Increase Economic Value of ‘Sugarcane’ by Developing Weed Control Substances to Promote Thai Bio Industry

Sugarcane is an industrially significant crop for the Thai economy, primarily as a major exporter of sugar, ranking second globally, after Brazil. Additionally, sugarcane is an industrial plant with numerous stakeholders at various levels. In the production year 2565/66, Thailand yielded approximately 93.88 million tons of sugarcane. Moreover, Thailand possesses abundant raw materials for the bio-industry, particularly from the sugarcane and sugar industry. However, the bio-industry has not experienced substantial growth, primarily due to the high production costs associated with bio-based products. Promoting and supporting the use of sugarcane and sugar in generating value-added bio-products could significantly contribute to the expansion of the bio-industry in the future. This approach not only enhances the competitiveness of the Thai sugarcane and sugar industry but also aligns with the global emphasis on environmentally friendly practices. 

1. Growth Opportunities in Thai Bio Industry 

Thanks to Thailand’s readiness in the production of raw materials for the bio-industry, particularly in the sugarcane and sugar industry, the Office of the Cane and Sugar Board envisions the potential in this sector. However, the bio-industry has not seen significant growth due to high production costs and the reliance on imported equipment. If there is encouragement for investment and support in utilizing sugarcane and sugar to create value-added products, it could lead to an expansion of the bio-industry, unlocking greater potential. 

The acquisition of raw materials for the production of bio-based products necessitates obtaining high-quality source materials. A primary challenge encountered by most farmers, with significant implications for productivity, is the proliferation of weeds, which inflicts substantial damage to agricultural plots. Weeds serve as reservoirs for plant diseases and act as habitats for crop-damaging insects. Given the elevated costs of weed control agents, The office of the Cane and Sugar Board collaborates with and provides financial support to Prince of Songkla University in a joint initiative. This initiative aims to develop a starting material derived from sugarcane, specifically Levulinic acid, for use as an environmentally friendly herbicide. This approach aligns with the World Trade Organization’s (WTO) advocacy for supporting farmers in reducing the burning of sugarcane, mitigating environmental issues, and addressing air pollution and PM 2.5 particulate matter.  

The aforementioned project has received funding from the office of the Cane and Sugar Board for the fiscal year 2023. Associate Professor Jantakan Taweekul, Ph.D., the Head of the Energy Technology program at the Faculty of Engineering, Prince of Songkla University, serves as the project leader. The research team comprises members from the Faculty of Engineering and the Faculty of Natural Resources at Prince of Songkla University, totaling 12 individuals. The research teams are divided into two: the engineering team, led by Associate Professor Pakamas Chetpattananondh, Ph. D., responsible for the production and enhancement of Levulinic acid, and the natural resources team, supervised by Associate Professor Narit Thaochan, Ph. D., focusing on the potential of Levulinic acid in weed control. Narit Thaochan, Ph. D., will oversee the overall aspects of the project.

2. Levulinic Acid 

Levulinic acid, derived from the sugar present in sugarcane juice through a chemical reaction, is a versatile acid with various benefits. Typically used as a precursor for further reactions to produce substances employed in pharmaceuticals, cosmetics, and skincare, it is renowned for promoting healthy skin and reducing acne. However, in the context of this research project, there is a departure from these conventional applications, as the focus shifts towards utilizing Levulinic acid as herbicidal agents. 

3. The production process of Levulinic acid and performance monitoring 

The production process begins in the Faculty of Engineering, where sugarcane with sugarcane juice is subjected to a reaction at relatively high temperatures (typically ranging from 150 to 200 degrees Celsius). Various catalysts can induce the reaction, but sulfuric acid is commonly chosen due to its efficiency and cost-effectiveness. Specifically, the reaction involves the conversion of sugar into Levulinic acid. To achieve this, highly concentrated sulfuric acid is required. The equipment and tools used must be resistant to both high acidity and pressure. Initially, imported equipment in the field, such as high-pressure reaction vessels, was employed. However, these tools proved inadequate as they could not withstand the corrosive nature of the highly concentrated sulfuric acid. Therefore, a dedicated Levulinic acid production apparatus was designed and constructed to address these challenges. 

The resulting Levulinic acid obtained after the reaction process still contains various impurities such as formic acid, sulfuric acid, and residual sugar. Therefore, a purification process is employed. Previous research has explored the use of activated carbon to reduce color impurities and the use of resin to separate impurities such as sulfuric acid and formic acid. However, these methods were found to be less effective in achieving thorough impurity separation. Consequently, a new approach was devised, and it was discovered that using lightweight soil for impurity separation in the production of Levulinic acid yielded significantly better results. This innovative method involves straightforward steps, proving to be both less complex and highly efficient. Following impurity separation with lightweight soil, water and formic acid are evaporated, resulting in high-concentration Levulinic acid—a desired end product. 

After obtaining Levulinic acid, the research team from the Faculty of Natural Resources conducted preliminary laboratory tests to assess its efficacy. The extracted substance was evaluated for its performance in controlling various types of weeds, including Narrow-leaved weeds, Broad-leaved weeds, and Sedge. The results revealed a high level of effectiveness, ranging from 80% to 90% within a 72-hour timeframe, leading to the demise of the tested weeds. These findings underscore the promising herbicidal properties of the extracted substance, demonstrating its potential as an efficient weed control agent in laboratory settings.  

Subsequently, the extracted substance was tested for its phytotoxicity on sugarcane plants. The results indicated that the substance exhibited phytotoxic effects, manifesting as localized necrotic lesions on the areas where it was applied. Notably, the symptoms did not spread beyond the treated regions even after a 96-hour period. Furthermore, there were no observable adverse effects on the subsequent growth and development of the sugarcane plants, suggesting that the substance, while demonstrating localized phytotoxicity, did not have a lasting impact on the overall growth of the sugarcane crops. 

After obtaining results from the laboratory, further field experiments were conducted on a 5-acre plot. However, the efficacy of the substance remained inconclusive due to various environmental factors, including differences in weed species and their ages. These variables made it challenging to confirm the optimal effectiveness of the substance in weed control. It is crucial to acknowledge that environmental factors, such as the age and species of weeds, can influence the outcomes. Therefore, it is not possible to definitively assert that the tested substance is the most effective for weed control. Farmers need to be informed about these factors when considering its application. Consequently, ongoing research efforts will focus on innovating and developing alternative methods to enhance the potential of this initial substance for environmentally friendly weed control. This aims to address the issue of sugarcane burning, which is one of the contributing factors to PM 2.5 air pollution, in the future. 

4. Development Plan for Commercial Production and Distribution 

For the development plan of Levulinic acid as a precursor in various industries, there are two operational plans: one for developing it as a herbicidal substance and the other as a precursor in other industries. The operational plans are as follows: 

1. Herbicidal Substance Development Plan: This plan spans 5 years. In the first year, the project will focus on studying the enhancement of Levulinic acid purity in the laboratory. In the second year, production capacity will be expanded by constructing large-scale apparatus with a capacity of 50 – 100 liters to accommodate real-world production and evaluate the technical-economic feasibility of the process. In the third year, additional testing on the herbicidal effectiveness will be conducted. In the third and fourth years, the development of herbicidal formulations and real-world testing will be carried out. Finally, in the fifth year, the product will be submitted for registration. 

2. Development Plan as a Precursor in Other Industries: This plan also spans 5 years. In the first year, the focus will be on studying the enhancement of Levulinic acid purity in the laboratory to serve as a precursor for producing various products such as supplements, cosmetics, additives in plastic production, or fuel. In the second year, the study will extend to testing the properties of different products according to specified standards, adjusting the production conditions appropriately, and expanding production capacity by constructing large-scale apparatus with a capacity of 50 – 100 liters to accommodate real-world production. In the third year, product testing will be conducted with the target group to assess the commercial viability, using methods such as target group opinion surveys, testing purchasing behavior, or conducting product trials in a limited market. In the fourth year, product formulations will be adjusted to align with the target group’s needs and ensure technical-economic feasibility. Finally, in the fifth year, product registration will be sought. 

Finally, the research project and long-term plans would not materialize without financial support from the Office of the Cane and Sugar Board. Assistant Professor Jantakarn Taweekul, Ph. D., serves as the project leader, and the research team is composed of members from the Faculty of Engineering and the Faculty of Natural Resources at Prince of Songkla University. Initial tests have indicated the potential of the identified substance in weed control. However, its effectiveness remains unclear due to various environmental factors. Thus, further studies are essential for future refinement, seeking suitable models and applications. This effort aims to maximize the utilization of products derived from locally sourced sugarcane, reducing reliance on chemical imports and enhancing the value of sugarcane-derived products within the country.