We might not be reaping the full environmental benefits of biodegradable products, according to new research. In fact, in some cases, the landfill disposal of biodegradable materials might be causing more harm than good.
Morton Barlaz, head of North Carolina State University’s Department of Civil, Construction, and Environmental Engineering and co-author with James Levis of a paper describing the research, spoke with me recently about the findings — and what we can do about the damage.
Why might biodegradable products actually harm, rather than help, the environment?
If a biodegradable material is placed in a landfill, then during biodegradation it’s going to be converted into methane and carbon dioxide. Some landfills recover the methane for energy. Some recover it, but just burn it. Some do not recover it. According to the EPA, about 35 percent of waste is in landfills that use the methane for energy. About 34 percent is in landfills that burn it, but don’t recover energy. And about 31 percent is in landfills that just release it to the environment.
Even when we say methane is a good energy source, which is true, it’s only good if you recover it and use it. That’s not always happening. That’s one major point. The landfills that don’t collect the methane and just have it released in the atmosphere are the subset causing the environmental problem.
Does the problem also have to do with how long it takes the biodegradable materials to break down?
That’s the second point. There’s going to be some rate of biodegradation. You can imagine that a rotten apple might biodegrade faster than a newspaper. We have a race between how fast the methane is being produced and when the landfill is installing the gas collection system. The percent of gas that’s collected increases with time. On average, landfills don’t put in gas collection for two years. If something biodegrades rapidly, much of the methane can be produced before the gas collection system is in place. On the other hand, if something biodegrades slowly, then you have an opportunity to capture most of that methane because the gas collection system is installed.
How did you conduct this research?
We used an analytical framework referred to as life cycle assessment, which is a well-known process for comparing the environmental implications of different activities. When we apply that to a landfill, we consider the energy and emissions that are associated with building the landfill, operating the landfill, closing the landfill, [treating the leachate] and the way in which the gas is managed. If methane is emitted into the environment, that’s a net positive. If methane is burned to form carbon dioxide, that’s a neutral. If the methane is recovered for energy, then it’s actually a net negative because we avoid the production of energy from [fossil fuels]. It’s a positive benefit to the environment. We’re thinking about all the different factors that influence the total global warming gases going into the atmosphere from the landfill and adding them up.
The other thing we consider is carbon storage. If a tree falls in the forest and it completely decomposes, then all the carbon in that tree goes back to the atmosphere. But if you put that tree in a landfill, it doesn’t all biodegrade. Some of that carbon is stored in the landfill. That also is a positive for the environment because you’re taking carbon out of the atmosphere.
What should be done to deal with this problem?
The study was done from the perspective of a manufacturer who wants to do the right thing. Imagine if you’re [a big box store] and you want to do the right thing. Someone says, ‘We can sell you laundry detergent in biodegradable plastic containers. You can sell that to your customers and tell them it’s better for the environment.’ We want [the store] to take a step back and say, ‘Is this really good for the environment?’ To do that, we need to consider the emissions associated with producing that container, plus the emissions associated with the disposal of that container. We need to do that with the biodegradable container and for the conventional container. We gave the manufacturers a way to analyze the disposal phase. They’ve still got to analyze the production phase. A major message to the packaging manufacturers is: Don’t assume biodegradable is better. You’ve got to do a more careful analysis.
Let’s imagine you’re on the consumer end. What’s a consumer to do? A consumer can call their elected officials and ask, ‘How do you manage the methane at the landfill that this city’s waste goes to?’ They can demand aggressive gas collection.
Have there been other studies showing this before?
Nobody has asked the question that we asked and analyzed it the way we analyzed it, to my knowledge. The major advances were to focus on the national average situation and to put together a lot of information coming from different sources.
I think it’s going to hit biodegradable packaging manufacturers [the most] because they don’t understand disposal. Society got in its head that biodegradable was always good. That’s what we’re trying to challenge.
Photo, top: Morton Barlaz
Photo, bottom: James Levis
