County landfill personnel at a Florida landfill conducted a pilot study with five competitive products to determine if they could improve the effectiveness of an on-going odor control program. Odors are generated throughout areas receiving the trash and are especially bad during wet weather due to wet soil covers and standing puddles. A more effective means of control was necessary to satisfy neighboring property owners. Closed trash cells use gas burners to oxidize methane and other gases, eliminating odor problems from these areas.more...
Report: Effective Odor Control Part 1
In Landfills: Odor can be said to occur in several ways in a landfill. It can come from the chemicals or products put in the landfill that are reacting with the heat and moisture generated deep within the landfill. Those odor sources can be creating gas or gases of their own, such as hydrogen sulfide gas that can come from the placing of waste gypsum board in a landfill. This calcium sulfate material is converted with heat,pressure and water into hydrogen sulfide (rotten egg) gas. In addition, the carbon dioxide and methane gases that are generated by the anerobic degradation of the organics deep in the landfill are working their way toward the surface through cracks and other gaps in the waste. Attached to the methane gas molecules are other odorous substances that are being degraded. Lastly, you have at the surface of the landfill, material that are moist and wet, and also carries with it a lot of odor. These odors are different but are generally similar to the odors that you might experience when walking by a full waste bin that has not been picked up in a week. Although the odor is coming from the rotting garbage, you smell it because the surface of the rotting garbage is evaporating the moisture and with it comes the odor molecules.
So in summary, the smell is coming from the following:
- the chemical change occurring causing solids to turn into gases (hydrogen sulfide gas example)
- the odor molecules attached to the methane gas molecules escaping from the landfill. The methane coming from the anaerobic degradation of waste in the landfill. The Aerobic side creates water and carbon dioxide, while the anaerobic side creates methane and water.
- the evaporation of moisture from rotting waste carries with it odor molecules which we smell
In Transfer Stations: Odor in a transfer station largely comes from the decomposing waste in its early stages of decomposition. The odor molecules are escaping from the waste on the floor and in areas where the waste is being loaded onto rail cars or on waste trucks going to the landfill.
Contaminated Sediments: Many contaminated sediments have odors that are the result of the chemistry which has contaminated the sediments. Hydrocarbon contaminated waste can have odors of sulphur. Coal coking operations have over the years released lots of coal tar, pesticides, PCB’s and dense nonaqueous phase liquids with the coal tar contaminated sediments often carrying a uniquely bad odor. Creosote contaminated sediment also have bad odors. When removing some contaminated sediments regulations may require focused ambient -air monitoring, field observations of odors at regular intervals, and focused odor testing. Odor testing (via) can also be performed in accordance with ASTM Method E 679 (modi fied) due to the subjectivity of odor detection and the difficulty in quantifying odors using standard air monitoring equipment. This method utilizes a trained odor panel to evaluate air samples for odor character and average intensity.
How to Control the Odor
Four Complimentary methods:
Gas Extraction Systems: Since Methane gas can be generated 24 hours per day and is generated deep in the landfill, the best method of eliminating odors coming from this source is to engineer and install a gas collection system. Once collected, the methane can be either flared and burned, or cleaned of the water component and then used as a fuel to run a gas operated turbine to generate electricity. The gas extraction process generally involves the installation of perforated piping in horizontal rows deep in the landfill. Generally this is installed as the landfill is being filled, but can be installed after the fact. The system runs on negative air pressure in the piping which sucks the gas out of the landfill.
These systems are generally designed by an engineering firm, and installed by an experienced contractor or the landfill personnel.
