Biodegradable Solid Waste Research Articles

Two-stage anaerobic process for bio-hydrogen and bio-methane combined production from biodegradable solid wastes

A two-stage anaerobic digestion process intended for biohydrogen and bio-methane combined production from organic fraction of municipal solid wastes was investigated. In thermophilic conditions blocking of methanogenesis at the first stage of the anaerobic fermentation was achieved at pH 9.0. Cumulative hydrogen production made 82.5 l/kg volatile solids. Pretreatment of organic fraction of municipal solid wastes and exploitation of mixed cultures of anaerobic thermophilic cellulolytic and saccharolytic bacteria of Clostridia sp resulted in the increase of hydrogen cumulative production up to 104 l/kg volatile solids. Content of methane in biohydrogen didn’t exceed 0.1%. Cumulative bio-methane production made 520 l/kg volatile solids. Methane percentage in produced biogas was 78.6%. Comparison of energy data for two-stage anaerobic digestion with those for solely methane production shows the increase in energy recovery from biodegradable fraction of municipal solid wastes. Results obtained make a foolproof basis for the development of cost-effective technological process providing hydrogen and methane combined production from solid organic wastes. Technology can be implemented at large scale biogas plants improving economical and ecological characteristics of the overall process.

Evaluation of treatment technologies for biodegradable municipal solid waste

The New Technologies Demonstrator Programme (NTDP) was established in 2003 by the UK Department for Environment, Food and Rural Affairs to encourage the development and implementation of new technologies to help the UK meet the requirements of the EU landfill directive in respect of the diversion of biodegradable municipal waste away from landfill. The NTDP ended in 2010. This paper summarises the outputs from the programme and the key lessons learned for biodegradable municipal solid waste management. Anaerobic digestion is demonstrated as a viable technology, while composting and anaerobic digestion may have benefits in terms of energy that can be offset against conventional nitrogen fixation if the output displaces an artificial fertiliser. In both processes, the quality of the incoming waste stream is crucially important. Mechanical heat treatment can be a viable process for the recovery of clean recyclables and solid recovered fuel from raw municipal solid waste, but further work is needed to investigate and possibly improve the efficiency and effectiveness of new thermally based technologies using wastes or refuse-derived fuels to generate electricity. Thermally based processes were, in general, found to be much more problematic than their biologically based counterparts, in terms of both establishment and operation of the facility.

Aerobic microbial activity and solid waste biodegradation in a landfill located in a semi-arid region of Argentina

The sanitary landfill of Bahia Blanca city, Argentina, located in a semiarid region, receives 270 tons/day of municipal solid waste. The objectives of the study were: (1) to determine aerobic microbial activity (MA) and waste biodegradation taking into account the age of the waste, and (2) to evaluate the degree of waste stabilization of the oldest cell. MA was determined by CO2 release and chemical characterization in four cells of different ages of landfill. Furthermore, enzymatic methods were used to determine the effect on MA of leachate addition. Low annual rainfall, the sandy characteristics of the soil, and the use of landfill techniques where rigorous compaction is not performed, contribute to maintaining microenvironments with a sufficient quantity of O2 to support aerobic degradation processes. Under these conditions, degrading processes are faster, thus explaining why MA in the landfill cell closed in 1992 is stabilized and behaves as an anthrosol. In areas where MA is limited by lack of water (arid and semiarid zones), refuse degradation is limited to favorable humid periods. For that reason, operations favoring fast and efficient aerobic activity should be implemented.

The potential reuse of biodegradable municipal solid wastes (MSW) as feedstocks in vermicomposting

There is an urgent need globally to find alternative sustainable steps to treat municipal solid wastes (MSW) originated from mismanagement of urban wastes with increasing disposal cost. Furthermore, a conglomeration of ever-increasing population and consumerist lifestyle is contributing towards the generation of more MSW. In this context, vermicomposting offers excellent potential to promote safe, hygienic and sustainable management of biodegradable MSW. It has been demonstrated that, through vermicomposting, MSW such as city garbage, household and kitchen wastes, vegetable wastes, paper wastes, human faeces and others could be sustainably transformed into organic fertiliser or vermicompost that provides great benefits to agricultural soil and plants. Generally, earthworms are sensitive to their environment and require temperature, moisture content, pH and sometimes ventilation at proper levels for the optimum vermicomposting process. Apart from setting the optimum operational conditions for the vermicomposting process, other approaches such as pre-composting, inoculating micro-organisms into MSW and redesigning the conventional vermireactor could be introduced to further enhance the vermicomposting of MSW. Thus the present mini-review discusses the potential of introducing vermicomposting in MSW management, the benefits of vermicomposted MSW to plants, suggestions on how to enhance the vermicomposting of MSW as well as risk management in the vermicomposting of MSW.

Bioenergy II: Bio-Ethanol from Municipal Solid Waste (MSW): The Role of Biomass Properties and Structures During the Ethanol Conversion Process

The emerging biofuel industry demands large amount of biomass feedstock. Although commercial ethanol has been produced from primary biomass sources such as corns, the global food crisis caused by the use of primary biomass has been raised. Thus, lignocellulosic biomass, known as second generation of biomass, has become a promising source for ethanol production. However, the more complex structure requires more advance technology. MSW with more than 60% of biodegradable composition, as one of the promising biomass sources has the potential benefits of replacing primary biomass and preventing environment from MSW pollution.In this paper, three major biodegradable municipal solid waste (BMSW) components: kitchen organic waste (KOW), green organic waste (GOW) and paper and card waste (PCW), are classified and characterised according to substrate composition, cellulose crystallinity, bulk density and particle size. The substrate composition indicates how much cellulose, lignin, hermicellulose each model waste has. The cellulose content shows the potential glucose/ethanol product yield. Other chemical composition such as lignin and hemicellulose indicates how easy of each model waste can be converted. These contents are also important information when selecting pretreatment methods and conversion process conditions in the following steps.Based on the comprehensive understanding of biomass structures and compositions, studies look into the effects of substrate properties (such crystallinity, presence of lignin and cellulose content on process performances during enzymatic hydrolysis adsorption. Results indicated how the adsorption process is affected by the substrate properties. This provides understanding of the role of substrate properties during enzyme-cellulose adsorption.

Secondary Compression of Municipal Solid Wastes and a Compression Model for Predicting Settlement of Municipal Solid Waste Landfills

The estimation of the capacity and settlement of landfills is critical to successful site operation and future development of a landfill. This paper reports the results of a study on biodegradation behavior and the compression of municipal solid wastes. An experimental apparatus was developed which had a temperature-control system, a leachate recycling system, a loading system, and a gas and liquid collection system. Experiments were performed both with and without optimal biodegradation for comparative purposes. Test results indicated that settlement resulting from creep was relatively insignificant when the biodegradation process was inhibited. Compression due to decomposition under optimal biodegradation conditions was found to be much larger than compression associated with creep. The biodegradation process was significantly influenced by the operational temperature. A one-dimensional model is proposed for calculating settlement and estimating the capacity of the landfill under relatively optimal biodegradation conditions. The model was developed to accommodate the calculation of settlement in landfills when a multistep filling procedure was used. The calculation method is relatively simple and convenient for design purposes. Simulations of the physical processes showed that enhancing solid waste biodegradation during the filling stage can considerably increase the capacity of the landfill and reduce postclosure settlements.

Study on the inhibition of methane production from anaerobic digestion of biodegradable solid waste

The inhibition effects and mechanisms of chlorinated methane, anthraquinone and acetylene on methanogenesis in the anaerobic digestion process of biodegradable solid wastes were investigated. It was found that both chloroform and acetylene could effectively inhibit methanogens. Acetylene inhibited the activity of methanogens, while chloroform inhibited metabolic process of methanogenesis. A central composite design (CCD) and response surface regression analysis (RSREG) were employed to determine the optimum conditions and interaction effects of chloroform and acetylene in terms of methane and hydrogen production. Acetylene promoted the inhibition efficiency (F = 31.14; P < 0.01) more effectively than chloroform (F = 2.46; P > 0.05). In addition, a maximum hydrogen production of 1.6 ml was estimated under the optimum conditions of chloroform concentration of 6.69 mg kg(-1) and acetylene concentration of 3.08 x 10(-3) (v/v). Chloroform had a significant effect on enhancing the production of propionic acid and a minimum molar ratio of acetic acid to propionic acid of 0.707 was reached with the chloroform concentration of 9.24 mg kg(-1) and acetylene concentration of 4.0 x 10(-3) (v/v). Hence, methanogens can be inhibited while the stabilization process of solid wastes can still work well. Moreover, co-inhibition technology practice at landfills was feasible and the environmental damage was negligible, according to the analysis and experimental results.

Modeling microbiological and chemical processes in municipal solid waste bioreactor, part I: Development of a three-phase numerical model BIOKEMOD-3P

The numerical computer models that simulate municipal solid waste (MSW) bioreactor landfills have mainly two components--a biodegradation process module and a multi-phase flow module. The biodegradation model describes the chemical and microbiological processes. The models available to date include predefined solid waste biodegradation reactions and participating species. Some of these models allow changing the basic composition of solid waste. In a bioreactor landfill several processes like anaerobic and aerobic solids biodegradation, nitrogen and sulfate related processes, precipitation and dissolution of metals, and adsorption and gasification of various anthropogenic organic compounds occur simultaneously. These processes may involve reactions of several species and the available biochemical models for solid waste biodegradation do not provide users with the flexibility to simulate these processes by choice. This paper presents the development of a generalized biochemical process model BIOKEMOD-3P which can accommodate a large number of species and process reactions. This model is able to simulate bioreactor landfill operation in a completely mixed condition, when coupled with a multi-phase model it will be able to simulate a full-scale bioreactor landfill. This generalized biochemical model can simulate laboratory and pilot-scale operations in order to determine biochemical parameters important for simulation of full-scale operations.

Heavy metal contamination of a mixed waste compost: Metal speciation and fate

The aims of this study were to assess changes in heavy metal availability in two contrasting feedstocks during aerobic composting, and the availability of said metals in the finished composts. A high C-to-N ratio mixed biodegradable municipal solid waste (MSW) feedstock was successfully composted on its own and in combination with green waste. Changes in heavy metal speciation throughout the composting process were studied using the modified BCR sequential extraction protocol. It was found that total Cu, Pb and Zn concentrations increased over time due to the progressive mineralization of the compost feedstock. Metals were fractionated differently within the two feedstocks, although only Cu showed significant redistribution (mostly to the oxidisable fraction) over the 5 month composting period. The MSW-derived composts performed comparably with other commercially-available composts in a series of plant growth trials. Plant metal accumulation was not influenced by the heavy metals present in the MSW-derived compost implying that they are not plant available. It is recommended that these relatively low value/quality composts may be used for remediation of acidic heavy metal contaminated sites.

Two-stage anaerobic digestion of biodegradable municipal solid waste using a rotating drum mesh filter bioreactor and anaerobic filter

A rotating drum mesh filter bioreactor (RDMFBR) with a 100 μm mesh coupled to an anaerobic filter was used for the anaerobic digestion of biodegradable municipal solid waste (BMW). Duplicate systems were operated for 72 days at an organic loading rate (OLR) of 7.5 gVS l −1 d −1. Early in the experiment most of the methane was produced in the 2nd stage. This situation gradually reversed as methanogenesis became established in the 1st stage digester, which eventually produced 86–87% of the total system methane. The total methane production was 0.2 l g −1 VS added with 60–62% volatile solids destruction. No fouling was experienced during the experiment at a transmembrane flux rate of 3.5 l m −2 h −1. The system proved to be robust and stably adjusted to a shock loading increase to 15 gVS l −1 d −1, although this reduced the overall methane production to 0.15 l g −1 VS added.

Development of a coarse membrane bioreactor for two-stage anaerobic digestion of biodegradable municipal solid waste

A laboratory-scale coarse membrane bioreactor was developed to test its potential for the enhanced degradation of biodegradable municipal (solid) waste. The purpose of the mesh was to retain solid substrate and biomass in the reactor, promoting optimal degradation while also allowing intermediate soluble compounds to be removed and degraded in a second reactor. Three reactors with nylon woven mesh membranes of pore sizes 30, 100 and 140 mum were operated at a solid and liquid retention time of 20 and 1.5 days respectively and fed at an organic loading rate of 3.75 gVS l(-1) d(-1). Liquid effluent was fed to an anaerobic filter reactor. The total methane production for the two stage systems was very similar at 0.21-0.22 l g(-1) VS added (c.f. 0.26 l g(-1) VS added for BMP). The effect of increasing the pore size of the mesh was to reduce the methane production in the first stage and transfer more of this to the filter reactor, with the proportion of the total methane produced in the first stage changing from 72% to 49% between 30 and 140 mum meshes. The VS content of the first stage effluent also increased with pore size so it is likely that the mechanism for the differences in methane production is one of solids/biomass retention. The 30 mum pore size is recommended for further work since it transmitted a lower solid and soluble loading to the anaerobic filter. Solids accumulation in the second stage, although causing no problems in the 85-day operational period of this trial, could lead to blocking of the anaerobic filter, which is undesirable on a large scale.

A New and Sound Technology for Biogas from Solid Waste and Biomass

Organic waste, as a main constituent of municipal solid waste, has as well as solid biomass a high potential for biogas generation. Despite the importance of biogas generation from these materials, the availability of large-scale biogas processes lacks behind the demand. A newly developed double-stage solid–liquid biogas process, consisting of an open hydrolysis stage and a fixed-bed methane reactor, allows the biogas production from almost all biodegradable solid waste and renewable resources like maize, grass, sugar cane, etc. Furthermore, residues from industrial processes, like the glycerine waste water from biodiesel production, can also be converted into biogas successfully. Due to the strong separation of hydrolysis and methanation, the process is extremely stable. No malfunction has been detected so far. The open hydrolysis releases CO2 and allows oxidation of sulfur. Consequently, the biogas has a high methane (>72%) and low H2S concentration (<100 ppm). Stirrers or other agitation equipment are not necessary; only liquids are pumped. The biogas generation becomes controllable for the first time; thus, the actual generation can be easily adapted to the consumption.

Solid Waste Management by Composting: State of the Art

One of the most versatile and remunerative techniques for handling biodegradable solid wastes is composting. A large variety of such wastes of plant, animal, and synthetic origins can be gainfully composted, at scales varying from a household bin to a large industry. Compost also has an inexhaustible market as a soil conditioner and fertilizer. Apart from being a source of nitrogen, phosphorus, potassium, and other nutrients for plants, compost is also believed to suppress soil-borne diseases in plants. These virtues make composting an ideal option for processing the enormous quantities of biodegradable solid wastes that are generated in the world. In this article, a review of the state of the art of compost science is presented, encompassing the history, the mechanism, the production, the characteristics, and the effects of composting. It is hoped that this effort would stimulate further interest in composting and in the appreciation of its benefits.

Permeability of Municipal Solid Waste in Bioreactor Landfill with Degradation

Bioreactor landfills are operated for rapid stabilization of waste, increased landfill gas generation for cost-effective energy recovery, gain in landfill space, enhanced leachate treatment, and reduced post closure maintenance period. The fundamental process of waste stabilization in bioreactor landfill is recirculation of generated leachate back into the landfills. This creates a favorable environment for rapid microbial decomposition of the biodegradable solid waste. In order to better estimate the generated leachate and design of leachate recirculation system, clear understanding of the permeability of the Municipal Solid Waste (MSW) with degradation and the factors influencing the permeability is necessary. The objective of the paper is to determine the changes in hydraulic properties of MSW in bioreactor landfill with time and decomposition. Four small-scale bioreactor landfills were built in laboratory and samples were prepared to represent each phase of decomposition. Then, the changes in hydraulic properties of MSW in bioreactor landfill with time and decomposition were determined. A series of constant head permeability tests were performed on the samples generated in laboratory scale bioreactor landfills to determine variation of permeability of MSW with degradation. The test results indicated that the permeability of MSW in bioreactor landfills decreases with decomposition. Based on the test results, the permeability of MSW at the first phase of degradation was estimated as 0.0088 cm/s at density 700 kg/m3. However, with degradation, permeability decreased to 0.0013 cm/s at the same density, for MSW at Phase IV.

Sources and factors controlling the disposal of biodegradable municipal solid waste in urban and rural areas of Cyprus

An inventory of sources of biodegradable municipal soil waste (BMSW) was constructed for urban and rural areas in the EU accession region of Cyprus. Composition analysis was performed on source-separated BMSW collected from households in the rural Ergates Community and an urban area within the Agglanjia Municipality. The data were statistically scrutinized to identify the main factors influencing the quantities of BMSW disposed by urban and rural communities in Cyprus. The results were extrapolated to predict the quantities and types of BMSW disposed by the entire communities. Significantly more BMSW was disposed in the urban area compared to the rural community due to lower diversion rates for green waste and the disposal of food waste from commercial sources. The quantity of food waste collected from households was influenced by socio-economic (household size, income, percentage of children) and behavioural (feeding of food waste to domestic animals, consuming processed 'ready' food) factors, whereas garden size, the type of vegetation, the reuse of trimmings and home composting were the main factors controlling the disposal of green waste.

Study of thin biocovers (TBC) for oxidizing uncaptured methane emissions in bioreactor landfills

Bioreactor landfills are designed to accelerate municipal solid waste biodegradation and stabilization; however, the uncaptured methane gas escapes to the atmosphere during their filling. This research investigates the implementation of a novel methane emission control technique that involves thin biocovers (TBC) placed as intermediate waste covers to oxidize methane without affecting the operation of bioreactor landfills. Batch incubation experiments were conducted for selecting the optimum TBC materials, capable of oxidizing methane to carbon dioxide by methanotrophic bacteria. Column experiments were performed to investigate the TBC performance under varying moisture content, compost-to-sawdust ratio, methane flow rate, and biocover thickness. Overall, the optimum TBC is comprised of a 30-cm thick bed of 0-10mass% sawdust mixed with compost, having a moisture content of 52% ww, which showed 100% CH4 oxidation efficiency over an extended period of time even at a relatively high methane inlet load of 9.4gm(-3)h(-1).

The Physical, Chemical and Microbial Characteristics of Biodegradable Municipal Waste Derived Composts

A comparative study of the physical, chemical and microbial properties of 12 composts sourced from United Kingdom commercial composting plants was carried out. The aim was to ascertain whether these composts could be used as growing media or for application to agricultural land. The composts were produced from either source segregated biodegradable municipal waste (BMW) or mixed municipal solid waste (MSW). Ten composts contained 100% source segregated BMW including green, fruit, vegetable, meat and kitchen waste, paper and cardboard. One compost was 72% mixed MSW plus 18% source segregated BMW, and one compost was 100% mixed MSW. Composts were analyzed for pH, electrical conductivity, carbohydrates, nutrients and contaminants. The composts sourced from mixed MSW contained higher levels of physical contaminants (glass, plastic and metal) than the source segregated BMW composts. Nitrogen concentrations (as % dry weight) were 1.7-2.2% where kitchen or meat waste was included and 1.0-1.6% otherwise. Phosphorus concentration ranged from 23 to 247 mg kg−1, and K from 1851 to 6615 mg kg−1. Total salts were higher in mixed waste composts (15-23 g kg−1), predominantly due to high concentrations of K, Ca, S and Na. Electrical conductivity varied from 670 μ cm−1 to 3320 μS cm−1. The levels of the heavy metals examined in the 10 source segregated BMW composts were much lower than the limits for composts in the United Kingdom (PAS 100). However, the 100% mixed MSW compost exceeded the PAS 100 levels in four of the seven heavy metals tested (Cu, Ni, Pb and Zn) which may have implications for repeated applications to agriculture. Salmonella was absent from all twelve composts, however, five composts contained levels of E. coli which exceeded the UK PAS 100 limits. Five composts produced from source segregated BMW could be applied to agricultural land, however, high levels of E. coli would exclude the other five. Moreover, high levels of heavy metals and physical contaminants would render the two mixed MSW composts unsuitable.

Solid waste characteristics and their relationship to gas production in tropical landfill

Solid waste characteristics and landfill gas emission rate in tropical landfill was investigated in this study. The experiment was conducted at a pilot landfill cell in Thailand where fresh and two-year-old wastes in the cell were characterized at various depths of 1.5, 3, 4.5 and 6 m. Incoming solid wastes to the landfill were mainly composed of plastic and foam (24.05%). Other major components were food wastes (16.8%) and paper (13.3%). The determination of material components in disposed wastes has shown that the major identifiable components in the wastes were plastic and foam which are resistant to biodegradation. The density of solid waste increased along the depth of the landfill from 240 kg m(-3) at the top to 1,260 kg m(-3) at the bottom. Reduction of volatile solids content in waste samples along the depth of landfill suggests that biodegradation of solid waste has taken place to a greater extent at the bottom of the landfill. Gas production rates obtained from anaerobic batch experiment were in agreement with field measurements showing that the rates increased along the depth of the landfill cell. They were found in range between 0.05 and 0.89 l kg(-1) volatile solids day(-1). Average emission rate of methane through the final cover soil layer was estimated as 23.95 g(-2)day(-1) and 1.17 g(-2)day(-1) during the dry and rainy seasons, respectively.

The impact of the European Landfill Directive on waste management strategy and current legislation in Turkey's Specially Protected Areas

The European Landfill Directive (ELD) 99/31/EC has become the most influential piece of waste management legislation to have been produced for some time and calls for reduction of the amount of biodegradable municipal solid waste disposed of to landfill. Moreover, national solid waste strategies need to be changed to achieve increased waste recycling and recovery rates will have to be modified ultimately to meet the targets set in the ELD. This paper outlines the waste management strategy implemented in the Specially Protected Areas (SPAs) in Turkey and gives the key requirements of ELD. On the other hand, it also outlines the adaptation of the Turkish Solid Waste Legislation (TSWL) to ELD and gives comments on the improvement of the TSWL. This study showed that although the TSWL shares the broad objectives of the ELD and includes corresponding requirements of landfill of waste, it is less detailed; there are fewer specific targets and many of the requirements of the ELD are missing in the TSWL. There is no specific target set for the reduction in biodegradable municipal waste going to landfills. On the other hand deposit schemes and recovery rates are being applied on packaging waste without including strategy with long term targets. TSWL states that 45% of the total amount (by weight) of packaging waste produced should be recovered in 1995. However, Control of Packaging and Packaging Waste Legislation specifies the recovery rates between 2005 and 2014 and prohibits the packaging waste made of paper and carton to be landfilled. The Authority for the Protection of Special Areas (APSA) is responsible for the implementation of solid waste management strategies produced by Ministry of Environment and Forest. Implementation of the landfill directive must remain a long-term goal, to be achieved through a succession of incremental steps, in line with economic and institutional development. The improvement in waste management standards can therefore only progress by small incremental steps made in pace with economic development. A quick step change towards the EU standards cannot be achieved. In the short term, the policy should allow to keep a small number of larger landfill sites in operation, and use the resources available to upgrade them with leachate management and other environmental protection systems. As per the realities of Turkey's economy, the construction of new landfill sites, composting or incineration plants should be planned in the long term.

Employment of Anaerobic Digestion Process of Municipal Solid Waste for Energy

Jordan is a country with a population of about five million people. It is considered a developing country that is deficient in generating its own energy source, and it relies significantly on imports of fuels from other countries, which plays an important role in various environmental related problems and issues. Jordan is distinguished among the developing countries by its reasonable industrialization and significant agricultural activities. The amount of waste generated is on the increase due to a continuing significant increase in population and it currently faces pollution of its limited fresh water sources. To mitigate the current and future environmental problems facing Jordan due to fossil fuel use and associated environment problems, Jordan is taking into consideration steps including the utilization of the biogas technology to replace fossil fuel, since Jordan is a nation striving to meet the expected energy demand that grows annually by 6%. Studies of quantity per capita estimates Jordan's generated daily waste as 8,000 tons, which is comparable to that of most semi-industrialized nations. Of that, 3,200 tons is household waste and the rest of it is waste related to industry or agricultural. Much of the total waste is organic, which could be utilized through a process of anaerobic digestion and already has been in use for decades in industrialized nations to produce clean burning methane gas, electricity, fuel, and fertilizers. Anaerobic digestion process releases no greenhouse gases to the atmosphere. Jordan's generated daily waste is estimated around the same as that of most moderately developing nations. Most of the total waste is organic, which could be utilized through a process of anaerobic digestion that does not release greenhouse gases to the atmosphere. Renewable energy and energy conservation, if efficiently utilized, might help to meet the expected increase demand on energy that is growing rapidly. A combined facility (landfill operation and biogas plant) that is established in the capital of Jordan could help reduce the disposal and accumulation of biodegradable solid waste significantly; by 90%. This will help reduce emissions of green house gases (CO2), reduce the dependency of foreign fossil fuel and would improve issues related to the general environment. This project would be self-supported. This project, if proved to be successful, would be an example that others will follow throughout.