig. 2 Chemical structure of sucrose, a disaccharide present in sugarcane (author). The D-glucose moiety is on the left, and the D-fructose moiety is on the right linked by a-|3-D-disac — charide bonds. Author Sflvio Vaz Jr