Potential for enhanced phytoremediation of landfills using biosolids – a review

Despite the use of recyclable materials increasing worldwide, waste disposal to landfill remains the most common method of waste management because it is simple and relatively inexpensive. Although landfill disposal is an effective waste management system, if not managed correctly, a number of potential detrimental environmental impacts have been identified including soil and ground water contamination, leachate generation, and gas emissions. In particular, improper post-closure treatment of landfills or deterioration of the conventional clay landfill capping were shown to result in land degradation which required remediation to secure contaminants within the landfill site.Phytoremediation is an attractive technology for landfill remediation, as it can stabilize soil and simultaneously remediate landfill leachate. In addition, landfill phytoremediation systems can potentially be combined with landfill covers (Phytocapping) for hydrological control of infiltrated rainfall. However, for the successful application of any phytoremediation system, the effective establishment of appropriate, desired vegetation is critical. This is because the typically harsh and sterile nature of landfill capping soil limits the sustainable establishment of vegetation. Therefore, the physicochemical properties of landfill capping soils often need to be improved by incorporating soil amendments. Biosolids are a common soil amendment and will often meet these demanding conditions because they contain a variety of plant nutrients such as nitrogen, phosphate, potassium, as well as a large proportion of organic matter. Such amendment will also ameliorate the physical properties of the capping soils by increasing porosity, moisture content, and soil aggregation. Contaminants which potentially originate from biosolids will also be remediated by activities congruent with the establishment of plants and bacteria.     

Evaluation of alternative landfill cover soils for attenuating hydrogen sulfide from construction and demolition (C&D) debris landfills

Hydrogen sulfide (H(2)S) generated from C&D debris landfills has emerged as a major environmental concern due to odor problems and possible health impacts to landfill employees and surrounding residents. Research was performed to evaluate the performance of various cover materials as control measures for H(2)S emissions from C&D debris landfills. Twelve laboratory-scale simulated landfill columns containing gypsum drywall were operated under anaerobic conditions to promote H(2)S production. Five different cover materials were placed on top of the waste inside duplicate columns: (1) sandy soil, (2) sandy soil amended with lime, (3) clayey soil, (4) fine concrete (particle size less than 2.5 cm), and (5) coarse concrete (particle size greater than 2.5 cm). No cover was placed on two of the columns, which were used as controls. H(2)S concentrations measured from the middle of the waste layer ranged from 50,000 to 150,000 ppm. The different cover materials demonstrated varying H(2)S removal efficiencies. The sandy soil amended with lime and the fine concrete were the most effective for the control of H(2)S emissions. Both materials exhibited reduction efficiencies greater than 99%. The clayey and sandy soils exhibited lower reduction efficiencies, with average removal efficiencies of 65% and 30%, respectively. The coarse concrete was found to be the least efficient material as a result of its large particle size.     

The potential contribution of sustainable waste management to energy use and greenhouse gas emission reduction in the Netherlands

Future limitations on the availability of selected resources stress the need for increased material efficiency. In addition, in a climate-constrained world the impact of resource use on greenhouse gas emissions should be minimized. Waste management is key to achieve sustainable resource management. Ways to use resources more efficiently include prevention of waste, reuse of products and materials, and recycling of materials, while incineration and anaerobic digestion may recover part of the embodied energy of materials. This study used iWaste, a simulation model, to investigate the extent to which savings in energy consumption and CO₂ emissions can be achieved in the Netherlands through recycling of waste streams versus waste incineration, and to assess the extent to which this potential is reflected in the LAP2 (currently initiated policy). Three waste streams (i.e. household waste, bulky household waste, and construction and demolition waste) and three scenarios compare current policy to scenarios that focus on high-quality recycling (Recycling+) or incineration with increased efficiency (Incineration+). The results show that aiming for more and high-quality recycling can result in emission reductions of 2.3 MtCO₂ annually in the Netherlands compared to the reference situation in 2008. The main contributors to this reduction potential are found in optimizing the recycling of plastics (PET, PE and PP), textiles, paper, and organic waste. A scenario assuming a higher energy conversion efficiency of the incinerator treating the residual waste stream, achieves an emission reduction equivalent to only one third (0.7 MtCO₂/year) of the reduction achieved in the Recycling+ scenario. Furthermore, the results of the study show that currently initiated policy only partially realizes the full potential identified. A focus on highest quality use of recovered materials is essential to realize the full potential energy and CO₂ emission reduction identified for the Netherlands. Detailed economic and technical analyses of high quality recycling are recommended to further evaluate viable integrated waste management policies.     

Seasonal greenhouse gas emissions (methane, carbon dioxide, nitrous oxide) from engineered landfills: daily, intermediate, and final California cover soils

Compared with natural ecosystems and managed agricultural systems, engineered landfills represent a highly managed soil system for which there has been no systematic quantification of emissions from coexisting daily, intermediate, and final cover materials. We quantified the seasonal variability of CH, CO, and NO emissions from fresh refuse (no cover) and daily, intermediate, and final cover materials at northern and southern California landfill sites with engineered gas extraction systems. Fresh refuse fluxes (g m d [± SD]) averaged CH 0.053 (± 0.03), CO 135 (± 117), and NO 0.063 (± 0.059). Average CH emissions across all cover types and wet/dry seasons ranged over more than four orders of magnitude (<0.01-100 g m d) with most cover types, including both final covers, averaging <0.1 g m d with 10 to 40% of surface areas characterized by negative fluxes (uptake of atmospheric CH). The northern California intermediate cover (50 cm) had the highest CH fluxes. For both the intermediate (50-100 cm) and final (>200 cm) cover materials, below which methanogenesis was well established, the variability in gaseous fluxes was attributable to cover thickness, texture, density, and seasonally variable soil moisture and temperature at suboptimal conditions for CH oxidation. Thin daily covers (30 cm local soil) and fresh refuse generally had the highest CO and NO fluxes, indicating rapid onset of aerobic and semi-aerobic processes in recently buried refuse, with rates similar to soil ecosystems and windrow composting of organic waste. This study has emphasized the need for more systematic field quantification of seasonal emissions from multiple types of engineered covers.     

Economic comparison of recycling over-ordered fresh concrete: A case study approach

Recycling of construction material helps save the limited landfill space. Among various types of materials, concrete waste accounts of about 50% of the total waste generation. Current off-site practices for ready mixed concrete batching plant generate a significant quantity of fresh concrete waste through over-order from construction sites. The use of concrete reclaimer is one of the methods to reclaim these concrete wastes, which separates coarse aggregate, sand and cement from fresh concrete. Although there are some concrete producers in Hong Kong providing concrete reclaimers in their plants, they are only used to flush and dilute the cement slurry from the concrete, which will still be ultimately send all to dumping areas. The reluctance of most concrete producers in reclaiming aggregate from the concrete waste is due to its high cost of treatment and lack of space around the plant. Therefore, this paper puts forth a scheme of economical considerations in recycling over-ordered concrete by concrete reclaimer. A comparative study on costs and benefits between the current practices and the proposed recycling plan is examined. The study shows that the costs of the current practices in dumping over-ordered fresh concrete waste to landfill areas are double that of the proposed aggregate recycling plan. Therefore, the adoption of concrete reclaimer in recycling the over-ordered fresh concrete can provide a cost-effective method for the construction industry and help saving the environment.     

Management of old landfills by utilizing forest and energy industry waste flows

The lack of landfill capacity, forthcoming EU waste disposal and landfill management legislation and the use of non-renewable and energy intensive natural resources for the end-treatment of old landfills increase pressures to develop new landfill management methods. This paper considers a method for the end-management of old landfills in Finland, which is based on the utilization of forest and paper industry waste flows, wastes from paper recycling (de-inking) and wastes from forest industry energy production. Fibre clay wastes from paper mills, de-inking sludges from de-inking of recovered waste paper and incineration ash from forest industry power plants serve to substitute the use of natural clay for the building of landfill structures for closed landfills. Arguably, this method is preferable to existing practices of natural clay use for landfill building, because it (1) substitutes non-renewable natural clay, (2) consumes less energy and generates less CO2 emissions than the use of natural clay, and (3) eliminates considerable amounts of wastes from paper production, paper consumption and from forest industry energy production. Some difficulties in the application of the method are considered and the waste flow utilization is incorporated into a local forest industry recycling network.     

Use of recycled products in UK construction industry: An empirical investigation into critical impediments and strategies for improvement

Construction industry consumes about half of all material resources taken from nature, and generates a large portion of waste to landfill. A way of tackling negative environmental impacts impending from continuous material extraction and waste generation is the use of recycled materials for construction projects. However, the use of recycled materials is yet to become a commonplace in construction industry. This study evaluates the factors hampering the use of recycled products in UK construction industry as well as strategies that could be adopted to enhance its use in the industry. In order to identify the impediments and critical strategies, a two-fold methodical approach was used. An unstructured interview preceded a quantitative questionnaire survey which was used to elicit broader industry practitioners’ opinion.The study shows that designers rarely specify recycled products. This is due to lack of adequate information about quality and market availability of the products, negative perception from clients, and unexpectedly high cost of the products, despite its perceived low quality. The study suggests that a number of strategies could be adopted to promote the use of the products. These include allocation of points to the use of recycled products in sustainable design appraisal tools, governments legislative measures, improved collaboration between designers, contractors and materials suppliers, contractors involvement at earlier stage of design, improved education of the professionals about the products, and the use of tax break to influence the cost of the products. The findings of this study would therefore help policy makers, manufacturers and construction professionals to identify the factors hampering the use of recycled products for construction projects as well as the strategies that could be adopted in order to create market for the products.     

元素赋存状态的研究及其在矿产资源综合利用中的意义

元素赋存状态的研究是指研究元素在矿石中的存在状态，且尽可能对其进行定量研究的工作。目前元素赋存状态的研究手段很多，不同的矿山和企业可根据实际情况有选择地采用。我国是资源短缺型国家，元素赋存状态的研究是资源合理有效利用的关键，可以避免盲目开采对资源的浪费和经济上的损失。     

Odour-impact assessment around a landfill site from weather-type classification, complaint inventory and numerical simulation

Gases released from landfill sites into the atmosphere have the potential to cause olfactory nuisances within the surrounding communities. Landfill sites are often located over complex topography for convenience mainly related to waste disposal and environmental masking. Dispersion of odours is strongly conditioned by local atmospheric dynamics. Assessment of odour impacts needs to take into account the variability of local atmospheric dynamics. In this study, we discuss a method to assess odour impacts around a landfill site located over complex terrain in order to provide information to be used subsequently to identify management strategies to reduce olfactory nuisances in the residential neighbourhoods. A weather-type classification is defined in order to identify meteorological conditions under which olfactory nuisances are to be expected. A non-steady state Gaussian model and a full-physics meteorological model are used to predict olfactory nuisances, for both the winter and summer scenarios that lead to the majority of complaints in neighbourhoods surrounding the landfill site. Simulating representative scenarios rather than full years make a high resolution simulation of local atmospheric dynamics in space and time possible. Results underline the key role of local atmospheric dynamics in driving the dispersion of odours. The odour concentration simulated by the full-physics meteorological model is combined with the density of the population in order to calculate an average population exposure for the two scenarios. Results of this study are expected to provide helpful information to develop technical solutions for an effective management of landfill operations, which would reduce odour impacts within the surrounding communities.     

An energetic life cycle assessment of C&D waste and container glass recycling in Cape Town,South Africa

This study presents the results of a comparative life cycle assessment (LCA) on the energy requirements and greenhouse gas (GHG) emission implications of recycling construction and demolition (C&D) rubble and container glass in Cape Town, South Africa. Cape Town is a medium sized city in a developing country with a growing population and a rising middle class, two factors that are resulting in increased generation of solid waste. The City is constrained in terms of landfill space and competing demands for municipal resources.The LCA assessment was based on locally gathered data, supplemented with ecoinvent life cycle inventory data modified to the local context. The results indicated that recycling container glass instead of landfilling can achieve an energy savings of 27% and a GHG emissions savings of 37%, with a net savings still being achieved even if collection practices are varied. The C&D waste results, however, showed net savings only for certain recycling strategies. Recycling C&D waste can avoid up to 90% of the energy and GHG emissions of landfilling when processed and reused onsite but, due to great dependence on haulage distances, a net reduction of energy use and GHG emissions could not be confidently discerned for offsite recycling. It was also found that recycling glass achieves significantly greater savings of energy and emissions than recycling an equivalent mass of C&D waste.The study demonstrated that LCA provides an important tool to inform decisions on supporting recycling activities where resources are limited. It also confirmed other researchers’ observations that strict adherence to the waste management hierarchy will not always result in the best environmental outcome, and that more nuanced analysis is required. The study found that the desirability of recycling from an energy and climate perspective cannot be predicted on the basis of whether such recycling conserves a non-renewable material. However, recycling that replaces a virgin product from an energy-intensive production process appears to be more robustly beneficial than recycling that replaces a product with little embodied energy. Particular caution is needed when applying the waste management hierarchy to the latter situations.     

碳达峰碳中和目标下固体废物治理的法律因应

我国在联合国大会上提出了“2030年碳达峰2060年碳中和”的目标。为达成此目标,固体废物治理领域也需要积极作出响应。固体废物治理体系的核心是固体废物的处置。不同的固体废物处置方式有着不同的碳排放结果,填埋或焚烧方式处置所排放的温室气体量都远大于循环利用的方式。应以固体废物领域碳排放统一核算制度为基石,从推进政策实施和立法修改等的多个层面上去因应。立法面向上,《固体废物污染环境防治法》《清洁生产促进法》《循环经济促进法》乃至编纂中的“环境法典”都应当围绕减碳模式的固体废物处置方式改进和制定相关法律规范;制度建设面向上,以固体废物碳排放强制核算法律制度建设为主,通过碳排放强制核算制度规范相关主体及其权利义务关系并深度挖掘固体废物处置的碳减排潜力。     

Effect of collection system on mineral content of biowaste

The EU is committed to encourage biological treatments of organic waste as an alternative to landfill and also to enhance organic matter recycling. When these wastes are composted, the composition of the initial raw materials is very important in order to obtain a good quality product. In this article, the mineral composition of the organic fraction obtained from source-sorted collection (SC) and the organic fraction mechanically separated (MS) from mass-collected municipal solid waste was evaluated. Also, the compositions of these 2 raw materials that are used in the current Spanish municipal solid waste biological treatment facilities were compared. The mineral elements analyzed were the total content of the heavy metals Zn, Cu, Ni, Cr, Pb and Cd, and the plant nutrients P, K, Na, Ca, Mg, Fe and Mn. The results obtained were expressed on dry matter basis and on mineral matter basis. Important differences were detected between SC and MS samples, on both dry and mineral matter basis. In general, nutrient contents are higher in SC than in MS, and heavy metal contents are significantly lower in SC. Our results also support the idea that the heavy metal migration from the non-compostable materials to the decomposable matrix takes place from the beginning of the process while both types of materials are in contact.     

Municipal solid waste production and composition in Finland—Changes in the period 1960–2002 and prospects until 2020

Waste reduction was recognised as the main goal of waste management policy in the EU in the 1990s. Although knowledge of past waste generation is essential for effective waste reduction policy there are no comprehensive statistics on the past development of municipal solid waste (MSW) production. MSW management is currently under turmoil in many EU countries as the requirements of the EC landfill directive (1999/31/EC) are set into force. In this study, the production and composition of MSW in Finland between 1960 and 2002 is presented using historical data. The impact of population, affluence and technology on MSW production are analysed using the IPAT equation and three scenarios are constructed until year 2020. The results are compared with national future targets on MSW production. Production of MSW increased in Finland until 1990, declined to year 1997, increased to 2000 and then declined again. The share of organic and plastic waste increased over the study period while the share of paper and cardboard declined. The results suggest that so far national targets on MSW reduction have been set fairly low. Moreover, our scenarios depict a wide range of future MSW production, even though the time horizon is not longer than 15 years into the future. In order to narrow this range, continuous improvement of the statistics of MSW is essential.     

Techno-economic analysis and environmental impact assessment of energy recovery from Municipal Solid Waste (MSW) in Brazil

Due to the lack of appropriate policies in the last decades, 60% of Brazilian cities still dump their waste in non-regulated landfills (the remaining ones dump their trash in regulated landfills), which represent a serious environmental and social problem. The key objective of this study is to compare, from a techno-economic and environmental point of view, different alternatives to the energy recovery from the Municipal Solid Waste (MSW) generated in Brazilian cities. The environmental analysis was carried out using current data collected in Betim, a 450,000 inhabitants city that currently produces 200 tonnes of MSW/day. Four scenarios were designed, whose environmental behaviour were studied applying the Life Cycle Assessment (LCA) methodology, in accordance with the ISO 14040 and ISO 14044 standards. The results show the landfill systems as the worst waste management option and that a significant environmental savings is achieved when a wasted energy recovery is done. The best option, which presented the best performance based on considered indicators, is the direct combustion of waste as fuel for electricity generation. The study also includes a techno-economical evaluation of the options, using a developed computer simulation tool. The economic indicators of an MSW energy recovery project were calculated. The selected methodology allows to calculate the energy content of the MSW and the CH₄ generated by the landfill, the costs and incomes associated with the energy recovery, the sales of electricity and carbon credits from the Clean Development Mechanism (CDM). The studies were based on urban centres of 100,000, 500,000 and 1,000,000 inhabitants, using the MSW characteristics of the metropolitan region of Belo Horizonte. Two alternatives to recovering waste energy were analyzed: a landfill that used landfill biogas to generate electricity through generator modules and a Waste-to-Energy (WtE) facility also with electricity generation. The results show that power generation projects using landfill biogas in Brazil strongly depend on the existence of a market for emissions reduction credits. The WtE plant projects, due to its high installation, Operation and Maintenance (O&M) costs, are highly dependent on MSW treatment fees. And they still rely on an increase of three times the city taxes to become attractive.     

Waste minimisation in practice

One of the major hindrances to waste minimisation on a construction site is the difficulty in establishing a methodology and using this methodology to benchmark future construction projects. This paper introduces SMARTWaste, a software tool that has been used to audit, reduce and target waste arisings on a construction site. This tool tries to link the construction process and the waste hierarchy. That is reducing waste on a construction site rather than landfilling it. Three applications of the SMARTWaste software will be discussed using case studies from three different types of construction. An evaluation of these case studies shows that, by implementing a waste minimisation scheme on-site, you can improve material recovery for reuse. Also, by using the waste arisings as a benchmark you can reduce your waste arisings on future sites. Application of SMARTWaste or a similar waste minimisation tool on a wider basis could reduce waste arisings and could result in a built environment that consumed less natural resources and energy, and also produced less pollution and waste. Such a built environment would be environmentally and socially more responsive and responsible.     

Clean fuels from municipal solid waste for fuel cell buses in metropolitan areas

Increasing volumes of municipal solid waste (MSW) pose disposal problems for many cities. Costs are rising as landfilling becomes more difficult. The production of clean transportation fuels (methanol or hydrogen) from MSW is one economically and environmentally promising option for dealing with these problems. An attractive feature is that elimination of essentially all air pollutant emissions is inherent in the process. Current and future air emissions standards should be easily met. Methanol or hydrogen used in fuel cell vehicles (FCV) can help address problems of deteriorating urban air quality due to vehicle pollution and heavy dependence of the transport sector on imported petroleum. Buses are initial targets for commercial application of fuel cells. Coupled with FCVs, MSW could become a major transportation energy resource. For example, less than 25% of New York City's MSW supply would be sufficient to produce the methanol or hydrogen needed to fuel the entire city's bus fleet, if the buses were fuel cell powered. Estimated breakeven tipping fees required for hydrogen or methanol from MSW to compete with the cost of these fuels made from natural gas today are $52 to $89/raw tonne MSW for hydrogen and $64 to $104/raw tonne MSW for methanol (in 1991$), depending on the gasification technology considered. For comparison, the average tipping fee today in New York City is $74/tonne (1991$). Because of the high fuel economies expected for fuel cell buses, total lifecycle costs per bus-km could be lower than for conventional diesel-engine buses.     

Landfill site selection using spatial information technologies and AHP: A case study in Beijing,China

Site selection is an important and necessary issue for waste management in fast-growing regions. Because of the complexity of waste management systems, the selection of the appropriate solid waste landfill site requires consideration of multiple alternative solutions and evaluation criteria. Based on actual conditions of the study area, we considered economic factors, calculated criteria weights using the analytical hierarchy process (AHP), and built a hierarchy model for solving the solid waste landfill site-selection problem in Beijing, China. A geographic information system (GIS) was used to manipulate and present spatial data. All maps are graded from 1 (lowest suitability) to 5 (highest suitability) using spatial information technologies. The candidate sites were determined by aggregation based on the criteria weights. The candidate sites are divided by ‘best’, ‘good’ and ‘unsuitable’ landfill areas. Best landfill areas represent optimal sites; good landfill areas can be used as back-up candidate sites. Our work offers a siting methodology and provides essential support for decision-makers in the assessment of waste management problems in Beijing and other rapidly developing cities in developing countries.     

Spectroscopic and wet chemical characterization of solid waste organic matter of different age in landfill sites, southern Germany

Landfill sites are potential sources of hazardous emissions by degradation and transformation processes of waste organic matter. Its chemical composition and microbial degradability are key factors for risk management, after-care, and estimation of potential emissions. The aim of the study is to provide information about composition and extent of transformation of waste organic matter in four landfill sites in Bavaria, Southern Germany by means of (13)C NMR spectroscopy, acid-hydrolyzable carbohydrates, chloroform-methanol extractable lipids, acid-hydrolyzable proteins, and lignin compounds after CuO oxidation. Ten samples of about 20 to 25 yr, 15 to 20 yr, and 5 to 10 yr of deposition each were taken at 2 m depth intervals by grab drilling till 10-m depth. Increasing temperatures from about 15 degrees C at 2-m depth to >40 degrees C at 10-m depth are found at some of the sites, representing optimum conditions for mesophile methane bacteria. Moisture contents of 160 to 310 g kg(-1) (oven dry), however, provide limiting conditions for anaerobic biodecay. Spectroscopic and chemical variables generally indicate a low extent of biodegradation and transformation at all sites despite a considerable heterogeneity of the samples. Independent of the time and depth of deposition more than 50% of the carbohydrate fraction of the waste organic matter provide a high potential for methane emissions and on-site energy production. There was no significant accumulation of long-chain organic and aromatic compounds, and of lignin degradation products even after more than 25 yr of rotting indicating higher extent of decomposition or stabilization of the waste organic matter. Installation of seepage water cleaning and recirculation systems are recommended to increase suboptimal moisture contents with respect to microbial methanogenesis, energy production, and long-term stabilization of municipal solid waste.     

Transitions of municipal solid waste management. Part I: Scenarios of Swiss waste glass-packaging disposal

All municipal solid waste (MSW) management systems—even “high quality systems” or those employing “best practices”—face multiple challenges, e.g., decreasing prices of secondary raw materials recovered by municipalities, increasing complexity of waste composition, technological lock-ins. Policy-making involves translating these challenges into goals that are generic in nature and implementing them on MSW fractions thanks to tailor-made policy tools, e.g., anticipated disposal fees. Anticipating the impacts of policies can provide valuable insights into the adequacy of policy tools with respect to economic, political, and social contexts of MSW. The goal of this paper is to construct consistent, future scenarios of Swiss waste glass-packaging disposal based on literature and stakeholder knowledge, including the allocation of waste to different disposal routes. These scenarios are future states to which the current system could transit to due to alternative policies in line with waste policy goals and varying societal constraints (e.g., commodity prices). Results of scenario construction show that policy has a limited effect on waste glass-packaging disposal because of economic constraints, preventing goals from consistently being achieved. For instance, increases in energy prices can impede a policy favoring recycling over downcycling to foam glass, an energy-saving product. The procedure applied to construct possible scenarios suits well the ambition of considering uncertain future developments affecting MSW management as it integrates qualitative and quantitative knowledge of various sources and disciplines.     

Transport and reaction processes affecting the attenuation of landfill gas in cover soils

Methane and trace organic gases produced in landfill waste are partly oxidized in the top 40 cm of landfill cover soils under aerobic conditions. The balance between the oxidation of landfill gases and the ingress of atmospheric oxygen into the soil cover determines the attenuation of emissions of methane, chlorofluorocarbons, and hydrochlorofluorocarbons to the atmosphere. This study was conducted to investigate the effect of oxidation reactions on the overall gas transport regime and to evaluate the contributions of various gas transport processes on methane attenuation in landfill cover soils. For this purpose, a reactive transport model that includes advection and the Dusty Gas Model for simulation of multicomponent gas diffusion was used. The simulations are constrained by data from a series of counter-gradient laboratory experiments. Diffusion typically accounts for over 99% of methane emission to the atmosphere. Oxygen supply into the soil column is driven exclusively by diffusion, whereas advection outward offsets part of the diffusive contribution. In the reaction zone, methane consumption reduces the pressure gradient, further decreasing the significance of advection near the top of the column. Simulations suggest that production of water or accumulation of exopolymeric substances due to microbially mediated methane oxidation can significantly reduce diffusive fluxes. Assuming a constant rate of methane production within a landfill, reduction of the diffusive transport properties, primarily due to exopolymeric substance production, may result in reduced methane attenuation due to limited O(2) -ingress.