Environmental impacts and leachate analysis of waste rubber incorporated in construction and road materials: A review.

In recent years, the recycling of waste tyre rubber in construction and road materials has emerged as a potential innovative solution to the growing waste rubber tyre dilemma. However, to determine the feasibility of any recycling method, it is crucial to assess the potential environmental implications of the proposed method. The environmental conditions waste tyre rubber products are exposed to are often not accurately simulated in leachate studies, leading to incomplete findings. The Toxicity Characteristics Leaching Procedure (TCLP) (1997) and Australian Bottle Leaching Procedure (ABLP) (1992), which have been used in most leachate studies in the past, have been criticised for inadequate replication of site conditions when applied to assess the leachability of modified materials. The objective of this study is to (1) review standard leachate testing methods and subsequently investigate the adequacy of these methods, (2) review all available major research focusing on the leaching characteristics and environmental and health implications of products recycled with waste tyre rubber, (3) prepare recommendations for the improvement of future leachate studies and testing based on the assessment of existing research. The existing leachate analysis studies that assess the environmental implications of different applications of waste tyre rubber have demonstrated that considerable knowledge gaps exist in the current body of knowledge. It was found leachate studies involving the recently published ABLP (2019) and Leaching Environmental Assessment Framework (LEAF) (2017) appeared to better replicate local environmental conditions and yield results of higher integrity and precision due to improved testing procedures. This study recommends that the ABLP and LEAF testing methods be applied to assess the leachability of heavy metals and organic materials (on which minimal research has been conducted) of all currently available products incorporated with waste tyre rubber, as well as in future leachate studies of waste tyre rubber.

Polycyclic Aromatic Hydrocarbons (PAHs) in Fired Clay Bricks Incorporating Cigarette Butts.

Cigarette butts (CBs) are the most common littered waste in the world and may contain polycyclic aromatic hydrocarbons (PAHs) from the incomplete combustion of tobacco during burning. Therefore, to investigate the potential PAH residual remaining in fired clay bricks (FCBs) incorporating CBs and examine the environmental impact of utilizing toxic waste in the production of FCBs, a comprehensive PAH extraction analysis was conducted. The Soxhlet extraction method was utilized to conduct a qualitative and quantitative analysis of sixteen toxic Environmental Protection Authority (EPA) Polycyclic Aromatic Hydrocarbons (PAHs) in FCB samples incorporating CBs using gas chromatography-mass spectrometry (GC-MS). The concentrations of the mean total (Σ)PAHs for FCBs incorporating 0%, 0.5%, 1%, 1.5%, and 2% CBs by weight (wt) were found to be 0.183, 0.180, 0.242, 0.234, and 0.463 µg/mL. As expected, PAHs with higher water solubility and volatility, naphthalene, fluorene, anthracene, pyrene, fluoranthene, and chrysene were found at higher concentrations compared to lipophilic PAHs. The ΣPAH concentrations for all five FCB-CB mixes were well below the EPA Victoria solid waste hazard categorization threshold for industrial waste. Moreover, the samples were studied for their carbon content using the carbon, hydrogen, nitrogen, and sulfur (CHNS) analyzer and thermogravimetric analysis (TGA). The results confirm an almost 100% combustion process of CBs during the firing process. A content less than 0.3% suggests that all carbon within the FCB-CB mixture relatively disappeared during the firing process up to 1050 °C. However, further research regarding the emission of volatile organic compounds (VOCs) during the production of FCBs incorporating CBs should be conducted.

Implementation of Recycling Cigarette Butts in Lightweight Bricks and a Proposal for Ending the Littering of Cigarette Butts in Our Cities.

Our cities, parks, beaches, and oceans have been contaminated for many years with millions of tonnes of unsightly and toxic cigarette butts (CBs). This study presents and discusses some of the results of an ongoing study on recycling in fired-clay bricks. Energy savings: the energy value of CBs with remnant tobacco was found to be 16.5 MJ/kg. If just 2.5% of all bricks produced annually worldwide included 1% CB content, all of the CBs currently produced could be recycled in bricks, and it is estimated that global firing energy consumption could be reduced by approximately 20 billion MJ (megajoules). This approximately equates to the power used by one million homes in Victoria, Australia, every year. Bacteriological study: CBs were investigated for the presence of ten common bacteria in two pilot studies. Staphylococcus spp. and Pseudomonas aeruginosa were detected in fresh used CB samples, and Listeria spp. were detected in old used CB samples. All of the CB samples except the dried sample had significant counts of Bacillus spp. Some species of the detected bacteria in this study are pathogenic. Further confirmation and comprehensive microbiological study are needed in this area. The contact of naphthalene balls with CBs had a significant disinfecting effect on Bacillus spp. The implementation procedure for recycling CBs in bricks, odour from Volatile Organic Compound (VOC) emissions in CBs, sterilization methods, CB collection systems, and safety instructions were investigated, and they are discussed. Proposal: when considering the combined risks from many highly toxic chemicals and possible pathogens in cigarette butts, it is proposed that littering of this waste anywhere in cities and the environment be strictly prohibited and that offenders be heavily fined.

Leachate Analysis of Heavy Metals in Cigarette Butts and Bricks Incorporated with Cigarette Butts.

Billions of cigarette butts (CBs) are discarded as litter in the environment every year worldwide. As CBs have poor biodegradability, it can take several years for them to break down while leaching toxic chemicals and heavy metals. Mohajerani et al. (2016), based on long-term research, developed a method for the recycling of CBs in fired clay bricks with promising results. This paper presents and discusses the leaching behavior of potentially hazardous metals from used, unused, and shredded used CBs, and unfired and fired clay bricks incorporating CBs. The leachate analysis was conducted according to the Australian Bottle Leaching Procedure (ABLP) for pH values 2.9, 5.0, and 9.2. The aim was to quantify the amount of heavy metals leached, determine the relationship between the metal concentration leachate, pH of the solution and condition of the sample, and examine the effect of firing on the leaching capability of bricks. The leachate results were then compared to the concentration limits for heavy metals set by the United States Environmental Protection Authority (USEPA) national primary drinking water and the Environmental Protection Authority (EPA) solid industrial waste hazard categorization thresholds to assess the suitability of fired clay bricks incorporating CBs. Metals Cu, Zn, Mn, Al, Fe, Ti, and Ba demonstrated the highest leachate concentrations for pH 2.9 and pH 5.0 for used CBs. This suggests that used CBs are more prone to leaching heavy metals in areas with highly acidic rain compared to the natural range of precipitation. The leaching behavior of fired bricks incorporating CBs was considerably lower than that for the unfired bricks due to the immobilization of heavy metals during the firing process. However, the leaching of Cr and Ni was almost completely impeded after the firing of the bricks, and more than 50% of all the tested heavy metals were hindered.

Microplastics and pollutants in biosolids have contaminated agricultural soils: An analytical study and a proposal to cease the use of biosolids in farmlands and utilise them in sustainable bricks.

Treated waste-water sludge (biosolids) are frequently recycled in agricultural lands; however, this practice has polluted soils with microplastics (MPs), nanoplastics (NPs), synthetics, heavy metals, pharmaceuticals and engineered nanoparticles. This study analyses many of the significant research outcomes in this area and proposes the urgent reduction of biosolids recycling in farmlands, aiming to eliminate their use altogether as soon as practicable, and instead, to utilise this material as a source of brick firing energy in the manufacturing of fired clay bricks and as a replacement for virgin brick soil. Based on a comprehensive data analysis, this study has calculated that in the European Union, the United States, China, Canada and Australia, approximately 26,042, 21,249, 13,660, 1,518 and 1,241 tonnes of microplastics, respectively, are added to farmlands annually as a result of biosolids application. The accumulation of microplastics produces detrimental effects on soil organisms and increases the accumulation of other micropollutants, such as heavy metals. The degradation of MPs over time is a source for the creation of nanoplastics, which pose a greater threat to ecosystems and human and animal health, as their size allows for their absorption into plant cells. On the other hand, the results of a comprehensive study at RMIT, including a comprehensive Life-Cycle Assessment, confirm that recycling biosolids in fired clay bricks (Bio-Bricks) is a promising sustainable alternative. This study proposes the mandatory addition of 7% biosolids in all brick manufacturing worldwide to utilize all biosolids production in fired clay bricks. This will reduce brick firing energy by over 12.5%.

Recycling of Waste Materials for Asphalt Concrete and Bitumen: A Review.

Waste management has become an issue of increasing concern worldwide. These products are filling landfills and reducing the amount of livable space. Leachate produced from landfills contaminates the surrounding environment. The conventional incineration process releases toxic airborne fumes into the atmosphere. Researchers are working continuously to explore sustainable ways to manage and recycle waste materials. Recycling and reuse are the most efficient methods in waste management. The pavement industry is one promising sector, as different sorts of waste are being recycled into asphalt concrete and bitumen. This paper provides an overview of some promising waste products like high-density polyethylene, marble quarry waste, building demolition waste, ground tire rubber, cooking oil, palm oil fuel ash, coconut, sisal, cellulose and polyester fiber, starch, plastic bottles, waste glass, waste brick, waste ceramic, waste fly ash, and cigarette butts, and their use in asphalt concrete and bitumen. Many experts have investigated these waste materials and tried to find ways to use this waste for asphalt concrete and bitumen. In this paper, the outcomes from some significant research have been analyzed, and the scope for further investigation is discussed.

Recycling of Cigarette Butts in Fired Clay Bricks: A New Laboratory Investigation.

Cigarette butts (CBs) are the most commonly littered waste material in the world. It is estimated that over 5.7 trillion cigarettes are consumed worldwide each year. Consequently, millions of tonnes of highly toxic waste are contaminating the environment. CBs are composed of cellulose acetate filters-a polymer with poor biodegradability-and which, depending upon the environmental conditions, can take many years to decompose. In this study, fired clay bricks were manufactured with 0.5%, 1%, 1.5%, and 2% CBs by mass and tested against control bricks with 0% CBs. The results revealed a decrease in compressive strength from 48.6 MPa for 0% CB content bricks to 30.8 MPa for 1% CB content bricks, and a decrease in dry density with the increase in CB content, from 2114 kg/m3 for the control bricks to 1983 kg/m3 and 1969 kg/m3 for 1% and 2% CB content bricks. The highest value of water absorption appeared for 2% CB content bricks, which reached an absorption rate of 13.1% compared to 9% for the control bricks. The energy required during the firing process was calculated with a saving of up to 10.20%, for bricks incorporating 1% CBs. The thermal conductivity of the samples showed a reduction of 17% from 1.078 to 0.898 W m-1·K-1 with the addition of 1% CBs. In addition, the manufactured bricks were tested for efflorescence, an initial rate of absorption (IRA), microstructural analysis, and shrinkage. A life-cycle assessment (LCA) is recommended to analyze the environmental impacts of bricks incorporating CBs.

Possible Recycling of Cigarette Butts as Fiber Modifier in Bitumen for Asphalt Concrete.

Littering waste is among the top environmental issues in the world, and the management of the waste has turned into a challenge in almost every city. It has been reported that 75% of smokers dispose of their cigarette butts (CBs) on the ground, even in public places. Researchers have discovered that CBs make up more than one-third of the total littered waste on the planet. Cigarette butts predominantly consist of a cellulose acetate fiber (plastic)-based filter wrapped in paper. Waste CBs contain burnt tobacco and tar, along with many other toxic chemicals. They take years to biodegrade depending on the environmental conditions, and toxic chemicals leach out and contaminate the environment. As part of an ongoing project, this paper presents a novel and sustainable technique to recycle cigarette butts in bitumen for the construction of flexible pavements. In this research, CBs have been pre-processed and mixed with bitumen classes C320, C170, and PMB A10E as a fiber modifier. Comprehensive laboratory investigations, including a penetration test, softening point test, and viscosity test, have been performed along with a binder drain off test to evaluate the performance of the modified samples. During this investigation, samples were prepared with 0.3% cellulose fiber, 0.2%, 0.3% 0.4%, and 0.5% CBs. The results of the CB-modified samples were compared with the sample with cellulose fiber and fresh bitumen (0% fiber). The results show that the physical and rheological properties of bitumen incorporating CBs improve significantly, and CBs could be used instead of virgin cellulose fiber as a fiber modifier.

The toxicity and valorization options of cigarette butts.

Cigarette butts, one of the most abundant forms of waste in the world, contain more than 4000 toxic chemicals and pose serious risks to the health of wildlife, humans, and marine and freshwater organisms. Although trivial in size, trillions of cigarettes are produced every year worldwide, resulting in the accumulation of tonnes of toxic waste litter. In 2016, a world production of over 5.7 trillion cigarettes was reported with the majority comprising cellulose acetate filters - a polymer with poor biodegradability. Depending on the environmental conditions, cellulose acetate filters can take up to 10 years to decompose during which time they leach heavy metals and toxic chemicals into the environment. Although possible disposal methods for collected cigarette butt waste include incineration and landfilling, both techniques may result in the release of hazardous fumes and can be costly. However, recycling CBs in different materials could be a possible solution for this concurrent environmental pollution. A number of novel studies have been publicized on recycling cigarette butts with encouraging results, and several methods have been studied, including recycling of cigarette butts in asphalt concrete and fired clay bricks, as a carbon source, sound absorbing material, corrosion inhibitor, biofilm carrier, and many more. Hence, this paper provides a comprehensive review and discussion of various studies that have been carried out on the toxicity and valorization of cigarette butt waste and investigates the feasibility and sustainability of recycling methods adopted. Further research and developments are essential for the widespread application of recycling cigarette butts.

Nanoparticles in Construction Materials and Other Applications, and Implications of Nanoparticle Use.

Nanoparticles are defined as ultrafine particles sized between 1 and 100 nanometres in diameter. In recent decades, there has been wide scientific research on the various uses of nanoparticles in construction, electronics, manufacturing, cosmetics, and medicine. The advantages of using nanoparticles in construction are immense, promising extraordinary physical and chemical properties for modified construction materials. Among the many different types of nanoparticles, titanium dioxide, carbon nanotubes, silica, copper, clay, and aluminium oxide are the most widely used nanoparticles in the construction sector. The promise of nanoparticles as observed in construction is reflected in other adoptive industries, driving the growth in demand and production quantity at an exorbitant rate. The objective of this study was to analyse the use of nanoparticles within the construction industry to exemplify the benefits of nanoparticle applications and to address the short-term and long-term effects of nanoparticles on the environment and human health within the microcosm of industry so that the findings may be generalised. The benefits of nanoparticle utilisation are demonstrated through specific applications in common materials, particularly in normal concrete, asphalt concrete, bricks, timber, and steel. In addition, the paper addresses the potential benefits and safety barriers for using nanomaterials, with consideration given to key areas of knowledge associated with exposure to nanoparticles that may have implications for health and environmental safety. The field of nanotechnology is considered rather young compared to established industries, thus limiting the time for research and risk analysis. Nevertheless, it is pertinent that research and regulation precede the widespread adoption of potentially harmful particles to mitigate undue risk.

Amazing Types, Properties, and Applications of Fibres in Construction Materials.

Fibres have been used in construction materials for a very long time. Through previous research and investigations, the use of natural and synthetic fibres have shown promising results, as their presence has demonstrated significant benefits in terms of the overall physical and mechanical properties of the composite material. When comparing fibre reinforcement to traditional reinforcement, the ratio of fibre required is significantly less, making fibre reinforcement both energy and economically efficient. More recently, waste fibres have been studied for their potential as reinforcement in construction materials. The build-up of waste materials all around the world is a known issue, as landfill space is limited, and the incineration process requires considerable energy and produces unwanted emissions. The utilisation of waste fibres in construction materials can alleviate these issues and promote environmentally friendly and sustainable solutions that work in the industry. This study reviews the types, properties, and applications of different fibres used in a wide range of materials in the construction industry, including concrete, asphalt concrete, soil, earth materials, blocks and bricks, composites, and other applications.

A study of gas emissions during the firing process from bricks incorporating biosolids.

This paper investigates the five different gas emissions during the firing process of clay bricks and bricks incorporating biosolids. In this study, three different biosolids produced at the Western Treatment Plant and Eastern Treatment Plant, Melbourne, were used as an alternative raw material to the conventional brick soil to produce bricks. Three sets of bricks were manufactured incorporating 25% of biosolids by weight. Initially, three biosolids samples and brick soil were characterised by their chemical and mineral compositions, organic content and particle size distribution. Brick samples were fired in a tube furnace at a temperature of 1050 °C for three hours. Five different gas emissions - SO2, CO2, NO, CO, and HCN - were measured at different temperatures throughout the firing process. The results indicated that all the gas emissions were increased with the addition of biosolids. The energy input and production based factors were developed based on the experimental results, which were then used in the life cycle assessment of biosolids-amended bricks. The cradle-to-gate results of life cycle assessment revealed that the production of biosolids bricks reduced environmental impacts for all impact categories except water depletion impact when compared to conventional bricks.

Leachate analysis of green and fired-clay bricks incorporated with biosolids.

The substantial increase in biosolids production throughout the world requires sustainable routes for reuse. This study describes the leaching behaviour of potentially hazardous metals from the green and fired bricks incorporating four different biosolids samples from the Eastern treatment plant (ETP) and Western treatment plant (WTP) in Melbourne. The biosolids samples were characterized by XRD, XRF, TGA, particle size distribution, and organic content. The leaching of As, Ag, Ba, Be, Cd, Cr, Cu, Mo, Ni, Pb, Sb, Se, and Zn was evaluated for both the green and the fired bricks according to the Toxicity characteristic leaching procedure (TCLP) and the Australian bottle leaching procedure (ABLP). The leaching of heavy metals from both the green and the fired bricks was compared to investigate the effect of firing on the leaching capability of bricks. The results showed that the leaching of heavy metals from fired bricks was significantly lower than that for the green bricks. The ABLP concentrations of heavy metals were higher than those found using the TCLP method, mainly due to the higher specific surface area of the particles used in the ABLP method. Moreover, bricks were evaluated by the technological properties, such as compressive strength, density and water absorption.

The urban heat island effect, its causes, and mitigation, with reference to the thermal properties of asphalt concrete.

The Urban Heat Island (UHI) is a phenomenon that affects many millions of people worldwide. The higher temperatures experienced in urban areas compared to the surrounding countryside has enormous consequences for the health and wellbeing of people living in cities. The increased use of manmade materials and increased anthropogenic heat production are the main causes of the UHI. This has led to the understanding that increased urbanisation is the primary cause of the urban heat island. The UHI effect also leads to increased energy needs that further contribute to the heating of our urban landscape, and the associated environmental and public health consequences. Pavements and roofs dominate the urban surface exposed to solar irradiation. This review article outlines the contribution that pavements make to the UHI effect and analyses localized and citywide mitigation strategies against the UHI. Asphalt Concrete (AC) is one of the most common pavement surfacing materials and is a significant contributor to the UHI. Densely graded AC has low albedo and high volumetric heat capacity, which results in surface temperatures reaching upwards of 60 °C on hot summer days. Cooling the surface of a pavement by utilizing cool pavements has been a consistent theme in recent literature. Cool pavements can be reflective or evaporative. However, the urban geometry and local atmospheric conditions should dictate whether or not these mitigation strategies should be used. Otherwise both of these pavements can actually increase the UHI effect. Increasing the prevalence of green spaces through the installation of street trees, city parks and rooftop gardens has consistently demonstrated a reduction in the UHI effect. Green spaces also increase the cooling effect derived from water and wind sources. This literature review demonstrates that UHI mitigation techniques are best used in combination with each other. As a result of the study, it was concluded that the current mitigation measures need development to make them relevant to various climates and throughout the year. There are also many possible sources of future study, and alternative measures for mitigation have been described, thereby providing scope for future research and development following this review.

A practical proposal for solving the world's cigarette butt problem: Recycling in fired clay bricks.

The disposal and littering of cigarette butts (CBs) is a serious environmental problem. Trillions of cigarettes are produced every year worldwide, resulting in millions of tonnes of toxic waste being dumped into the environment in the form of cigarette butts. As CBs have poor biodegradability, it can take many years for them to break down. This paper reviews and presents some of the results of a study on the recycling of CBs into fired clay bricks. Bricks with 2.5%, 5%, 7.5%, and 10% CB content by weight were manufactured and tested, and then compared against control clay bricks with 0% CB content. The results showed that the dry density decreased by up to 30% and the compressive strength decreased by 88% in bricks with 10% CBs. The calculated compressive strength of bricks with 1% CBs was determined to be 19.53Mpa. To investigate the effect of mixing time, bricks with 7.5% CB content were manufactured with different mixing times of 5, 10, and 15min. To test the effect of heating time on the properties of CB bricks, the heating rate used during manufacturing was changed to 0.7, 2, 5, and 10°Cmin(-1). Bricks with 0% and 5% CB content were fired with these heating rates. Leachate tests were carried out for bricks with 0%, 2.5%, 5%, and 10% CB content. The emissions released during firing were tested for bricks with 0% and 5% CB content using heating rates of 0.7, 2, 5, and 10°Cmin(-1). The gases tested were carbon monoxide (CO), carbon dioxide (CO2), chlorine (Cl2), nitrogen oxide (NO), and hydrogen cyanide (HCN). Finally, estimations were made for the energy that could be saved by firing bricks incorporating CBs. Calculations showed that up to 58% of the firing energy could potentially be saved. Bricks were shown to be a viable solution for the disposal of CBs. They can reduce contamination caused by cigarette butts and provide a masonry construction material that can be either loadbearing or non-loadbearing, depending on the quantity of CBs incorporated. This paper proposes the use of bricks with 1% CB content throughout the brick-manufacturing industry. If bricks contained as little as 1% CB content, they would still provide a solution for the issue of CB recycling while maintaining properties very similar to those of a non-CB brick. Our calculations show that, theoretically, only 2.5% of the world's annual brick production is necessary to completely offset the worldwide, annual cigarette production.