This Halloween, think of turning seasonal municipal solid waste (MSW) to energy as a very important “trick”! The Department of Energy’s Bioenergy Technologies Office (BETO) wants to illustrate how even common holiday waste can have a positive environmental impact.

Normally these seasonal items—hay, pumpkins, candy, and autumn leaves, for example—are thrown away and sent to landfills. From there, the MSW decomposes and eventually turns into methane (CH4)—a potent greenhouse gas that plays a part in climate change, with more than 20 times the warming effect of carbon dioxide (CO2). However, MSW actually has the potential to play a positive role in advancing a sustainable energy supply during Halloween—and every month.

When MSW is used to harness bioenergy—rather than simply being thrown away—the end result benefits the environment and the country in general: bioenergy displaces fossil fuels and allows the United States to create its own supply of clean energy; reduces greenhouse gas emissions because CO2 is emitted instead of CH4; limits stress on landfills; and ultimately creates jobs for manufacturing, installing, and maintaining energy systems.

Candy, leaves, and pumpkins enter a conversion device to create energy to power a haunted house

This spooky image demonstrates how seasonal waste could be used to generate both heat and power through anaerobic digestion.

So how does this process work? Similar to composting, one method of converting waste-to-energy (WTE) is called anaerobic digestion. This is a natural process where microorganisms are used to break down organic waste materials in a tank—it is sealed-deprived of oxygen, and the temperature is elevated to encourage faster processing.

This allows the waste material to decompose quickly and produce biogas that can be captured and used as fuel. In turn, this fuel can be used to power homes and run vehicles—and the heat that results from the process can often be used onsite to reheat the digester. Other WTE conversion processes exist and are being explored, like gasification, but anaerobic digestion—as illustrated above—currently is the most commonly used process for converting organic wastes to energy.

The United States generates nearly 250 million tons of trash annually, so it is important to be aware of the potential for WTE conversion on a scope that extends beyond seasonal MSW. Pumpkins and hay are indeed capable of producing bioenergy, but everyday MSW—such as packaging, newspapers, and food—shows the same promise. Therefore, BETO is working actively to explore WTE pathways in the United States, specifically with regard to anaerobic digestion at landfills to recycle organic waste biomass into renewable energy—thereby enabling a national network of distributed power and biofuel production sites.