Understand Nonroad Diesel Engine Emissions Regulations

Current EPA Tier 4 Interim emissions standards apply to most new diesel engines used in oil and gas exploration, and even more strict Tier 4 Final regulations are just around the corner. While the onus of compliance is on engine manufacturers, drillers and producers need to be aware of how emissions regulations will affect their operations.

The Tier 4 Interim fracturing engine that meets all current EPA emissions regulations without the need for exhaust aftertreatment. (Photos courtesy of MTU and Stewart & Stevenson)

For decades, diesel engines have found wide application in oil and gas exploration and production, from powering pumps to running mechanical oil rigs to generating onsite electricity. A fairly recent application is driving the powerful pumps used in deep well fracturing operations, where banks of large diesel engines provide the hydraulic forces to fracture petroleum-bearing rock formations to liberate the oil and gas.

In the past, the exhaust gases from these essential workhorses in the oil patch and other nonroad uses were uncontrolled and resulted in emissions of nitrogen oxides (NOx), carbon monoxide (CO), non-methane hydrocarbons (NMHC) and particulate matter (PM or soot). Just as with emissions from on-highway trucks, buses and cars, these uncontrolled nonroad engines contributed their share to damaging air pollution.

Then in 1996, the U.S. Environmental Protection Agency (EPA) began to enforce limits on diesel exhaust emissions from new nonroad diesel engines and then from new stationary diesel-engine generator sets in 2006. Implemented in a series of steps called tier levels, these regulations have introduced successively more stringent limitations on NOx, CO, PM and NMHC.

In response to these regulations, engine manufacturers began introducing innovative design changes and sophisticated engine control systems that have successfully reduced the major pollutants in diesel exhaust to comply with each successive tier level. This article explains the latest and near-term emissions requirements for new nonroad diesel engine applications and discusses the technologies used to comply with the current and pending standards.