A sticky, toxic by-product that has long plagued renewable energy production may soon become a valuable resource, according to a new review published in Biochar.
When biomass such as crop residues, wood, or other organic matter is heated to produce clean energy and biochar, it also generates a thick liquid known as bio-tar. This tar easily clogs pipelines, damages equipment, and poses environmental risks if released into the atmosphere. For decades, researchers have sought ways to eliminate or neutralize it.
Now, a team led by scientists at the Chinese Academy of Agricultural Sciences argues that instead of being treated as waste, bio-tar can be converted into “bio-carbon” — a novel material with applications ranging from water purification to clean energy storage.
“Our review highlights how turning bio-tar into bio-carbon not only solves a technical problem for the bioenergy industry, but also opens the door to producing advanced carbon materials with high economic value,” said senior author Dr. Zonglu Yao.
The review examines how chemical reactions inside bio-tar, particularly those involving oxygen-rich compounds like carbonyls and furans, naturally promote polymerization — processes where small molecules link together to form larger, more stable carbon structures. By carefully adjusting temperature, reaction time, and additives, researchers can harness this process to produce bio-carbon with tailored properties.
The resulting material, the authors note, is distinct from ordinary biochar. Bio-carbon typically has higher carbon content, lower ash, and unique structural features that make it especially suited for advanced uses. Early studies suggest that bio-carbon could serve as:
- Adsorbents to clean polluted water and air by trapping heavy metals and organic contaminants.
- Electrode materials for next-generation supercapacitors, which are vital for renewable energy storage.
- Catalysts that speed up industrial chemical reactions more sustainably than traditional fossil-based options.
- Clean-burning fuels with lower emissions of harmful nitrogen and sulfur oxides.
Importantly, recent economic and life-cycle assessments suggest that converting bio-tar into bio-carbon can deliver net-positive energy, financial, and environmental benefits. For example, replacing coal with bio-carbon fuels could cut carbon dioxide emissions by hundreds of millions of tons annually, while also generating profits for biomass processing plants.
Still, challenges remain. The chemical complexity of bio-tar makes it difficult to fully control the polymerization process, and large-scale production has not yet been achieved. The authors recommend combining laboratory experiments with computer simulations and machine learning to optimize reaction pathways and design bio-carbon with specific functions.
“Bio-tar polymerization is not just about waste treatment — it represents a new frontier for creating sustainable carbon materials,” said first author Yuxuan Sun. “With further research, this approach could significantly improve the efficiency of biomass energy systems while providing new tools for environmental protection and clean technology.”
The study provides a roadmap for scientists and industry partners to turn one of bioenergy’s biggest obstacles into a powerful resource for the future.
