Methane is a primary constituent of landfill gas (LFG) and a potent greenhouse gas when released into the atmosphere. Each day, millions of tonnes of municipal solid waste are disposed of in sanitary landfills and dump sites around the world. Globally, landfills are the third largest anthropogenic emission source, accounting for about 13% of methane emissions, or over 818 million tonnes of carbon dioxide equivalent (MMTCO2e).
Figure 1 identifies some of the countries with significant methane emissions from landfills. Globally, the predominant practice for solid-waste management is depositing solid wastes from households and commercial and industrial activities into a landfill, where methanogenic bacteria decompose the organic material. A product of the bacterial decomposition is landfill gas, which is composed of methane and carbon dioxide in approximately equal concentrations.
Figure 1. World landfill methane emissions (MMTCO2e) in 2000
Landfill gas capture and control
LFG contains approximately 50% methane and has a heat content of about half the value of natural gas – 500 British Thermal Units per standard cubic foot (18,662 kJ/m3) compared with 1000 Btu/scf. LFG is also generated 24 hours per day, seven days a week.
A common method of controlling methane emissions from landfills is to install a gas collection system in the landfill to collect and convey the methane to a gas control system. Figure 2 depicts a landfill with a gas collection and control system. Landfill gas is extracted from landfills using a series of wells and a blower (or vacuum) system. This system directs the collected gas to a central point where it can be processed and treated depending on the ultimate use for it.
Figure 2. A landfill with a gas collection and control system
From this point, the gas can be destroyed by a flare or can be used to generate electricity, replace fossil fuels in industrial and manufacturing operations, fuel greenhouse operations or be upgraded to pipeline-quality gas. As a rule of thumb, about 11,600 m3 per day of LFG is produced from every 1 million tonnes of MSW placed in a landfill, which can produce about 0.8 MW of electricity. Moreover, landfill gas energy (LFGE) projects have on-line reliability of over 90%.
Reducing emissions by capturing LFG and using it as an energy source can yield significant energy, and economic and environmental benefits. Moreover, the implementation of LFGE projects reduces greenhouse gases and air pollutants while contributing to energy independence and economic benefits. Internationally, significant opportunities exist for expanding LFGE and an increasing number of conventional and emerging technology applications are becoming commercially viable to target this untapped market.
LFG is currently extracted at over 1200 landfills worldwide for a variety of energy purposes, such as:
- generation of electricity with engines, turbines, microturbines and other emerging technologies
- processing the LFG to make it available as an alternative fuel to local industrial or commercial customers
- creating pipeline-quality gas or an alternative fuel for vehicles.
Types of LFG utilization projects
Figure 3 shows the types of landfill gas projects that have been implemented at landfills in the past few years, both in the United States and globally. The projects that produce a beneficial product such as electricity or process heat from landfill gas should be viewed as achieving two aims: reducing methane emissions from the landfill and using renewable energy to offset greenhouse gas emissions from fossil fuel combustion.
Figure 3. Types of LFG projects implemented recently worldwide
When landfill gas is used in CHP systems, the environmental and economic benefits increase dramatically. A CHP project powered by LFG not only provides significantly better energy efficiency and cost savings, it also achieves the significant environmental benefits of using a locally produced biomass fuel.
Developing LFG CHP projects
CHP is a proven, highly efficient alternative to separate power and heat production. CHP LFGE projects will produce electricity as well as shaft power, hot water, steam, chilled water or dehumidification.
Combined with LFG, CHP projects cogenerate electricity and thermal energy, usually by using waste engine heat to produce steam or hot water. LFG cogeneration projects that use turbine or spark ignited (SI) reciprocating engine generators have been installed at industrial operations. The efficiency gains of capturing the thermal energy in addition to generating electricity can make CHP LFGE projects particularly attractive.
The US Environmental Protection Agency (EPA) implements several voluntary partnership programmes, including the Landfill Methane Outreach Program (LMOP) and the CHP Partnership to reduce the environmental impact of power generation. In the past six years, the CHP Partnership has helped CHP Partners put more than 250 projects into operation in the US. These CHP Partnership-assisted projects contribute more than 3570 MW of electricity-generating capacity.
The LMOP Database shows that there are 16 CHP LFGE projects currently operating in the United States, and they range in size from 120 kW to 12 MW. Some 60% of the existing CHP LFGE projects use SI engines. These projects are located in nine states and have a combined capacity of 55 MW. In addition, three of the 25 LFGE projects under construction in 2007 are CHP.
CHP LFGE projects can create additional environmental benefits by offsetting demand for fossil-fuel-based electricity and steam or heating with a renewable fuel. In 2007, the existing CHP projects fueled by LFG in the US will result in greenhouse gas reductions equivalent to preventing the use of approximately 1.3 million barrels of oil.
Also, using the waste heat from LFG-fired generators in a CHP configuration can improve a project’s financial results by as much as 100%, increasing the feasibility of developing LFGE projects.
Projects that reclaim heat from engine generators that are fueled by LFG provide the typical benefits of CHP projects. Fuel-use efficiency is improved, emissions are reduced and fuel and operating costs decrease. CHP can provide industrial and commercial facilities with greater reliability and increased process flexibility compared with conventional generation methods. Because cogeneration technology is proven, CHP projects represent low technology risk.
Turbines and SI engines using LFG have heat conversion efficiencies similar to that of small natural gas generators and are approximately 28%-33% efficient. In comparison, SI engines with CHP systems have been found to have an effective (overall) energy efficiency of 69%-84%.
To evaluate the financial benefit of LFG-fuelled CHP projects compared with standard electricity generation projects, LMOP applied its preliminary feasibility tool, the Landfill Gas Energy Cost Model (LFGcost) to two LFGE projects – straight electricity generation with a standard 3 MW SI engine and a CHP project based on a similar engine generator.
LFGcost estimates costs based on typical project designs and for typical landfill situations. The model attempts to include all equipment, site work, permits, operating activities and maintenance that would normally be required for constructing and operating the project. LMOP default input parameters were used in this comparison to model project development by a private entity (in other words, industrial end-user or a third-party developer) which would finance 80% of the project capital costs at an 8% interest rate over 10 years. The initial-year product prices listed in Table 1 reflect the current LFGcost model default prices for electricity, LFG production and waste heat. They are also escalated annually at a rate of 2%.
The LFGcost comparison assumed a 6.4 km pipeline between the landfill and thermal host. In addition, the waste heat application was assumed to be 160 metres from the engine. It also assumed that both projects operate year-round.
LMOP also compared the environmental benefit of displacing conventional electricity generation and, for the CHP project, the additional displacement of a thermal energy demand fired by natural gas.
As shown in Table 1, CHP LFGE project financials can be as much as 100% better than a traditional engine generator project using LFG.
These LFGcost analyses are preliminary estimates and should be used for general guidance only. Projects for specific landfills require unique design modifications and may add to the cost predicted by LFGcost. A detailed final feasibility assessment should be conducted by a qualified LFG professional prior to preparing a system design, initiating construction, purchasing materials or entering into agreements to provide or purchase energy from an LFGE project.
Using the heat and power output
Potential LFG users may not have considered the benefits of LFGE for several reasons. First, it is not a common fuel. The end user may be concerned about its reliability or may believe their process requires commercial fuels and energy systems.
Users must also determine how their energy demand corresponds with the relatively stable LFG production rate from a nearby landfill. If an industry’s energy demand is seasonal, CHP applications provide an opportunity to balance LFG use between electricity and other energy demands. Natural gas can be blended with LFG or other auxiliary fuels to add energy if necessary during peak periods. Operating risk can be minimized through power purchase agreements (PPAs) that tie LFG costs to the price of the commercial gas supply.
Financing can pose a barrier to LFGE projects due to high upfront capital costs or competition with low electricity prices in some markets. The collection system, pipeline and project investment can be significant for a landfill that has not yet developed a gas management system. But an end user interested in green power can offset some of the financial risk with long-term agreements that provide steady future revenue for the landfill and continuing energy cost savings for the user.
Another potential source of funding for CHP LFGE projects is through the sale of carbon credits on a carbon market. These credits are generated as a direct result of the collection and destruction of methane and as offsets from using a renewable energy source to generate electricity.
The Lancaster County Solid Waste Management Authority (USA) in Pennsylvania, mentioned in the case study above, has sold some of the carbon credits from its CHP LFGE project on the Chicago Climate Exchange (CCX). CCX is a voluntary, but legally binding, greenhouse gas reduction and trading programme in North America which verifies the CO2e reductions from renewable projects and creates so-called carbon financial instruments that can be sold to other CCX members.
Project development challenges
One important issue for project development in many developing countries is that open dumps and unmanaged landfills are the predominant disposal options. These sites can be less than optimal candidates for LFG energy development and, to CHP projects especially, can be a challenge because they produce small amounts of methane (resulting from aerobic degradation and rapid waste decomposition). Also, the industries that would benefit from CHP may be limited. On-site CHP LFG is limited due to low demand for hot water or steam at a landfill. However, many developing countries are transitioning to engineered landfills from more uncontrolled systems. Landfills will provide a more environmentally sound disposal option for these countries, but they will also produce more methane. The Methane to Markets Partnership can help facilitate a transition to landfilling by sharing information on effective landfill design and management, and how to integrate landfill methane capture and beneficial use into these planning processes.
Another important issue for the viability of LFGE projects in both developing and developed countries is energy price structure. Government policies on energy and solid waste management can promote or hinder the beneficial use of LFG. An uncertain regulatory environment is often a concern among potential investors. For example, project developers can be subject to different and sometimes conflicting laws at the local, regional and national levels. Moreover, a lack of regulations governing landfills and LFGE projects in some countries (in other words, there being no requirement or incentive to collect and combust LFG) can inhibit project development.
As countries begin to implement laws, regulations and policies to improve solid waste management practices, promote alternative energy and address greenhouse gas emissions, the economic viability of traditional LFGE and LFG CHP projects will improve. Moreover, creating an atmosphere where potential investors (private sector investors, international development banks and financiers) are secure in the technical and policy framework that supports LFGE projects will be essential to project development.
The Methane to Markets Partnership brings together the collective resources and expertise of the international community to address technical and policy issues and facilitate LFGE projects. Early initiatives will likely include:
- assisting with solid waste management capacity building
- identifying potential landfill resources
- performing initial gas generation and feasibility studies, including CHP applications.
LFGE projects, especially CHP projects, are becoming even better prospects in today’s escalating energy market, which is acquiring a taste for local renewable power. LMOP and Methane to Markets are providing support for the development of these projects, which produce more environmental benefits than a typical LFGE electricity project and make more efficient use of the renewable LFG resource.
Today, only a few LFGE projects benefit from CHP design. However, LMOP and Methane to Markets are working with more and more municipalities and businesses that are installing CHP LFGE projects in their facilities to cut energy costs and reduce greenhouse gas emissions.
LFGE projects using CHP technology are win-win-win opportunities. They represent renewable energy achievements that result in higher efficiency, environmental gains and an improved bottom line.
Brian Guzzone is Team Leader at the Landfill Methane Outreach Program at the US Environmental Protection Agency, Washington, DC, US.
Mark Schlagenhauf is the Global Oil and Gas Advisor at the Economic Growth, Agriculture, and Trade Bureau of the US Agency for International Development, Washington, DC, US.
The Methane to Markets Partnership centres on identifying landfill sites for methane recovery and on promoting cost-effective electricity generation or direct use of the resource. Efforts include the identification of barriers to project development, the improvement of enabling legal, regulatory and institutional conditions, and the creation of efficient energy markets. The active involvement by private sector entities, financial institutions and other non-governmental organizations is considered essential to build capacity, transfer technology and promote private investment that will ensure the Partnership’s success.
The EPA Landfill Methane Outreach Program (LMOP) is a voluntary assistance programme that helps to reduce methane emissions from landfills by encouraging the recovery and use of landfill gas as an energy resource. LMOP forms partnerships with communities, landfill owners, utilities, power marketers, states, project developers, tribes and non-profit organizations to overcome barriers to project development by helping them assess project feasibility, find financing and market the benefits of project development to the community.
EPA launched LMOP to encourage productive use of this resource as part of the United States’ commitment to reduce greenhouse gas emissions under the United Nations Framework Convention on Climate Change.
The LMOP website (www.epa.gov/lmop) contains a variety of tools and services to assist stakeholders in evaluating project potential, technical documents, case studies and funding opportunities.
This article is on-line: www.cospp.com
CHP LFGE case studies
Modern Landfill Inc, New York
The LFG-fired cogeneration facility at Modern Landfill in New York provides 100% of the electrical and heating requirements for H2Gro Hydroponic Greenhouses, with excess electricity sold to the grid. Innovative Energy Systems started the initial phase of this CHP LFGE project in 2001, when it designed and installed a 5.6 MW project to power and heat a 2024 m2 greenhouse test plot. In its first year, the project yielded 82,000 kg of tomatoes. After a successful test plot, this greenhouse was expanded to 30,352 m2 and 12 MW of generating capacity.
Today, this H2Gro facility produces over 1600 tonnes of tomatoes per year. Innovative Energy Systems has received multiple awards for the project, which provides the community with employment and a new year-round exportable crop.
Creswell and Frey Farm Landfills, Pennsylvania
Lancaster County Solid Waste Management Authority, PPL Corporation and Turkey Hill Dairy formed a unique partnership to achieve a CHP LFGE project using gas from two landfills in Lancaster County, Pennsylvania. The LFG is sold to PPL Energy Services, which operates two Caterpillar 3520 engines to produce 3.2 MW of electricity. The engine heat is captured to generate steam, which is sold to the nearby Turkey Hill Dairy through a closed-loop steam pipeline.
Two Caterpillar 3520 engines fuelled by landfill gas generate 3.2 MW of electricity. Boilers capture heat from the engines, generating steam that is
The dairy has met 80% of its steam demands using LFG. It also offsets the use of 855,000 litres of diesel fuel per year.
Brazil, Mexico and India landfills
The US Agency for International Development (USAID) and the EPA are working together in these three Methane to Market Partner countries to support landfill projects. The impacts on and the re-employment of families who make their living scavenging the sites have been identified as key factors for international landfill projects. Brazil’s Fortaleza region together with the United Nations Development Programme has completed a technical analysis on a landfill site and has identified and mitigated social impacts.
In India, two projects are proposed, including a $7 million landfill as part of the West Bengal solid waste project.
In Mexico, USAID and the EPA have been carrying out technical analyses on several sites near the US border together with Semarnat, the Mexican environmental regulator.