Indian researchers use orange peels to develop biofuel precursors

A group of researchers at the Indian Institute of Technology, Mandi have used hydrochar derived from orange peels as a catalyst to convert biomass-derived chemicals into biofuel precursors. The research will help develop biomass-based fuel to overcome the socio-political instabilities associated with dwindling petroleum reserves.

The method developed by researchers at IIT Mandi will help the country in producing clean green power from biomass and will hasten India’s journey towards sustainable fuel development getting free from the stronghold of fossil fuels.

Findings of the research published in the journal ‘Green Chemistry’ recently indicates that the use of catalysts for the conversion is particularly useful because such processes can be carried out with minimal energy input and the type of product obtained from the biomass can be controlled through the right choice of catalysts and reaction conditions.

Biomass-derived products from naturally occurring materials are currently the fourth most significant energy source that can meet the energy demand after coal, oil, and natural gas, in the country. Lignocellulosic biomass obtained from forestry and agricultural waste, for example, can potentially be converted to a variety of useful chemicals by various methods.

The research that saw the hydrochar derived from orange peels was led by Dr. Venkata Krishnan, associate professor, School of Basic Sciences, IIT Mandi, and co-authored by his students Tripti Chhabra and Prachi Dwivedi.

Of the various methods available to convert biomass-derived chemicals into biofuel precursors, the researchers found the use of catalysts like orange peels to be particularly useful because such processes can be carried out with minimal energy input and the type of product obtained from the biomass can be controlled through the right choice of catalysts and reaction conditions.

Talking about the research, Dr Venkata Krishnan, said, “One of the driving interests among the renewable energy community is the development of relatively clean and energy-efficient processes to convert biomass into useful chemicals, including fuel.”

Considered to be the simplest and most low-cost catalyst that has been studied by the researchers for biomass conversion reactions, hydrochar is typically obtained by heating the biomass waste (orange peels in this case) in the presence of water through the hydrothermal carbonization process. The use of hydrochar as a catalyst for biomass conversion was considered to be attractive because it is renewable and its chemical and physical structure can be altered for better catalytic efficiencies.

The researchers used hydrochar derived from orange peels to catalyse the conversion of biomass-derived chemicals into biofuel precursors. As a part of their research, the team heated dried orange peel powder with citric acid under pressure in a hydrothermal reactor (a lab-level ‘pressure cooker’) for many hours. The hydrochar that was produced was then treated with other chemicals to introduce acidic sulfonic, phosphate, and nitrate, functional groups, to it.

“We used these three types of catalyst to bring about hydroxy alkylation (HAA) reactions between 2-methyl furan and furfural, compounds that are derived from lignocellulose, to produce fuel precursors,” Tripti Chhabra said. The scientists found that the sulfonic functionalized hydrochar catalyst was able to catalyze this reaction effectively, to produce biofuel precursors in good yield.

Dr. Venkata Krishnan added that they were able to synthesize the biofuel precursors under solventless and low-temperature conditions, which brought down the overall cost of the process and also made it environment-friendly and attractive from an industry point of view.

This is the first comparative study in which the three types of acid functionalization have been assessed. The IIT Mandi team also performed green metric calculations and temperature-programmed desorption (TPD) studies to gain deeper insights into the catalytic activity of sulfonic, nitrate, and phosphate functionalized hydrochar derived from orange peels.

The development of such catalysts for biomass conversion bodes well for the biofuel sector in the country which is already a pioneer in biomass-based power in recent years. In 2015, India announced its goal to achieve 15 GW of power from biomass, small hydropower, and waste-to-energy plants. Within five years, the country has already achieved the 10 GW target of biomass power.