EVALUATION OF THE BIODIESEL POTENTIALS OF SELECTED PLANT BIOMASSES IN IBADAN NORTH LOCAL GOVERNMENT AREA, NIGERIA

Abstract

There has been an increasing emphasis on renewable sources of energy following recurrent economic crises and environmental concerns associated with petrodiesel. In Nigeria, there is an abundance of oil-bearing inedible plant biomasses, which are underutilized. Research into biodiesel production from these renewable oil sources can provide a more sustainable alternative to petrodiesel. This study was designed to evaluate the biodiesel yielding potentials of selected locally available plant biomasses.

Four plant biomasses (Moringa oleifera, Elaeis guineensis, Thevetia peruviana and Spirogyra africana) were utilised. Oil extraction from the biomasses was carried out using Soxhlet and Cold-solvent extraction methods. Hexane-only (H-only) solvent was used in the Soxhlet extraction while two solvent systems were used in the Cold extraction [Hexane/Ether (H/E) mixture and H-only]. The extracted oils were processed to biodiesel via transesterification reaction using sodium hydroxide as catalyst, and two alcohol systems [Methanol/Ethanol (M/E) mixture and Methanol-only (M-only)]. Samples of biomasses were analysed for moisture content and levels of the elements-Phosphorus (P), Calcium (Ca), Sodium (Na) and Sulphur (S)]; and the oil samples for Kinematic Viscosity (KV), Free Fatty Acid (FFA) level and Saponification value. Samples of the biodiesels were also analysed for KV, Flash Point (FP), Acid Value (AV) and the levels of P, Ca, Na and S according to the methods described by the American Standard for Testing and Materials (ASTM D6751). Results of analyses were compared with ASTM D6751 guidelines. Data were analysed using descriptive statistics and t-test at 5% level of significance.

The oil yields from Soxhlet extraction, Cold extraction (H/E mixture) and Cold extraction (H-only) were: Moringa (45.0%, 27.7% and 18.0%), PK (38.4%, 33.2% and 25.4%), Thevetia (62.3%, 51.9% and 45.8%) and Spirogyra (22.3%, 11.5% and 6.4%) respectively. Similarly, biodiesel yield from the extracted oils in the M/E and M-only transesterification processes were: Moringa (61.2% and 65.5%), PK (72.4% and 75.3%), Thevetia (78.4% and 85.2%) and Spirogyra (19.1% and 26.2%) respectively. The M-only alcohol proved to be more effective than the M/E mixture as it gave better biodiesel yield. Moisture content of the seeds of Moringa, PK, Thevetia and Spirogyra were 9.4%, 8.3%, 6.6% and 39.7% respectively. The KV, FFA level and Saponification value of the oils were Moringa (44.5 mm2/s, 3.0%, 192.5 mgKOH/g), PK (4.9 mm2/s, 1.9%, 230.2 mgKOH/g), and Thevetia (21.5 mm2/s, 0.6%, 120.1 mgKOH/g). Also, the KV, FP, and AV of the biodiesels were Moringa (5.0 mm2/s, 176oC and 0.7 mgKOH/g), PK (2.4 mm2/s, 166oC and 0.4 mgKOH/g), and Thevetia (4.7 mm2/s, 130oC and 0.4 mgKOH/g). Analyses of elemental composition of the biomasses and biodiesels revealed a significant decline in the percentage compositions of P, Ca, Na and S in the biomasses when compared to their respective biodiesel. Spirogyra oil and biodiesel were insufficient to undergo the physiochemical tests.

The seeds of Moringa, Palm kernel and Thevetia are good sources of oil for biodiesel production but Thevetia proved to be the highest oil- and biodiesel-yielding biomass. The quality parameters of the biodiesels were found to be within international acceptable standard.