Landfill gas is roughly half methane and half carbon dioxide, produced as waste decomposes. Capturing it and burning it in an engine turns a climate liability into electricity. The plant only works if the gas is collected efficiently and cleaned before it reaches the engine.
Quick Answer
The gas is about 50 to 60 percent methane when the site is active.
A gas engine needs treatment to remove moisture, sulphur and siloxanes.
Gas yield falls as the waste ages, so plan for a declining supply.
A 1 MW engine needs a steady gas flow, not a variable one.
Flaring is the safety fallback when the engine is down.
What is landfill gas?
Landfill gas to energy is the capture of methane-rich gas from decomposing waste and its use as fuel for engines or boilers.
It means converting a waste site into a small power plant with gas collection, cleaning and generation.
landfill gas in practice
Typical gas components and their effect:
| Component | Typical share | Effect on the plant |
|---|---|---|
| Methane | 50 to 60 percent | Fuel value |
| Carbon dioxide | 40 to 45 percent | Dilutes the fuel |
| Nitrogen | 2 to 10 percent | Lowers heating value |
| Oxygen | 0 to 2 percent | Corrosion risk |
| Hydrogen sulphide | 10 to 500 ppm | Acid and engine wear |
| Siloxanes | Trace | Deposits on engine parts |
| Water vapour | Variable | Condensation and corrosion |
| Trace metals | Trace | Catalyst and valve damage |
What does a landfill gas to energy plant cost in Nigeria?
A 1 MW landfill gas engine package costs about 350,000,000 to 600,000,000 naira.
Gas collection wells and pipework cost about 40,000,000 to 120,000,000 naira.
Gas cleaning equipment adds 60,000,000 to 150,000,000 naira.
Grid connection and protection cost 30,000,000 to 90,000,000 naira.
Annual operation and maintenance runs 5 to 10 percent of capital cost.
A feasibility study costs 8,000,000 to 25,000,000 naira.
How is landfill gas carried out?
- Assess the waste volume, age and expected gas yield.
- Drill gas extraction wells and connect them to a header.
- Install a flare for safe disposal during commissioning.
- Measure gas flow, methane content and contaminants.
- Specify cleaning and engine equipment for the measured gas.
- Commission, connect and set a long-term gas monitoring plan.
Sources
IPCC waste methane guidance, Engine maker gas specifications, IEC 60034 rotating electrical machines, Nigerian environmental and energy regulation
How the gas is produced
Bacteria break down organic waste in the absence of oxygen. The process produces methane and carbon dioxide over years.
A young landfill produces gas quickly but with variable quality. An old site produces less gas but often at a steadier rate.
Rain and compaction affect the process. A wet, well-managed site usually yields more gas than a dry open dump.
Collection and flaring
Gas extraction wells are drilled into the waste and connected to a common header. A blower pulls the gas to the plant.
A flare burns surplus gas safely when the engine is offline. Never vent methane to the atmosphere.
Monitor oxygen in the header. Too much air means the wells are drawing from the surface, which risks a fire.
Cleaning the gas
Water and hydrogen sulphide are the first targets. A knockout drum and a scrubber remove most of both.
Siloxanes form hard deposits on pistons and valves. Carbon filters or a dedicated siloxane scrubber protect the engine.
Gas quality varies with the weather and waste age. Design the cleaning train for the worst measured value, not the average.
Engine selection
Gas engines are specially configured for low methane content and high sulphur. A standard natural gas engine will not last.
Size the engine for the sustainable gas flow, not the peak. A plant that runs at full load for fewer hours is better than one that stops constantly.
Plan for declining gas yield. Modular engines let you add or remove capacity as the site ages.
Grid connection and controls
A generator connected to the grid needs protection for over/under voltage, frequency and islanding.
If the plant runs in island mode, it needs its own voltage and frequency control and a load bank for testing.
Meter the exported and imported energy separately. The commercial case depends on accurate measurement.
Economics and regulation
Revenue comes from electricity sales, avoided waste fees and sometimes carbon credits. Each stream has its own contract.
Check environmental permits for gas extraction, flaring and emissions. A plant that ignores them can be shut down.
Model a declining gas curve. A project that only works at peak gas output is a project that fails in year 8.
Related guides from this series
- Waste Heat Recovery for Nigerian Facilities
- Carbon Reporting for Manufacturers
- Renewable Integration for Facilities in Nigeria
About the author
Illuminate Engineering Limited supports renewable and industrial power projects, including gas-to-energy feasibility and electrical integration in Nigeria.
Frequently Asked Questions
How much methane is in the gas?
Usually 50 to 60 percent in an active site, with carbon dioxide making up most of the rest.
Why does the gas need cleaning?
Moisture, sulphur and siloxanes damage engines. Cleaning protects the engine and keeps maintenance costs down.
Can I connect a gas plant to the grid?
Typically 15 to 30 years, with output declining as the organic waste is consumed.
Can I connect a landfill gas plant to the grid?
Yes, with the right protection and a grid connection agreement. Island mode is also possible for a dedicated site.
Conclusion
Gas to energy is a long-term infrastructure project, not a quick generator install. Gas quality and quantity decide the design.
Measure the resource, clean the gas and plan for decline. The plant then turns a waste problem into steady power.