After a history of unforeseen explosions, researchers were able to track them back to deadly landfill gas emissions. Even today, dangers and risks of landfill gases continue to challenge present day landfill management professionals.  See how the latest revolutionary laser technology helps landfill decision makers minimize methane gas explosion risks.

Examples of Landfill Methane Gas Explosions

In 1967, two people were killed and a further two injured when a methane gas explosion tore apart a single story home in Atlanta, Georgia. The building was situated close to a landfill site and although the basement was sealed, an open pipe ran from this enclosed area to the rooms above. Investigators believe that the landfill gas seeped into the basement, passed through the pipe, and exploded when someone lit a cigarette.

Two years later, an armory close to a disused landfill site at Winston-Salem in North Carolina suffered a similar fate. Three people died and twenty five were injured. At first it was unclear why the gas should enter the building at this particular time because the armory was already seven years old and had been constructed when the landfill site was still in use. But investigators established that a week prior to the explosion, someone had dumped fresh garbage on the site, thereby causing the gas underneath to change its usual course and work its way into the building.

In 1986, at Loscoe in the United Kingdom, a gas explosion demolished one home and damaged several others. The nearby landfill site was to blame. It had originally been a brickworks from the 1850s until the start of the 1970s. Then from 1973 to 1982, contractors used it to dispose of general, untreated domestic waste despite the site’s location in the middle of a housing development.

The first danger signs at Loscoe appeared in 1984: grass and plants began to die for no apparent reason, and the soil started to feel warm (a phenomenon now thought to be caused by the bacteria that feeds on methane). These signs were ignored, and two years later, the explosion occurred.

Where Does Landfill Gas Come From?

When we dump garbage into a hole in the earth, deadly landfill gas begins to form. It does not matter whether the landfill site is neglected or strictly controlled, a gas is created that is on average 60% methane, 39% carbon dioxide and 1% trace gases (of which there can be more than 550).

The precise make-up of the gas and the amount produced depend on the type of waste and the conditions of the site. Many sites are monitored and the gas is burned off (or sometimes channeled to a pipeline to provide energy for a nearby town or facility). But a lot of sites – from an estimated total of more than 10,000 in the United States – are neglected and have no safety measures in place.

The lack of safety is a serious matter when you consider that one ton of garbage can produce 400-500 cubic yards of gas. How does it do this? The answer lies in the organic nature of the waste that is dumped. Bacteria immediately sets to work decomposing food scraps, garden trimmings and paper-based products. If there is plenty of oxygen present, this decomposition process (known as aerobic) happens fairly quickly and the resulting gas consists mainly of carbon dioxide. When the site is filled and capped, however, or if the site has a deep pit of garbage, there is no oxygen present and anaerobic decomposition occurs. The resulting gas is largely methane and highly explosive.

Traditional Methods of Limiting Gas Explosion Risk

In the United States, garbage landfill sites are the main cause of human-generated methane gas. It is estimated that between them, U.S. sites emit 38 MMTCE (million metric tons of carbon equivalent) each year. This is a staggering amount of methane – and when you realize that much of it is not released in a managed and safe manner, there is obviously a need to detect it and lessen the threat of an explosion.

Previous means of detecting methane have included surveys using a device called a flame ionization detector. Also called an FID, it requires the surveyor to carry this apparatus consisting of a hydrogen tank, a flame chamber, optics and analytical equipment. The surveyor must enter the area where gas is suspected, use the FID to suck in a sample of air. The air is sent passed the flame where optics and analytical equipment determine methane content of the air sampled. This process of surveying landfill gas requires personnel to enter the potentially dangerous area with a hydrogen tank and heat source.

Though it may sound like Russian Roulette, Flame Ionization Detection is still used today by many landfill methane gas surveyors. The surveyor will typically make a serpentine pattern throughout the landfill, stopping every few feet to take a sample. Surveys are usually performed on a quarterly basis. If methane presence is detected, survey frequency increases.  Using FID, the entire survey process is a long, monotonous and dangerous process.