WASTE-TO-ENERGY VS. LANDFILL

Which will produce less greenhouse gas (GHG)?

Waste-to-Energy is internationally recognized as a way to reduced GHG emissions from managing the wastes left over after recycling, (saving about a ton of GHGs compared to landfill), but how?

Let's start at the beginning.

Every time we place waste or recyclables
out at the curb, we are impacting the climate.

How much of an impact depends on what happens next.

Recycling has the smallest impact. After collection, sorting, and processing, recyclables are returned to the economy. This avoids the greenhouse gases emitted from using raw materials.

For source separated organics, well designed and operated composting and anaerobic digestion facilities are also smart choices with low greenhouse gas impacts.

For what’s left over (about 250 million tons every year in the U.S.) there are two options:

landfilling and
waste-to-energy.

The climate
impact...


...Depends on
which option
we choose

Comparing the climate impacts starts with looking at the greenhouse gas emissions from each facility.

In a waste-to-energy facility, waste is combusted to release the heat energy. The heat energy generates steam, turning a turbine and generating electricity. The combustion also releases carbon dioxide (CO₂), a greenhouse gas.
‍
At some facilities, steam is also exported to provide heat for businesses, homes, and manufacturing processes.

In a landfill, waste is buried. Over time, bacteria break down the biogenic materials in the waste without oxygen, generating methane and carbon dioxide. Biogenic materials are those made by, or derived from, living things, including food waste, paper, cardboard, yard waste, and some fabrics, like cotton.

Landfills emit less cO₂  than do Waste-to-Energy facilities

But the methane emitted by landfills from the same waste is far more potent than CO₂

Once in the atmosphere, methane is much better at trapping heat than CO₂.

Methane is
continUously emitted from landfills over decades

When it comes to climate change, a little methane has a big impact

Scientists compare the strengths of different gases using global warming potentials over different time periods.

Over 100 years, methane is 28 - 34 times stronger than CO₂

However, over 20 years, a timeframe increasingly seen as relevant to combating climate change,

METHANE IS 84 TIMES STRONGER.

CO₂ impact

METHANE impact

Taking methane’s strength into account, [conservatively using the 100-yr methane global warming potential of 28,] landfills emit more greenhouse gases as CO₂ equivalents, but that’s just part of the story.

For a more accurate comparison, a lifecycle analysis allows us to take into account a few more factors. Lifecycle analysis looks at the environmental effects of all stages of a product or service.

This analysis allows a direct comparison between the climate impacts of landfills and waste-to-energy.

Biogenic CO₂

Both landfills and waste-to-energy facilities emit CO₂ from biogenic materials. The carbon in these emissions is part of the normal carbon cycle. Composting and anaerobic digestion also release CO₂ from biogenic material.

Historically, biogenic CO₂ emitted when biogenic materials decompose or are combusted was considered “carbon neutral” meaning it was assumed to have no impact on the climate system. We now know this is not always the case. However, waste sources of biogenic carbon are widely recognized by the scientific community as being very close to carbon neutral.

Waste-to-energy facilities do emit fossil-based CO₂, which is included in greenhouse gas comparisons.

Energy

Some landfills and all waste-to-energy facilities recover energy from the waste received. In most cases, this energy takes the form of electricity exported to the power grid.

This electricity avoids the need to burn fossil fuels to generate electricity, saving greenhouse gas emissions.

Waste-to-energy facilities reduce more greenhouse gases than landfills because they generate much more electricity from a ton of waste.

Metals

Waste contains metal, even in communities with really good recycling programs.
‍
Waste-to-Energy facilities also recover ferrous and non-ferrous metals that would otherwise be lost forever in a landfill. Landfills don't recycle any metals.

Recycling these metals helps reduce greenhouse gas emissions that would have occurred if new metals were manufactured from raw materials.

Managing a ton of Municipal Solid Waste (MSW)
(as CO₂ equivalents)

methane

biogenic co₂

fossil co₂

energy

metals
recycling

0.2 ton

0.5 ton

0.9 ton

1.0 ton

Therefore, by diverting a ton of MSW from landfilling to Waste-to-energy, we can save, on average, 1 ton of CO₂.

The actual GHG savings can vary, based on the carbon intensity of the electrical grid, the materials in the waste, the design of the WTE facility, and the design and operation of the landfill.

One ton of CO₂ is the amount of CO₂ in 1,000 pounds of coal, or the amount of CO₂ released by driving 2,250 miles.

On average after recycling, a family of 4 generates 3.5 tons of garbage every year. Diverting that waste to Waste-to-energy saves more GHG emissions than switching to a hybrid car!

The actual climate
benefits of
Waste-to-Energy are almost certainly much higher.

Researchers are finally beginning to directly measure methane emissions from landfills. On average, they are finding actual [measured] emissions [2-3 times] those predicted by the models.

Policy makers and scientists are also calling for a new look at methane, given its role as a leading short lived climate pollutant. One approach, already taken by California, New Jersey, and New York is to compare methane to CO₂ using the 20-year global warming potential.

RESOURCES

Return to top