Clean Tech 101

Methane Gas - What is Methane Gas and Converting Landfill Gas into a Form of Renewable Energy

Introduction
What is Methane Gas?
The Greenhouse Gas Properties of Methane Gas
Emission Sources of Methane
Methane Emissions from Landfills
Turning Landfill Gas into Energy
Benefits of Landfill Gas Energy

Introduction

Landfill gas is generated as a result of decomposition of solid waste in landfills. Landfill gas primarily consists of carbon dioxide and methane. Both carbon dioxide and methane gas are considered as a form of greenhouse gas that leads to global warming. Since all landfills generate methane, it makes perfect sense to use this landfill gas for energy generation rather than emitting it to the atmosphere.

What is Methane Gas?

Methane gas is a form of greenhouse gas that is over 20 times more effective than carbon dioxide in trapping heat in the atmosphere. Methane gas can remain in the atmosphere for about 9 to 15 years.

Methane is emitted from a number of natural and human-influenced sources. Human-influenced sources include natural gas and petroleum systems, agricultural activities, coal mining, landfills, stationary and mobile combustion, wastewater treatment, and certain industrial process.

Methane is also a primary component of natural gas and an important energy source. As a result, efforts to prevent or utilize methane emissions can provide significant economic, energy and environmental benefits.

The Greenhouse Gas Properties of Methane Gas

Methane is created and released into the atmosphere by biological processes that occur in an anaerobic environment. Methane absorbs terrestrial infrared radiation that would otherwise escape to space once methane is released into the atmosphere. This characteristic can lead to the warming of the atmosphere, hence methane is a greenhouse gas.

As stated earlier, methane is about 21 times more powerful at warming the atmosphere than carbon dioxide by weight. The chemical lifetime of methane in the atmosphere is approximately 12 years. The relatively short atmospheric lifetime of methane, coupled with its potency as a greenhouse gas, makes it a candidate for mitigating global warming over the near-term.

Emission Sources of Methane

Methane emission levels from a source can vary significantly from one country or region to another, depending on many factors such as climate, industrial and agricultural production characteristics, energy types and usage, and waste management practices.

For example, moisture and temperature can affect the anaerobic digestion process, which is one of the key biological processes that cause methane emissions in both human-related and natural sources. Also, the implementation of technologies to capture and utilize methane from sources such as landfills, coal mines, and manure management systems affects the emission levels from these sources.

The largest source of methane emissions come from the decomposition of wastes in landfills, ruminant digestion and manure management associated with domestic livestock, natural gas and oil systems, and coal mining.

Methane Emissions from Landfills

Methane is generated in landfills and open dumps as waste decomposes under anaerobic conditions. The amount of methane generated is dependent on the quantity and moisture content of the waste and the design and management practices at the site.

Methane emissions from landfills represent a lost opportunity to capture and use a significant energy resource. Landfill gas is created as solid waste decomposes in a landfill. Landfill gas is composed of approximately 50 percent methane, about 50 percent carbon dioxide, and a small amount of non-methane organic compounds.

Turning Landfill Gas into Energy

Instead of allowing landfill gas to escape into the air, it can be captured, converted, and used as an energy source. Landfill gas can be extracted from landfills using a series of wells and a blower/flare or a vacuum system. This system directs the collected gas to a central point where the extracted landfill gas can be processed and treated depending upon the final use for the gas.

From this point, the extracted landfill gas can be simply flared or used to generate electricity, replace fossil fuels in industrial and manufacturing operations, fuel greenhouse operations, or be upgraded to pipeline quality gas.

Figure 1. Landfill Gas System (Image source EPA)

Benefits of Landfill Gas Energy

Using landfill gas for energy is a win/win opportunity. Landfill gas emitted from decomposing garbage is a reliable and renewable fuel option that remains largely untapped at many landfills.

Generating energy from landfill gas creates a number of environmental benefits such as directly reducing the amount of greenhouse gas emitted into the atmosphere. Producing energy using landfill gas avoids the need to use non-renewable resources like coal or oil to produce the same amount of energy.

Source: AZoCleantech
Last update 17th January 2008

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit