I am an engineer. So that means I get utterly obsessed with a topic for a short period and dig and dig and dig until I understand how it works. If you have an engineer in your life, you probably understand this common quirk of engineers. Today, it was landfill gas. How it is produced, how the composition changes, factors contributing to landfill gas emissions, how it is recovered to produce energy, and (probably most interestingly) the considerable debate over the accuracy of U.S. Environmental Protection Agency (EPA) emission factors required (by law) to calculate landfill gas emissions. If you are planning to keep reading…. you might be an engineer as well.

According to the EPA, the waste industry is the 3rd most significant source of greenhouse gas emissions.

82% of the waste industry emissions are from municipal solid waste (MSW) landfills. These are the ones that contain the trash from residential sources.

When organic material like food, paper, and yard waste decomposes in landfills, it emits CO₂ and/or methane.

Only MSW landfills with over 25,000 metric tons of CO₂e emissions must follow EPA reporting guidelines. However, according to the EPA, that covers 74% of landfills and 93% of landfill gas emissions¹.

Of the 74% reporting to the EPA, 74% of those utilize gas collection and control systems (GCCS) to capture emissions¹. The efficiency of these systems is the topic of controversy. So, let’s dig in!

Within a given landfill location, the operation is split up into cells. A cell is active for about one year. When a cell is active, MSW is added to it during the day, and then it is covered at night to reduce emissions. This is called daily cover.  The effectiveness of the daily cover is a significant factor that drives the variability of landfill gas emissions. In a given operation, if they are religious about ensuring good daily cover each day, they have lower emissions during the time the cell is active.

Figure adapted from ATSDR 2008. Chapter 2: Landfill Gas Basics. In Landfill Gas Primer – An Overview for Environmental Health Professionals⁴

After a cell is full, it is closed and capped. It takes about a year to establish anaerobic conditions¹.  In the above chart, you have reached anaerobic conditions when oxygen goes down to ZERO.

EPA regulations are very prescriptive on how emissions from landfills must be calculated, and this is a source of much controversy. Waste industry operators say this method over-estimates emissions, and environmentalists say this method underestimates emissions. The one thing both sides agree on is that the technique of using emission factors rather than direct measurements is not ideal. Depending on how it is calculated, there are estimates that landfill gas recovery systems recover as low as 50% or as high as 91% of the emissions.

A Solid Waste Association of North America (SWANA) funded study of 5 landfills with landfill gas recovery systems found the average collection efficiency to be 90% for a closed and capped MSW landfill. However, the EPA AP 42 factors use an estimate of 75% efficiency³.

What does this have to do with biodegradable EPS?

EVRgreen® is engineered to biodegrade in anaerobic conditions. That means when the cell is open to the atmosphere, and the organics are causing high levels of CO₂ emission, EVRgreen® has not started to biodegrade and does not emit to the atmosphere.

Only after the cell is closed and anaerobic conditions are created does EVRgreen® start decomposing, and contributing to methane generation, the same as food waste. Epsilyte has engineered the biodegradation rate so that EVRgreen® only starts biodegrading in anaerobic conditions, that is after the cell is closed, capped, and the landfill gas recovery system is operational.  This is the most sustainable way to take advantage of biodegradation technology.

The FTC requires that a material can only be labeled “biodegradable” without a qualifier if it fully degrades in less than one year. If EVRgreen® biodegraded in those conditions, however, it would emit greenhouse gases into the atmosphere while the cell is still open. We do not want that. We want it to lay in the landfill and wait until the conditions are suitable for methane collection. That way, less greenhouse gas is emitted plus the captured methane is a renewable fuel that is then used to produce electricity.

So Epsilyte follows the FTC rules and puts a qualifier on our biodegradability claim because it takes more than one year to degrade. However, as an engineer, I will hold my head high knowing that my company has engineered a truly more sustainable way to biodegrade.

EVRgreen® will sit in that landfill and wait. Then when conditions are just right, transform, and ascend to be turned into renewable fuel.

Sources:

1 – Greenhouse Gas Reporting Program Industrial Profile: Waste Sector (epa.gov)

2 – Cutting Landfill Methane To Fight Climate Change : NPR

3 – Landfill Gas Collection System Efficiencies | MSW Management

4 – https://www.atsdr.cdc.gov/HAC/landfill/PDFs/Landfill_2001_ch2mod.pdf (PDF)