From Pollutant to Electricity - The Use of Landfill Gas for Energy

From Pollutant to Electricity - The Use of Landfill Gas for Energy Energy Law Ainat Margalit May 2003

From Pollutant to Electricity - The Use of Landfill Gas for Energy • Science • Numbers • Benefits • Disadvantages • Regulation • Case Study – Kibbutz Evron

What is Landfill Gas (LFG)? • LFG is generated when organic materials in landfills are naturally decomposed by bacteria • LFG is roughly 50% methane with carbondioxide being the second most prevalent gas. • All solid waste landfills emit this gas in amounts that depend on a variety of factors, such as waste composition and landfill size.

How is LFG Collected? • Landfill is sealed from above. i.e. by a layer of clay. • Gas collection wells are placed in the landfill. • Passive gas collection – uses natural variations in landfill gas pressure and concentrations (not considered very reliable)

How is LFG collected?(cont.) • Active gas collection – use of vacuum or pumps to move gas out of the landfill

Treatment of gas after collection • Combustion – open or closed flame flares, enclosed combustion which creates energy (boilers, process heaters, gas turbines, internal combustion engines) • Noncombustion – • Energy recovery technology – phosphoric acid fuel cell, other fuel cells are being developed. • Gas to product technologies – converting LFG into commercial products, (natural gas, methanol, purified CO2 or methane)

The Process

Determining if a Site is a Good Candidate for LFG Utilization Site Characteristics • Site Location • Landfill still receives waste (or is recently closed) • Landfill is near power grid or industry that could use the gas • Landfill has land available for alternative applications

Determining if a Site is a Good Candidate for LFG Utilization (cont.) Site Acceptance • Landfill gas utilization project is accepted by the local government and community Determining Methane Production Potential • Quantity of Waste in the Landfill • 1.2 million metric tons of waste in place • Waste Composition • Organics produce high quantities of methane

Determining if a Site is a Good Candidate for LFG Utilization (cont.) • Waste Placement History • Older waste produces less methane Site Conditions • Status of Landfill Operation • Open • Recently closed (less than 5-7 years)

Determining if a Site is a Good Candidate for LFG Utilization (cont.) Landfill Type • Managed Landfills • daily cover • compaction • final cover • Open Dumps

Determining if a Site is a Good Candidate for LFG Utilization (cont.) Landfill Depth • Greater than 10 meters Climate • More than 10 cm of rain annually

Determining if a Site is a Good Candidate for LFG Utilization (cont.) Management of Moisture in the Landfill • Leachate Management Landfill Stability Geology/ Hydrogeology • Lined landfill site • Unlined landfills produce higher methane generation if located in soils that have low permeability, such as clay • Temperature - methane production is maximized between 50-60 degrees Celsius

Numbers • There are 2,500 municipal solid waste landfills currently operating in the United States, approximately 340 have LFG utilization projects, 230 of which are electricity generation projects. Approximately 60 more projects are currently under construction.

Numbers (cont.) • A landfill with 1 million tons of waste-in-place can typically support an 800 kilowatt (kW) to 1 MW electricity generation project • Costs to generate electricity from landfill gas typically range from 4 to 6 cents/kWh (for reciprocating engine projects).

To determine the environmental and energy benefits of an LFG utilization project, LMOP compiled the following figures: 1 million tons of municipal solid waste in a landfill typically generates 300 cubic foot per minute (cfm) of landfill gas that could then generate 7,000,000 kilowatt hours (kWh) per year. 7,000,000 kWh is enough energy to power 700 homes for a year. In order to determine greenhouse gas benefits for a specific LFG utilization project replace the waste in a landfill in the first bullet above with the actual tons of waste in a particular landfill and calculate what the environmental and energy benefits will be for that project.

Benefits • Using LFG as a fuel suppresses release of methane to the atmosphere and results in reduction of greenhouse gas emissions. An LFG electricity project captures roughly 85% of the methane emitted from the landfill.

Greenhouse Gas Methane Sources U.S. Sources of Methane Emissions EPA 1997 Estimate

DOE Estimates of Methane Emissions by Source

Benefits (Cont.) • Suppression of the characteristic land fill odors and the elimination of potential explosions in nearby areas. • Indirectly reduces air pollution by offsetting the use of non-renewable resources. • Avoids the need to use non-renewable resources such as coal, oil, or natural gas to produce the same amount of electricity.

Benefits (Cont.) • LFG projects promote environmental awareness among citizens involved in sustainable community planning, creating partnerships, and promoting common interests among local entities. • Using LFG can benefit environmental compliance

Benefits (Cont.) • Only LFG energy recovery or use offers communities and landfill owners the opportunity to reduce the costs associated with regulatory compliance by turning pollution into a valuable community resource. • Using LFG can benefit the local economy

Disadvantages • Does not create sufficient electricity because of make up of specific site. • (e.g. Distance from landfill site) • Does not create sufficient electricity because of lack of appropriate sites. • Not completely “clean”. there may still be emissions from combustion engines • Economic feasibility

Regulation • Applicable regulations under the Clean Air Act • NSPS • Emission Guidelines • NESHAP • PSD/NSR • TITLE V • State and local

Regulation (Cont.) • General requirements for LFG Handling & Disposal • Emission monitoring • Emission testing • Reporting • Report keeping • NMOC reporting • Gas collecting • Well monitoring

Landfill Methane Outreach Program • LMOP works in voluntary partnership with states, communities, the landfill industry, utilities, and energy users, providing technical assistance for Municipal Solid Waste LFG use projects. • Created by the USEPA in 1994.

Kibbutz Evron Landfill

Landfill Statistics • Approximately 20 acres of landfill • 2-2.5 million tons of waste • 60 cm clay cover • Landfill opened in 1968 • Landfill is currently closed (not accepting new waste), because it does not comply with regulations • The landfill contains 70-80% household waste.

Gas Collection System • 25 collection wells, each containing a plastic pipe. • Gas is collected from individual plots until each plot is emptied • Collection wells are 90 cm in diameter and 25 meters deep. • The bottom section of the collection pipe is perforated.

Gas Collection System (cont.) • Each well is connected to a pipe which leads the gas to a pipeline connected to the engine site. • The gas is collected by vacuum.

Methane Disposal Before Energy Generation • In order to comply with pollution regulations the LFG had to be collected and disposed of. • LFG was disposed of by simple combustion. CO2 was the expectorant. • This was not entirely “clean” but a considerable reduction of methane emissions was achieved.

Combustion tower

Energy Creation Process • Evron discovered that the LFG from their site contained Methane (57%) and CO2 (38%). The gas also contains about 0.1% Oxygen. • At least 50% Methane is necessary in order to create electricity. • An internal combustion engine was installed. • Currently the engine creates 850 kilowatt electricity per hour. The maximum potential is 1,400 KW per hour.

Energy Creation Process (cont.) • The anaerobic activity which creates the gas should continue for at least 20 years.

Internal Combustion Engine

From Pollutant to Electricity - The Use of Landfill Gas for Energy