Biodiesel: A sustainable renewable energy source

By Dr. Tan Yie Hua and Yat Yu Dong 

The traditional way of extracting vegetable oil using the blending technique does not resolve issues such as viscosity value, free fatty acids (FFA) composition, acid content and gum formation of the oil. However, modern fourth-generation biodiesel has enabled the transformation of solar energy into fuel through the use of photosynthetic microorganisms that have been modified using biotechnology.

The metabolically or genetically modified microorganisms are cultured in a bioreactor to improve the energy conversion of solar photon emissions. This improves the simplicity, speeds up the reaction rate, and improves the production yield of the process. Hence, fourth-generation biodiesel has become a prominent fuel product that is both effective and          sustainable in terms of economic and environmental aspects.

As one factor causing global warming is the increased sea surface temperature due to growing carbon dioxide concentration, the increased use of such renewable energy can lessen the toxic emissions of greenhouse gases.

Although there is a variety of available green energy such   as hydroelectric and geothermal energy, biofuel is positioned as a prominent energy source as it can be integrated with current fossil-fuel distribution infrastructure with minor cost repercussions. In addition, to avoid dependency on one single energy source, local biomass is used to enhance the variety of green energy sources.

On the other hand, biodiesel’s manufacturing and its applications have limitations in cost, cold performance, storage stability, wastewater issues, and life cycle analysis (LCA).

Currently, costly edible oils are employed on a large industrial scale, and this presents a significant challenge in maintaining a reasonable margin of manufacturing cost. In the coming years, continuous growth in waste feedstock usage is projected to sustain the biodiesel business while widening the gap between biodiesel’s break-even and selling price.

The savings gained from selecting the right raw materials need to be higher than the   pre-treatment costs or it may result in a trade-off. In the meantime, analyses of cheaper sources of biodiesel continues to be carried out. This can ease the supplementing of cheaper feedstocks for biodiesel whenever shortages in conventional oil supply happens.

Cold flow properties are important as they allow biodiesel to be used in a broader geographic and season range. In biodiesel, high saturation levels cause crumbling at low temperatures, leading to poor cold temperature characteristics.

Ethyl esters can improve cold qualities to suit the needs of cold climate zones. Alternatively, cold performance issues may be resolved by mixing biodiesel with petroleum diesel and kerosene, transesterification using branched-chain alcohol, and modifying the oil’s fatty acid composition.

As biodiesel is a blend of saturated and unsaturated fatty acid esters, it is prone to auto-oxidation which causes poor fuel quality by degrading the biodiesel and developing undesirable by-products. Hence, oxidation stability is an essential parameter in determining biodiesel quality.

The main focuses of a specific operation in LCA are the overall cost, energy, and waste. However, the critical part of LCA is to define the boundaries for each aspect. For instance, non-renewable fossil fuel is used to produce biofuel. In that case, it is unclear whether to consider the effect of fossil fuels on the ecosystem. Thus, it raises doubts about the credibility of the LCA studies. Also, the influence of indirect land use is often overlooked although the carbon and energy balances are considered throughout the research.

In conclusion, it is very challenging to synergise the benefits of different generations of biodiesel into a single conversion strategy. Apart from that, as feedstock availability is the key challenge, a strategy of incentivising biomass owners and farmers has to be developed to encourage biomass-related activities such as aggregation, storage, and handling.

Such action can create rural employment and ensure the consistency of feedstock supplies. Furthermore, interstate taxes can be abolished to encourage the smooth flow of feedstock and biofuel throughout the country. The government should also foster public-private partnerships in the biofuel industry to guarantee fuel security. Hence, the production of biodiesel can be effectively commercialised.

Dr. Tan Yie Hua is a senior lecturer in the Department of Chemical and Energy Engineering, Curtin University Malaysia. She obtained her Bachelor’s degree in chemical engineering at Universiti Kebangsaan Malaysia (UKM) and worked as a customer project engineer at X-FAB Sarawak for two years before pursuing postgraduate studies in chemical engineering at Universiti Malaysia Sarawak (UNIMAS). Biodiesel production is one of the areas of her research work. Her research interests also include biomass utilisation and biofuel conversion technology. Dr. Tan can be contacted at

Yat Yu Dong was a final-year Chemical Engineering student at Curtin University Malaysia in 2022.