We live in a world where hunger is a significant problem and yet food routinely goes to waste, in countries both rich and poor. At the same time, the fragile state of the global energy system continues to underscore the importance of shifting toward cleaner and more secure energy technologies.

What if these two problems could be addressed by a single solution — one that diminishes food waste by turning it into energy? That is the promise of the growing interest in the production of biogas — a renewable energy source created by the breakdown of carbon-based (organic) material like food waste. Or, to put it another way, energy powered by leftovers.

It might be surprising to learn that biogas has actually been in use since ancient times, though it would take several milestones along the way to make it a viable player on the world energy stage. Scientific interest in the manufacture of biogas was sparked by 17th century observations that connected the release of flammable gas to sediment disturbance; in the late 18th century, Italian physicist Alessandro Volta, known for his invention of the electric battery, would identify the primary component of this “marsh gas” as methane (although its name would not be coined until several decades after his death). By the mid-19th century, this knowledge would catalyze the invention of an early type of anaerobic digester (AD), one of the primary technologies still used for biogas production today.

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In anaerobic digestion, microorganisms break down biodegradable materials in the absence of oxygen. The process releases a mixture of gases including methane and carbon dioxide, both of which act as climate pollutants; of the two, methane is the more efficient trap for heat, with 86 times over a 20-year period. An anaerobic digester re-creates the conditions that Volta observed in nature, with one critical difference: Instead of being released into the atmosphere, the biogas is captured inside the digester’s chamber and repurposed as a renewable fuel. In addition, the nutrient-rich waste solids left at the bottom of the chamber can be extracted and used in agriculture as fertilizer or turned into a base material for the production of bioplastics.

Anaerobic digestion produces two valuable outputs: biogas and digestate. Image: EPA.gov

ADs have emerged as a waste management alternative to the growing proliferation of landfills, which according to the Environmental Protection Agency are the third-largest source of human-caused methane emissions in the U.S. One example of the technology in action can be seen in the San Francisco Bay area, where the East Bay Municipal Utility District (EBMUD) has focused on perfecting the process of converting food scraps to renewable energy. As noted in the video directly below, from cleantech and sustainability solutions platform ReneEnergy.com, EBMUD’s wastewater treatment plant processes around 1,300 tons of food waste annually, generating renewable energy, reducing the volume of waste sent to landfills, saving on energy costs and minimizing greenhouse gas emissions.

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A larger-scale implementation can be seen in the U.K., where the country’s leading AD operator, Biogen, annually recycles about one-half million tons of organic waste. This generates around 25 MW of electricity for the national grid; as noted in this entertaining inside look at the technology from the Institution of Engineering and Technology (IET), that’s enough to power the North Yorkshire spa town of Harrogate for a year. Biogen sends the biogas it generates from its ADs to gasholders, where it is stored until needed to fuel engines that produce electricity. At the facility shown in the video, 2.7 MW of electricity is produced every hour, or 64 MW per day. By comparison, an average three- to four-bedroom home will consume 2.9 MW of electricity per year. Also, as noted above, the process leaves behind a biofertilizer that can be used as an alternative to fossil fuel-derived fertilizers, creating a true “closed loop” system: What starts on the farm as crops grown for food is returned to the farm as fertilizer, where it will support the continued growth of those crops.

While anaerobic digestion represents a promising technology for generating renewable energy, there are obstacles to wide-scale deployment, including technical, economic and environmental challenges. Among the technical challenges are factors that can reduce AD performance, including foaming, salt buildup and buffer capacity. Economic challenges include high operating and transportation costs; environmental challenges include the potential for methane leaks from pipes where organic waste is stored before treatment.

To be sure, there are other technologies in use for turning food waste into energy, and the viability of each is impacted by similar factors. Biomass gasification, for instance, uses a controlled process involving heat, steam and oxygen to convert organic wastes and residues to a gas mixture (known as syngas) without combustion. As noted by the U.S. Department of Energy, challenges include finding ways lowering capital costs, both for the feedstock used as a base material and the equipment used in the gasification process.

Still, the continued development of food waste-to-energy solutions offers significant potential as a future-facing strategy for creating a greener planet. Resources to learn more include the World Biogas Association (WBA), which hosts events such as the World Biogas Summit and the World Biogas Expo, which will next happen in Birmingham, U.K., in July 2025. The International Energy Agency (IEA) also maintains a database of country-specific biogas energy policies.

Armed with the knowledge available from these and other resources, don’t be surprised if you never look at your leftovers the same way again.