From waste to wonder: turning leftovers to clean energy

Food waste, often dismissed as mere garbage, holds untapped potential as a key resource to tackle both waste management and clean energy generation. And researchers at the CSIR-Indian Institute of Chemical Technology (IICT) have now turned leftovers into a powerhouse of possibility, unveiling a breakthrough method to produce biohydrogen (bioH₂) from food waste.

This sustainable innovation not only fuels the global shift toward renewable energy but also plays a critical role in reducing carbon emissions, says lead scientist S. Venkata Mohan, who conducted the study along with research associate J. Santosh.

The team has successfully enhanced hydrogen production while minimising the environmental impact of biogas generation (methane and carbon dioxide). Using an upflow reactor, food waste underwent continuous fermentation to produce biohydrogen, a valuable clean energy source.

The system’s self-regulated buffering capacity was key to maintaining stable conditions to boost fermentation efficiency and hydrogen production with minimal energy consumption. This balance of efficiency and sustainability makes the process highly viable, explains Venkata Mohan, who has since been appointed as the director of CSIR-National Environmental Engineering Research Institute.

The study underscores the immense potential of converting food waste into biohydrogen, addressing both waste management and clean energy needs. With hydrogen playing a growing role in global energy strategies, this approach offers a means to decarbonise sectors such as heavy industry, transportation, and energy storage.

Beyond emissions reduction, the method also supports a more sustainable food system, contributing to global net-zero targets, Venkata Mohan notes. The findings have been published in the latest issue of the ‘International Journal of Hydrogen Energy’.

Ethanol and acetic acid

The chief scientist also contributed to another innovative project that demonstrated an eco-friendly, carbon-negative gas electro-fermentation process. This method enhances the conversion of carbon dioxide into ethanol and acetic acid, improving efficiency while reducing emissions.

By transforming CO₂ into valuable chemicals, such as ethanol and acetic acid, the process supports carbon isolation for sustainable energy systems. Acetic acid, a platform chemical, is used for producing solvents, polymers (VAM), food preservatives and pharmaceuticals.

In this study conducted in collaboration with research scholar Athmakuri Tharak, Venkata Mohan explored ways to enhance CO₂ fermentation efficiency using a custom-designed high-pressure gas fermentation (HPGF) reactor. This innovative system, embedded with an electrode assembly, eliminates the need for hydrogen as an external electron donor.

Traditionally, hydrogen is required to drive CO₂ conversion into valuable products like methane, ethanol, or acetic acid. However, by bypassing hydrogen, this process becomes more sustainable, energy-efficient, and cost-effective, resulting in higher yields of acetic acid and ethanol, Venkata Mohan explains.

The study revealed that for every unit of acetic acid or ethanol produced, seven kilograms of CO₂ equivalent emissions are removed from the environment, making the process carbon-negative, adds the scientist. The findings were published in the latest issue of ACS Sustainable Chemistry & Engineering.