In northern California's Stanislaus County, next to a landfill, there's a company managing waste in a very different way: by burning trash instead of burying it.
The energy recovery facility run by New Jersey-based Covanta harnesses steam to make enough electricity to power 18,000 homes in the area. A portion of the waste comes from companies including American Airlines, Quest Diagnostics, Sunny Delight and Subaru.
"When a major car manufacturer like Subaru says they're zero landfill, they have done the reduce, the reuse, recycle, and what's leftover they send to a facility like a waste-to-energy facility," said Paul Gilman, chief sustainability officer for Covanta, which has more than 40 sites across the globe.
Major retailers like Amazon also use this combustion method to dispose of returns they deem unfit to recycle, resell, or donate. Amazon told CNBC that it sends some returns to energy recovery as a "last resort," though the company declined to say which facilities it uses. Covanta said it doesn't handle Amazon returns.
About 10% of the 270,000 tons of waste Covanta burns at its plant in Crows Landing, California, a two-hour drive east from San Francisco, comes from companies. The rest mostly comes from waste collection in nearby municipalities.
Corporations account for "the fastest growing part of the business," Gilman said, as an increasing number of companies try to reduce their environmental footprint.
In Covanta's energy recovery facility, waste is burned at temperatures around 2,000 degrees Fahrenheit. There are 21 miles of pipes around the combustor, where the intense heat converts water into steam that turns a turbine, which powers a generator. The process also creates carbon and toxic ash, but unlike landfills, it doesn't emit any methane.
The U.S. is one of the most wasteful developed countries in the world. Of the record 292 million tons of waste generated by Americans each year, more than half is landfilled, about a third is recycled, and 12% is incinerated at waste-to-energy facilities, according to the World Bank.
Online commerce poses a particular problem.
Not only are internet purchases breaking records in terms of volume, but roughly 20% of items get returned, which is a higher number than for in-store purchases. Returns solutions provider Optoro says U.S. returns generate an estimated 5.8 billion pounds of landfill waste each year. Amazon told CNBC it sends no items to landfills.
"There are a number of items that we can't recover or are not recyclable, for reasons such as legal reasons, or reasons for, you know, hygienic reasons, or even product damage," said Cherris Armour, Amazon's head of North American returns. "In those cases, we do pursue energy recovery for those items."
In parts of Europe and Asia, the picture looks quite different.
Countries like Japan, Denmark and Germany rely on energy recovery far more than landfills. In the EU, waste incineration doubled from 1995 to 2019.
But burning waste is still a carbon-intensive process, and critics like Neil Tangri of the Global Alliance for Incinerator Alternatives (GAIA) argue some countries have come to rely on it too heavily.
"Denmark now realizes that it incinerates too much waste and if it is going to meet its greenhouse gas emissions targets it's going to need to reduce waste incineration," Tangri said.
In the U.S., the first incinerator was built in New York in 1895. A decade later, the city was using it to generate enough electricity to light the Williamsburg Bridge.
More than half of U.S. states define waste-to-energy as a renewable energy source. Unlike landfills, many governments and non-governmental organizations consider it a source of greenhouse gas mitigation. That includes the U.S. Environmental Protection Agency, where Susan Thorneloe leads research on materials management.
In terms of burning or burying waste, "it was hands down better to combust it because you get energy value from it, you get metals from it, and you're not producing methane," Thorneloe said.
U.S. climate experts say these are the three reasons the burning process produces a net reduction of greenhouse gasses. First, it keeps waste out of landfills, which emit methane that the EPA estimates is 86 times greater than carbon dioxide over a 20-year period.
Second, waste-to-energy facilities reduce the need for mining because they recover 700,000 tons of metal each year. And finally, they produce energy, reducing the need to burn fossil fuels.
"For every ton of garbage that you burn, you save a ton of CO2 that you would otherwise create from, say, burning a fossil fuel," said Marco J. Castaldi, director of the Earth System Science and Environmental Engineering Program at the City College of New York.
The steam can also be captured and piped up to a mile away to heat or cool entire buildings, like Target Field in Minneapolis.
While landfills can harness energy from rotting organic material, they're far less efficient for production purposes. Landfill gas generates enough power for 810,000 U.S. homes per year, compared to 2.3 million homes powered by far fewer waste-to-energy facilities.
Covanta's public data shows emissions coming out of the stack in its northern California facility are far below U.S. federal standards. That's because Covanta cleans toxins out of its combustion gasses using an intense filtration process, with activated carbon and limestone "scrubbers."
"The air pollution control systems, they weren't present on old-fashioned incinerators, the object of a lot of people's ire," Gilman said.
The EPA estimates that for every megawatt-hour of electricity generated, waste-to-energy emits an average of just over half a metric ton of carbon dioxide equivalent gasses. Landfills emit six times that, and coal plants emit nearly double.
Dioxin and mercury are some of the most dangerous emissions that concern critics of the process. GAIA points to facilities like one in the Netherlands, which regulators found was emitting so much dioxin it was contaminating grass and chicken eggs in the surrounding area.
"Despite the air pollution control equipment and the monitoring, there are still a lot of toxins in that smoke plume, from particulates to heavy metals, lead, mercury, arsenic, cadmium," Tangri said. "Here in the U.S., our monitoring systems and our standards are much lower than in Europe."
But other scientists say air pollution technology has come so far in the last two decades that most common toxins have largely been eliminated.
"The amount of dioxin that's emitted from all waste-to-energy facilities in one year is less than a fraction of what gets formed from forest fires," Castaldi said.
Still, the incineration process does produce a lot of toxic ash, which Covanta tests regularly to make sure hazardous materials aren't able to leach out.
"Happily, we've always passed our tests," Gilman said.
In Europe, facilities separate the more toxic "fly ash" and use the safer "bottom ash" to make things like concrete for road construction. In the U.S., the fly and bottom ash are usually mixed together, making it too toxic to be reused, so it's buried in a monofill on site.
"There's probably more municipal solid waste ash that we can use, but because of the negative connotation, I just don't see that occurring," said Thorneloe of the EPA.
Landfills in the U.S. are big business. While Castaldi estimates waste-to-energy is a $10 billion industry, the overall waste management industry is measured at $208 billion. Landfill companies like Waste Management and Republic Services have outperformed the market since 2015, allowing them to keep prices down as they grow.
There are approximately 1,450 active landfills today, compared to 76 waste-to-energy plants, said Bryan Staley of the Environmental Research Education Foundation. That makes it tough for many businesses to participate.
"We've got to haul it by rail halfway across the United States to get it there, because you typically find most waste energy facilities located in the northeast part of the United States, in Florida, and Minnesota and then a smattering of facilities elsewhere," Staley said.
The transport creates an additional carbon footprint for companies choosing energy recovery over landfill. The Covanta facility is one of only two energy recovery plants in California. Europe has more than 400.
"There's a real question about why California and why most of the U.S. for that matter, are so in love with our landfills," Gilman said. "But it's a fact. It happens that we have a lot of land, something Europe didn't have that luxury with."
But turning waste into energy is lucrative business. Each ton of waste generates $20 to $30 of revenue, according to the EPA. Covanta was on a big upward swing before a Swedish investment firm took the company private last year in a $5.3 billion deal. In fact, incineration is one of the most expensive commercial ways to generate energy and to handle waste, more than double the costs of sending it to a landfill.
Giant companies like Amazon can often negotiate special rates. Burning waste instead of sending it to landfills helps them fulfill sustainability targets. Tangri said it can also help with optics.
"If Amazon sends all of its returns to a landfill, somebody could go to the landfill and see them, and that would be a horrifying visual," Tangri said. "When you burn something, you hide the evidence."
Tangri said that companies and consumers need to be focused more on truly cutting emissions through reducing, reusing and recycling.
"You're arguing for last place," Tangri said. "We know that the important thing to do is to keep as much material and particularly organics out of the waste stream...If Amazon returns were being repackaged and sold to people at discount instead of being disposed of, then we wouldn't have to have this question about whether it's better or worse to bury plastic or burn it."
Amazon doesn't provide much by way of specific details. But the company has been adding programs to make sure more returns are resold as used, refurbished, or liquidated. And while there's no target date for its lofty objectives, Amazon says it's "working toward a goal of zero product disposal."