IWWG Task Group on
LANDFILL AERATION

TG Leaders: Marco Ritzkowski, Marlies Hrad & Osamu Hirata

Scope

The creation of sustainable landfills is a fundamental objective in recent waste management concepts. The main objectives of modern landfill operation are to control and utilize the energy provided by landfill gas (LFG) and to prevent environmental pollution caused by polluted leachate and migrating LFG. Landfills should be constructed and operated in line with state-of-the-art technologies focusing on waste pre-treatment, lining systems, and landfill gas and leachate collection. However, over time many modern landfills continue to exhibit a significant emission potential for both leachate and LFG. This is particularly the case for older landfills constructed some decades ago, the design of which is not as effective as modern landfills.
Landfill aeration is a methodology which tends to control and reduce both landfill emissions as well as long term emission potential. By converting conventional anaerobic landfills into an aerated treatment unit, a biologically stabilized waste with minimized emission potential can be achieved. The objectives of landfill aeration vary depending on the geographical region, specific legislation, and available financial resources.
In Japan, the semi-aerobic landfill is operated with the specific intent of achieving enhanced biological degradation. The objective of landfill aeration in the US is to increase biodegradation rates and settlement leading to earlier recovery of air-space in which to place additional waste and to reduce post-closure care periods.  In Europe, however, the objective of aerobic in situ stabilization is to achieve and maintain a controlled reduction of emissions and in emission potential from old landfills in order to shorten the period of landfill aftercare. Landfill aeration can be beneficially combined with controlled liquid (e.g. pretreated leachate) infiltration.
The IWWG set up a task group on the topic of landfill aeration to bring together international perspectives and expertise in the field in order to better define the technology and to disseminate experiences to the public. The IWWG Task Group “Landfill Aeration” was established in 2004 during the 3rd Intercontinental Landfill Research Symposium (ICLRS) held in Sapporo, Hokkaido, Japan.

Objectives

Specific objectives of the group include:

• Exchange of information between group members
• Preparation of joint publications and joint workshops
• Development of procedures and standards for aeration, including analytical programs
• Joint research activities

Topics

Topics dealt with by the Task Group include:

• Heat generation and processes under elevated temperatures, Settlements
• Air distribution inside aerated landfill bodies & modelling
• Substance balances
• Leachate quality
• Costs
• Stabilisation criteria (completion of aeration), time periods to achieve stabilization
• Semi-aerobic landfills
• Nitrogen-dynamic
• Monitoring programs during Landfill Aeration
• Possibilities and limitations of aeration measures (e.g. waste densities, landfill height etc.)
• Pre-tests: Are they necessary and how long should they be practised?

Members and Membership

Structure and operation mode

The task-group operates in close contact with other IWWG task groups, particularly the “Sustainable Landfill Management” and “CLEAR” groups. Meetings are held at least once a year either during the Sardinia Waste Management and Landfill Symposium or the Intercontinental Landfill Research Symposium (ICLRS). These events serve as the main meeting platforms. Additional meetings are conducted in the short term if required, at times involving only several of the TG members.

Group activities are coordinated by the task group leaders and communication between members is conducted mainly via email and through this section of the IWWG web-page. The group welcomes new members provided that candidates have proven expertise in one or more of the above-mentioned fields and are members to the IWWG.

Contact person:

Dr. Marco Ritzkowski

JOMA Umweltberatungsgesellschaft mbH
c/o Hamburg University of Technology
Sustainable Resources and Waste Management
Blohmstrasse 15
21079 Hamburg - Germany
Phone: +49 (0) 40 42878-2053 
E-Mail: m.ritzkowski(at)tuhh(dot)de

Previous workshops and sessions organized by TGLA

SARDINIA 2019: Workshop on optimal performances and fake aeration

The IWWG Task Group Landfill Aeration (TGLA) was organizing a workshop on the issue of "Optimal performances and fake aeration" in the framework of the International Waste Management and Landfill Symposium – Sardinia 2019 which was held 30 September to 4 October 2019 in Sardinia, Italy.

The workshop was attended by more than 20 participants and included 3 short presentations to stimulate the discussion. With the introduction by Marco Ritzkowski it was stated that published data on landfill aeration projects suggest that the passive aeration concept is increasing by number. This concept has the advantage that the required infrastructure (thus the investment costs) are relatively low since the piping system can be design as a single-line (only negative pressure) and no second blower unit is required. Moreover, benefits may be generated by energy recovery from the extracted landfill gas. But what is often disregarded is the relatively slow stabilisation effect and operational challenges in cases where the landfilled wastes are fully water saturated or even leachate tables are present on the landfill liner. During the workshop this and other existing methodologies for landfill aeration have been discussed in view of the workshop title, namely how to ensure quality performance and sufficient results of landfill aeration projects.

After  these  methodical  issues  have  been  discussed,  the  workshop  focused  on benchmarks in connection with landfill aeration. Here, the focus was on the technical implementation and the discussion scame up with indications on how to optimize future aeration projects. This discussion will be proceeded during the upcoming Sardinia 2021 symposium.

ICLRS 2018: Workshop on long term emission behavior of in situ bio-stabilized landfills

The IWWG Task Group Landfill Aeration (TGLA) was organizing a workshop on the long term emission behavior of in situ bio-stabilized landfills in the framework of the Intercontinental Landfill Research Symposium – ICLRS 2018 which was held 26-28 June in Sunderbyn, Sweden. The aims of the workshop were a summary on currently applied and eventually required completion criteria and values, some first indications on the potential long term emission behavior (i.e. the degree of bio-stabilisation achieved during aeration) of in situ aerated landfills as well as the identification of further research needs.

The workshop was attended by approx. 20 participants and included 6 presentations by researchers from 5 different countries. After an introductory presentation by the workshop organizer and leader of the IWWG Task Group on Landfill Aeration, Marco Ritzkowski, Johann Fellner from the Vienna University of Technology, Austria raised the question on How to assess the success of landfill aeration projects in his presentation. It became apparent that in particular the assessment of solid waste samples is quite problematic and implies significant uncertainties due to the waste/landfill heterogeneity and sampling errors. In contrary, online parameter (e.g. carbon loads) and lab scale simulations may act as reliable tools for the assessment of the stabilization process. New projects, both in full and lab scale have been presented by Timo Heimovaara and Nora Fricko from Delft University of Technology, The Netherlands and Vienna University of Technology, Austria, respectively. Whereas the new lab scale project is going to focus on nitrogen pathways, processes and transformation in aerated landfills, the field scale aeration currently conducted in the Netherlands will come up with valuable and detailed data on temperatures and settlings (beside many others) to develop during the bio-stabilisation process of landfills. Roberto Raga from the University of Padova, Italy presented results on the influence of aeration rates on emissions from landfill simulation reactors. These results are very much in line with findings presented by the workshop organizer during the beginning of the session and clearly demonstrate that the intensity of aeration is directly associated with the progression of leachate quality in the framework of the bio-stabilisation process. The main impact seem to be on nitrogen compounds (mainly ammonium nitrogen) since these are oxidized only after the bio-conversion of the organic carbon compounds. With the final presentation, Hideki Yoshida from the Muroran Institute of Technology, Japan summarized latest findings on the in situ stabilization of a closed landfill by installing passive landfill gas extraction wells. Semi aerobic landfills are often applied in Japan and do hold the advantage of reduced environmental impact (in comparison to anaerobic landfills) in combination with accelerated bio-stabilisation times.

In conclusion, the workshop demonstrated that there is still a further need to define and implement criteria for the completion of landfill aeration projects. It became clear that these criteria have to consider side specific aspects and cannot be universal for all aeration projects. In addition, the participants agreed that the issue of long term emissions from bio-stabilized landfills has to be further investigated since the currently available results show a potential increase in the level of emissions after the stabilization process has been terminated. However, the overall positive impact of aeration on the emission potential of landfills has been underlined by all workshop participants.

SARDINIA 2017: IWWG TGLA Workshop on Landfill aeration - achievements and challenges after two decades of experience

In the late nineties the first landfill aeration projects started in Europe. Meanwhile, the methodology is widely accepted as a means for enhanced, controlled and sustainable bio-stabilisation of MSW landfills. Positive effects are related to a significant reduction of current and future greenhouse gas emissions, a widely completion of landfill settlings as well as improved leachate quality. However, results reported from different aeration projects are not always concordant and may differ significantly with regard to the achieved level of stabilisation. Against this background the aim of the workshop was to identify both the potential of the methodology and further research needs. Click here to read the full report.

ICLRS 2016: Session on Status quo and future developments in landfill aeration

A couple of new projects for landfill aeration have recently started or are under preparation in Europe. In Germany, landfill aeration is officially considered a contribution towards the avoidance of Greenhouse gases (GHGs) and necessary investment costs are subsidized by the accordant Ministry. Beside climate aspects, the creation of sustainable landfills remains one of the fundamental goals in connection with landfill aeration.
On the scientific level there is still demand for further investigations into the processes to occur during aeration. In this connection the IWWG Task Group on Landfill Aeration (comprising 20 international experts in the field) is focusing on a number of issues, such as “Behaviour of heavy metals during aeration”, “Temperature development in aerated landfills” and “Nitrogen dynamic during aeration”. These issues have been further developed until and during the proposed session.
The session was opened by Marco Ritzkowski presenting a short overview on the session outline and stressing the intended outcomes. A couple of short presentations (max. 10 min. each) were provided by different participants (according to the submitted abstracts) and an introductory was given by the session chair. The session was focusing on recent examples of landfill aeration projects including challenges regarding operation, monitoring and completion. Emphasis was given to issue related to the semi aerobic landfill approach which is often practiced in Japan and other Asian countries.

SARDINIA 2015: Session on Lessons learned from landfill aeration projects

The IWWG Task Group on Landfill Aeration organized a workshop in the framework of the 15th International Waste Management and Landfill Symposium in Sardinia, Italy. The aim of the workshop was to identify similarities and discrepancies between different landfill aeration projects (e.g. kind of aeration system, aeration volumes, pressures, flow rates, temperatures, etc.). These information should serve as a basis to define some main criteria which can be considered essential for future successful applications.
The main questions which have been discussed in the framework of the workshop were:

• What are the limits (upper and lower) for application of landfill aeration in terms of biodegradable organic material?
• What aeration strategy (both, plant operation and plant design) should be applied in order to reach the stabilization targets?
• What are the most critical aspects which may prevent the aeration project from being successful?

Read the full report here.

ICLRS 2014: Session on Recent developments in landfill aeration (20 October 2014)

A couple of new projects for landfill aeration have recently started or are under preparation in Europe. In Germany, landfill aeration is officially considered as a contribution towards the avoidance of Greenhouse gas (GHG) emissions and necessary investment costs for the aeration infrastructure are subsidized by the German Ministry of the Environment. Beside climate aspects, the creation of sustainable landfills remains one of the fundamental goals in connection with landfill aeration.

On the scientific level there is still a demand for further investigations into the processes to occur during aeration. In this regard the IWWG Task Group Landfill Aeration (comprising 20 international experts in the field) is focusing on a number of issues, such as “Behaviour of heavy metals during aeration”, “Temperature development in aerated landfills”, “Nitrogen dynamic during aeration” and “Landfill aeration Database”. Some of these issues will be discussed and further developed during the session as well as in the framework of a task group meeting in the framework of the symposium.

In particular, the session is going to focus on recent examples of landfill aeration projects in France and Austria (including challenges regarding operation, monitoring and completion) as well as the role of changing (increasing) temperatures in the course of aeration. The latter have been found to be a key factor related to processes to occur during landfill aeration.

Workshop during Sardinia 2013 (4 October 2013)

The IWWG Task Group on Landfill Aeration organised a workshop in the framework of the 14^th International Waste Management and Landfill Symposium in Sardinia, Italy. Based on the scientific discussion and publications in the field the Group has identified specific tasks of major interest. These tasks comprise, amongst others, the behaviour of heavy metals during landfill aeration. Available data have been evaluated and structured in order to provide some indications on a potential mobilization or fixation of metals in the course of aeration projects. In addition to the behaviour of heavy metals, further processes are to be considered. This includes organic carbon degradation, changes in the solid waste characteristic, settlements devolutions and temperatures. Information from full and lab scale aeration projects have been evaluated and compiled in a database ‘Landfill Aeration’. On Friday morning, 4 October 2013, approximately 25 participants attended the first part of the workshop and contributed towards a lively and constructive discussion.

Following a short introduction on the background, aims, objectives and important outcomes of the Task Group so far (e.g. the IWWG Monograph Series volume “Landfill Aeration”, edited by Rainer Stegmann and Marco Ritzkowski), a first introductory presentation by the Task Group Leader (Marco Ritzkowski, Hamburg University of Technology, Germany) provided an overview on aeration technologies and fundamental processes to occur in landfills during in-situ aeration. Published results indicate the almost instantaneous transmission from anaerobic into aerobic conditions, a time depending quota of biological oxygen consumption in connection with an accordant CO₂ production, an intensive thermal energy generation associated with a significant warming of the landfilled waste as well as improved leaching characteristics (in terms of organic and inorganic nitrogen compounds) of the biological stabilized waste material. At the same time, limited data have been published on the behaviour of heavy metals during aerobic in-situ stabilization. In this connection Gülsen Öncü from the University of Stuttgart, Germany, presented the intermediate results of the accordant task she is currently leading. As expected, both the oxidation-reduction potential and the pH value have a high impact on the mobilization of heavy metals. During landfill aeration; however, waste pre-stabilisation has to be taken into consideration thus metals mobilization will be significantly attenuated.

Christian Brandstätter (Vienna University of Technology, Austria) presented the status quo and future aims in connection with the landfill aeration database. So far only a limited number of data sets are available and at the same time the comparability of the data is restricted. One of the major deficits is the lack of a common denominator for different aeration projects. During the discussion among the workshop participants it became obvious that there is a demand for a list of standard parameters and measurements that ought to be included in new aeration projects. Existing data should be standardized and harmonized in order to ensure a wider comparability. These aspects will be included in the proceeding work on the task “Landfill aeration database”.

During the second part of the workshop the focus was set on the fate of nitrogen during landfill aeration. Applying aeration to a landfill has a significant impact on the accordant leachate quality. However, simulation experiments in laboratory scale often do not adequately consider the conditions to arise when aeration is performed at a full scale landfill. One of the major factors to determine the leachate composition during aeration is temperature. Raising temperatures stimulate / intensify both, nitrogen mineralization rates (ammonification) as well as bioconversion of organic compounds. In consequence pH values are increasing and becoming the major driver of further processes. Due to a shift in the ammonium – ammonia equilibrium (towards free ammonia) nitrification processes are further inhibited and the same applies for microbial bioconversion processes of organic compounds. With the beginning of NH₃-N volatilization both, organic and nitrogen compounds in the leachate are reduced. Furthermore, with the transition into the long term cooling phase (at reduced microbiological activity) the positive impact of aeration on the leachate composition (quality) becomes apparent. The question of a potential long term release of ammonium nitrogen (incorporated in the microbial biomass) once the aeration has been completed seems to be circumstantial. Investigations in laboratory scale indicate that the nitrogen mineralization rates (ammonification) after a widely bio-stabilization are in a range of 30% in comparison with the situation at the start of aeration. In any case leachate concentrations (ammonium nitrogen) are expected to adjust at low levels after completion of aeration.

Marlies Hrad from the University of Natural Resources and Life Sciences, Vienna, Austria presented an overview on the nitrogen dynamic including possible pathways of N-transformation/ removal during landfill aeration. On the basis of available results from task group members she raised the question if we are able to set up a complete nitrogen balance for an aerated landfill and which additional value would be associated with such a balance? During the presentation as well as in the subsequent discussion it became clear that both experimental and analytical difficulties prevent from balancing the nitrogen dynamic so far. There was a consensus among the participants that the development and application of a standard lab test procedure may be a promising tool in order to overcome some of the problems. Furthermore, a more detailed characterisation of the nitrogen pool contained in the waste mass (organic or inorganic nitrogen, specific compounds, etc.) in combination with an identification of the individual conversion rates of different N-transformation processes may contribute towards a better understanding of the nitrogen dynamic during landfill aeration.

The final presentation about the intermediate results of the task on “Temperature development during landfill aeration” was provided by Thomas Wohlhuter (Arcadis, France). This task is of particular importance since increased temperatures are not only a concern in connection with potential waste self-ignition but also driving several reactions, e.g. the ammonification and nitrification processes inside the aerated waste mass. The heat balance is mainly based on three major elements, namely the microbial heat generation as well as thermal energy injection and discharge through aeration and off-gas extraction. In consequence, well-adjusted aeration rates (in particular during the early stages of aeration) and possibly intermittent aeration modes may contribute towards an effective temperature control.

To conclude, the dynamics of the discussion during the workshop underlined the remarkable interest shown towards landfill aeration. The possibility of bio-stabilizing closed MSW landfills has already been implemented into the German and Austrian legislation and approved CDM methodologies demonstrate that in-situ aeration contributes towards climate protection. Tasks for the near future exist with a standardisation of both lab and full scale aeration procedures as well as a better understanding of specific processes involved in the bio-stabilization.

Next TGLA meeting:

The next regular meeting of the Landfill Aeration Task Group will take place during the Sardinia Symposium 2023.