In the last 10 years there has been an increased global interest in the generation of energy from renewable sources. The global interest is driven by air quality concerns and reduction of greenhouse gases such as methane. One of the major global contributors to anthropogenic methane is from landfill waste disposal.
Although, the disposal methods used in the past were inconsistent and recognized as being hazardous to the environment and local inhabitants, modern refuse collection and disposal helps consolidate and enhances the ability to mitigate the methane release to the environment by using the methane that was created during digestion of the organic matter as the fuel source in an internal combustion engine instead of allowing the methane to dissipate to the atmosphere.
This unconventional natural gas, characterized as landfill or biogas, that is created during anaerobic digestion of the organic material can be rich in contaminant materials, which are incorporated in the discarded waste stream. The contaminants, which are soluble in the gas stream are deleterious to the engine componentry and severely impact engine life, increasing maintenance cycles and operational costs.
Reducing costs from the corrosive effects to the engine from landfill or biogas is one of the main goals for the engine operator to provide engine availability and continued uptime. In addition, higher brake mean effective pressure (BMEP) engines are being incorporated at these biogas facilities because of their increased energy efficiency and higher power density capabilities per unit of engine displacement. Unfortunately, higher BMEP engines are more demanding on components and engine lubricants, which decreases the oil drain interval compared to older less severe engine models in an aggressive gas environment.
In the past, lubricant suppliers have addressed corrosive fuels, such as landfill or biogas, with the simplistic approach of increasing the base number, which meant adding additional detergent and thus the sulfated ash would rise as well. Higher BMEP engines are ash sensitive due to the higher cylinder pressures and reduced volumes in the combustion chamber. Additional deposits levels in the cylinder power assembly raise the compression ratio, creating higher pressures and temperatures, increasing the detonation or “knock” tendency. Furthermore, decreased piston crevice volume impacts the exhaust emissions being produced during engine operation and may require increased deposit removal or “decoking” to maintain emission limits in strict air quality districts.
Specific lubricants are required to contend with the rigors of a landfill or biogas environment and require the lubricant to effectively neutralize the various acids created from the dynamic gas streams. Providing a lubricant solution with minimal impact to oil life and the ability to effectively reduce deposits was the basis for the creation of a next generation landfill and biogas lubricant for today’s demanding high BMEP engines.