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While the biogas industry offers innovative energy solutions, it also poses unique challenges for operators of biogas engines and the engine oil they count on to protect their equipment.
With the growth of this industry, engine manufacturers have adapted their stationary gas engines for biogas and landfill gas applications. Not surprisingly, there are certain considerations when selecting a lubricant to protect these specialized engines.
Besides having the necessary Original Engine Manufacturer (OEM) approval, two important steps that will help ensure the right Stationary Gas Engine Oils for optimal performance in biogas engines are planning for the highly variable gas composition your engine will see during service and continual used oil analysis.
Methane is the largest component of biogas, followed by carbon dioxide and other harmful gases. Fuel analysis is required to determine exact gas composition – this is especially critical for landfill biogas, which can be made up of a wide variety of components. When selecting a lubricant for biogas engines, gas composition is the number-one consideration. Lubricants must be able to protect the engine from the contaminants present within the fuel.
Another consideration for biogas engines is that operating and combustion temperatures are lower than pipeline engines, so the heat can't be relied upon in the same way to drive off water as it is in pipeline gas applications. The presence of water in oil will increase acid formation. Since acids can attack the engine's metal parts and cause pitting, a lubricant that can neutralize the acid is essential in biogas applications.
One strategy for combating the severe effects that accompany biogas is through pre-treatment of the fuel gas. This can help to remove moisture, halogens, and siloxane particles. As siloxanes accumulate in the oil, they agglomerate into larger particles and become abrasive, acting like "liquid sandpaper." This results in premature engine wear. OEMs provide maximum silicon content limits for warranty purposes; the oil must be changed once this limit is reached.
As a result, if the fuel gas is not pre-treated, the amount of contaminants in the oil will increase much more quickly; correspondingly, oil drain and maintenance intervals will need to be shortened to accommodate. This makes effective used oil analysis even more critical in this type of application.
Even the best lubricant in its class will not perform well if it was not selected to meet the unique gas composition of the bio and landfill fuels. Biogas engines need a lubricant formulated with the correct ash level (as specified by the OEM) for engine durability, along with a robust detergent system to neutralize acids and extend drain intervals. Using a non-optimal lubricant, with too much or too little ash, can cause a ripple effect in terms of durability, output and oil life.
Too much ash can lead to durability issues. For example, excessive ash can cause piston rings to stick, and create ash build-up on valves. Valves may not close as a result, leading to more issues such as torching. Another consequence of too much ash is that it may carry through to the exhaust and poison the catalytic converter, rendering it inactive.
Detergents are the primary additives used to neutralize acids during engine operation. A higher level of detergency typically results in a higher level of ash being formed in the combustion chamber. However, newer detergents and additive systems can have greater neutralization potential without increased ash production. Too little ash/detergency can lead to corrosion or mechanical damage. An effective lubricant needs to neutralize halogens and hydrogen sulfide, as well as other contaminants, or acid will form. As discussed, this causes pitting, which shortens engine durability and oil drain intervals. All of this leads to frequent engine stoppage and reduced output.
Drain intervals for biogas engines are much shorter than those of pipeline engines. Operators can expect intervals in the hundreds of hours (e.g., 400) for biogas engines as compared to pipeline, which can last up to 8,000 hours before oil change-out. This underscores the need to be diligent in gas composition testing, used oil analysis, and lubricant selection to ensure performance along with maximum oil life.
Location can also play a role in engine and lubricant needs. In many biogas and landfill gas applications, the gas is being used as a means to create electricity. Emissions regulations can also play a role, which drives to higher engine technology and thus harsher environments for the lubricant. As a result, as emission restrictions continue to tighten, a higher-quality lubricant may be required for newer, more severe engine designs.
For operators of biogas engines, it comes down to doing your homework in order to select the right lubricant for your engines, application and fuel gas. Testing and determining the gas composition is the number-one priority. Look to OEM approvals, recommendations, lubricant supplier and field technician experience to determine required ash levels. Reviewing your equipment’s maintenance history can also provide valuable insights.
The bottom line is that biogas engines need a lubricant that has the required ash and detergent levels to neutralize acids, extend drain intervals and maintain engine durability. SENTRON™ from Petro-Canada Lubricants offers a full line of Stationary Gas Engine Oils that stands up to the ever-fluctuating gas compositions and productivity requirements of engines used for biogas.
SENTRON stationary gas engine oils are premium-performance engine oils specially formulated to lubricate large stationary gas engines. Specific SENTRON oils also meet the more severe operational needs of biogas and landfill gas operations.
The SENTRON lineup is unparalleled in the market, citing acid neutralization, a robust detergent system and longer drain intervals as key advantages realized by SENTRON users. The number of OEM approvals we’ve achieved is proof positive of the efficacy of the lineup.
SENTRON CG 40 and SENTRON CG 40 Plus have approvals in many different fuel categories and engine types. A competitor, in comparison, offers multiple products to cover what SENTRON can do alone.
Customers also speak up when asked about SENTRON in their biogas operations.
"Switching to SENTRON LD 5000 set new standards for drain intervals at Biogas Aholfing GmbH, up to 3,000 hours, even when being exposed to intermittent contaminated gas of 49% higher H2S than typical pretreated levels for over seven weeks," says Biogas Aholfing GmbH co-owner John Busl, whose company produces methane fermented from corn, grasses and chicken manure using a biogas fermenter. "The robust nature of SENTRON LD 5000 and its long-term performance benefits led Biogas Aholfing GmbH to sustainable cost savings and reduced downtime in addition to reducing costs of operations."
Unique challenges require unique solutions. When it comes to biogas engines, the right lubricant can protect against and allow for inevitable changes to the fuel gas. Start with a lubricant that meets OEM approval, and ensure it provides the required ash level and additive system for acid neutralization. An engine oil specially formulated for biogas engines will deliver equipment longevity, longer drain intervals and optimized output.
