Landfill Gas – Understanding the Threats to Your Biogas Engine

Landfill gas differs from biogas. The lack of consistency in what “ingredients” go into landfill gas means a lack of control in levels of siloxanes, halogens and H2S; contaminants that cause abrasive and acid wear on engines. Treating landfill gas to remove contaminants prior to use, or understanding the greater severity of landfill based fuel and managing your equipment accordingly, can be an effective way to protect your engine and achieve top performance.


This article will discuss:

  • Properties of landfill gas that make it a challenge for stationary gas engine operators
  • Factors to consider when selecting a gas engine oil for engines operating in landfill gas applications

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Landfill gas is not the most common form of biogas used in North America, but it is an effective option for stationary gas engine operators. As with any fuel, it is essential to know how to use it for maximum engine performance and protection.


"Landfill gas, collected at a landfill site, is considered a 'non-controlled' biogas because so many different materials could be involved – from pesticides, plastics, shampoos and soaps, to construction materials," explains Brett Lubbock, Product Specialist of Stationary Gas Engine Oils, Petro-Canada Lubricants. "'True' biogas, on the other hand, is considered a 'controlled' gas because you can control the quantity and proportions of organic materials, such as manure and corn, that are being digested."


Lubbock adds that the life cycle of the landfill can also impact the gas quality. "The highest-quality fuel is obtained when the landfill is first tapped," he says. "As it gets depleted, the gas quality decreases."


Due to this fuel variability, even on the same site, operators need to be aware of the possible effects on their engine to achieve maximum engine performance and protection.


"Fuel analysis testing is required to determine exact gas composition of landfill biogas," adds Lubbock. "Testing is actually quite critical as composition will change over time."

Consistency of the fuel is the main challenge for biogas engines – whether true biogas or landfill gas is being used. The lack of consistency in which 'ingredients' go into landfill gas means a lack of control in levels of key contaminants such as siloxanes and hydrogen sulfide (H2S).


Siloxanes turn into glass or sand-like material after combustion, causing abrasion and contributing to engine wear. H2S increases the amount and rate of acidic by-products during operation that can lead to shorter oil life and damage the engine. Fuel-gas testing shows significantly higher levels of H2S are found in landfill gas as compared to pipeline quality gas.

Pre-treating (or pre-cleaning) the bio or landfill gas to remove harmful contaminants can be an effective strategy for extending oil and engine life. This process also helps to remove moisture.

“During the fermentation process, high levels of water are created as a natural vapor,” explains Lubbock. “Water should be removed as it is not a good medium and can hamper the combustion process within the engine while increasing rate of acid formation.” By removing the water as part of pre-treating, power will not be wasted driving off moisture in the fuel; this way, greater engine efficiency can be obtained.

However, pre-treating is a business decision with cost implications and may not be a feasible option for every operation. “Operators need to weigh the cost of the pre-treatment versus the possible cost of added maintenance to engines due to the contaminants in the fuel,” says Lubbock. “If pre-treating is not a viable option, operators may have to shorten maintenance intervals and oil drains in order to accommodate the greater fuel gas severity,” he says. 

Operators also need to consider original engine manufacturer (OEM) criteria – exceeding OEM limits for fuel quality may nullify the warranty.
 

Biogas engines require a lubricant that is formulated to meet the specific challenges present when landfill gas is used as the primary fuel source. Key factors for selecting the right lubricant include fuel gas composition based on landfill outputs, OEM requirements and ash level of the lubricant. For instance, a higher-ash product and robust detergent system offers greater neutralization potential. As increased rate of acid formation is expected with untreated gas, an oil with an optimized additive system to neutralize them is beneficial.

If the landfill gas is pre-treated and fuel analysis shows that contaminants have been effectively reduced, operators can use SENTRON premium products from Petro-Canada Lubricants, which are designed for pipeline-quality gas – as there is not a need for a specialized landfill or biogas product. For example, if you pre-treat the fuel and reduce contaminants (such as H2S and siloxanes) below concerning thresholds, a product such as SENTRON LD 5000 is a good fit.


If the landfill gas is not pre-treated, however, operators will need a specialized lubricant. The SENTRON line-up has you covered in this case as well – SENTRON CG 40 and SENTRON CG 40 PLUS both have advanced detergent systems potent enough to deal with the acids created from untreated gas.


In summary, treating landfill gas to remove contaminants prior to use or carefully monitoring fuel quality and adjusting maintenance intervals can be effective strategies to protect your engine and achieve top performance. Strategic lubricant selection plays a key role in both scenarios.

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