The Science of the City: Some Maryland counties burn food waste; others jus...

This story by MIT Environmental Solutions Journalism Fellow Paul Ruffins was originally published in Streetcar Suburbs News. It is the third in a series of articles exploring landfills, food waste, and methane emissions in Prince George's County and neighboring jurisdictions. While the previous article focused on composting, this piece explores two other approaches to handling Maryland’s food wastes, including the agricultural waste from making the food itself.

 

Just as the existential threat of global warming has caused many environmentalists to reconsider the possible benefits of nuclear energy, it has also created some new support for Maryland’s waste-to-energy (WTE) plants, which burn trash to generate electricity. Currently, the state’s two WTE facilities are operated in Baltimore, by BRESCO, and in Dickerson, Montgomery County, by Covanta.

Opponents charge that these incinerators are dirtier than coal-powered power plants. However, in a February 2025 Maryland Matters editorial, Ashwani Gupta, a professor of mechanical engineering at the University of Maryland, argued that landfills create methane, a greenhouse gas 28 times more potent than the CO₂ produced by incinerators when measured over a 100-year period. He also noted that the Baltimore City landfill is essentially full, and that using diesel trucks to move the 700,000 tons of waste “the Baltimore WTE safely processes every year” to landfills out of state would “have a devastating effect on public health and the environment.” Recently, the Maryland General Assembly roundly rejected this argument when it voted to make incinerators ineligible for renewable energy credits. 

Nevertheless, Gupta is not alone. WTE facilities are common in Europe, which has some of the highest environmental standards and recycling rates in the world. Desirée Plata, co-director of the MIT Climate and Sustainability Consortium, believes that “with the latest equipment, incinerators can dramatically reduce emissions” and produce electricity that reduces the need for fossil fuels. 

Plata also notes that Europeans carefully sort out items like batteries, which are a major source of lead and cadmium emissions. In contrast, Baltimore has a recycling rate of only 15% and no publicly owned recycling facility. And, because food waste is relatively wet, Plata argues, “Any effort to remove food waste would be a major boost to the efficiency of the energy generation. However, it is important to note that current WTE facilities are paid based on weight — so their bottom line would be impacted by the removal of wet materials.”

A moral hazard of incinerators is that they are very expensive, but handle a wide variety of unsorted materials. Therefore, they can reduce a city’s incentive to sort and recycle waste, and consume its resources to do so. Dante Davidson-Swinton, who ran for Baltimore mayor in 2020, argues that the city’s BRESCO incinerator “cannot function effectively without massive amounts of trash, making incineration and true waste diversion basically incompatible.” Baltimore is locked into its contract until 2030, and Montgomery County into its contract until 2031.

By contrast, anaerobic digesters, which are also widely used in Europe, would seem to meet all the golden rules of environmental sustainability, particularly in agricultural areas. The process uses different combinations of microbes and water to break down a wide variety of organic materials (but not wood) inside a sealed vessel without oxygen. Like a landfill, this produces biogas that is about 55-60% methane, but it is captured and filtered to generate heat or electricity. The remaining materials are used as compost or liquid fertilizer.

Finding a solution to the solid waste produced by Maryland agriculture is critical because it is the state’s largest industry. In 2023, the state had 157,000 head of cattle. Dairy farms produce at least 150 pounds or about 18 gallons of manure per day per lactating cow. Farmers have traditionally disposed of this manure by spreading it on their fields. However, modern farming has concentrated more animals than ever in smaller spaces, producing huge amounts of manure, which is often stored in methane-spewing lagoons.

Another, possibly larger, problem is the over 250,000 tons of manure generated annually by Maryland’s poultry industry. Tightly concentrated on the Delmarva Peninsula, these factory farms send nutrient pollution running off into the Chesapeake Bay.  

Kilby Dairy Farm in Cecil County operates an anaerobic digester and received a grant to evaluate how well it performed over 13 months. The farm had 750 cows, and the digester processed the dairy’s manure and a mixture that was 75% waste from processing chickens and 25% from cranberries. 

The 28% of the manure that was solid was separated out for composting. Every week, 120,000 gallons of the liquid portion were combined with 36,000 gallons of the food waste and put into the digester. The resulting biogas was fed into an engine that produced heat to run the digestion process and also generated electricity. Unfortunately, the engine was only big enough to handle 72% of the gas produced, and the excess was simply burned off. After processing, the remaining liquid was used as fertilizer and injected directly into the ground to protect nearby waterways.

University of Maryland researchers concluded that on a yearly basis, the system would offset the CO₂ emissions of 4,000 cars, generate enough electricity to power 190 homes, and produce 4,200 metric tons of compost. They also noted that the system released few odors or greenhouse gases, and could have produced even more electricity if the generator had been bigger.

The largest anaerobic digester in Maryland is at the Maryland Bioenergy Center, in Jessup, which can handle up to 120,000 tons of organic waste a year. It was built in 2021 to serve the large food producers operating at the 400-acre Maryland Food Center campus near Interstate Highway 95, Baltimore/Washington Thurgood Marshall International Airport and the Port of Baltimore. In part, the digester was a response to the state’s requirement that, starting January 2023, certain businesses and institutions producing more than two tons of food waste (now one ton) had to divert it from landfills or incinerators. Maryland Matters reported that when the facility, which is operated by Bioenergy Devco, opened, it was the perfect solution for Coastal Sunbelt Produce — a large food company headquartered in Howard County that distributes fresh and processed produce along the mid-Atlantic. At the time, Coastal produced about 200 tons of food waste a week and was forced to send 80% to landfills. 

“It’s been frustrating,” said Jason Lambros, vice president of Coastal’s food division.  “For years we’ve been working with compost facilities, but they generally can’t handle our volume, and have been very transient.”

According to Bioenergy Devco, the facility generates enough energy to “power over 7,000 homes and abates CO₂ emissions equivalent to removing 19,000 gasoline cars annually.” In 2024, the plant won two industry-sponsored awards honoring its work in transitioning towards green energy.

Nevertheless, some environmentalists, including Maryland Del. Lorig Charkoudian (D-District 20), who sponsored the original legislation promoting organics diversion, worry that the digester could lead to so-called “greenwashing.” Kilby Farm turns its biogas into electricity right on site. Bioenergy Devco represents the first time in Maryland that biogas from an anaerobic digester was connected to Baltimore Gas and Electricity’s natural gas infrastructure for distribution as renewable natural gas, also called RNG, which qualifies for tax credits as a non-fossil fuel. Charkoudian maintains that adding a small amount of biogas does not make BGE’s natural gas environmentally friendly or sustainable.

Larry Martin, who holds a doctorate in environmental sustainability and co-founded Edmonston’s nonprofit Community Forklift, told the Life & Times, “Some activists believe we should simply abandon our aging, leaky natural gas infrastructure because it’s delaying the transition to a completely electric future. I feel that we should at least repair and preserve the largest gas mains and use biogas to help power new, smaller generating plants to meet peak demand when wind or solar power isn’t available.”

Incineration, composting, and anaerobic digestion are all more sustainable when any contaminants are removed. Unfortunately, the “ick factor” makes it nearly impossible to motivate Americans to separate 100% of their food scraps. However, the next and final article in this series will explore ways to raise our low rates of food recycling much higher.

As Martin said, “One of the environmental movement’s biggest challenges is not letting the perfect be the enemy of the good.”