SWANA Landfill Gas Management 3

Question 1

What is the lower explosive limit (LEL) of methane in air, above which methane-air mixtures become potentially explosive?

Accepted Answer

5% by volume

Answer

Methane is flammable and potentially explosive when its concentration in air falls between 5% (LEL) and 15% (UEL) by volume, making LFG migration into enclosed structures a serious safety hazard.

Question 2

LFG-to-energy projects that generate electricity at the landfill most commonly use which prime mover technology?

Accepted Answer

Internal combustion engines or combustion turbines fueled by LFG

Answer

Reciprocating internal combustion engines and combustion turbines are the most widely used technologies for direct LFG-to-electricity generation due to their efficiency, scalability, and cost-effectiveness at typical landfill gas flow rates.

Question 3

What parameter is typically adjusted at individual LFG wellheads to balance gas collection evenly across a landfill wellfield?

Accepted Answer

Vacuum (negative pressure) applied to each well

Answer

Operators throttle the valve at each wellhead to adjust the applied vacuum, balancing gas yield across the wellfield and preventing excessive air intrusion from high-vacuum wells in dry or shallow waste areas.

Question 4

What is the primary purpose of a landfill wellfield monitoring program?

Accepted Answer

Assess gas collection system efficiency and overall wellfield performance

Answer

Wellfield monitoring tracks gas flow rates, pressures, temperatures, and gas composition at individual wells and headers to evaluate collection efficiency, detect system problems, and maintain regulatory compliance.

Question 5

Which EPA voluntary program assists landfill owners and operators in developing LFG energy projects by providing technical and financial guidance?

Accepted Answer

Landfill Methane Outreach Program (LMOP)

Answer

EPA's Landfill Methane Outreach Program (LMOP) is a voluntary assistance program that helps landfills convert LFG into a productive energy resource by connecting stakeholders and providing technical and market development support.

SWANA - Solid Waste Association of North America Practice Test

SWANA - Solid Waste Association of North America Practice Test

SWANA Landfill Gas Management 3