How Last Night's Leftovers Could Become Tomorrow's New Clean Energy Source

 By Fernanda Castillo

    Have you ever given thought to what happens when you order too much takeout and throw the rest away? One of the most prevalent contributors to excess global waste is food waste. Megatons (millions of tons) of food are thrown away each year due to restaurants, food processing, and of course, household waste (EPA 2021).

A Promising Solution:

    Various studies have found that it is possible to turn food waste into energy by using anaerobic bacteria (bacteria that don’t require oxygen) to break down organic matter. This method creates methane, except the gas is trapped and then used as energy! However, these studies ran into a problem— the bacteria cannot properly digest food waste because it is too high in salt and fat. So, one study found a sustainable way to improve the methane production from the bacteria. In addition to anaerobic digestion (AD), the study used a microbial electrolysis cell pretreatment (MEC). The microbial electrolysis cell uses microbes to produce electrons and protons from the breakdown of organic matter, which is then converted into hydrogen. The study created an AD-MEC reactor, and found that methane production doubled compared to AD alone or AD with an electron mediator. AD alone yielded 330.6 mL of methane after 30 days, the MEC- absent reactor yielded 380.19 mL of methane after 30 days, and the AD-MEC reactor yielded 710.79 mL of methane after 30 days. These findings suggest that the reactor was successful in breaking down the food waste that was high in fat and salt content, unlike previous studies (Deb et al. 2024). 

A diagram of the AD-MEC reactor (Deb et al. 2024)

So, why does it matter? It's just food, doesn't it decompose?

    Food waste is the most common material in landfills. Rotting food in landfills produces methane, an extremely potent greenhouse gas that is even more harmful than carbon dioxide. The findings in this study create a way to maintain levels of greenhouse gasses by reducing the amount of landfilled food waste.

    Of course, further research is needed to identify the best way of implementing these findings in food waste management. This technology is promising for future integration of more environmentally sustainable energy sources and effective waste management. 

Deb N, Rahman T, Alam Z, Jami MS, Mansor MFBt. 2024. Efficient technology for food waste valorization: an integrated anaerobic digestion—microbial electrolysis cell for biomethane production. Int J Environ Sci Te. doi:

https://doi.org/10.1007/s13762-024-06011-x.

US EPA. 2021 Nov 17. From Farm to Kitchen: The Environmental Impacts of U.S. Food Waste. https://www.epa.gov/land-research/farm-kitchen-environmental-impacts-us-food-waste.