Renewable energy has long been a major topic worldwide, but for countries like Indonesia, the challenges feel more tangible. Dependence on fossil fuels not only impacts the environment but also raises issues of energy independence. Amid these concerns, a group of researchers from Universitas Sumatera Utara offers an intriguing solution: utilizing waste from the Indigofera zollingeriana plant as an eco-friendly catalyst to produce biodiesel from palm oil.

 

The article titled Sustainable production of CaO rich-indigofera (Indigofera zollingeriana) as heterogeneous catalyst of biodiesel from refined bleached deodorized palm olein using associated transesterification process was published in 2025 in Results in Engineering. The article was authored by Taslim, Silvia Nova, Renita Manurung, Iriany, Vikram Alexander, and Anggara Dwita Burmana.

 

This research stems from the urgent need for alternative energy. Indonesia, as one of the world’s largest palm oil producers, has enormous potential to produce biodiesel. Refined bleached deodorized palm olein (RBDPO), in particular, can be processed into eco-friendly fuel through a transesterification process. However, the key lies in the use of catalysts. Until now, chemical-based homogeneous catalysts such as sodium hydroxide have been used, but they generate liquid waste that is difficult to handle.

 

This is where the team’s idea emerged: to use a heterogeneous calcium oxide (CaO)-based catalyst derived from the biomass of the Indigofera zollingeriana plant. This plant is better known as livestock feed, but its abundant leaf waste is rarely utilized. Through a calcination process—heating at high temperatures—dried indigofera leaves can yield ash rich in CaO. This ash was tested as a new catalyst.

According to Taslim, this approach touches on two issues at once: energy and sustainability. “We are not only talking about biodiesel but also about how to utilize local resources that are cheap, abundant, and environmentally friendly,” he said.

 

The process they used was transesterification, a chemical reaction that converts triglycerides in palm oil into methyl esters (biodiesel) with the help of alcohol and a catalyst. The catalyst’s role is crucial here. Homogeneous catalysts are effective, but problematic because after the reaction, their byproducts are difficult to separate from the biodiesel. In contrast, heterogeneous catalysts can be easily separated, reused, and generate much less waste.

 

The study found that the CaO-based catalyst from indigofera worked effectively in converting RBDPO into biodiesel. Laboratory tests showed that the biodiesel yield met international standards. Moreover, this catalyst could be reused multiple times without significant performance degradation.

 

Another interesting point is the sustainability of its raw material. Indigofera grows quickly, does not directly compete with food crops, and is often planted as livestock feed or ground cover. Thus, using its leaves as a catalyst does not disrupt the food supply chain. Instead, it opens up new added-value opportunities from a plant previously considered to have limited uses.

 

In this study, the team also emphasized the importance of local context. Indonesia is not only rich in palm oil but also faces environmental challenges from palm oil waste and air pollution caused by burning fossil fuels. Eco-friendly catalyst-based biodiesel offers a dual solution: reducing dependence on fossil energy while minimizing the impact of industrial waste.

 

Taslim emphasized that this research is an initial step. He said, “We have proven the effectiveness of indigofera catalysts in the laboratory. The next step is to test them on a larger scale so they can truly be applied in industry.”

 

Beyond technical aspects, this research also touches on socio-economic dimensions. If further developed, producing catalysts from indigofera could create new jobs in rural areas, especially in regions where this plant is cultivated. Communities could be involved in collecting, drying, and processing the leaves into catalyst ash. In this way, the benefits would not stop at the laboratory but would also be directly felt by society.

 

The study also signals positive implications for circular economy development. Agricultural waste that is usually discarded can now become an important raw material in clean energy production. This concept aligns with the global trend toward decarbonization and the utilization of sustainable resources.

 

Nevertheless, the research team acknowledged that challenges remain. The calcination process requires high energy, so ways must be found to reduce costs and emissions from this stage. In addition, long-term tests on catalyst durability are needed, especially when used on a large industrial scale. However, these initial results are promising enough to encourage further research.

 

At the international level, research on biomass-based catalysts is indeed developing. However, the use of Indigofera zollingeriana as a CaO source is still relatively rare. The findings from the USU team show that Indonesia has great potential to contribute to clean energy innovation—not only as a consumer of technology but also as a producer of knowledge.

 

In his reflection, Taslim stated that the main spirit of this research is to seek solutions suited to local conditions. “Biodiesel is often called the energy of the future. But to be truly sustainable, we must ensure that its production process is also environmentally friendly. That is what we are trying to prove with indigofera,” he explained.

 

Ultimately, this story is not just about biodiesel or catalysts, but about a new way of looking at waste. What was once considered useless can in fact be the key to the future of clean energy. The research by Taslim and his colleagues shows that major solutions can arise from simple things, as long as there is the will to study and develop them.