**3. Results and discussion**

Table 3 shows the physicochemical characteristics of CNSL obtained including the decarboxy‐ lated CNSL. The quantity and characteristics of the CNSL extract varies with the extraction method.


**Table 3.** Physico-chemical characteristics of CNSL obtained including the decarboxylated CNSL.

CNSL obtained by pyrolysis although a little less in quantity than the soxhlet extraction, is denser (943 kg/m3 ) with less moisture content (4.1%) and higher saponification value (58.5%). Solvent-extracted CNSL presented higher contents of cardol and anacardic acid and a lower percentage of cardanol than thermally extracted CNSL (Table 4). The higher content of cardanol, viscosity and impurity were the significant differences in CNSL obtained through pyrolysis. This gave credence to the report of Rodrigues *et al*. [22].


**Table 4.** Composition of the extracted CNSL

Decarboxylation of raw CNSL involves loss of a carbon dioxide molecule from anacardic acid. The anacardic acid in the oil was converted to cardanol. This is reflected in the composition variation of the components reported in table 4. It is also significant that the pyrolysis of the CNS results in loss of the carboxylic acid content of the cashew nut shell to the process. The decarboxylated anacardic acid is termed CNSL biodiesel. The biodiesel obtained from CNSL does not require further processing like Trans esterification.

CNSL biodiesel is considered as offering many advantages, including sustainability, decrease of HC, CO, NOx gas emissions and many harmful pollutants [23]. Reference [24] explains the pyrolysis procedure of CNSL. The decarboxylation of CNSL is responsible for the trend in the pH obtained for the extracts.

Most of the characteristics evaluated gave similar results as those already reported in the literature. In the present findings, the highest occurrence of cardanol was in the decarboxylated CNSL while anacardic acid and cardol occur most in the hexane-extracted and pyrolysis CNSL, respectively. This gave credence to the report of [25].

Heating CNSL decomposed the anacardic acid into cardanol and CO2. Decarboxylation of CNSL to convert anacardic acid into cardanol could be done by heating, with an optimum heating temperature of 140°C for 1 h.
