Forest products decomposition in municipal solid waste landfills

Evaluation of greenhouse gas emission and reduction potential of high-food-waste-content municipal solid waste landfills: A case study of a landfill in the east of China

This study proposes a comprehensive evaluation method based on a two-stage model to assess greenhouse gas (GHG) emissions and reductions in high-food-waste-content (HFWC) municipal solid waste (MSW) landfills. The proposed method considers typical processes such as fugitive landfill gas (LFG), LFG collection, flaring, power generation, and leachate treatment. A case study of an HFWC MSW landfill in eastern China is considered to illustrate the evaluation. The findings revealed that the GHG emissions equivalent of the case landfill amounted to 21.23 million tons from 2007 to 2022, averaging 1.03 tons CO2-eq per ton of MSW. There was a potential underestimation of LFG generation at the landfill site during the initial stages, which led to delayed LFG collection and substantial fugitive LFG emissions. Additionally, the time distribution of GHG emissions from HFWC MSW was significantly different from that of low-food-waste-content (LFWC) MSW landfills, with peak emissions occurring much earlier. Owing to the rapid degradation characteristics of HFWC MSW, the cumulative LFG production of the landfill by 2022 (2 years after the final cover) was projected to reach 77 % of the total LFG potential. In contrast, it would take until 2030 for LFWC MSW landfills to reach this level. Furthermore, various scenarios were analyzed, in which if the rapid LFG generation characteristics of HFWC MSW are known in advance, and relevant facilities are constructed ahead of time, the collection efficiency can be improved from 31 % to over 78 %, resulting in less GHG emissions.

Semi-quantitative study on the secondary compression characteristics of municipal solid waste in aerobic and anaerobic bioreactors

Aeration plays a crucial role in accelerating the secondary compression of municipal solid waste (MSW) for the scientific implementation of aerobic bioreactor technology. There are few comparative reports on the secondary compaction characteristics of MSW in aerobic and anaerobic bioreactors. In this study, six long-term compression tests were conducted to analyze the impact of aeration on MSW compression characteristics, considering two degradation conditions (i.e. aerobic and anaerobic conditions) and three overburden stresses (i.e. 30, 50 and 100 kPa). Model-fitting analysis was employed to examine the data from the tests and exiting literatures. The results showed that aeration effectively increased the rate of secondary compression, and slightly enhanced the steady-state secondary compression strain. In addition, these enhancements tended to decrease with increasing stresses. The increment ratio of the secondary compression rate constant (Rk) was concentrated in the range of 25 % to 100 %, and increases with the increase of aeration rate. The increment ratio of the steady-state secondary compression strain (Rε) ranged from 10 % to 90 %, for the MSW with higher content of paper and wood exhibited higher Rε. The advance ratio of the secondary compression stabilization time (Rt) fell within the range of 20-50 %, and Rt is higher when the moisture content is in the range of 50-65 %. These findings provide valuable guidance on the accelerated stabilization in aerobic bioreactors, providing practical references for the application of aerobic technology to informal landfills.

Discussion on key issues of carbon footprint accounting for bast fiber textiles

Bast fiber textiles have become increasingly popular as a sustainable alternative in recent years. Although the carbon emissions of bast fiber textiles have been studied using life cycle assessment method, there is a lack of comprehensive literature analyzing and summarizing the results. This study reviews the current state of research on the carbon emissions of bast fiber textiles. Compared to other plant fibers, there are fewer studies on the carbon footprint or life cycle assessment of bast fiber textiles, and these studies lack a comprehensive "cradle to grave" or "gate to grave" analysis. In addition, inconsistencies exist in the allocation methods used for carbon footprint assessments. This study suggests a combination of physical and economic allocation to conduct a more accurate environmental impact assessment of bast fiber textiles. On the basis of the above review, this study modularizes the process of the entire life cycle of textiles and analyzes the carbon sequestration and emission characteristics to determine the main considerations for carbon footprint assessment. The carbon sequestration effect of bast fiber textiles should be analyzed at the raw material extraction stage and at the end-of-life stage. Oxygen release and consumption are also considered as additional factors to be quantified and analyzed in this study. In the future, the modular method should be used for all carbon footprint evaluation reports for bast fiber textiles. This method helps to comprehensively quantify and evaluate the carbon footprint of bast fiber textiles throughout their entire life cycle. It can provide recommendations for green design, green production and sustainable consumption.

Metagenomic analysis unveils the underexplored roles of prokaryotic viruses in a full-scale landfill leachate treatment plant

Enormous viral populations have been identified in activated sludge systems, but their ecological and biochemical roles in landfill leachate treatment plants remain poorly understood. To address this knowledge gap, we conducted an in-depth analysis using 36 metagenomic datasets that we collected and sequenced during a half-year time-series sampling campaign at six sites in a full-scale landfill leachate treatment plant (LLTP), elucidating viral distribution, virus‒host dynamics, virus-encoded auxiliary metabolic genes (AMGs), and viral contributions to the spread of virulence and antibiotic resistance genes. Our findings demonstrated that viral and prokaryotic communities differed widely among different treatment units, with stability over time. LLTP viruses were linked to various prokaryotic hosts, spanning 35 bacterial phyla and one archaeal phylum, which included the core microbes involved in biological treatments, as well as some of the less well-characterized microbial dark matter phyla. By encoding 2364 auxiliary metabolic genes (AMGs), viruses harbored the potential to regulate microbial nucleotide metabolism, facilitate the biodegradation of complex organic matter, and enhance flocculation and settling in biological treatment plants. The abundance distribution of AMGs varied considerably across treatment units and showed a lifestyle-dependent pattern with temperate virus-associated AMGs exhibiting a higher average abundance in downstream biological treatment units and effluent water. Meanwhile, temperate viruses tended to carry a higher load of virulence factor genes (VFGs), antibiotic resistance genes (ARGs), and biotic and metal resistance genes (BMRGs), and engaged in more frequent gene exchanges with prokaryotes than lytic viruses, thus acting as a pivotal contributor to the dissemination of pathogenicity and resistance genes in downstream LLTP units. This study provided a comprehensive profile of viral and prokaryotic communities in the LLTP and unveiled the varying roles of different-lifestyle viruses in biochemical processes and water quality safety.

Effect of increased temperature and leachate recirculation on biogas production and settlement of municipal solid waste

This study evaluated the effects of increased temperature and leachate recirculation on volatile solids (VS), biogas, hydrogen sulphide (H₂S) leachate quality (pH and chemical oxygen demand) and the settlement of municipal solid waste (MSW). Three large-scale tests were conducted with no leachate recirculation at 21°C, weekly leachate recirculation at 20°C and weekly leachate recirculation at 50°C. Leachate recirculation and increased temperature accelerated biodegradation and pushed forward the onset time (from 27 to 8 days). The increase of biodegradation activity was reflected in the change of biogas production, VS and settlement. Compressibility index Cc, increased from 0.71 and 0.77 at 21°C to 0.83 when the temperature was 50°C. In addition, leachate recirculation and high temperature reduced H₂S concentration levels by inhibiting the growth of sulphate-reducing bacteria and leachate recirculation lowered H₂S production by dissolving the high H₂S presence. The results showed that MSW can have significantly changed mechanical and biochemical behaviour under different temperatures and saturations. The results help understand the processes in landfills for more effective short-term and long-term design and management.

Biogas production from the landfilled easily degradable fraction of municipal solid waste: mining strategy for energy recovery

The growing demand for space and financial resources to manage current and new municipal solid waste (MSW) landfills has become a massive challenge for several countries. Additionally, landfills contribute to adverse environmental impacts such as pollution and CO2 (carbon dioxide) and CH4 (methane) emissions. This paper has analyzed the possibility of producing biogas from landfilled MSW. An easily degradable fraction of landfilled MSW with 8 years of landfilling was mined and subjected to chemical characterization and elemental composition analysis. The abbreviation for the study sample was called ED8 - Mined. The low values of lignin (24.5%) and nitrogen content (0.7%) and high values of holocellulose (75.9%) and C/N (46.1%) on dry basis were obtained resulting in materials with the potential to be used for biogas generation. Recalcitrant materials were found in greater amounts than easily biodegradable fresh MSW fractions. The reuse of energy from landfilled MSW can contribute positively to the country's environment and economy, reducing environmental liabilities and generating energy in a controlled way. In Delta A Sanitary Landfill, Southeastern Brazil, the recovery of the ED8 - Mined would reflect a significant recovery of about 100,000 tonnes of landfilled materials for annual MSW cells of about 450,000 tonnes, allowing recovery of materials and space expansion for rejects.

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Bacterial Community Structure and Predicted Metabolic Function of Landfilled Municipal Solid Waste in China

The biodegradation behavior of municipal solid waste (MSW) depends on the diversity and metabolic function of bacterial communities, which are affected by environmental factors. However, the diversity of the bacterial communities and metabolic functions in MSW, as well as their influencing factors, remain unclear. In deep-aged MSW, the abovementioned deficiencies are more significant, and will effectively hamper landfill disposal. In this study, high-throughput sequencing was performed to examine the bacterial community structure and metabolic function from depths of 10 m to 40 m, of two large MSW landfills on the southeast coast of China. Thermotogota (1.6–32.0%), Firmicutes (44.2–77.1%), and Bacteroidota (4.0–34.3%) were the three dominant phyla among the 39 bacterial phyla identified in aged MSW samples. Bacterial genera associated with the degradation of many macromolecules, e.g., Defluviitoga, Hydrogenispora, and Lentimicrobium were abundantly detected in MSW samples, even in aged MSW. Redundancy analysis (RDA) showed that bacterial diversity in the landfills was most strongly correlated with electrical conductivity, age, and moisture content of the MSW. Tax4fun2 analysis predicted that there were abundant metabolism functions in aged MSW, especially functional enzymes (e.g., glycine dehydrogenase and cellulase) related to amino acids and cellulose degradation. This study increases our understanding of the bacterial diversity and functional characteristics in landfilled MSW.

Recycling Paper-Plastic laminate coffee cups using a Single-Disk Refiner: Energy requirements and recovered fiber quality

Over 64 billion paper-plastic laminate (PPL) coffee cups are consumed between the United States and Canada annually, the majority accumulating in landfills due to a hydrophobic plastic inner-lining. Recycling can mitigate environmental damage and provide economic value from repurposed products. We found that standard repulping methods were insufficient to separate fiber from plastic due to the low intensity of treatment. To increase process intensity, we mechanically refined shredded PPL coffee cups and Kraft eucalyptus sheets (control) at 2%, 3%, and 4% consistencies with three passes to determine the energy required to separate fibers from plastic and the effects on fiber quality. 2% and 3% consistency PPL cups measured under 40 kWh/tonne of input material for one refiner pass and ∼ 80 kWh/tonne for 4% consistency PPL cups. Recovered fiber fraction totaled 87.7%, 85.3%, and 80.5% of input mass of Kraft eucalyptus and 72.3%, 72.6%, and 79.6% of input mass of PPL cups at 2%, 3%, and 4% consistency, respectively. Fines content of PPL cups jumped from 8% pre-refining to ∼ 30% post-refining while Kraft eucalyptus fibers were unaffected, suggesting that breaking the plastic-fiber bonds results in fines generation. Mean fiber length of PPL cups slightly decreased with consistency and tensile strength improved. Freeness decreased with consistency only in PPL cup samples. These results demonstrate a low energy requirement to effectively separate fiber and plastics in PPL cups as well as minimal impact on fiber quality using existing refining technology, and provides an estimate of the financial costs of local recycling efforts.

Numerical Model of Leachate Recirculation in Bioreactor Landfills with High Kitchen Waste Content

Surface spraying, horizontal trenches, and vertical wells are the most common leachate recirculation system used at landfills in engineering practice. In order to quantify the efficiency of the three aforementioned recirculation systems, a hydro–biochem–mechanical-coupled model was developed in the present work, which can describe hydrodynamic and biochemical behaviors in food-waste-rich landfills. A typical landfill cell was modeled in COMSOL. The results indicate that leachate recirculation can accelerate the decomposition of municipal solid waste (MSW) with food-rich waste content, relieving acidification, improving gas generation efficiency, and consequently, increasing the early settlement in landfills.

In Situ Characterization of Municipal Solid Waste Using Membrane Interface Probe (MIP) and Hydraulic Profiling Tool (HPT) in an Active and Closed Landfill

Municipal solid waste (MSW) landfills near a metropolitan area are renewable energy resources to produce heat and methane that can generate electricity. However, it is difficult to use those sources productively because disposed MSW in landfills are spatially and temporally heterogeneous. Regarding the prediction of the sources, the analysis of in situ MSW properties is an alternative way to reduce the uncertainty and to understand complex processes undergoing in the landfill effectively. A hydraulic profiling tool (HPT) and membrane interface probe (MIP) test measures the continuous profile of MSW properties with depth, including hydraulic pressure, temperature, electrical conductivity (EC), and the relative concentration of methane at the field. In this study, we conducted a series of the tests to investigate the MSW characteristics of active and closed landfills. MIP results showed that the methane existed closer to right below the top cover in the active landfill and several peak concentrations at different layers of the closed landfill. As the depth and age of the waste increased, the hydraulic pressure increased for both landfills. The average EC results showed that the electrical conductivity decreased with the landfill age. The results of hydraulic properties, temperature, and EC obtained from active and closed sites could be used to estimate the waste age and help designing energy recovery systems.

Temporally-differentiated biogenic carbon accounting of wood building product life cycles

Although standards have identified temporary carbon storage as an important element to consider in wood product LCAs, there has been no consensus on a methodology for its accounting. This work aims to improve the accounting of carbon storage and fluxes in long-life wood products in LCA. Biogenic carbon from harvested roundwood logs were tracked using the Carbon Budget Model Framework for Harvested Wood Products (CBMF-HWP). Carbon flows through wood product manufacturing, building life and end-of-life phases, and carbon stocks and fluxes from harvest to the atmosphere were estimated. To cover the products commonly used in the Canadian building industry, a range of softwood products types, provinces and territories and building lifetimes were considered. In addition, policy scenarios were considered in order to model the effects of dynamic parameters through time as a policy target is reached. Most wood products have similar emissions profiles, though cross-laminated timber has higher sawmill emissions and oriented-strand board has higher initial post-demolition emissions. The region of construction is also predictive of the initial post-demolition emissions. Higher recycling rates shift materials from landfills into subsequent product systems, thus avoiding landfill emissions. Landfill decay rates are affected by climate and results in a large range of landfill emissions. The degree of postponement of end-of-life emissions is highly dependent upon the wood product type, region and building lifespan parameters. This work develops biogenic carbon profiles that allows for modelling dynamic cradle-to-grave LCAs of Canadian wood products.

The Evaluation System of the Sustainable Development of Municipal Solid Waste Landfills and Its Application

Improving the understanding of the stabilization process is of great significance to guide the sustainable development of municipal solid waste (MSW) landfills. An evaluation system of the stabilization process of MSW landfills has been established. The indices of the evaluation system involve the degradation degree of MSW, the release of landfill gas production potential, and the settlement of landfills. Based on the biochemical-consolidation-solute migration coupled model, an evaluation method of the MSW landfill stabilization process is proposed by combining field tests with numerical simulation. The stabilization process of the Jiangcungou landfill in China is investigated by using the proposed method. The analyzed results show that the stabilization process of high kitchen waste content landfills can be divided into three stages, which is different from the stabilization process of landfills in developed countries. For the Jiangcungou landfill, the ratio of cellulose to lignin in MSW decreases rapidly during the fast degradation stage when obvious settlement occurs. During the slow degradation stage, the hydrolysis rate is slow and settlement develops slowly. When the landfill reaches the stabilization stage, the ratio of cellulose to lignin of MSW changes very slowly; most of the landfill gas potential has been released; the settlement stabilization is completed basically. The change processes of the three evaluation indices are different, of which the degradation stabilization index is the main one. According to the findings above, leachate recirculation is recommended to adjust the degradation environment in the landfill, which can be helpful to avoid acidification at the fast degradation stage. Temporary cover is suggested to improve landfill gas collection efficiency at the beginning of the stable methanogenic stage. The landfill site closure should be operated when the settlement rate is low.

Application of enzymatic and bacterial biodelignification systems for enhanced breakdown of model lignocellulosic wastes

This paper explores the extent to which enzymatic and bacterial biodelignification systems can breakdown lignocellulose in model wastes to potentially enhance biogas generation. Two representative lignocellulosic wastes (newspaper and softwood) commonly found largely undegraded in old landfills were used. A fungal peroxidase (lignin peroxidase) enzyme and a recently isolated lignin-degrading bacterial strain (Agrobacterium sp.) were used. Tests were conducted in stirred bioreactors with methanogens from sewage sludge added to produce biogas from breakdown products. Addition of lignin peroxidase resulted in ~20% enhancement in cumulative methane produced in newspaper reactors. It had a negative effect on wood. Agrobacterium sp. strain enhanced biodegradation of both wood (~20% higher release of soluble organic carbon and enhanced breakdown) and newspaper (~2-fold biogas yield). The findings of this paper have important implications for enhanced breakdown in old landfills that are rich in these wastes, and anaerobic operations utilising lignocellulosic wastes for higher degradation efficiencies and biogas production.

Carbonation is affecting biodegradability testing of fiber cement composites

Fiber cement composites (FCCs) containing natural cellulosic fibres are emerging materials in the building industry. At the end of life, FCCs are often disposed of as part of the C&DW in a landfill. The production of landfill gasses in landfills needs to be kept as low as possible. Generally, leaching of total dissolved organic carbon (DOC) is used as a proxy for the biodegradability of a waste material and the subsequent production of landfill gasses, and is, therefore, used to evaluate biodegradability of waste. In this study, FCC samples with varying average diameter and varying age were subjected to both a batch leaching test (determine DOC leaching) and to a standardized biodegradability test. The batch leaching showed that the DOC leaching ranged between 520 and 1300 mg kg^-1 for the tested samples, and that leaching of DOC decreases with increasing particle diameter and with increasing effects of ageing. Yet, the biodegradability results indicated that the leaching of DOC from FCCs does not result in the release of landfill gasses. This study hypothises that the DOC that leaches from the FCCs is being degraded to CO₂, but that the formed CO₂ is immediately captured by the material itself through the process of carbonation. An inpermeable layer is formed around the material that stops further leaching of DOC. The results of this study therefore suggest that leaching of DOC is a poor indicator for the biodegradability of FCCs.

Conventional and fourier transform infrared characterization of waste and leachate during municipal solid waste stabilization

Solid waste and leachate samples from bench-scale anaerobic bioreactors and flushing bioreactors (FBs), containing mature waste were characterized using Fourier Transform Infrared Spectroscopy (FTIR) to provide a better understanding of the changes in waste characteristics when waste transitions from mature to stabilized. Humic acid (HA) extracted from mature waste and waste removed from the FBs were characterized using FTIR and ¹³C nuclear magnetic resonance. FBs were operated under three different treatment scenarios (flushing with clean water, recirculation of leachate treated by chemical oxidation, and recirculation of leachate treated by chemical oxidation with waste aeration. FTIR spectra of FB waste and leachate supported the stabilization of waste that occurred after the additional treatment. There was a shift in the dominance of organic to inorganic functional groups when compared to changes in conventional parameters that aligned with published values on waste stability. HA extracted from the mature waste were dominated by aliphatic carbon and aromatic carbon was less intense. Treatment by flushing resulted in a decrease in aliphatic carbon and an increase in aromatic carbon. HA extracted from reactors with oxidized leachate recirculation and aeration decreased in aliphatic carbon content, with minimal change in aromatic carbon. Therefore, the additional treatment did not result in an increase in the reactivity potential of the HA which aligns with FTIR and principal component analysis. Results suggest that spectroscopic techniques could be used to assess the stability of waste samples as opposed to more time-consuming analyses.

Improving understanding of carbon storage in wood in landfills: Evidence from reactor studies

Approximately 1.5 million tonnes (Mt) of wood waste are disposed of in Australian landfills annually. Recent studies have suggested that anaerobic decay levels of wood in landfills are low, although knowledge of the decay of individual wood species is limited. The objective of this study was to establish the extent of carbon loss for wood species of commercial importance in Australia including radiata pine, blackbutt, spotted gum and mountain ash. Experiments were conducted under laboratory conditions designed to simulate optimal anaerobic biodegradation in a landfill. Bacterial degradation, identified by both light microscopy and electron microscopy, occurred to a varying degree in mountain ash and spotted gum wood. Fungal decay was not observed in any wood samples. Mountain ash, the species with the highest methane yield (20.9 mL CH₄/g) also had the highest holocellulose content and the lowest acid-insoluble lignin and extractive content. As the decay levels for untreated radiata pine were very low, it was not possible to determine whether impregnation of radiata pine with chemical preservatives had any impact on decay. Carbon losses estimated from gas generation were below 5% for all species tested. Carbon losses as estimated by gas generation were lower than those derived by mass balance in most reactors, suggesting that mass loss does not necessarily equate to carbon emissions. There was no statistical difference between decay of blackbutt derived from plantation and older, natural forests. Addition of paper as an easily digestible feedstock did not increase carbon loss for the two wood species tested and the presence of radiata pine had an inhibitory effect on copy paper decay. Although differences between some of the wood types were found to be statistically significant, these differences were detected for wood with carbon losses that did not exceed 5%. The suggested factor for carbon loss for wood in landfills in Australia is 1.4%. This study confirms that disposal of wood in landfills in Australia results in long-term storage of carbon, with only minimal conversion of carbon to gaseous end products.

Intergovernmental panel on climate change's landfill methane protocol: Reviewing 20 years of application

The Intergovernmental Panel on Climate Change (IPCC) protocol for predicting national methane emission inventories from landfills was published 22 years ago in the 1996 Revised Guidelines. There currently exists a broad dataset to review landfill parameters and reported values and their appropriateness in use and application in a range of site-specific, regional, and national estimates. Degradable organic carbon (DOC) content was found to range from 0.0105 to 0.65 g C/g waste, with an average of 0.166 g C/g waste. The fraction of DOC that would anaerobically degrade (DOC _f) was reported to range from 50-83%, whereas higher and lower values have been experimentally determined for a variety of waste components, such as wood (0-50%) and food waste (50-75%). Where field validation occurred for the methane correction factor, values were substantially lower than defaults. The fraction of methane in anaerobic landfill gas ( F) default of 50% is almost universally applied and is appropriate for cellulosic wastes. The methane generation rate constant ( k) varied widely from 0.01 to 0.51 y^-1, representing half-lives from 1 to 69 years. Methane oxidation (OX) default values of 0 and 10% may be valid, but values greater than 30% have been reported for porous covers at managed sites. The IPCC protocol is a practical tool with uncertainties and limitations that must be addressed when used for purposes other than developing inventories.

Case study comparison of functional vs. organic stability approaches for assessing threat potential at closed landfills in the USA

Municipal solid waste (MSW) landfills in the USA are regulated under Subtitle D of the Resource Conservation and Recovery Act (RCRA), which includes the requirement to protect human health and the environment (HHE) during the post-closure care (PCC) period. Several approaches have been published for assessment of potential threats to HHE. These approaches can be broadly divided into organic stabilization, which establishes an inert waste mass as the ultimate objective, and functional stability, which considers long-term emissions in the context of minimizing threats to HHE in the absence of active controls. The objective of this research was to conduct a case study evaluation of a closed MSW landfill using long-term data on landfill gas (LFG) production, leachate quality, site geology, and solids decomposition. Evaluations based on both functional and organic stability criteria were compared. The results showed that longer periods of LFG and leachate management would be required using organic stability criteria relative to an approach based on functional stability. These findings highlight the somewhat arbitrary and overly stringent nature of assigning universal stability criteria without due consideration of the landfill's hydrogeologic setting and potential environmental receptors. This supports previous studies that advocated for transition to a passive or inactive control stage based on a performance-based functional stability framework as a defensible mechanism for optimizing and ending regulatory PCC.

Methods for determining the methane generation potential and methane generation rate constant for the FOD model: a review

In the first order decay (FOD) model of landfill methane generation, the methane generation potential ( L₀) and methane generation rate constant ( k) for both bulk municipal solid waste (MSW) and individual waste components have been determined by a variety of approaches throughout various literature. Differences in the determination methods for L₀ and k are related to differences in our understanding of the waste decomposition dynamics. A thorough understanding of the various available methods for determining L₀ and k values is critical for comparative study and the drawing of valid conclusions. The aim of this paper is to review the literature on the available determining methods and the ranges for L₀ and k values of both bulk MSW and individual waste components, while focusing on understanding the decomposition of waste, including the role of lignin. L₀ estimates in the literature are highly variable and have been derived from theoretical stoichiometric calculations, laboratory experiments, or actual field measurements. The lignin concentration in waste is correlated with the fraction of total degradable organic carbon (DOC_f) that will actually anaerobically degrade in the landfill. The k value has been determined by precipitation rates, laboratory simulations, aged-defined waste sample, and model fitting or regression analysis using actual gas data. However, the lignin concentration does not correlate well with the k value, presumably due to the impact of lignin arrangement and structure on cellulose bioavailability and degradation rate. In sum, this review summarizes the literature on the measurement of L₀ and k values, including the dynamics and decomposition of bulk MSW and individual waste components within landfills.

Wood waste decomposition in landfills: An assessment of current knowledge and implications for emissions reporting

Large quantities of wood products have historically been disposed of in landfills. The fate of this vast pool of carbon plays an important role in national carbon balances and accurate emission reporting. The Republic of Ireland, like many EU countries, utilises the 2006 Intergovernmental Panel on Climate Change (IPCC) guidelines for greenhouse gas reporting in the waste sector, which provides default factors for emissions estimation. For wood products, the release of carbon is directly proportional to the decomposition of the degradable organic carbon fraction of the product, for which the IPCC provides a value of 0.5 (50%). However, in situ analytic results of the decomposition rates of carbon in landfilled wood do not corroborate this figure; suggesting that carbon emissions are likely overestimated. To assess the impact of this overestimation on emission reporting, carbon decomposition values obtained from literature and the IPCC default factor were applied to the Irish wood fraction of landfilled waste for the years 1957-2016 and compared. Univariate analysis found a statistically significant difference between carbon (methane) emissions calculated using the IPCC default factor and decomposition factors from direct measurements for softwoods (F = 45.362, p = <.001), hardwoods (F = 20.691, p = <.001) and engineered wood products (U = 4.726, p = <.001). However, there was no significant difference between emissions calculated using only the in situ analytic decomposition factors, regardless of time in landfill, location or subsequently, climate. This suggests that methane emissions from the wood fraction of landfilled waste in Ireland could be drastically overestimated; potentially by a factor of 56. The results of this study highlight the implications of emission reporting at a lower tierand prompts further research into the decomposition of wood products in landfills at a national level.

A high-performance protocol for extraction of microplastics in fish

So far, several classes of digesting solutions have been employed to extract microplastics (MPs) from biological matrices. However, the performance of digesting solutions across different temperatures has never been systematically investigated. In the first phase of the present study, we measured the efficiency of different oxidative agents (NaClO or H₂O₂), bases (NaOH or KOH), and acids [HCl or HNO₃; concentrated and diluted (5%)] in digesting fish tissues at room temperature (RT, 25°C), 40, 50, or 60°C. In the second phase, the treatments that were efficient in digesting the biological materials (>95%) were evaluated for their compatibility with eight major plastic polymers (assessed through recovery rate, Raman spectroscopy analysis, and morphological changes). Among the tested solutions, NaClO, NaOH, and diluted acids did not result in a satisfactory digestion efficiency at any of the temperatures. The H₂O₂ treatment at 50°C efficiently digested the biological materials, although it decreased the recovery rate of nylon-6 (NY6) and nylon-66 (NY66) and altered the colour of polyethylene terephthalate (PET) fragments. Similarly, concentrated HCl and HNO₃ treatments at RT fully digested the fish tissues, but also fully dissolved NY6 and NY66, and reduced the recovery rate of most or all of the polymers, respectively. Potassium hydroxide solution fully eliminated the biological matrices at all temperatures. However, at 50 and 60°C, it degraded PET, reduced the recovery rate of PET and polyvinyl chloride (PVC), and changed the colour of NY66. According to our results, treating biological materials with a 10% KOH solution and incubating at 40°C was both time and cost-effective, efficient in digesting biological materials, and had no impact on the integrity of the plastic polymers. Furthermore, coupling this treatment with NaI extraction created a promising protocol to isolate MPs from whole fish samples.

A degradation model for high kitchen waste content municipal solid waste

Municipal solid waste (MSW) in developing countries has a high content of kitchen waste (KW), and therefore contains large quantities of water and non-hollocellulose degradable organics. The degradation of high KW content MSW cannot be well simulated by the existing degradation models, which are mostly established for low KW content MSW in developed countries. This paper presents a two-stage anaerobic degradation model for high KW content MSW with degradations of hollocellulose, sugars, proteins and lipids considered. The ranges of the proportions of chemical compounds in MSW components are summarized with the recommended values given. Waste components are grouped into rapidly or slowly degradable categories in terms of the degradation rates under optimal water conditions for degradation. In the proposed model, the unionized VFA inhibitions of hydrolysis/acidogenesis and methanogenesis are considered as well as the pH inhibition of methanogenesis. Both modest and serious VFA inhibitions can be modeled by the proposed model. Default values for the parameters in the proposed method can be used for predictions of degradations of both low and high KW content MSW. The proposed model was verified by simulating two laboratory experiments, in which low and high KW content MSW were used, respectively. The simulated results are in good agreement with the measured data of the experiments. The results show that under low VFA concentrations, the pH inhibition of methanogenesis is the main inhibition to be considered, while the inhibitions of both hydrolysis/acidogenesis and methanogenesis caused by unionized VFA are significant under high VFA concentrations. The model is also used to compare the degradation behaviors of low and high KW content MSW under a favorable environmental condition, and it shows that the gas potential of high KW content MSW releases more quickly.

Comparison of Field Measurements to Methane Emissions Models at a New Landfill

Estimates of methane emissions from landfills rely primarily on models due to both technical and economic limitations. While models are easy to implement, there is uncertainty due to the use of parameters that are difficult to validate. The objective of this research was to compare modeled emissions using several greenhouse gas (GHG) emissions reporting protocols including: (1) Intergovernmental Panel on Climate Change (IPCC); (2) U.S. Environmental Protection Agency Greenhouse Gas Reporting Program (EPA GHGRP); (3) California Air Resources Board (CARB); and (4) Solid Waste Industry for Climate Solutions (SWICS), with measured emissions data collected over three calendar years from a young landfill with no gas collection system. By working with whole landfill measurements of fugitive methane emissions and methane oxidation, the collection efficiency could be set to zero, thus eliminating one source of parameter uncertainty. The models consistently overestimated annual methane emissions by a factor ranging from 4-31. Varying input parameters over reasonable ranges reduced this range to 1.3-8. Waste age at the studied landfill was less than four years and the results suggest the need for measurements at additional landfills to evaluate the accuracy of the tested models to young landfills.

Application of landfill treatment approaches for stabilization of municipal solid waste

This research sought to compare the effectiveness of three landfill enhanced treatment approaches aimed at removing releasable carbon and nitrogen after anaerobic landfilling including flushing with clean water (FB 1), leachate recirculation with ex-situ treatment (FB 2), and leachate recirculation with ex-situ treatment and in-situ aeration (FB 3). After extensive treatment of the waste in the FB scenarios, the overall solids and biodegradable fraction were reduced relative to the mature anaerobically treated waste. In terms of the overall degradation, aeration did not provide any advantage over flushing and anaerobic treatment. Flushing was the most effective approach at removing biodegradable components (i.e. cellulose and hemicellulose). Leachate quality improved for all FBs but through different mechanisms. A significant reduction in ammonia-nitrogen occurred in FB 1 and 3 due to flushing and aeration, respectively. The reduction of chemical oxygen demand (COD) in FB 1 was primarily due to flushing. Conversely, the reduction in COD in FBs 2 and 3 was due to oxidation and precipitation during Fenton's Reagent treatment. A mass balance on carbon and nitrogen revealed that a significant fraction still remained in the waste despite the additional treatment provided. Carbon was primarily converted biologically to CH4 and CO2 in the FBs or removed during treatment using Fenton's Reagent. The nitrogen removal occurred through leaching or biological conversion. These results show that under extensive treatment the waste and leachate characteristics did meet published stability values. The minimum stability values achieved were through flushing although FB 2 and 3 were able to improve leachate quality and solid waste characteristics but not to the same extent as FB 1.

Modelling carbon stocks and fluxes in the wood product sector: a comparative review

In addition to forest ecosystems, wood products are carbon pools that can be strategically managed to mitigate climate change. Wood product models (WPMs) simulating the carbon balance of wood production, use and end of life can complement forest growth models to evaluate the mitigation potential of the forest sector as a whole. WPMs can be used to compare scenarios of product use and explore mitigation strategies. A considerable number of WPMs have been developed in the last three decades, but there is no review available analysing their functionality and performance. This study analyses and compares 41 WPMs. One surprising initial result was that we discovered the erroneous implementation of a few concepts and assumptions in some of the models. We further described and compared the models using six model characteristics (bucking allocation, industrial processes, carbon pools, product removal, recycling and substitution effects) and three model-use characteristics (system boundaries, model initialization and evaluation of results). Using a set of indicators based on the model characteristics, we classified models using a hierarchical clustering technique and differentiated them according to their increasing degrees of complexity and varying levels of user support. For purposes of simulating carbon stock in wood products, models with a simple structure may be sufficient, but to compare climate change mitigation options, complex models are needed. The number of models has increased substantially over the last ten years, introducing more diversity and accuracy. Calculation of substitution effects and recycling has also become more prominent. However, the lack of data is still an important constraint for a more realistic estimation of carbon stocks and fluxes. Therefore, if the sector wants to demonstrate the environmental quality of its products, it should make it a priority to provide reliable life cycle inventory data, particularly regarding aspects of time and location.

Release of Per- and Polyfluoroalkyl Substances (PFASs) from Carpet and Clothing in Model Anaerobic Landfill Reactors

Discarded carpet and clothing are potential sources of per- and polyfluoroalkyl substances (PFASs) in landfill leachate, but little is known about their release when disposed in landfills. The concentrations of 70 PFASs in the aqueous phase of anaerobic model landfill reactors filled with carpet or clothing were monitored under biologically active and abiotic conditions. For carpet, total PFAS release was greater in live than abiotic reactors, with an average of 8.5 nmol/L and 0.62 nmol/L after 552 days, respectively. Release in live carpet reactors was primarily due to 5:3 fluorotelomer carboxylic acid (FTCA - 3.9 nmol/L) and perfluorohexanoic carboxylic acid (PFHxA - 2.9 nmol/L). For clothing, release was more dependent on sample heterogeneity than the presence of biological activity, with 0.63, 21.7, 2.6, and 6.3 nmol/L for two live and two abiotic reactors after 519 days, respectively. Release in the clothing reactors was largely due to perfluorooctatonic carboxylic acid (PFOA), with low relative concentrations of measured biotransformation precursors (FTCAs). For carpet and clothing reactors, the majority of PFAS release was not measured until after day 100. Results demonstrate that carpet and clothing are likely sources of PFASs in landfill leachate.

Dry Matter Losses and Methane Emissions During Wood Chip Storage: the Impact on Full Life Cycle Greenhouse Gas Savings of Short Rotation Coppice Willow for Heat

A life cycle assessment (LCA) approach was used to examine the greenhouse gas (GHG) emissions and energy balance of short rotation coppice (SRC) willow for heat production. The modelled supply chain includes cutting multiplication, site establishment, maintenance, harvesting, storage, transport and combustion. The relative impacts of dry matter losses and methane emissions from chip storage were examined from a LCA perspective, comparing the GHG emissions from the SRC supply chain with those of natural gas for heat generation. The results show that SRC generally provides very high GHG emission savings of over 90 %. The LCA model estimates that a 1, 10 and 20 % loss of dry matter during storage causes a 1, 6 and 11 % increase in GHG emissions per MWh. The GHG emission results are extremely sensitive to emissions of methane from the wood chip stack: If 1 % of the carbon within the stack undergoes anaerobic decomposition to methane, then the GHG emissions per MWh are tripled. There are some uncertainties in the LCA results, regarding the true formation of methane in wood chip stacks, non-CO₂ emissions from combustion, N₂O emissions from leaf fall and the extent of carbon sequestered under the crop, and these all contribute a large proportion of the life cycle GHG emissions from cultivation of the crop.

Estimating methane emissions from landfills based on rainfall, ambient temperature, and waste composition: The CLEEN model

Accurately estimating landfill methane emissions is important for quantifying a landfill's greenhouse gas emissions and power generation potential. Current models, including LandGEM and IPCC, often greatly simplify treatment of factors like rainfall and ambient temperature, which can substantially impact gas production. The newly developed Capturing Landfill Emissions for Energy Needs (CLEEN) model aims to improve landfill methane generation estimates, but still require inputs that are fairly easy to obtain: waste composition, annual rainfall, and ambient temperature. To develop the model, methane generation was measured from 27 laboratory scale landfill reactors, with varying waste compositions (ranging from 0% to 100%); average rainfall rates of 2, 6, and 12 mm/day; and temperatures of 20, 30, and 37°C, according to a statistical experimental design. Refuse components considered were the major biodegradable wastes, food, paper, yard/wood, and textile, as well as inert inorganic waste. Based on the data collected, a multiple linear regression equation (R(2)=0.75) was developed to predict first-order methane generation rate constant values k as functions of waste composition, annual rainfall, and temperature. Because, laboratory methane generation rates exceed field rates, a second scale-up regression equation for k was developed using actual gas-recovery data from 11 landfills in high-income countries with conventional operation. The Capturing Landfill Emissions for Energy Needs (CLEEN) model was developed by incorporating both regression equations into the first-order decay based model for estimating methane generation rates from landfills. CLEEN model values were compared to actual field data from 6 US landfills, and to estimates from LandGEM and IPCC. For 4 of the 6 cases, CLEEN model estimates were the closest to actual.

Dry Matter Losses and Greenhouse Gas Emissions From Outside Storage of Short Rotation Coppice Willow Chip

This study examined the dry matter losses and the greenhouse gas (GHG) concentrations within two short rotation coppice (SRC) willow wood chip storage heaps. One heap was built on a grassland area (East Midlands) and the other (Rothamsted) on a concrete hard standing. A series of 1- and 3-m probes were embedded in the heaps in order to retrieve gas samples for analysis, and pre-weighed net bags were positioned in the core of the heap to detect dry matter losses. The bagged samples showed dry matter losses of 18 and 19 % in the East Midlands and Rothamsted heaps after 210 and 97 days storage, respectively. The Rothamsted heap showed a whole-heap dry matter loss of 21 %. During this time, the wood chips dried from 54 to 39 % moisture content in the East Midlands heap and 50 to 43 % at Rothamsted. The results from analysing the whole Rothamsted heap indicated an overall loss of 1.5 GJ per tonne stored, although measurements from bagged samples in the core suggested that the chips dried sufficiently to have a minimal energy loss from storage. The process of mixing the heap, however, led to incorporation of wet outer layers and hence the average moisture content was higher in an average sample of chip. After establishment of the heaps, the temperature rose rapidly and this correlated with a peak in carbon dioxide (CO2) concentration within the heap. A peak in methane (CH4) concentration was also detected in both heaps, though more noticeably in the East Midlands heap after around 55 days. In both instances, the peak CH4 concentration occurred as CO2 concentrations dropped, suggesting that after an active period of aerobic decomposition in the first 2 months of storage, the conditions in the heap became anaerobic. The results from this study suggest that outside wood chip storage is not an efficient method of storing biomass, though this may be location-specific as there are some studies showing lower dry matter losses. It is necessary to explore other methods of harvesting SRC to minimise losses and optimise land use efficiency. Further research is required to detect whether there are fugitive emissions of CH4 from wood chip heaps, as this will compromise the net GHG savings from utilising the biomass stored in this way.

Physical and Biological Release of Poly- and Perfluoroalkyl Substances (PFASs) from Municipal Solid Waste in Anaerobic Model Landfill Reactors

A wide variety of consumer products that are treated with poly- and perfluoroalkyl substances (PFASs) and related formulations are disposed of in landfills. Landfill leachate has significant concentrations of PFASs and acts as secondary point sources to surface water. This study models how PFASs enter leachate using four laboratory-scale anaerobic bioreactors filled with municipal solid waste (MSW) and operated over 273 days. Duplicate reactors were monitored under live and abiotic conditions to evaluate influences attributable to biological activity. The biologically active reactors simulated the methanogenic conditions that develop in all landfills, producing ∼140 mL CH4/dry g refuse. The average total PFAS leaching measured in live reactors (16.7 nmol/kg dry refuse) was greater than the average for abiotic reactors (2.83 nmol/kg dry refuse), indicating biological processes were primarily responsible for leaching. The low-level leaching in the abiotic reactors was primarily due to PFCAs ≤C8 (2.48 nmol/kg dry refuse). Concentrations of known biodegradation intermediates, including methylperfluorobutane sulfonamide acetic acid and the n:2 and n:3 fluorotelomer carboxylates, increased steadily after the onset of methanogenesis, with the 5:3 fluorotelomer carboxylate becoming the single most concentrated PFAS observed in live reactors (9.53 nmol/kg dry refuse).

Evaluation of monitoring indicators for the post-closure care of a landfill for MSW characterized with low lignin content

To understand the applicability of the termination indicators for landfill municipal solid waste (MSW) with low initial lignin content, four different accelerated landfill stabilization techniques were applied to anaerobic landfilled waste, including anaerobic flushing with water, anaerobic flushing with Fenton-treated leachate, and aerobic flushing with Fenton-treated and UV/H2O2-treated leachate. Termination indicators, including total organic carbon (TOC), ammonia-N (NH4(+)-N), the ratio of UV absorbance at 254 nm to TOC concentration (SUVA254), fluorescence spectra of leachate, methane production, oxygen consumption, lignocellulose content, and humus-like content were evaluated. Results suggest that oxygen consumption related indicators used as a termination indicator for low-lignin-content MSW were more sensitive than methane consumption related indicators. Aeration increased humic acid (HA) and (HA+FA)/HyI content by 2.9 and 1.7 times compared to the anaerobically stabilized low-lignin-content MSW. On the other hand, both the fulvic acid (FA) and hydrophilic (HyI) fractions remained constant regardless of stabilization technique. The target value developed for low-lignin-content MSW was quite different than developed countries mainly due to low residual biodegradable organic carbon content in stabilized low-lignin-content MSW.

Enhanced enzymatic hydrolysis of waste paper for ethanol production using separate saccharification and fermentation

Ethanol produced from lignocellulosic biomass is a renewable alternative to diminishing petroleum-based liquid fuels. In this study, the feasibility of ethanol production from waste paper using the separate hydrolysis and fermentation (SHF) was investigated. Two types of waste paper materials, newspaper and office paper, were evaluated for their potential to be used as a renewable feedstock for the production of fermentable sugars via enzymatic hydrolysis of their cellulose fractions. Hydrolysis step was conducted with a mixture of cellulolytic enzymes produced locally by Trichoderma reesei Rut-C30 (cellulase-overproducing mutant) and Aspergillus niger F38 cultures. Surfactant pretreatment effect on waste paper enzymatic digestibility was studied and Triton X-100 at 0.5 % (w w(-1)) has improved the digestibility of newspaper about 45 %. The effects of three factors (dry matter quantity, phosphoric acid pretreatment and hydrolysis time) on the extent of saccharification were also assessed and quantified by using a methodical approach based on response surface methodology. Under optimal hydrolysis conditions, maximum degrees of saccharification of newspaper and office paper were 67 and 92 %, respectively. Sugars released from waste paper were subsequently converted into ethanol (0.38 g ethanol g(-1) sugar) with Saccharomyces cerevisiae CTM-30101.

Decomposition of forest products buried in landfills

The objective of this study was to investigate the decomposition of selected wood and paper products in landfills. The decomposition of these products under anaerobic landfill conditions results in the generation of biogenic carbon dioxide and methane, while the un-decomposed portion represents a biogenic carbon sink. Information on the decomposition of these municipal waste components is used to estimate national methane emissions inventories, for attribution of carbon storage credits, and to assess the life-cycle greenhouse gas impacts of wood and paper products. Hardwood (HW), softwood (SW), plywood (PW), oriented strand board (OSB), particleboard (PB), medium-density fiberboard (MDF), newsprint (NP), corrugated container (CC) and copy paper (CP) were buried in landfills operated with leachate recirculation, and were excavated after approximately 1.5 and 2.5yr. Samples were analyzed for cellulose (C), hemicellulose (H), lignin (L), volatile solids (VS), and organic carbon (OC). A holocellulose decomposition index (HOD) and carbon storage factor (CSF) were calculated to evaluate the extent of solids decomposition and carbon storage. Samples of OSB made from HW exhibited cellulose plus hemicellulose (C+H) loss of up to 38%, while loss for the other wood types was 0-10% in most samples. The C+H loss was up to 81%, 95% and 96% for NP, CP and CC, respectively. The CSFs for wood and paper samples ranged from 0.34 to 0.47 and 0.02 to 0.27gOCg(-1) dry material, respectively. These results, in general, correlated well with an earlier laboratory-scale study, though NP and CC decomposition measured in this study were higher than previously reported.

The Outer Loop bioreactor: a case study of settlement monitoring and solids decomposition

The Outer Loop landfill bioreactor (OLLB) located in Louisville, KY, USA has been in operation since 2000 and represents an opportunity to evaluate long-term bioreactor monitoring data at a full-scale operational landfill. Three types of landfill units were studied including a Control cell, a new landfill area that had a piping network installed as waste was being placed to support leachate recirculation (As-Built cell), and a conventional landfill that was modified to allow for liquid recirculation (Retrofit cell). The objective of this study is to summarize the results of settlement data and assess how these data relate to solids decomposition monitoring at the OLLB. The Retrofit cells started to settle as soon as liquids were introduced. The cumulative settlement during the 8years of monitoring varied from 60 to 100cm. These results suggest that liquid recirculation in the Retrofit cells caused a 5-8% reduction in the thickness of the waste column. The average long-term settlement in the As-Built and Control Cells was about 37% and 19%, respectively. The modified compression index (Cα(')) was 0.17 for the Control cells and 0.2-0.48 for the As-Built cells. While the As-Built cells exhibited greater settlement than the Control cells, the data do not support biodegradation as the only explanation. The increased settlement in the As-Built bioreactor cell appeared to be associated with liquid movement and not with biodegradation because both chemical (biochemical methane potential) and physical (moisture content) indicators of decomposition were similar in the Control and As-Built cells. The solids data are consistent with the concept that bioreactor operations accelerate the rate of decomposition, but not necessarily the cumulative loss of anaerobically degradable solids.

Measurement of carbon storage in landfills from the biogenic carbon content of excavated waste samples

Landfills are an anaerobic ecosystem and represent the major disposal alternative for municipal solid waste (MSW) in the U.S. While some fraction of the biogenic carbon, primarily cellulose (Cel) and hemicellulose (H), is converted to carbon dioxide and methane, lignin (L) is essentially recalcitrant. The biogenic carbon that is not mineralized is stored within the landfill. This carbon storage represents a significant component of a landfill carbon balance. The fraction of biogenic carbon that is not reactive in the landfill environment and therefore stored was derived for samples of excavated waste by measurement of the total organic carbon, its biogenic fraction, and the remaining methane potential. The average biogenic carbon content of the excavated samples was 64.6±18.0% (average±standard deviation), while the average carbon storage factor was 0.09±0.06g biogenic-C stored per g dry sample or 0.66±0.16g biogenic-C stored per g biogenic C.

The effect of aging on the bioavailability of toluene sorbed to municipal solid waste components

Past practice of co-disposing priority pollutants with municipal solid waste (MSW) has led to the placement of more than 150 MSW landfills in the US on the National Priorities List of Superfund. Interactions between organic contaminants and MSW constituents and the effects of these interactions on contaminant fate are poorly understood. The objective of this study was to evaluate the effects of sorbate-sorbent aging time and sorbent decomposition on toluene bioavailability and fate. The bioavailability of (14)C-toluene sorbed to individual MSW constituents [office paper, newsprint, model food and yard waste, high density polyethylene (HDPE), and poly(vinyl chloride) (PVC)] was evaluated after aging times of 1, 30, and 180 d. Biodegradable sorbents were tested in both fresh and anaerobically degraded forms to evaluate the effect of sorbent decomposition. At the termination of bioavailability tests, the distribution of (14)C that was not converted to (14)CO(2) was measured by sequential lipophilic solvent and base extractions of sorbents followed by combustion of extracted sorbents. Increasing the toluene-sorbent aging time reduced the rate of toluene biodegradation for all MSW components except for HDPE. (14)C remaining in sorbents at the completion of bioavailability tests was physically sequestered within and/or covalently bound to sorbent organic matter, and this fraction increased with increasing aging time. Up to 18.6% of (14)C was associated with humic matter (humic and fulvic acids, humin) at the completion of bioavailability tests.

An attempt at quantifying factors that affect efficiency in the management of solid waste produced by commercial businesses in the city of Tshwane, South Africa

Objective. The objective was to investigate factors that affect the efficient management of solid waste produced by commercial businesses operating in the city of Pretoria, South Africa. Methods. Data was gathered from 1,034 businesses. Efficiency in solid waste management was assessed by using a structural time-based model designed for evaluating efficiency as a function of the length of time required to manage waste. Data analysis was performed using statistical procedures such as frequency tables, Pearson's chi-square tests of association, and binary logistic regression analysis. Odds ratios estimated from logistic regression analysis were used for identifying key factors that affect efficiency in the proper disposal of waste. Results. The study showed that 857 of the 1,034 businesses selected for the study (83%) were found to be efficient enough with regards to the proper collection and disposal of solid waste. Based on odds ratios estimated from binary logistic regression analysis, efficiency in the proper management of solid waste was significantly influenced by 4 predictor variables. These 4 influential predictor variables are lack of adherence to waste management regulations, wrong perception, failure to provide customers with enough trash cans, and operation of businesses by employed managers, in a decreasing order of importance.

Life cycle assessment perspectives on delivering an infant in the US

This study introduces life cycle assessment as a tool to analyze one aspect of sustainability in healthcare: the birth of a baby. The process life cycle assessment case study presented evaluates two common procedures in a hospital, a cesarean section and a vaginal birth. This case study was conducted at Magee-Womens Hospital of the University of Pittsburgh Medical Center, which delivers over 10,000 infants per year. The results show that heating, ventilation, and air conditioning (HVAC), waste disposal, and the production of the disposable custom packs comprise a large percentage of the environmental impacts. Applying the life cycle assessment tool to medical procedures allows hospital decision makers to target and guide efforts to reduce the environmental impacts of healthcare procedures.

Converting lignocellulosic solid waste into ethanol for the State of Washington: an investigation of treatment technologies and environmental impacts

There is little research literature on the conversion of lignocellulosic rich waste streams to ethanol, and even fewer have investigated both the technical aspects and environmental impacts together. This study assessed technical and environmental challenges of converting three lignocellulosic waste streams to ethanol: municipal solid waste (MSW), low grade mixed waste paper (MWP), and organic yard waste (YW). Experimental results showed high conversion yields for all three streams using suitable conversion methods. Environmental impacts are highly dependent on conversion technology, and process conditions used. Life cycle assessment results showed that both chemicals production and waste collection are important factors to be included within a waste-to-ethanol study.

One-dimensional model for municipal solid waste (MSW) settlement considering coupled mechanical-hydraulic-gaseous effect and concise calculation

A new model entitled the coupled mechanical-hydraulic-gaseous effect and biochemical degradation for municipal solid waste (MSW) is proposed to simulate and predict the MSW settlement in this study. The coupled model can be used to simulate and predict the distributions of gas and water pressure as well as total waste settlement. Model verification indicates that because of degradation, the excess pore gas pressure increases rapidly and reaches a peak value in a short time, and then it dissipates gradually. But the excess pore water pressure may not always increase at the beginning, which depends on hydraulic conductivity of MSW. Dissipation of the excess pore water pressure is slower than that of the excess pore gas pressure. A waste settlement experiment was conducted in the laboratory using a synthetic MSW. The data was used to verify the developed model, which gave satisfactory results. Based on the experimental results, a new formula is proposed to simulate biochemical degradation.

Bioassessments of anaerobically decomposing organic refuse in laboratory lysimeters with and without leachate recycling and pH adjustment

In this paper, various microbial characteristics of degrading refuse in three lysimeters were compared to bioassess the operating conditions with and without leachate recycling and pH adjustment. Laboratory lysimeters with leachate recycling produced more gas and took less time to reach the highest methane percentage than a lysimeter without leachate recycling. Generally, lysimeters with leachate recycling showed high ATP (adenosine triphosphate) contents in the leachate. But there were no significant differences in dehydrogenase activities among the lysimeters. Leachate of all lysimeters inhibited the bioluminescence activities of the strain tested. Bioluminescence activity was more inhibited by the lysimeter with no leachate recycling (high inhibition corresponds to high toxicity of leachate). Generally, less inhibition was observed in the middle of the operation phase, which was related with the biodegradation activity.

Modeling microbiological and chemical processes in municipal solid waste bioreactor, Part II: Application of numerical model BIOKEMOD-3P

Biodegradation process modeling of municipal solid waste (MSW) bioreactor landfills requires the knowledge of various process reactions and corresponding kinetic parameters. Mechanistic models available to date are able to simulate biodegradation processes with the help of pre-defined species and reactions. Some of these models consider the effect of critical parameters such as moisture content, pH, and temperature. Biomass concentration is a vital parameter for any biomass growth model and often not compared with field and laboratory results. A more complex biodegradation model includes a large number of chemical and microbiological species. Increasing the number of species and user defined process reactions in the simulation requires a robust numerical tool. A generalized microbiological and chemical model, BIOKEMOD-3P, was developed to simulate biodegradation processes in three-phases (Gawande et al. 2009). This paper presents the application of this model to simulate laboratory-scale MSW bioreactors under anaerobic conditions. BIOKEMOD-3P was able to closely simulate the experimental data. The results from this study may help in application of this model to full-scale landfill operation.

Global warming factor of municipal solid waste management in Europe

The global warming factor (GWF; CO(2)-eq. tonne(-1) waste) performance of municipal waste management has been investigated for six representative European Member States: Denmark, France, Germany, Greece, Poland and the United Kingdom. The study integrated European waste statistical data for 2007 in a life-cycle assessment modelling perspective. It is shown that significant GWF benefit was achieved due to the high level of energy and material recovery substituting fossil energy and raw materials production, especially in Denmark and Germany. The study showed that, despite strong regulation of waste management at European level, there are major differences in GWF performance among the member states, due to the relative differences of waste composition, type of waste management technologies available nationally, and the average performance of these technologies. It has been demonstrated through a number of sensitivity analyses that, within the national framework, key waste management technology parameters can influence drastically the national GWF performance of waste management.

Accumulation and fragmentation of plastic debris in global environments

One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly understood.

Accumulation and fragmentation of plastic debris in global environments

One of the most ubiquitous and long-lasting recent changes to the surface of our planet is the accumulation and fragmentation of plastics. Within just a few decades since mass production of plastic products commenced in the 1950s, plastic debris has accumulated in terrestrial environments, in the open ocean, on shorelines of even the most remote islands and in the deep sea. Annual clean-up operations, costing millions of pounds sterling, are now organized in many countries and on every continent. Here we document global plastics production and the accumulation of plastic waste. While plastics typically constitute approximately 10 per cent of discarded waste, they represent a much greater proportion of the debris accumulating on shorelines. Mega- and macro-plastics have accumulated in the highest densities in the Northern Hemisphere, adjacent to urban centres, in enclosed seas and at water convergences (fronts). We report lower densities on remote island shores, on the continental shelf seabed and the lowest densities (but still a documented presence) in the deep sea and Southern Ocean. The longevity of plastic is estimated to be hundreds to thousands of years, but is likely to be far longer in deep sea and non-surface polar environments. Plastic debris poses considerable threat by choking and starving wildlife, distributing non-native and potentially harmful organisms, absorbing toxic chemicals and degrading to micro-plastics that may subsequently be ingested. Well-established annual surveys on coasts and at sea have shown that trends in mega- and macro-plastic accumulation rates are no longer uniformly increasing: rather stable, increasing and decreasing trends have all been reported. The average size of plastic particles in the environment seems to be decreasing, and the abundance and global distribution of micro-plastic fragments have increased over the last few decades. However, the environmental consequences of such microscopic debris are still poorly understood.