In 2021, over 30% of Indonesia’s roads were damaged, with nearly 16% being severely damaged. This infrastructure crisis is worsened by the high cost of quality asphalt and the declining availability of petroleum-based raw materials. To address this, a research article by Bazlina Dawami Afrah and colleagues, published in the journal Cantilever, investigates a more sustainable and economical solution: producing bio-asphalt using tar residue from coconut shell pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More. The researchers explored how adding biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More and gondorukem to a mixture of this bio-tar and petroleum asphalt could create a product that competes with traditional oil asphalt.

The research involved three main stages: pyrolysis, distillation, and mixing. The pyrolysis of coconut shells at temperatures between 300∘C and 400∘C produced bio-oil and biochar. This bio-oil was then distilled at 250∘C to isolate the heavy, dark, and sticky tar residue, which shares physical similarities with petroleum asphalt. The final stage involved creating a mixture of 30% tar and 70% petroleum asphalt, to which different quantities of powdered biochar and gondorukem were added as stabilizers and fillers.

The team tested four different mixtures: a control (Sample A1) with no additives, Sample A2 with 6 grams of gondorukem, Sample A3 with 6 grams of biochar, and Sample A4 with 3 grams each of biochar and gondorukem. The goal was to find the optimal formulation that met the specifications for Hard Asphalt Pen 60/70, a common type of asphalt.

The results show that the additives significantly impacted the bio-asphalt’s properties. In the penetration test, which measures asphalt hardness, Sample A3 (with 6 grams of biochar) had the lowest penetration value at 48.4 mm, while Sample A4 (with both additives) was a close second at 66.4 mm. Both samples A2 and A4 came closest to meeting the required 60-70 mm standard. This is because biochar acts as an effective binder, and its large surface area and pores help it spread evenly and create strong bonds within the mixture.

All samples exceeded the minimum ductility requirement of 100 mm. Sample A1, with only bio-tar and asphalt, had the highest ductility at 136.6 mm, but Sample A4 was a close second at 132.33 mm. This indicates that while biochar and gondorukem can increase the mixture’s consistency and reduce its crack resistance, the bio-tar helps maintain the asphalt’s plastic deformation ability at low temperatures.

Regarding thermal resistance, the additives were highly effective. The soft point of the bio-asphalt mixtures increased with the addition of biochar and gondorukem. The highest soft point of 52.8∘C was achieved by Sample A4, which surpassed the required minimum of 48∘C. Similarly, the flash point of all samples met or exceeded the minimum requirement of 232∘C. Sample A3 and A4 achieved the highest flash points, at 259∘C and 254∘C, respectively. Gondorukem, in particular, was found to improve high-temperature resistance due to its natural resins and terpenes, which increase the soft point and prevent plastic deformation.

The research concluded that the optimal mixture, Sample A4, was the most promising. It met the specifications for penetration, ductility, soft point, and flash point. The only parameter it did not meet was specific gravity, which was 0.965 gr/cc, just below the required 1 gr/cc. Overall, the study demonstrates that bio-asphalt created with coconut shell waste and additives like biochar and gondorukem can serve as an effective, sustainable, and economical alternative for road maintenance in Indonesia and beyond.

Source: Afrah, B. D., Saputri, J. F. D., Putri, T. M. R., Riady, M. I., & Muzzaki, A. N. (2025). Pemanfaatan Tar Residu Bio-Oil Limbah Tempurung Kelapa dengan Aditif Biochar dan Gondorukem Menjadi Bio-Aspal. Cantilever: Jurnal Penelitian dan Kajian Bidang Teknik Sipil, 14(1), 61-68.