Effect of Oil Extraction Conditions on the Anaerobic Fermentation of <i>Jatropha curcas</i> Seed Cakes

Abstract

The production of biogas is a heathy way to convert biomass like seed cakes into energy. But before that, oil seeds like jatropha curcas are treated in some conditions in other to get oil first, and cakes after. And different levels of those conditions that are seed type, preheat temperature and extraction pressure can give different results on biogas production using those cakes. That is why in this study, biogas characteristics of cake, from three types of jatropha seeds (whole, kernels and crushed) preheated at four levels of temperature (25°C, 50°C, 75°C and 100°C) and submitted at three extraction pressures (181.81 bar, 324.66 bar and 422.06 bar), were assessed. It consisted in mixing 5 ml solid mixture (2.5 ml of cake sample and 2,5 ml cow dung) to the buffer solution (NH₄Cl, 100; NaCl, 10; MgCl 2 • 6H₂O, 10; CaCl₂.2H₂O, 5) at 1:1 ratio. The mixture was introduced in a reactor of 16 ml volume and then incubated in an electric oven at 37°C for 60 days. The measure of gas volume of each sample was done using the adapted method of displaced liquid. The gas calorific value estimation of each sample was theoretically done, using Buswell equation. And, the gas energy was obtained for each sample, using its gas volume and calorific value. The main results were as follows. The highest volume of biogas (8 ml / g) and highest energy (2485.85 J) were registered with whole seed cake at preheated temperature/extraction pressure couple of 100°C-324.66 bar. The highest calorific value (701.43 KJ/mol) was obtained with the whole seed cake at preheated temperature/extraction/ pressure couple of 100°C-422.06 bars. The main conclusion that can be made is that, there is an effect of oil extraction conditions on the anaerobic fermentation of jatropha curcas seed cakes.