São Paulo: Scientists have found that using small amounts of caustic soda can significantly improve biogas production from banana waste, offering a more cost-effective and environmentally friendly way to convert agricultural waste into renewable energy.
The study, conducted by researchers at São Paulo State University (UNESP), examined banana peels and other parts of the fruit unsuitable for sale. These wastes contain high amounts of organic material, but their energy potential is difficult to access because plant compounds such as cellulose and lignin restrict microorganisms from reaching fermentable sugars.
Researchers used a thermo-alkaline pretreatment method, heating the banana waste with different concentrations of sodium hydroxide, commonly known as caustic soda. The concentrations ranged from 0.2% to 3%.
The findings showed that higher amounts of caustic soda did not necessarily lead to better results. Instead, the lowest concentration tested, 0.2%, produced the highest rate of methane generation and significantly improved the breakdown of carbohydrates.
At 0.2% sodium hydroxide concentration, methane production reached 12,110 milligrams per litre, compared with 4,785 milligrams per litre from untreated banana waste. A slightly higher concentration of 0.4% produced the highest cumulative methane output.
Researchers said excessive use of sodium hydroxide can increase production costs and may inhibit the microorganisms responsible for methane generation. Lower concentrations can also reduce environmental impacts and make wastewater treatment easier.
The study also examined the microbial communities involved in the biogas production process. Researchers identified different bacteria and methane-producing microorganisms that helped break down organic matter and convert it into methane.
The findings could help industries make better use of agricultural waste, particularly in regions with large fruit production. Instead of sending discarded fruit and processing waste to landfills, the material could be used in bioreactors to generate renewable energy.
The research is part of a broader programme exploring ways to convert agroindustrial waste, including banana, orange and guava residues, into biogas, biohydrogen and other valuable products.
The study was published in the journal BioEnergy Research.