Dramatic reduction in emissions of methane from landfills in the Netherlands: additional measures considered

Abstract

The Netherlands has taken various measures to reduce the emission of methane from landfills, such as less waste disposal, separate collection of biodegradable waste, use of landfill gas for generating power, and flaring of landfill gas. These measures have led to a dramatic reduction in emissions. But more can be done by taking additional measures. The question of whether the costs justify the expected yields is an important one, and has been addressed in the research. Four types of additional measures have been selected as potential measures which show great promise: (1) flaring of low-calorific gas, (2) additional gas extraction wells, (3) early sealing of landfill, and (4) optimization of existing landfill gas extraction systems. Low-calorific gas flares are expected to be most for promising in future for landfills where extraction systems are already installed. The costs of installing additional landfill gas extraction wells usually exceed the revenues. Early sealing of a landfill is only feasible when this measure has additional benefits (such as reduced leachate amounts). This shall be detailed in a business case for the specific landfill. Quick wins can be achieved by improving the operation of existing landfill gas extraction systems.

Keywords:

• methane
• landfill
• greenhouse gas emission
• reduction

Introduction

Methane emission from landfills contributed to the total greenhouse gas emissions in the Netherlands by 6% in 1990, and was the greatest methane source in the Netherlands then. Various measures designed to reduce the methane emissions from landfill have been taken since 1990, resulting in a contribution to the total greenhouse gas emissions of approximately 3% in 2007. Measures include:

	less waste disposal;
	separate collection of biodegradable waste;
	the use of landfill gas for generating power;
	flaring of landfill gas.

The methane emission from landfills in the Netherlands was estimated at 572 kton methane (12 Mton CO₂-eq, based on a GWP of 21) in 1990. The methane emission from landfills in 2007 was assessed at 243 kton methane (5.1 Mton CO₂-eq). The methane emission from landfills has thus been reduced by 57% (See Figure 1).

The Netherlands has approximately 4000 landfill sites. Twenty-five of them are still in use; the others have been closed. Methane escapes from all these landfills, including those that have been closed. Emissions are at their highest just after waste has been disposed of, after which the level gradually diminishes. Emission registration data (SenterNovem 2007a) show that 129 million m³ landfill gas was extracted and used or flared at 60 Dutch landfill sites in 2006. Assuming an average methane content of 51.8%, the extraction at these sites lead to an emission reduction of circa 48 kton methane (1 Mton CO₂-eq) in the year 2006.

Dutch non-CO₂ reduction program tailored to landfills

The Dutch governmental agency SenterNovem promotes sustainable development and innovation, both within the Netherlands and abroad. One of their programs is the reduction program non-CO₂ greenhouse gases (“Reductieplan niet-CO₂ Broeikasgassen” or ROB). This program aims to reduce emissions by encouraging research into emission-factors and monitor emission levels from various sources, by funding research into new technologies, by encouraging the employment of existing reduction measures, and by promoting co-operation between government, industry organizations, and companies. SenterNovem is charged with implementing the program by the Dutch Ministry of Housing, Spatial Planning and the Environment (VROM).

Within the targets for CO₂ emission reduction, methane from landfills is a major subject. The project focuses on feasible measures for methane emission reduction, such as making effective use of low-concentration methane landfill gas, or using special techniques to generate electricity from landfill gas supplied on an irregular basis. By order of this SenterNovem ROB program, the landfills research is conducted by Royal Haskoning in close consultation with the Netherlands waste disposal sector (Vereniging Afvalbedrijven).

Goal of the research is to find out if additional cost effective measures can be taken to reduce the methane emission from landfills. The research lays the foundation of further improvement of the policy for the reduction program non-CO₂ greenhouse gases.

Basic assumptions

Landfills in the Netherlands can be distinguished into three types: former landfills, medium-sized landfills closed in the mid-1990s, and landfills still in use. The date of 1 September 1996 is important, because legislation prescribed controlled landfilling; landfills closed before 1 September 1996 did not have to fulfill new requirements which asked for large investment costs.

1. Former landfills which were closed well before 1 September 1996 have been examined as part of the national project “Aftercare of Former Landfills” (NAVOS). It was concluded that landfill gas emissions at these former landfills were not a significant hazard for which direct remediation measures should be taken. Emissions of former landfills were assumed to be relatively small. Discussions during the execution of our research where related to the contribution of these former landfills to the total methane emissions from landfills. The discussion is not ended yet, and will be subject to further research by SenterNovem in 2009.

2. Medium size landfills were closed just before 1 September 1996, when new landfill legislation came into force. These landfills mostly contain organic waste, and a large number of landfills are equipped with landfill gas extraction and utilization systems.

3. Landfills in use have to fulfill all obligations of the Environmental Management Act. SenterNovem published the “Guideline for reduction of methane from landfills” in 2007 (Handreiking methaanreductie stortplaatsen) (SenterNovem 2007b). The Guideline reflects the Best Available Technology and is appointed as such in the Dutch BAT regulation (“Regeling aanwijzing BBT-documenten”). The minimum level is called the base case: controlled landfills shall all comply to the base case when methane emissions are expected. The base case includes gas wells (at least 60% capture rate during operation), landfill gas extraction, high temperature flaring, and gas utilization when technical and economical feasible.

4. It is assumed that measures to be taken for nationwide reduction of methane emission from landfills will be only effective at medium size landfills that were closed just before 1 September 1996, landfills closed after 1 September 1996 and landfills in use. We expect that a structured approach of reduction of methane emission from old former landfills will not be cost effective. This assumption is subject to be verified in this study.

5. Monitoring of methane emissions from landfills for verification of measures is still subject to numerous international studies. These studies are needed to improve the cost effectiveness and reliability of monitoring, up to the level that monitoring of relatively small changes in emissions can be registered.

Potential additional measures

Short description of potential additional measures

For the research, a distinction was made between potential measures, which are additional to the base case (see Figure 2):

1. Related to the landfill type (dumpsite, controlled landfill), waste conditions (aerobic, anaerobic) and waste body (geometry).

2. Related to capture of landfill gas in the top layer (top soil layer, sealing).

3. End of pipe (extraction and flaring/utilization).

1. Landfill body and waste

   • A1. Shift waste to a controlled landfill. Waste is excavated from a former landfill and disposed in a controlled landfill with landfill gas extraction. Landfill taxes are seen as obstruction.

   • A2. Waste mining. Mining of former landfills is used to reduce environmental impact of former landfills, extracting recyclables out of the waste and shift remaining (organic) waste to a controlled landfill with landfill gas extraction. Landfill taxes are seen as obstruction.

   • A3. Anaerobic bioreactor landfill. (Re)infiltration of leachate and rain water improves the anaerobic digestion, increasing the methane generation rate and more efficient landfill gas capture.

   • A4. Aerobic bioreactor. Aeration of the waste body, preventing methane generation.

   • A5. Adjusting waste body shape. Steep slopes (1V:3H) and landfill thickness of more than 10 m improves the volumes of waste within the extraction system limits.

   • A6. Waste pretreatment. Pretreatment by size reduction and homogenization leads to better circumstances for digestion and therefore a higher methane generation rate and more efficient extraction opportunities. Separation of organic waste (for separate composting or digestion) leads to a lower methane potential.

   • A7. Waste management. Waste management resulting in less landfills which can be operated more efficiently as controlled landfill, improving landfill gas capture.

2. Landfill gas capture

   • B1. Methane oxidation in top layer. Measures stimulating methane oxidation in landfill top soil layers. Pilot tests show positive results, but uncontrolled emission, e.g. through cracks, is difficult to prevent, and monitoring is complex. International landfill gas models assume a standard 10% methane oxidation in the top layer, and higher oxidation rates are not (yet) accepted by international monitoring agencies.

   • B2. Early sealing of landfill. The early construction of an impermeable and gastight top cover improves the capture of landfill gas. A decrease of waste stabilization and landfill gas generation is expected due to shortfall of moisture in the landfill body. The measure is only technical feasible when limited differential settlements are expected.

   • B3. Aeration of top layer. This measure leads to improvement of oxidation of methane in the top layer. Drawbacks similar to B1 can be observed.

3. End of pipe techniques

   • C1. Installment of additional extraction wells. More extraction wells at the same surface lead to an increased landfill gas capture rate, especially during the period when a landfill is not sealed by a top cover.

     • C2.1. Flaring of low-calorific landfill gas (30% to 45% CH₄). Technical modifications of standard flares extend operational limits of standard flares, and consequently extend duration of the operation period. This technique also can be used simultaneously with other techniques, at landfills where part of the waste is producing low-calorific gas.

     • C2.2. Flaring of low-calorific landfill gas (15% to 30% CH₄). The use of this type of flare is subject of research and pilot studies. When successful, the period of methane reduction by flaring can be extended.

     • C2.3. Flaring of low-calorific landfill gas (8% to 15% CH₄). An innovative type of flare, still in the development stage.

     • C.2.4. Collection and flaring of landfill gas without the use of compressor. Technique using pressure increase in the landfill body. In development stage within a Dutch demonstration project.

   • C3. Gas utilization by Organic Ranking Cycle (ORC). Utilization of landfill gas by the ORC technique. Demonstration projects proves technical feasibility.

   • C4. Regenerative thermal oxidation (RTO). Very low-calorific gas (<1% CH4) non-catalytic oxidation process. High investment costs and critical operation parameters.

   • C5. Separate extraction and treatment of high-calorific and low-calorific landfill gas. Separate extraction of high-calorific landfill gas improves utilization rates. Extra costs for low-calorific landfill gas extraction system and flare.

   • C6. Discontinuous landfill gas extraction. Discontinuous extraction uses higher methane contents of generated landfill gas and extends the use of a standard flare.

   • C7. Optimization of existing landfill gas extraction systems. The efficiency of landfill gas extraction systems depends strongly on the frequency of control, and experience and specific knowledge of the operator. Improvement of operation leads to higher extraction rates rather easily.

Figure 1. Methane emission from landfills 1990–2007 (source: www.milieuennatuurcompendium.nl reference code PBL/MNC/aug08/0160 and (Emissieregistratie 2009)).

Figure 2. Schematic view of types of measures.

Ranking of potential measures

The feasibility of potential measures is ranked by using a weighted multicriteria analysis of these measures (Royal Haskoning 2009). The criteria used and the weighting factors (within brackets) include:

	Proven technology (1.2). Has the technology been used in landfill gas projects succesfully, and is the technology available for this purpose?
	Legislative aspects (1.1). Is the technology applicable within the landfill legislation in The Netherlands? Or do authorities have to give specific guidelines for it?
	Potential application at former landfills (1). Is the technology suitable at former landfill sites?
	Potential application at landfills in use (1.2). Is the technology suitable at landfills in use?
	Potential application at new landfill (cells) (1). Is the technology suitable at landfill (cells) which still have to be built?
	Economic performance (1.5). Will the operational costs and investments be covered by the benefits of the potential measure?
	Environmental outputs (1.5). A rough estimation of the environmental yield of a potential measure.
	Scale of the measure (1.5). The scale of the measure is related to the efficiency of the measure to reach a significant emission reduction.
	The likelihood of quantifiable monitoring (1.3). Can emission reductions be quantified easily, e.g. end of pipe techniques, or are that difficult to monitor?

Based on these criteria and weighting factors, an expert judgment has been executed by the authors and presented and discussed in a workshop with landfill operators, Dutch landfill gas experts, and relevant authorities (provinces, SenterNovem, Ministry of Environment).

Following the weighted multicriteria analysis, four potential measures show great promise:

1. C2.1. Flaring of low-calorific landfill gas (30–45% CH₄).

2. C1. Increasing the amount of extraction wells.

3. B2. Early sealing of landfill.

4. C7. Optimization of existing landfill gas extraction systems.

Feasibility of potential measures

Introduction

Several scenarios have been developed to scrutinize the feasibility of the costs of measures, expressed as costs per avoided CO₂-equivalent. As reference a (positive) market price of €20 per ton of CO₂ is assumed.

Scenarios have been worked out for former landfills, and an expert judgment is given for the feasibility of additional measures on landfills in use.

Former landfill scenarios

Five former landfill scenarios have been worked out, as described in Table 1. Waste characteristics: municipal (household) waste with a biodegradable carbon content of 130 kg/ton. Landfill gas generation is estimated using the Dutch TNO first order landfill gas model (Oonk et al. 1994; Oonk and Boom 1995).

Table 1. Former landfill types.

Scenario	Operation period	Area (hectare)	Waste amount (m^3 per year)
1. Very old landfill	1950–1960	2	4000
2. Small old landfill	1975–1980	2	8000
3. Large old landfill	1970–1985	10	54000
4. Small landfill	1990–1995	2	12000
5. Large landfill	1985–1995	15	150000

Table 2. Landfill gas extraction revenues (based on assumption of €20 per CO₂-equivalent) and conclusions.

Scenario	Operation period	Revenues period, 2009–2020 (Euro)	Conclusions (summary)
1. Very old landfill	1950–1960	2,500	Revenues do not cover costs of potential measures
2. Small old landfill	1975–1980	23,000	Revenues do not cover costs of potential measures
3. Large old landfill	1970–1985	500,000	Revenues are calculated for 100% utilization of methane. In practice a maximum of 70% is realistic. Then revenues will not cover costs of potential measures (over a period of 12 years)
4. Small landfill	1990–1995	156,000	Revenues do not cover costs of potential measures
5. Large landfill	1985–1995	3,132,000	Flaring of low-calorific landfill gas and increasing the amount of gas wells might be cost effective
			Early sealing of landfill specific for landfill gas capture is not viable
			A site specific business case shall give further insight in potential measures

The emission reduction of each scenario has been calculated, by estimating methane emissions and converting it all into CO₂ equivalents (tons). The next step was to calculate the maximum earnings, assuming that all methane is captured from the landfill, based on €20 per ton of CO₂.

The final step was to check whether the revenues of emission reduction will cover the investment (CAPEX) and operation (OPEX) costs of potential measures (See Table 2).

Landfills in use

Landfills in use, approximately 25 in The Netherlands, have to fulfill the requirements of the “Guideline for reduction of methane from landfills” in 2007 (Handreiking methaanreductie stortplaatsen). As mentioned, the Guideline reflects the Best Available Technology (BAT). Additional measures for emission reduction therefore have a minor impact on the methane emissions from landfills in The Netherlands.

Measure C7, the optimization of existing landfill gas extraction systems, will be very suitable to have “quick wins”, improving the performance of landfill gas extraction and thus reduction of methane emission from landfills in use (and former landfills with a landfill gas extraction installed).

Conclusions and recommendations

A dramatic reduction in emissions of methane of landfills in The Netherlands has been achieved by various measures since 1990. We conclude that potential additional measures for reduction of methane emission from former landfills in general will not be cost effective. Measures might be feasible if these are combined with multiple objectives, such as redevelopment of the landfill site when it has the potential to be redeveloped once it is cleaned up. Also waste mining (to gain back recyclables) or the capping of a landfill for reasons of groundwater protection might benefit reduction of methane emissions.

Low-calorific gas flares are most promising for additional reduction of methane emission when developed further for landfill gas extraction systems. These and several other measures for treatment of low-calorific landfill gas have future perspective, but will always have to deal with uncertain interpretation of waste parameters for landfill gas estimates, and uncertainties in the monitoring results.

For large (type 5) former landfills and landfills in use, methane emission mitigation measures shall always be subject of a feasibility study.

Additional measures at landfills in use will have a minor impact. Difficult is the monitoring of effects on (minor) reduction of the methane emission from these landfills. However, optimization of existing landfill gas extraction systems will be very suitable to improve the performance of it.