Chinese Landfill Research Articles

Complementary use of analytical equations and numerical models for composite liner designs

The finite element (FE) method is used to identify limitations and extend the applicability of an analytical solution for leakage through holed wrinkles in composite liners. The limiting assumption in the analytical model is relaxed based on FE results, providing a means of obtaining good agreement through the two methods over a wide spectrum of cases. Despite the flexibility of the FE, the analytical model has the advantage of readily accommodating a wide range of dimensions and material properties that, even with a very large mesh, may be difficult to analyze using FE. In addition, the analytical equation is well-suited for Monte Carlo simulation. This is illustrated by the use of the modified analytical equation and the Monte Carlo simulations to compare the performance of two types of composite liners currently approved for use in Chinese landfills with a generic design in Canada and other parts of the world. It is shown that even with a relatively small number of holed wrinkles leakage through the geomembrane composite liner can differ by up to two orders of magnitude between composite liners considered to be equivalent. The paper also notes the need to revise regulations to reflect the evolution of knowledge.

Carbon feasibility of terminating plastic waste leakage by landfill mining: A case study based on practical projects in China

Over 900 million tons (Mt) of plastic waste (PW) are disposed in Chinese landfills, posing a permanent risk of migration through environmental media. Landfill mining has emerged as a promising solution to this problem but requires incineration and a substantial energy supply for the excavation, sorting and recycling processes, which themselves exert environmental impacts, particularly on climate change. Based on the life cycle assessment of pilot-scale demonstration projects, this study investigates the carbon feasibility of landfill mining followed by several PW treatments to quantify whether terminating PW leakage from landfills will produce unaffordable greenhouse gas emissions in the drive towards carbon neutrality. The changing trend of the carbon feasibility was deduced considering the decarbonization scenarios of electricity sector and petrochemical industries. When all the sorted PW is treated by incineration with power generation, the climate-change impact of mining is 134.10 kg CO2-eq per ton of aged refuse, projected to increase by 100.47 % in 2050. To completely eliminate the PW in Chinese landfills, the incineration pathway would generate a minimum of 2457.66 Mt CO2-eq emissions, equivalent to 17.69 % of the 2020 emissions in China by carbon flow analysis. In all scenarios, the most carbon-feasible solution was mechanical recycling of high-quality PW combined with chemical recycling of low-quality PW, although the industrial application of chemical recycling technologies remains uncertain. This study provides stakeholders with systematic guidance for balancing the trade-off between PW management and climate action.

Breakthrough time assessment of liner system for MSW landfills with high leachate heads

This paper presents a design method for liner systems of municipal solid waste (MSW) landfills with high leachate heads based on the breakthrough time of an indicative contaminant (Chloride). The performance of liner systems with varying thicknesses of compacted clay liner and attenuation layer was assessed. The single composite liner consisting of a geomembrane and a 0.75-thickness compacted clay liner can meet the 50-year breakthrough time requirement of the liner system for cases with the thickness of the attenuation layer >3 m and the average height of waste HD < 60 m. The double liner system consisting of two geomembranes with one single 0.3 m-thickness compacted clay liner, as proposed in the Chinese landfill standards, cannot meet the 50-year breakthrough time requirement of the liner system, especially for large-scale landfills (e.g. HD > 60 m). The double composite liner with two composite liners consisting of a geomembrane and a 0.3 m-thickness compacted clay liner can be used for a landfill with an average height of over 60 m. Different liner systems for other cases with different average design heights of waste and the thickness of the attenuation layer were proposed. They can be easily used for MSW landfills with high leachate heads.

Improvement and optimization for the first order decay model parameters at typical municipal solid waste landfills in China

Landfill gas (LFG) generation is commonly modeled by using a first-order model. Methane generation potential (L0) and methane generation rate constant (k) are two key parameters in the first-order model. Coal-ash based default values or roughly analyzed values often used in China may not be appropriate for accurately estimating of LFG generation. In this study, seven groups of parameters were evaluated by comparing the theoretical predictions with real measurements from five Chinese landfills. The optimal approach for calculating L0 is the use of site-specific waste composition and the default values of degradable organic carbon (DOC) reported by the Chinese industry standard (CJJ133-2009), and the matching k can be adjusted by fitting and regression. The optimized average values were L0 = 67 m3 Mg−1, k = 0.06 per year for landfills in Beijing and Zhengzhou in cold–dry regions, L0 = 69 m3 Mg−1, k = 0.16 per year for landfill in Shanghai in cold–wet region, and L0 = 64 m3 Mg−1, k = 0.21 per year for landfills in Guangzhou and Shenzhen in hot–wet regions. Monte Carlo analysis showed that the uncertainty of LFG generation at closure year varied in −22.5% to 20.5%, −17.1% to 17.1% and −28.2% to 34.7% for three climatic regions, respectively. The k value is the key influencing factor, with a 95.6% contribution ratio in the hot–wet region landfill. The results provide references for future better waste management.

Performance of landfill low-permeability liners for minimizing groundwater contamination

Low-permeability liners are required at the base of municipal solid waste (MSW) landfills to minimize leachate leakage and contaminant migration into groundwater. This paper uses a two-dimensional coupled groundwater flow and contaminant transport model to examine the performance of three types of low-permeability liners specified by the current Chinese landfill standard: (1) a compacted clay liner (CCL), (2) a geomembrane (GMB) overlying a CCL, and (3) a GMB overlying a geosynthetic clay liner (GCL) on a CCL. The model simulates leachate leaking and contaminant migrating over the entire base of the landfill for the CCL and through the holed GMB wrinkles for the GMB composite liners. The performance of each type of low-permeability liners was evaluated and compared in terms of leakage rate and peak impact of chloride on the aquifer. Based on liner cases and conditions examined in this paper, the results show that the three types of low-permeability liners are not equivalent for minimizing the leakage rate and chloride impact on the aquifer. The GMB + GCL + CCL performs the best among the three low-permeability liners, and is effective for limiting the peak chloride impact on the aquifer below the acceptable level in drinking water.

An analytical model for contaminant transport in landfill liner with fluctuating leachate head

AbstractLeachate head in municipal solid waste (MSW) landfills can be very high (e.g., >10 m) in some Chinese landfills and can continuously change during the service life of the landfill. Variations of leachate head can induce time‐dependent seepage velocity changes in the liner, which may lead to a change of transport mechanisms of contaminants. An analytical model for contaminant transport through clay liner system considering the effects of leachate head variations is presented. The analytical solution is obtained using the recursive method and the Green's function approach. The proposed analytical solution is verified by numerical results. The model is then applied to investigate the effects of variable leachate head on the transport of contaminants. The results indicated that time‐dependent advection arising from leachate head variations may play a significant part when investigating contaminant transport through a clay liner. The contaminant concentrations at the bottom of the liner predicted by using fixed leachate head may be underestimated compared to the case with variable leachate heads. The bottom concentration of Pb2+ at t = 50 years for the case with HD = 60 m can be 6.6 times larger than that of the case with fixed leachate head. The mechanisms of contaminant transfer may change from a diffusion‐dominated process to an advection‐dominated process. For example, the molecular diffusion is the dominant process in Event 1 (e.g., t < 5 years with Peclet number < 1) while advection induced by the variations of leachate head may play a more important role for contaminant transport when t > 5 years. Increasing leachate head can result in an earlier breakthrough time and steady state for contaminant transport. The breakthrough time of DCM for the case with HD = 60 m can be 1.6 times lower than that for the case with fixed leachate head. Considering the effects of leachate head variations may be critical to design a more stable and reliable landfill liner.

Solidification/Stabilization of MSWI Fly Ash Using a Novel Metallurgical Slag-Based Cementitious Material

Four industrial wastes, i.e., blast furnace slag, steel slag, desulfurization ash, and phosphoric acid sludge, were used to prepare a low-carbon binder, metallurgical slag-based cementitious material (MSCM). The feasibility of solidification/stabilization of municipal solid waste incineration (MSWI) fly ashes by MSCM were evaluated, and the immobilization mechanisms of heavy metals were proposed. The MSCM paste achieved 28-day strength of 35.2 MPa, showing its high-hydration reactivity. While the fly ash content was as high as 80 wt.%, the 28-day strength of MSCM-fly ash blocks reached 2.2 MPa, and the leaching concentrations of Pb, Zn, Cr, and Hg were much lower than the limit values of the Chinese landfill standard (GB 16889-2008). The immobilization rates of each heavy metal reached 98.75–99.99%, while four kinds of MSWI fly ashes were solidified by MSWI at fly ash content of 60 wt.%. The 28-day strength of binder-fly ash blocks had an increase of 104.92–127.96% by using MSCM to replace ordinary Portland cement (OPC). Correspondingly, the lower leachability of heavy metals was achieved by using MSCM compared to OPC. The mechanisms of solidification/stabilization treatment of MSWI fly ash by MSCM were investigated by XRD, SEM, and TG-DSC. Numerous hydrates, such as calcium silicate hydrate (C-S-H), ettringite (AFt), and Friedel’s salt, were observed in hardened MSCM-fly ash pastes. Heavy metals from both MSWI fly ash and MSCM could be effectively immobilized via adsorption, cation exchange, precipitation, and physical encapsulation.

Diversity, abundance and expression of the antibiotic resistance genes in a Chinese landfill: Effect of deposit age

Landfills are the hotspots for the occurrence of antibiotic resistance genes (ARGs) in the environment. However, limited information is available on the profile of ARGs in response to the varying age of refuse in landfills. In this study, the diversity, abundance and expression of ARGs in a Chinese landfill were assessed by high-throughput quantitative PCR. A total of 154 ARGs were detected and 66% of them were transcriptionally active. The total abundance of ARG transcripts was one magnitude lower than that of ARGs. The ermT-01, tetX, sul2, aadA-02 and aadA2–03 genes were found to be the most abundant ARGs (ARG transcripts) and their sum abundance showed a linear relation with the total abundance of ARGs (ARG transcripts). The total abundance of ARGs (ARG transcripts) in young refuse was significantly higher than that in old refuse (p < 0.01) and the profile of ARGs (ARG transcripts) between the old and young refuse was distinct as revealed by the principal coordinates analysis. The variation partitioning analysis showed heavy metals (mainly Cr and Zn) were the major drivers that affect the profile of ARGs (ARG transcripts). These findings provided new insights into the ARGs in landfills and indicated their potential threats should not be neglected.

Recycled use of municipal solid waste incinerator fly ash and ferronickel slag for eco-friendly mortar through geopolymer technology

Due to the rapid urbanization and increased population, the production of municipal solid waste incineration fly ash (MSWI-FA) has become enormous and attracted attention worldwide. This study feasibly utilizes MSWI-FA as an immobilization host to co-dispose of ferronickel slag (FNS) through geopolymer technology. Due to the high content of heavy metals in MSWI-FA and FNS, the leachate of the geopolymer was tested with two leaching methods, in terms of acetic acid buffer solution method (AAM) and sulphuric acid & nitric acid method (SNM). Results showed that the leaching concentrations of heavy metal ions in geopolymers were less than the upper limit of Chinese landfill standard. For instance, the value of Cu, Zn, and Cr leachate in geopolymers are far lower than 100, 100, and 5 mg/L. Furthermore, various microstructural tests were performed to evaluate the stabilization/solidification behavior of MSWI-FA and FNS geopolymer, including electrochemical impedance spectroscopy (EIS) test, scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) test, and mercury intrusion porosimeter (MIP) test. The EIS results showed that geopolymer with the combination of 60 wt% MSWI-FA, 20 wt% ground granulated blast furnace slag (GGBS), and 20 wt% silica fume (SF) exhibited a compact and dense microstructure, which was beneficial to the physical encapsulation of heavy metal ions. The MIP result also confirmed that the capillary pore structure of geopolymer is also developed. The SEM, EDS, and XRD results showed that the C-A-S-H, Friedel's salts, and NaCl were the main hydration products in geopolymers. The C-A-S-H was capable contributed to improve the physical encapsulation of heavy metal ions. Friedel's salts were observed to adsorb heavy metal ions on its surface and had the good binding capacity of heavy metal ions. Based on these findings, the feasibility of geopolymers are confirmed, which promote the co-disposal of MSWI-FA and FNS and provide valuable information on the MSWI-FA based construction materials.

Cyclic Phenylmethylsiloxane Oligomers in Municipal Landfills and Their Elimination Mechanisms in Leachate Treatment Processes.

This study investigated some sources and elimination mechanisms of phenylmethylsiloxanes in landfill leachates. During a 20-day leaching experiment for electronic wastes collected from one Chinese landfill, significant release (4.9 ng/L to 1.3 μg/L) of cis-/trans-2,4,6-triphenyl-2,4,6-trimethylcyclotrisiloxanes (cis-P3 and trans-P3) and cis-/trans-2,4,6,8-tetraphenyl-2,4,6,8-tetramethylcyclotetrasiloxanes (cis-P4 and trans-P4a,b,c) in simulated leachates was found. From January 2017 to December 2018, P3 and P4 isomers were detected in raw leachates from active cells [<LOQ-990 ng/L, detection frequency (df) = 67-100%] and closed cells (<LOQ-282 ng/L, df = 2.1-98%) of this landfill. Generally, mean mass loads of total phenylmethylsiloxanes in raw leachates were larger in the summer (380 mg/d) and winter (295 mg/d) for active cells, while they decreased from 36.1 mg/d to <LOQ for closed cells during the entire period. During leachate treatment processes, sorption to sludge was responsible for major removal (64-84%) of phenylmethylsiloxanes, while Fenton treatment accounted for 8.5-25% removal. Simulated Fenton experiments indicated that hydroxylation half-lives of P3 (1.3-1.5 h) and P4 (0.65-0.86 h) were 15-91 times faster than their hydrolysis half-lives (22-59 h, pH 3.5). Furthermore, monohydroxylated P4 isomers with a hydroxyphenyl group had larger (3.2-3.9 times) concentrations than those with a hydroxymethyl group, meaning that a phenyl group may be more likely to be hydroxylated than a methyl group.

Simulation-based hazard management of a constructed landfill for flow slide scenario

Sanitary landfills have advantages in low investment, large treatment volume, and strong adaptability, which is now the main treatment for municipal solid waste in China. However, flow slides, which present serious threat to the safety of lives and properties, are prone to occur in Chinese landfill due to leachate mound. To achieve maximum reduction in disaster loss induced by flow slides at landfills, we preliminarily explored simulation-based hazard management of a constructed landfill for flow slides scenario. A well-calibrated in-house numerical method of smoothed particle hydrodynamics was employed to conduct hazard management of flow slides. The flow slide scenario at the landfill was firstly assessed by selecting velocity and runout of flow slides to quantify the hazard. Then, different control measures, including initiative and passive prevention and control measures, were evaluated based on the achievement of hazard assessment. The proposed frame of simulation-based hazard management of flow slides can be applied to constructed or planned landfills, which can mitigate or even prevent similar disasters.

Installation and performance of horizontal wells for dewatering at municipal solid waste landfills in China

Vertical wells are conventionally used to lower leachate levels or pressures in municipal solid waste (MSW) landfills. However, they are not always efficient or even effective, and in some circumstances retro-fitted horizontal wells represent a potential alternative. However, horizontal wells can be difficult to install and there is a lack of data on their performance. This paper describes the trial construction and operation of three horizontal wells in a landfill at Tianziling, China. The trial was used to develop an improved well installation technique, and to demonstrate the viability of the approach in a typical Chinese landfill. Three wells, between 50 m and 56 m in length, were successfully installed using an improved casing-protected directional drilling method. Average leachate flow rates of two wells were 10.66 m3/day and 3.93 m3/day, respectively. After 74 days of drainage, the maximum leachate level drawdown around the highest flow well was 2.7 m and its distance of influence was up to 50 m. Building on the experience gained at Tianziling, a wellfield comprising twelve horizontal wells having a total length of 1000 m was installed at Xingfeng landfill. After 157 days of drainage, a total volume of ~24,000 m3 leachate had been discharged and the leachate level had been lowered to near the elevation of the horizontal wells. This paper indicates the effectiveness of horizontal wells in reducing leachate level in landfills containing MSW typical of that generated in China, and gives data on installation and performance that may be useful for the design and operation of such an approach.

Experimental study of the intrinsic permeability of municipal solid waste

Changing patterns of municipal solid waste (MSW) management, for example sorting for recycling and mechanical–biological treatment (MBT), will change the nature of the residual material going to landfill and in particular its intrinsic permeability. This is an important parameter, not least because of its influence on gas and leachate flows and the ramifications for gas and leachate management. This paper reports the results of laboratory permeability tests on specimens of MSW recovered from boreholes drilled in a Chinese landfill, under both liquid and gas flow. The test results are used to assess the intrinsic permeability of the waste, and are compared with corresponding data from raw and MBT municipal solid wastes from developed countries in the context of differences in waste composition, porosity and particle size. For the Chinese waste, the intrinsic permeability decreased with depth, while at a given depth the permeability determined with gas flow was consistently larger than that determined with liquid flow. Intrinsic permeabilities determined in liquid flow showed no clear trend of variation with effective particle diameter d10, but reduced with drainable porosity (the drainable porosity, ne, being a more appropriate and useful measure than the total porosity, n). Conversely, intrinsic permeabilities determined in gas flow showed a clear decrease with decreasing d10, but no consistent variation with porosity. These differences are potentially significant in assessing the impacts and interactions between gas and liquid flows; some reasons for them are suggested.

Effect of the leachate head on the key pollutant indicator in a municipal solid waste landfill barrier system

In previous studies of municipal solid waste (MSW) landfill barrier systems, chemical oxygen demand has been found to be the key pollutant indicator when estimating the breakthrough time for. However, the leachate head in a municipal solid waste landfill can be very high (>10 m in some Chinese landfills). The key pollutant indicator could be different at different leachate heads. The leachate head will continuously change during the use of a landfill. Different pollutants have different transport characteristics in the leachate, so it is necessary to determine whether changes in the leachate head change the key pollutant indicator for identifying breakthrough in a landfill barrier system. In this study, numerical models were used to investigate transport of common leachate pollutants through four typical landfill barrier systems with different leachate heads. Chemical oxygen demand reached the breakthrough threshold before the other pollutants, irrespective of (1) the leachate head and (2) changes in the leachate head. It was therefore clear that the leachate head did not affect the selection of the key pollutant indicator for identifying breakthrough in a landfill barrier system.

Spatio-temporal estimation of landfill gas energy potential: A case study in China

Municipal solid waste (MSW) landfills are among the largest anthropogenic sources of methane. However, there are also potential sources of landfill gas (LFG), which can be used to produce energy products, meaning that the recycling of LFG has gained global attention. Scientific evaluation of spatio-temporal LFG recycling potential is necessary to accelerate the promotion of LFG utilization. However, for a big country with uneven regional development level like China, the amount of LFG that can be recycled and utilized is difficult to determine, and there has been limited research that considers variation in regional characteristics, landfill sites and technologies. Therefore, this research first used sub-regional parameter sets that embodied the MSW characteristics of different regions to calculate LFG generation in China from 1990 to 2020. Next, this research estimated the LFG recovery potential for different regions in 2020 based on analysis of LFG collection and utilization technology, including technical parameters and application in different landfill sizes. The results showed that LFG generation in China will reach peak value around 2019 (3.49 billion N m3 of methane), and decrease quickly after that. The quantity of LFG with the utilization condition in 2020 will be 3.30 billion N m3, which could produce 7.39 billion kW h of electricity or 1.70 billion N m3 of bio natural gas. This could substitute 85.5% of electricity consumption or 25.3% of natural gas consumption in the transportation sector in 2014 (8.63 billion kW h and 6.74 billion N m3 respectively). Moreover, the findings show that the peak in LFG generation and a massive closure period of Chinese landfills will coincide. This will provide an opportunity to promote LFG utilization during the closed field management of landfills. Overall, LFG recycling presents a strong opportunity, and is in urgent need of promotion policies.

Biochemical, hydrological and mechanical behaviors of high food waste content MSW landfill: Liquid-gas interactions observed from a large-scale experiment

The high food waste content (HFWC) MSW at a landfill has the characteristics of rapid hydrolysis process, large leachate production rate and fast gas generation. The liquid-gas interactions at HFWC-MSW landfills are prominent and complex, and still remain significant challenges. This paper focuses on the liquid-gas interactions of HFWC-MSW observed from a large-scale bioreactor landfill experiment (5m×5m×7.5m). Based on the connected and quantitative analyses on the experimental observations, the following findings were obtained: (1) The high leachate level observed at Chinese landfills was attributed to the combined contribution from the great quantity of self-released leachate, waste compression and gas entrapped underwater. The contribution from gas entrapped underwater was estimated to be 21–28% of the total leachate level. (2) The gas entrapped underwater resulted in a reduction of hydraulic conductivity, decreasing by one order with an increase in gas content from 13% to 21%. (3) The “breakthrough value” in the gas accumulation zone was up to 11kPa greater than the pore liquid pressure. The increase of the breakthrough value was associated with the decrease of void porosity induced by surcharge loading. (4) The self-released leachate from HFWC-MSW was estimated to contribute to over 30% of the leachate production at landfills in Southern China. The drainage of leachate with a high organic loading in the rapid hydrolysis stage would lead to a loss of landfill gas (LFG) potential of 13%. Based on the above findings, an improved method considering the quantity of self-released leachate was proposed for the prediction of leachate production at HFWC-MSW landfills. In addition, a three-dimensional drainage system was proposed to drawdown the high leachate level and hence to improve the slope stability of a landfill, reduce the hydraulic head on a bottom liner and increase the collection efficiency for LFG.

Archaeal community diversity in municipal waste landfill sites.

Despite the pivotal role of archaea in methane production in landfills, the identity, ecology, and functional diversity of these microorganisms and their link to environmental factors remain largely unknown. We collected 11 landfill leachate samples from six geographically distinct landfills of different ages in China and analyzed the archaeal community by bar-coded 454 pyrosequencing. We retrieved 121,797 sequences from a total of 167,583 sequences (average length of 464 bp). The archaeal community was geographically structured, and nonabundant taxa primarily contributed to the observed dissimilarities. Canonical correlation analysis (CCA) suggested that the total phosphorous (TP), nitrate, and conductivity are important drivers for shaping the archaeal community. The hydrogenotrophic methanogens Methanomicrobiales and Methanobacteriales greatly dominated 9 of 11 samples, ranging from 83.7 to 99.5 %. These methanogens also dominated the remaining two samples, accounting for 70.3 and 58.8 %, respectively. Interestingly, for all of the studied Chinese landfills, 16S rRNA analysis indicated the predominance of hydrogenotrophic methanogens.

Dependence of Gas Collection Efficiency on Leachate Level at Wet Municipal Solid Waste Landfills and Its Improvement Methods in China

Landfill gas (LFG) collection efficiency is low at many municipal solid waste (MSW) landfills in China. The relevant mechanism and potential solution for this problem are studied through laboratory gas permeability tests on MSW, field LFG extraction tests at a landfill subjected to leachate drawdown, numerical assessment of the LFG collection efficiency at the landfill with different leachate levels, and engineering application of the measures to improve LFG collection. The research work outcomes are as follows: High water content in the food-rich MSW is one of the major reasons causing the high leachate level at many Chinese landfills. High leachate mounds tend to result in a high degree of saturation in waste, and hence a low gas permeability of the waste. Therefore, the LFG collection efficiency at Chinese landfills with high leachate level is lower than expected. A drawdown of leachate level at a Chinese landfill by pumping resulted in a significant increase in the LFG collection rate and the influence radius of LFG extraction wells. The dependence of LFG collection efficiency on the leachate level relative to the total waste thickness was verified and quantified. The leachate level is suggested to be controlled to less than 30% of the total waste thickness to achieve a high LFG collection efficiency. Engineering application at a Chinese landfill indicated that the retrofitted facilities, including deep vertical wells and horizontal drainage trenches, were effective in lowering high leachate level. The drawdown of leachate level resulted in an increase of LFG collection efficiency from 10–20 to 60–90%.

Assessing the performance of gas collection systems in select Chinese landfills according to the LandGEM model: drawbacks and potential direction

In China, municipal solid waste (MSW) is primarily treated by landfilling. Landfill gas (LFG) collection effectively reduces methane emission from MSW landfills. An accurate system of LFG collection is important in landfill planning, design, and operation. However, China has not developed such systems. In this study, the efficiency of methane collection is calculated in three Chinese landfills with different collection systems (A: vertical wells for MSW before 2010; combined horizontal trenches and under-membrane pipes for MSW from 2011 onwards; B: combined horizontal trenches and vertical wells; C: vertical wells only). This efficiency was computed by dividing the quantity of methane obtained from landfill operation records by the quantity estimated based on the LandGEM model. Results show that the collection efficiencies of landfills with vertical wells and/or horizontal pipes ranged from 8.3% to 27.9%, whereas those of a system equipped with geomembrane reached 65.3%. The poor performance of the landfills was attributed to the open burning of early-stage LFG, LFG release from cracks in high-density polyethylene covers, and high levels of leachate within a landfill site. Therefore, this study proposes an integrated LFG collection system that can remove leachate and collect gas from landfills that accept waste with high moisture content.

Overview on LFG projects in China

Since the first landfill gas (LFG) power plant in China was built in 1998, by now more than 10 years have passed. In this period the LFG utilization process has progressed greatly in China. An overall review of the process is presented in this paper, which includes the background of policies, the information about the approval procedure of LFG projects, and the theoretical methods used to estimate the amount of LFG’s generation. Detailed analysis on the project practice, such as LFG collection techniques, LFG utilization condition in China, is made. According to statistic data, before the end of 2008, 26 LFG power projects have been built and put into operation with total power capacity around 56.8 MW, and 2.234 million tons of carbon dioxide equivalent abatement has been achieved annually by all of these LFG projects. The future of LFG industry in China is expected that there is still considerable developing space for LFG utilization in the near coming years, however after 2012, the progress speed may slow down because of some adverse aspects, such as available landfill resource becomes scarce, new laws implemented in China might exclude Chinese landfills from future CDM activities, etc.