Production And Life Cycle Assessment Of Biodiesel From Three Waste Oils

ABSTRACT

Converting the huge amount of waste cooking oils presently generated globally to biodiesel as

complementary energy source to fossil fuel is one of the major routes to sustainable energy

management. However, producing quality biodiesel at established optimum conditions, through a

clean technology with favourable environmental implications is of greater importance. This

research focused on achieving the latter through alkali catalysed trans-esterification process of

biodiesel production and life cycle assessment (LCA) of the biodiesel produced using SIMAPRO

7.3.3. In this research, the comparative analysis of the use of KOH and NaOH, as catalysts in the

trans-esterification of Waste Groundnut Oil (WGO), Waste Soyabean Oil (WSO) and Crude

Palm Kernel Oil (CPKO); as well as the life cycle assessment of the biodiesel produced from

WGO, WSO and CPKO were established. The results obtained showed that, under similar

conditions, biodiesel yields from the trans-esterification of oils using KOH as catalyst are higher

than the yields from the NaOH catalysed process. Comparatively, the optimum conditions for

biodiesel yield from KOH catalysed trans-esterification of WGO are; 10.67 methanol/oil mole

ratio, 0.86 w/w Oil catalyst concentration at 600C and 71 minutes reaction time. For NaOH

catalysed trans-esterification of WGO, the optimum conditions are 9.94 methanol/oil mole ratio,

0.70 w/w Oil catalyst concentration at 600C and 72 minutes reaction time. Optimum conditions

for biodiesel yield from KOH catalysed trans-esterification of WSO are; 9.76 methanol/oil mole

ratio, 1.04 w/w Oil catalyst concentration at 600C and 70 minutes reaction time. For NaOH

catalysed trans-esterification of WSO optimum conditions are 9.00 methanol/oil mole ratio, 0.70

w/w Oil catalyst concentration at 610C and 70 minutes reaction time. The optimum conditions

for biodiesel yield from KOH catalysed trans-esterification of CPKO are; 9.51 methanol/oil mole

ratio, 1.24 w/w Oil catalyst concentration at 620C and 80 minutes reaction time. For NaOH

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catalysed trans-esterification of CPKO, the optimum conditions are 9.57 methanol/oil mole ratio,

1.10 w/w Oil catalyst concentration at 620C and 85 minutes reaction time. The accuracy of the

optimal conditions obtained in all cases was justified by the optimal desirability values of

approximately 1 in all cases. A simple, cost effective and energy efficient model for the

prediction of biodiesel cetane number (CN) was derived. Statistical analysis showed low value of

3.28 % of Average Absolute Deviation (% AAD) for the proposed biodiesel CN model from the

reported biodiesel CN model (experimental). The values of biodiesel CN calculated using the

proposed model fall within ASTM specification. Analysis of the possible environmental impacts

through the LCA of the biodiesels from WGO, WSO and CPKO recorded the possible emissions

from the production processes as well as the products; and reports on the impacts of these

emission on human health, ecosystem quality and climate change. The emission effects are

potentially more pronounced on the ecosystem quality, followed by human health and least on

climate change.