Zero waste is not zero waste emissions

Even if we divert or eliminate all new waste, landfills will emit greenhouse gas for decades.

By Mark Mondik

According to the EPA, U.S. landfills emit about 100 million metric tons of CO2-equivalent (or about 21 million cars) of greenhouse gas annually[1]. Thus it’s no surprise that measuring corporate waste emissions is the hottest thing to hit carbon accounting since Kate Middleton’s wedding, and that terms like “compost” have become commonplace for solid waste managers and ordinary citizens alike.

Knowledge that may be less common is that waste diversion efforts like composting don’t by themselves solve our waste emissions problem. Even if we ultimately eliminate all new waste through diversion programs like composting and recycling, we are likely to have material GHG emissions from landfills for the next 100 years. There are two main reasons for this.

The Long Life of Waste

First, most of the methane gas being emitted from landfills comes from waste that was deposited in the landfill five or more years ago. The source of this methane is largely wood, textiles, office paper, and other organic materials that break down slowly over time (and not from food waste, which is the common assumption). As a result, landfills will typically produce methane for 40 years or more after they have been closed and stop accepting new waste. So even if we successfully divert 100% of organic waste going forward, the waste that’s already there will be adding to our GHG inventory beyond 2050.

Second, it’s going to take a while to get to zero waste. Waste reduction and diversion programs are still largely in a development and implementation phase in most parts of the U.S. They will require extensive education and behavioral changes at a mass scale to be successful. This will also entail the cooperation (perhaps by forcible legislation) of companies with respect to product packaging.

Methane Capture: On the Path to Zero Waste

The complementary solution to waste diversion, in the interim, is landfill gas capture. This is already being done at hundreds of landfills throughout the U.S., thanks in part to EPA regulations that require large landfills to do so. But EPA estimates that there are some 500 or more small and mid-sized landfills in the U.S. that are not required by law to collect methane. Many of these are owned by rural and semi-rural municipalities and small private operators that lack financial resources to implement such projects, forcing them to rely on external funding such as carbon offsets.

Critics of landfill gas projects sometimes decry such efforts, arguing that generating revenue from captured methane creates perverse incentives for landfill operators. One such incentive, they claim, is that landfill operators will artificially accelerate waste decay in order to increase methane production, and since gas collection systems don’t capture 100% of produced methane, this practice might actually lead to an increase in overall GHG emissions, at least in the near term.

Figure 1- Typical Landfill Methane Curves Under the Traditional and Bioreactor Methods (Source:

Figure 1- Typical Landfill Methane Curves Under the Traditional and Bioreactor Methods (Source:

TerraPass’ experience with landfill gas projects does not corroborate such assertions. The small and municipal landfills we support through the sale of carbon offsets don’t use the so-called “bioreactor” method (i.e., the practice of adding liquids to enhance the microbial process, thereby accelerating waste decay). In fact, if they did use such a method, they wouldn’t be eligible to produce carbon offsets because the protocols we use prevent them from doing so[2]. Having said that, TerraPass fully supports organic waste diversion and only recommends landfill gas capture as a means to address the waste that is already in place, and that which may slip through as new diversion programs get up and running.

No Time to Waste

No one appears to contest that landfill methane is a major problem. And it’s well documented that emission reduction from landfills is amongst the most feasible and cost‐effective measures to reduce GHG emissions. In the absence of waiting for the U.S. Congress (or anyone else) to take action, funding such “avoidable” emissions through offset projects may be a reasonable answer to the “unavoidable” (but hopefully declining) emissions that result from other activities. Or think of it as a chance to capture the methane from the reams of paper you (or your older colleagues) threw away in 1989.


[1] Inventory of U.S. Greenhouse Gas Emissions and Sinks:  1990-2011, April 2013

[2] Under the Climate Action Reserve’s U.S. Landfill Project Protocol, “bioreactor” projects are excluded from being able to generate and issue offsets.


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