Experts on Camera

Dr. Sintana Vergara: Garbage

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The average American produces 4.9 pounds of garbage per day, and every municipality manages it differently—a recent trend in some cities is the introduction or expansion of municipal composting programs.

On September 27, 2023, SciLine interviewed: Dr. Sintana Vergara, an associate professor of environmental resources engineering at California State Polytechnic University, Humboldt. She discussed topics including: her research on the different climate impacts of composting, landfilling, or incinerating various forms of garbage (including solid waste, biomass, and agricultural waste); the air pollution produced by the nation’s 72 municipal trash incinerators (operating in 21 U.S. states, including a high number in Florida, New York, Minnesota, Massachusetts, and Pennsylvania), and how it affects people and the environment nearby; what carbon sequestration is, and how it works; and what research indicates are the best ways to manage organic waste, and why.

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SINTANA VERGARA: My name is Sintana Vergara. I’m an associate professor at Cal Poly Humboldt in the department of environmental resources engineering. And I study waste management—and specifically the climate implications of managing our waste in alternative ways.

Interview with SciLine

What is organic waste?


SINTANA VERGARA: Organic waste includes any waste that is biodegradable, so: food waste, yard waste, anything that will decompose biologically.

Why is it better for the environment to compost food waste rather than send it to a landfill?


SINTANA VERGARA: If we send food waste to a landfill, it’s going to go to an environment that’s anaerobic. Basically, there’s no oxygen in that environment. And the microbes, when they break down that waste, they’re going to produce methane, which is a really powerful greenhouse gas. On the other hand, we could send that food waste to be composted, instead. And while that food waste is being degraded in a composting facility, it’s being degraded in the presence of oxygen, so we’re not going to get the formation of methane. But instead, we’re going to get formation of just CO2, or at least mostly CO2.

Why do we want to avoid releasing methane into the atmosphere?


SINTANA VERGARA: Methane is a really powerful greenhouse gas. So, one molecule of methane is 32 times more climate warming then one molecule of carbon dioxide.

What is carbon sequestration, and how does composting achieve this?


SINTANA VERGARA: Carbon sequestration is a fancy term for carbon storage. So, we see carbon sequestration in our day to day lives. If you look out the window, if you see any plants, they are sequestering carbon, and the way they’re doing that is that they’re photosynthesizing. So, they’re taking carbon out of the atmosphere, and they’re pulling it into their plant matter. What’s exciting about carbon sequestration in terms of waste management, is that we’ve found that applying compost to grasslands can actually enhance carbon sequestration. So, in other words, it can impel more carbon storage to actually occur. And the way we think this is happening is that when you apply compost to grasslands, for example, you get more grass growth. So, more photosynthesis, more carbon coming out of the atmosphere and getting pulled into that biomass. But not just the above ground biomass, it’s also going into the root system. And from the root system, it’s ending up as soil organic carbon. So, as we apply compost to grasslands, we get more plant growth, but we also get more carbon ending up sticking around in the soil. And that’s really good news from a climate change perspective, because we’re pulling carbon out of the atmosphere where we don’t want it and into the soil where we do. And there are some co-benefits of that as well because more soil organic carbon also means increased fertility.

Are plastic products that are marketed as compostable currently regularly composted?


SINTANA VERGARA: Perhaps under lab conditions, these materials might degrade. But under the timescales that we see in commercial composting facilities, these items just don’t break down. So, the facilities that I have visited, they screen out all of these bio plastics and they just throw them away. Because if you think about a banana peel, a paper towel, these different organic items degrade in a matter of weeks. I mean, they’re they’re pretty quick to break down. And these bio plastics just stay exactly the same way as they came in six weeks later. So, they end up getting screened out of the process and thrown away.

What can help municipal composting programs succeed?


SINTANA VERGARA: Sorting is the most important thing that they can possibly do. So, the quality of compost you get is directly related to the quality of the input that you have. So, if you have a mixed waste input, you’re gonna get a mixed bag compost that will be difficult to market and difficult to use and farmers won’t want to apply it to their lands. So, a couple of easy ways to get very good quality compost are to identify single streams of organic waste. So for example, farmers markets, restaurants—you know, behind the kitchen—restaurants, farms, places that really only produce organic waste you don’t really have to deal with the sorting part and you can be assured a high quality input. Places that have mixed quality input end up with poor quality compost.

What are the public health consequences of trash incineration?


SINTANA VERGARA: Incineration is the burning of trash. And anytime you have combustion, you’re going to have the production of a bunch of different air pollutants, including particulate matter, which is one we’re particularly interested in because it has a clear impact on human health. So, whenever you have combustion of anything near people, you’re going to have a health impact, you’re going to have some risk to the to the people living nearby. Now, for the case of incineration, it’s even a little bit trickier and a little bit riskier than some other fuels we might use to produce electricity. Because waste is such a varied mass of things, we can get the production of lots of different types of air pollutants, some that are very concerning—like dioxins, which are produced when you burn matter that contains chlorine at high temperatures, you get dioxins, which are these toxic and bio accumulating compounds that are very, very concerning from a health perspective. And whenever you burn plastic, for example, you have the potential of creating dioxins. So, incineration close to people certainly poses a direct health hazard.

What can you tell us about trash incineration in the United States?


SINTANA VERGARA: Now, in the United States, we have a pretty long history of siting incinerators in low-income communities and in communities of color. And we also have a long history of resistance to those facilities and resistance to siting those facilities near these people. So, for that reason, incineration remains very unpopular in the United States. We incinerate about 13% of our garbage right now. But that percentage has been flat for a really long time, because people really—the public acceptance of incineration in the United States is quite low.

What can individuals do to reduce waste and improve waste management?


SINTANA VERGARA: There are two aspects of waste management that are not talked about enough. One of them is consumption. So, the fact that the amount of waste we produce and what we produce is really a social process. It’s a cultural process. And it’s also a personal process. And one that we have a lot of agency around. We learned to consume the way that we consume. If you talk to your grandparents, for example, our grandparents didn’t produce a lot of waste. When something broke, they fixed it. They didn’t buy a lot of stuff. So, the ensuing generations have really learned to produce and to consume the way that we do now. So, I think that that process is reversible. But we do need to talk about it, we need to educate ourselves. The second thing I would say is that waste is most challenging to process when it’s mixed all together, if we’re able to separate our waste into parts—so, for example, if your organic wastes is separated from your paper and from your land, fillable waste—it’s a lot easier to reuse and to beneficially reuse the parts of our waste if they’re separated. Once they’re all mixed together, it really becomes trash and it becomes very difficult to recycle, to compost, to make beneficial use out of these products if they’re all mixed. So, that’s another role that we can have as individuals and that we should improve education about is the importance of separating our materials, too.

What advice do you have for reporters covering garbage?

[Posted September 27, 2023 | Download video]