Optimising pyrolysis conditions for thermal conversion of beauty leaf tree (Calophyllum inophyllum L.) press cake

Beauty leaf tree (BLT) has been recognised as one of the potential species for biodiesel production in the tropics as it can produce up to 3800 L of non-edible oil which can be converted to biodiesel. The BLT is also resilient to stress conditions so it can be cultivated on degraded lands such as salt- and drought-affected soils. Biodiesel production from BLT, however, generates wastes such as the husk, press cake and glycerol. These wastes will increase the cost of producing biodiesel, and they can also add waste management issues. The current study investigated conversion of BLT biodiesel production wastes into other forms of biofuels. Oven-dried press cake samples were pyrolysed using a batch reactor at 300, 400 or 500 °C, with a residence time of 30, 60 or 90 min. The gas generated from this process was condensed to produce bioliquor and biooil, and the uncondensed gas was quantified as syngas. The pyrolysed biomass residue was collected as biochar and quantified. Energy content of these four products was determined, and the results showed that more than 90% of the energy contained in the BLT press cake can be recovered as other forms of biofuel. It was also found that the temperature had greater influence on the conversion process than on residence time. Furthermore, the biochar yield decreased with an increase in temperature, in contrast to biooil and syngas yields. The optimum conditions for thermal conversion of BLT press cake were found to be 500 °C, with a residence time of 30 min. This study demonstrates that the wastes resulting from biodiesel production process can be used as the feedstocks for producing other forms of biofuels. This approach will not only solve the environmental issues, but it will also improve economic viability of BLT biodiesel production process. Based on these results and the additional tests, a portable and continuous feeding auger pyrolysis reactor is recommended for converting BLT whole fruits, press cake or husks into biofuels.