Abundance of 14C in biomass fractions of wastes and solid recovered fuels

In recent years thermal utilization of mixed wastes and solid recovered fuels has become of increasing importance in European waste management. Since wastes or solid recovered fuels are generally composed of fossil and biogenic materials, only part of the CO₂ emissions is accounted for in greenhouse gas inventories or emission trading schemes. A promising approach for determining this fraction is the so-called radiocarbon method. It is based on different ratios of the carbon isotopes ¹⁴C and ¹²C in fossil and biogenic fuels. Fossil fuels have zero radiocarbon, whereas biogenic materials are enriched in ¹⁴C and reflect the ¹⁴CO₂ abundance of the ambient atmosphere. Due to nuclear weapons tests in the past century, the radiocarbon content in the atmosphere has not been constant, which has resulted in a varying ¹⁴C content of biogenic matter, depending on the period of growth. In the present paper ¹⁴C contents of different biogenic waste fractions (e.g., kitchen waste, paper, wood), as well as mixtures of different wastes (household, bulky waste, and commercial waste), and solid recovered fuels are determined. The calculated ¹⁴C content of the materials investigated ranges between 98 and 135 pMC.     

Effect of thermal pretreatment on the physical and chemical properties of municipal biomass waste

The effects of thermal pretreatment on the physical and chemical properties of three typical municipal biomass wastes (MBWs), kitchen waste (KW), vegetable/fruit residue (VFR), and waste activated sludge (WAS) were investigated. The results show that thermal pretreatment at 175 °C/60 min significantly decreases viscosity, improves the MBW dewatering performance, as well as increases soluble chemical oxygen demand, soluble sugar, soluble protein, and especially organic compounds with molecular weights >10 kDa. For KW, VFR and WAS, 59.7%, 58.5% and 25.2% of the organic compounds can be separated in the liquid phase after thermal treatment. WAS achieves a 34.8% methane potential increase and a doubled methane production rate after thermal pretreatment. In contrast, KW and VFR show 7.9% and 11.7% methane decrease because of melanoidin production.     

物化性质对细颗粒长大过程影响的研究现状

燃煤产生的飞灰颗粒是除尘器去除的主体,研究颗粒的物化性质对提高除尘效率有重要的意义。燃煤产生的细颗粒不能被传统除尘器有效的脱除,颗粒长大技术是有效脱除燃煤细颗粒的一种除尘技术。针对颗粒长大技术,综述了细颗粒的物化性质对脱除效果的影响。     

A preliminary investigation into the physical and chemical properties of biomass ashes used as aggregate fillers for bituminous mixtures

Fly and bottom ashes are the main by-products arising from the combustion of solid biomass. Since the production of energy from this source is increasing, the processing and disposal of the resulting ashes has become an environmental and economic issue. Such ashes are of interest as a construction material because they are composed of very fine particles similar to fillers normally employed in bituminous and cementitious mixtures. This research investigates the potential use of ash from biomass as filler in bituminous mixtures. The morphological, physical and chemical characteristics of 21 different ashes and two traditional fillers (calcium carbonate and “recovered” plant filler) were evaluated and discussed. Leaching tests, performed in order to quantify the release of pollutants, revealed that five ashes do not comply with the Italian environmental re-use limits. Experimental results show a wide range of values for almost all the investigated properties and a low correlation with biomass type in terms of origin and chemical composition. Furthermore, sieving and milling processes were found to improve the properties of the raw material in terms of grading and sample porosity. The effectiveness of these treatments and the low content of organic matter and harmful fines suggest that most of the biomass ashes investigated may be regarded as potential replacements for natural filler in bituminous mixtures.     

Influence of combined aging on the mechanical and physical properties of reclaimed asphalt pavement mixtures blended with rejuvenator agents

Recently, reclaimed asphalt pavement (RAP) with high RAP contents with rejuvenator agents have been implemented in Japan. However, a unified view of the durability of RAP mixtures with rejuvenators has not been established. Therefore, this paper aims to assess the durability of RAP mixtures blended with different types of rejuvenators through combined aging, compared with that of hot mixed asphalt (HMA) mixture. Mechanical and physical properties of RAP mixtures with rejuvenators subjected to a combination of moisture, heat, and oxidation were investigated. Saturation aging tensile stiffness conditioning was used to simulate the combined aging. Four types of RAP mixtures were prepared by employing two types of oil-based rejuvenators with two RAP contents. HMA mixtures were also prepared. The test results demonstrated that the RAP mixtures did not exhibit a reduction in the retained stiffness, whereas the HMA mixtures exhibited a significant drop in stiffness with conditioning. In addition, the RAP mixtures exhibited a longer residual service life than the HMA mixtures after conditioning. Detailed analyses revealed differences in the stiffness and fatigue behaviors of the RAP mixtures with different types of rejuvenators. Finally, certain aspects of the deterioration mechanisms of RAP mixtures with rejuvenators were discussed.

     

Collection and transportation cost of household solid waste in Kuwait

The specific aim of this funded research project was to examine and evaluate the efficiency and the effectiveness of the municipal solid waste collection and transportation system in the State of Kuwait. The contract resources of the seven contracting firms, the annual contract budgets, and the district area and population of each service contract are presented. Service efficiency and effectiveness indicators for each collection/disposal contract are also computed and discussed. The cost of collection and transportation of household waste in Kuwait is also compared with those of a number of urban areas in other nations. The low energy and manpower costs are mainly responsible for the favorable cost of management, collection and transportation of residential waste in Kuwait.     

The effect of storage and mechanical pretreatment on the biological stability of municipal solid wastes

Modern mechanical–biological waste treatment plants for the stabilization of both the source-separated organic fraction of municipal solid wastes (OFMSW) and the mixed stream of municipal solid wastes (MSW) include a mechanical pretreatment step to separate recyclable materials such as plastics, glass or metals, before biological treatment of the resulting organic material. In this work, the role of storage and mechanical pretreatment steps in the stabilization of organic matter has been studied by means of respiration techniques. Results have shown that a progressive stabilization of organic matter occurs during the pretreatment of the source-separated OFMSW, which is approximately 30% measured by the dynamic respiration index. In the case of mixed MSW, the stabilization occurring during the reception and storage of MSW is compensated by the effect of concentration of organic matter that the pretreatment step provokes on this material. Both results are crucial for the operation of the succeeding biological process. Finally, respiration indices have been shown to be suitable for the monitoring of the pretreatment steps in mechanical–biological waste treatment plants, with a strong positive correlation between the dynamic respiration index and the cumulative respiration index across all samples tested.     

Eco-efficient concretes: the effects of using recycled ceramic material from sanitary installations on the mechanical properties of concrete

The aim of this research was to investigate some of the physical and mechanical properties of concrete mixed under laboratory conditions, where different proportions of coarse aggregate materials were substituted by porcelain from sanitary installations. The results of the tests show that the concrete produced has the same mechanical characteristics as conventional concrete, thus opening a door to selective recycling of sanitary porcelain and its use in the production of concrete.     

Compositional effects on the dynamic properties of municipal solid waste

Large-scale cyclic simple shear tests were conducted on reconstituted specimens of municipal solid waste (MSW) collected from the Tri-Cities landfill in Fremont, California, USA. The influence of waste composition and compacted unit weight on the shear wave velocity, small-strain shear modulus, and strain-dependent shear modulus reduction and damping ratio curves of MSW was investigated in these tests. Modulus reduction and damping ratio curves were evaluated over a strain range of 0.01-3%. Specimens were reconstituted using 100%, 65%, and 35%, by weight, of the material that passed through a 20mm screen and four different levels of compaction effort. All specimens were consolidated under a normal stress of 75 kPa prior to testing. The test results show a very strong dependence of shear wave velocity and small strain shear modulus on unit weight. Unit weight also had an influence on modulus reduction and damping ratio. Waste composition had a very strong influence on damping and also influenced shear wave velocity, small strain shear modulus, and modulus reduction. The interrelationship between unit weight and waste composition made it difficult to separate out the effects of these parameters.     

Moisture effect on the storage, handling and flow properties of poultry litter

Poultry litter, a combination of accumulated chicken manure, feathers and bedding materials, is a potential feedstock for bioenergy and other value-added applications. The effect of moisture on the physical properties, equilibrium moisture relations, flow properties and wall friction characteristics of poultry litter were measured. Poultry litter densities (bulk, particle and tap) reduced and compressibility increased with increase in moisture content. The fit of the GAB equation to poultry litter equilibrium moisture isotherm at 25 degrees C indicated that the monolayer moisture content for poultry litter is 5.5% (wb). Increasing the moisture content of the poultry litter reduced its flowability from easy flowing (flow index of 6.4) at moisture content of 10.3% (wb) to very cohesive (non-flowing) (flow index of 1.9) at moisture content of 30.9% (wb). Flow on a stainless steel surface was improved when the surface was mirror-finished or galvanized coated.     

Collection,compaction and storage of solid waste for space missions

Efficient trash collection and volume reduction becomes very important during extended, manned space flight missions because of the high rate of crew member generated trash and the limited volume available to store this trash. Trash management in manned space flight vehicles requires that the following considerations be addressed: definition of the trash model including quantities/rates of generation and the physico-chemical characteristics of the trash; methods of collection and temporary stowage prior to treatment or processing; the method of treatment/processing to affect biochemical stabilization and volume reduction; and storage of treated/ processed trash prior to final disposition. This paper discusses trash management design approaches with focus on trash collection, compaction and storage. This paper also discusses the trash compactor design currently being developed for the Space Station Freedom program.     

Effects of recycled glass substitution on the physical and mechanical properties of clay bricks

In this study, wasted glasses from structural glass walls up to 45 wt.% were added into clay mixtures in brick manufacturing process. Physical and mechanical properties of clay bricks were investigated as functions of the wasted glass content and the firing temperature. The results indicated that with proper amount of wasted glasses and firing temperature, clay bricks with suitable physical and mechanical properties could be obtained. The compressive strength as high as 26–41 MPa and water absorption as low as 2–3% were achieved for bricks containing 15–30 wt.% of glass content and fired at 1100 °C. When the glass waste content was 45 wt.%, apparent porosity and water absorption was rapidly increased.     

Organizing preliminary storage sites of organic material,waste fuels and recyclables and their separating distance from populated areas

European Union directives have urged member countries to enhance the recycling and separation of waste fractions, and this has increased the number of temporary storage sites of recyclables and waste fuels. Spontaneous fires at temporary storage sites have become common and pose social/health/environmental risks. Storage sites should be sited sufficiently far from populated regions, so that the concentration of released pollutants from open fires falls below the critical air quality index before the plume reach the downwind population. In this study, the open-burn/open-detonation model developed by the US Environmental Protection Agency was employed, and 540 simulations were performed for nine scenarios of open burning of household waste to estimate suitable sizes of storage heaps and adequate distances between storage sites and populated regions. Furthermore, sensitivity analysis was performed for 1,080 additional simulations to determine the effects of variations in the burn rate, storage dimension and volume of the waste heap on the model output. The resulting chart can be directly employed by waste operators/environmental agencies to organize storage sites to minimize externalities due to open fires. Furthermore, using ArcGIS software, first-cut information of the total Swedish population facing the risk of hazards due to spontaneous fires was provided.     

Effects of municipal solid waste compost application on the microbial biomass of cultivated and non-cultivated soil in a semi-arid zone.

The aim of this study was to assess whether soil microbial biomass could be used as an indicator of environmental changes following the application of organic residue (compost of municipal solid waste and farmyard manure) or mineral fertilizers (N and P) into cultivated or uncultivated loam-clayey soil, for three consecutive years. The carbon and nitrogen of the microbial biomass (B(C) and B(N) were studied using the fumigation-extraction method. For the two cultivated and uncultivated plots, B(N) and B(C) were more important in the superficial profile (0-20 cm) than in the deep one (20-40 cm). In the uncultivated soil, we observed a good linear relation between B(C) and B(N) at the level of upper soil horizon during the wet season with r coefficients of 0.95, 0.71 and 0.80 for the consecutive years 2000, 2001 and 2002, respectively. Microbial biomasses C and N increased during the rainy season and decreased during the dry season. Microbial biomass C and N showed the higher content with compost and farmyard manure at 40 tonnes ha(-1). Moreover, the results showed that at the beginning of the experiment, the microbial biomass was higher in the ploughed wheat-cultivated plot than in the uncultivated one. Microbial biomass C and N in the cultivated plot amended with compost at 40 tonnes ha(-1) were significantly different in comparison with the soil microbial biomass amended with farmyard manure. The combining of chemical fertilizer with the organic fertilizer, such as compost at 40 or 80 tonnes ha(-1) and farmyard manure, increased the microbial biomasses C and N after 1 and 2 years. In the cultivated or uncultivated plots the results revealed that the best application rate of the compost was 40 tonnes ha(-1) and when the compost rate was increased from 40 to 80 tonnes ha(-1) both B(C) and B(N) decreased significantly.     

Effect of pressure and atmosphere during hydrothermal treatment on the properties of sewage sludge-derived solid fuel

Journal of Material Cycles and Waste Management - Efforts to improve the performance of hydrothermal treatment (HT) in producing high-quality solid fuel from sewage sludge were carried out by...     

Impact of municipal solid waste incineration bottom ash on the properties and frost resistance of clay bricks

Journal of Material Cycles and Waste Management - This paper presents an experimental study on the properties, structure and durability (frost resistance: one-side and all-sides freezing and...     

Influence of pelletization process on the properties of fly ash aggregates

A pelletization process is used to manufacture artificial lightweight coarse aggregate using fly ash. Pelletization depends on the size of particles and their distribution, the wettability of particles and moisture content, along with the process related parameters. A review indicates that only limited studies have been reported on the pelletization of fly ash aggregates. The influence of the following parameters has been studied: (i) speed of revolution of pelletizer disc, (ii) angle of pelletizer disc, (iii) moisture content, and (iv) duration of pelletization. Fractional factorial experiments using the concept of Taguchi's orthogonal array is used in this study, which uses an orthogonal array table to arrange multifactor experiments and uses statistical methods to analyze the experimental results. The relative influence of the factors above and their interaction effects on the strength, water absorption and size growth of fly ash aggregates are discussed.     

Sorting efficiency and combustion properties of municipal solid waste during bio-drying

One aerobic and two combined bio-drying processes were set up to investigate the quantitative relationships of sorting efficiency and combustion properties with organics degradation and water removal during bio-drying. Results showed that the bio-drying could enhance the sorting efficiency of municipal solid waste (MSW) up to 71% from the initial of 34%. The sorting efficiency was correlated with water content negatively (correlation coefficient, r = −0.89) and organics degradation rate positively (r = 0.92). The higher heating values (HHVs) were correlated with organics degradation negatively for FP (i.e. the sum of only food and paper) (r = −0.93) but positively for the mixing waste (MW) (r = 0.90), whereas the lower heating values (LHVs) were negatively correlated with water content for both FP (r = −0.71) and MW (r = −0.96). Other combustion properties depended on organics degradation performance, except for ignition performance and combustion rate. The LHVs could be greatly enhanced by the combined process with insufficient aeration during the hydrolytic stage. Compared with FP, MW had higher LHVs and ratios of volatile matter to fixed carbon. Nevertheless, FP had higher final burnout values than MW.     

Mechanical and physical properties of cement blended with sewage sludge ash

The aim of this paper is to evaluate the compatibility of sewage sludge ash (SSA) with various types of commercially available cements (CEM I and CEM II types, cements with several proportions of clinker). The behaviour of mortars fabricated with various percentages (10-30% by weight) of the cement replaced by SSA has been analyzed in terms of workability, mechanical strength, porosity and shrinkage/expansion. SSA exhibits moderate pozzolanic activity; the highest compressive strengths were obtained with 10% of the cement replaced by SSA. The CEM II/B-M (V-LL) 42.5R cement is considered ideal for preparing mortars containing SSA. Shrinkage data demonstrate that sulphates present in SSA are not reactive towards cement.