SWANA tackles landfill odor control in new report

The SWANA Applied Research Foundation (ARF) has released a new report that provides solid waste managers with up-to-date information and guidance on materials and strategies to control offensive odors emanating from the working face of landfills.

Landfills are often one of the major sources of nuisance odors in their host communities and can cause vociferous complaints from residents living near the facilities.

Sources of landfill odors are not only landfilled waste itself but can include other facilities on the landfill site such as leachate, stormwater ponds, and landfill gas condensate tanks. Landfill odors are mainly associated with the dispersion of landfill gas that is produced during the biodegradation
of landfilled waste. Landfill gas is a mixture of hundreds of different gases. By volume, landfill gas typically contains 45 to 60 percent methane and 40 to 60 percent carbon dioxide. Landfill gas also includes small amounts of nitrogen, oxygen, ammonia, sulfides, hydrogen, carbon monoxide, and non-methane organic compounds, some of which stink.

Most of the hardest-to-control odors at landfills are generated at the landfill working face, due to the nature of ambient air, which enables them to travel. Major types of odiferous waste that cause odor challenges at the landfill working face include wastewater treatment sludges and aging wastes. These wastes have decomposed significantly before reaching the landfill and, as a result, it’s more challenging to control their odors.

The report details the types of odor control available and how each works. these include:

Tarps – Geosynthetic covers or tarps are large pieces of plastic or fabric material that are deployed by
equipment or hand, similar to rain tarps placed over a baseball diamond during rain delays. The advantages of tarps include using no airspace, minimal utilization cost, speed of deployment and removal, and reusablity. Some drawbacks include difficulty of deploying tarps (especially in windy conditions), exposure of employees to waste, and tearing that often occurs when tarps are dragged across waste.
• Films – An alternative that can be used to address tarp odor issues is to use a non-reusable geosynthetic film that provides a complete impermeable daily cover for landfilled waste. Since the film is not removed but left in place after it is placed, odor emissions from the landfill working face are minimized.
• Slurries – Slurry ADCs are made by mixing solids with water and spraying the mixture on the landfill working face. Solids commonly used to make slurries include wood fiber, newspaper, cement kiln dust, and fly ash.
• Foams – Foam ADCs are applied to the landfill working face using foam generation and application
equipment specifically designed for each particular foam. There are both hardening and non-hardening
foams. The latter are effectively broken up by the placement of additional wastes on the next operating day.

Odor issues associated with the landfill working face are also commonly managed through odor neutralizing or masking agents. Neutralizing agents are chemicals that convert odiferous chemicals to non-odiferous ones before they reach the receptor’s nose. The goal is to eliminate the odor, not mask it.

The research concluded that more than 100 odorous compounds have been identified as contributors to landfill odors, including hydrogen sulfide (H2S), methyl mercaptan (CH3SH), dimethyl sulfide ((CH3)2S), and ammonia (NH3) Among the sulfur compounds, H2S has been identified as a major contributor to odors at landfills.

The main source of sulfur in a landfill includes gypsum drywall, sulfur-containing organic
waste (mainly food waste and paper), and sludge from wastewater treatment plants.

The monitoring of odor generation from organic wastes in municipal solid waste on a laboratory scale
showed that food waste is the main source for NH3 and H2S generation. It was also found that nitrogenous compounds were released more rapidly than sulfur compounds from mixed-waste landfills.

A recent study concluded that the utilization of compost as an ADC in landfill operations can significantly reduce H2S emissions. Another study recommended the utilization of compost as an ADC option when markets for food and yard waste compost generated by municipal facilities are weak and compost quality does not meet market requirements.

Based on this review, an optimum strategy for controlling odors generated at the landfill working face is the use of non-removable ADCs in conjunction with odor masking/neutralizing agents.

Management strategies for controlling odor at the working face include diversion of food waste and gypsum waste from landfill disposal.

“We are proud to be able to provide this report that addresses such an important and timely topic for SWANA ARF subscribers,” said Jeremy O’Brien, SWANA’s director of applied research. “SWANA would like to recognize and thank the organizations that comprise the ARF’s Disposal Group Subscribers that identified and voted on this topic as well as supported and assisted in the research.”

The report, Landfill Odor Control with Alternative Daily Covers, is available to SWANA members.