Carbon Footprint of Waste-Derived Composites

The modern world is facing unprecedented population growth and increasing demand for consumer goods which, in turn, causes a demand for an increasing supply of materials. At the same time, technological advancement has enabled the development of novel materials suitable for a wide range of applications. Composites are a great example of such materials because they can be produced from feedstock which is not suitable for other applications, such as waste. A substantial body of research has been conducted exploring various industrial and municipal waste streams. Composite matrices can be made of low-quality recycled plastic originating from construction and demolition activities while fillers can be made from a variety of waste streams, such as primary sludge, wood waste, sawdust, agricultural residues, mineral wool, and plasterboard, among others. Generally, the cumulative share of the matrix and filler is above 90% of the composites, thus significantly contributing to a potential reduction in environmental impacts, including climate change. The climate change impacts of waste-derived composites (WDC) can be best assessed using the carbon footprint (CF) methodology. The CF is a specific node of life cycle assessment (LCA) focusing on climate change impacts. The method accounts for the emissions and removal of greenhouse gases during all life-cycle stages of composites or parts thereof.Post-print / Final draf

The role of waste pretreatment on the environmental sustainability of waste management

The ever-increasing world population has exerted unprecedented pressure on the world’s natural ecosystems through both the production and consumption of various products. Human behaviour is having a destructive impact on the environment, and waste generation and disposal represents one of the key sources of this negative impact. To tackle the problem, a systematic transition towards a circular economy, which is largely built on the possibilities of waste recycling, has been initiated. The continually increasing waste recycling rates can only be achieved by exploiting the advanced waste treatment technologies that are available. However, the operation of such technologies often requires substantial amounts of energy or materials, thereby potentially eliminating the benefits of waste recycling. The primary goal of the research presented in this dissertation was to examine the contribution of the waste pretreatment (PT) activities on the overall environmental impact of waste recycling. An analysis of this nature has not previously been performed on a systematic basis across a variety of waste types and environmental impact categories. The specific objectives of this research study were as follows: (i) to quantify the environmental impact of waste PT activities, (ii) to identify the factors that make the most significant contribution to the impact of the PT activities, (iii) to compare the cumulative induced environmental impact caused by waste PT activities and the final recovery process versus the cumulative avoided impact caused by the conventional disposal of waste and product substitution, and (iv) to identify the potential conditions in which break-even points can be achieved. The goal and the objectives set for this research were achieved by conducting six life cycle assessment (LCA) studies in accordance with the ISO 14040 and ISO14044 international standards. The impact of the recycling or recovery of multiple waste types via a wide number of recycling methods was assessed in terms of the global warming potential (GWP), abiotic depletion potential (ADP), and human toxicity potentials (HTP). The results of the research reveal that, in general, the need to pretreat waste does not increase the environmental impact of waste recycling activities when compared to the conventional disposal in the majority of scenarios and impact categories; however, a significant variation in the relative importance of the PT activities amongst the alternative studies and the impact categories was identified. The lowest relative importance of the PT of 0.44-0.52% was achieved for the carcinogenic HTPC in the scenario in which a mineral fraction from the treatment of the municipal solid waste incineration bottom ash (MSWI BA) was recycled via either a road construction or garden stone production process. On the contrary, the highest relative importance of the PT activities of 64% was recorded for the GWP in the scenario in which phosphorous was recovered from sewage sludge ash. The results of the GWP analysis revealed that the PT activities incorporating advanced waste treatment methods had a significant contribution of 29-64% to the overall impact of the entire waste management systems. On the contrary, the low contribution of PT activities of 0.3-3.7% to the overall GWP was recorded when conventional disposal processes that have a high impact on the GWP, such as landfilling of organic waste, were avoided. Furthermore, PT activities could have a low impact on GWP when waste recycling results in the substitution of materials that have substantial carbon footprints; e.g., burned lime or cement. In terms of the ADP, the significant importance of the PT, which ranged from 21- 36%, could be expected when the PT activities require a comparatively high amount of fuels, while also having a low impact on conventional disposal and product substitution. On the contrary, the PT activities may have a low contribution of 0.24-1.2%, when waste recycling results in the substitution of materials or fuels that have a high impact on the ADP; e.g., phosphorous or cement. Straightforward results were achieved for the carcinogenic HTPC, in which only a low (0.44-0.52%) and low-to-moderate (3.7-5.0%) share of the overall impact was associated with the PT activities since the toxicity was mainly related to the release of heavy metals during thermal residue recycling processes. On the contrary, a moderate (1.9-9.2%) and a significant (12-41%) share of the non-carcinogenic HTPNON-C was associated with the PT activities in situations in which the major contributors were the consumption of fuels required for transporting and incorporating the waste in the final recovery process. The factors that have the largest impact on the contribution of PT activities varied across the studies; however, the variation of the factors studied in the sensitivity analysis revealed that break-even points are seldom achieved. One break-even point was achieved for the GWP in the scenario in which nitrogen recovery was incorporated into the thermally drying of sewage sludge. In this case, the GWP increased from the avoided impact of 18% to the induced impact of 2.6%. Another break-even point was identified for the non-carcinogenic HTPNON-C in the scenario in which the mineral fraction obtained during the treatment of MSWI BA in the garden stone production process was recycled. In this scenario, the avoided HTPNON-C of 14% transformed into the additional impact of 17%. It is important to acknowledge an anticipated variation in the inventory data used in the study, which might alter the results achieved. Furthermore, some significant environmental areas of concern were not considered in the research due to limitations in the scope of the study and the inventory data available. Finally, the impact of the system boundaries on the relative importance of the PT should be studied in more depth to achieve comprehensive insights into the relationship between PT activities and environmental impact throughout the entire life cycle of a product

Sustainability of Waste Management System: Waste Generation and Collection

Waste means any substance or object, which the holder discards or intends or is required to discard. Waste generation begins at the point in time when it is being discarded. After that, generation cannot be prevented or reduced. Solid waste includes, among others, municipal, agricultural, mining, industrial, commercial solid waste, construction and demolition waste, electronic waste, and sludge generated during wastewater treatment. Solid waste is generated in all the stages of the life cycles of different products and materials. The largest volumes of waste are usually generated during mining and quarrying of raw materials, as well as from construction and demolition activities. Municipal solid waste (MSW) is the most commonly known, very heterogeneous waste which is defined as solid waste originating from households and similar kind of waste generated in commerce, offices, public institutes, and municipal services. Generation rate of waste from different business fields is varying according the volume of the business activities and specific waste generation of producing a unit of each product. Municipal solid waste generation rate is affected mostly by the population and gross domestic product (GDP) per capita. Waste collection systems consist of the waste collection bins on the yards of the houses or enterprises, loading of the waste to the collection vehicles, and further transportation to the waste treatment or disposal facilities. Waste can be collected as separate fractions or mixed waste straight from the households or other sources, or from regional collection points. If waste is not being collected, it is considered as littering, which should be avoided. Collection systems are commonly not working properly in developing counties. Waste generation phase defines the amount and composition of waste that has to be treated, recovered, and disposed. Waste collection phase has good potential to separate recyclables and recoverables from disposable waste. Thus, these phases are very important for the sustainability of waste management.Post-print / Final draf

Sustainability of Waste Management System: Treatment and Separation for Material Recovery

Increased global concern on the state of our climate has driven also the waste management sector to look for solutions that enable lowering of the environmental impacts by increasing waste reduction and material recycling. Material recycling is more feasible and efficient when there is source separation in place because source separation usually leads to the best quality of the separated materials. However, sometimes source separation does not work properly (e.g., because of the low education level of people) or it is difficult to apply (e.g., because of a fixed and dense city infrastructure). The strict material recycling targets in the EU necessity that mechanical separation is included as a tool for increasing the recycling rate. The aim of the mechanical treatment is to separate materials suitable for recycling from the mixed waste stream by separating recoverable components and impurities to different streams. A multitude of processes is usually required to obtain recyclable materials out of the mixed waste stream, for example, from mixed municipal solid waste (MSW) or mixed construction and demolition waste (C&D waste). However, it should be borne in mind that often the most important factors from the environmental impacts point of view for recovery of materials by mechanical treatment are yield of recoverables, quality and demand of recovered materials as well as the environmental impact of replaced virgin materials. At the end of the day, the tightened recycling rates strive for the development of various treatment and separation technologies and their better performance is achieved.Post-print / Final draf

Sustainability of Waste Management Systems: Energy Recovery

Energy recovery from waste represents an economically, socially, and expectedly environmentally acceptable option of waste management. Energy recovery is widely represented by waste incineration, gasification, pyrolysis, and anaerobic digestion. Sustainability of all energy recovery methods is not only determined by the recovery processes themselves but by a wide range of components of the energy recovery systems, such as waste properties, operating conditions, types of products, and demand on them, to name a few. For example, biowaste is more suitable for anaerobic digestion than incineration. At the same time, incineration of waste without the possibility to utilize heat produced neither as district, nor process heat, could have a higher impact on the environment than its gasification or pyrolysis. When systematically assessing energy recovery methods, the types of products being derived (electricity, heat, chemicals, biogas, monomers, oils, etc.), and the alternatives substituted on the market plays one of the most important roles in the sustainability of energy recovery from waste.Post-print / Final draf

Wooden and Plastic Pallets: A Review of Life Cycle Assessment (LCA) Studies

Pallets are the tiny cogs in the machine that drive transportation in the global economy. The profusion of pallets in today’s supply chain warrants the investigation and discussion of their respective environmental impacts. This paper reviews the life cycle assessment studies analyzing the environmental impacts of pallets with the intent of providing insights into the methodological choices made, as well as compiling the inventory data from the studies reviewed. The study is a meta-analysis of eleven scientific articles, two conference articles, two peer-reviewed reports, and one thesis. The review was implemented to identify the key methodological choices made in those studies, such as their goals, functional units, system boundaries, inventory data, life cycle impact assessment (LCIA) procedures, and results. The 16 studies reviewed cumulatively analyzed 43 pallets. Mostly pooled (n = 22/43), block-type (n = 13/43), and wooden (n = 32/43) pallets with dimensions of 1219 mm × 1016 mm or 48 in. × 40 in. (n = 15/43) were studied. Most of the studies represented pallet markets in the United States (n = 9/16). Load-based (e.g., 1000 kg of products delivered), trip-based (e.g., 1000 trips), and pallet-based (e.g., one pallet) functional units were declared. A trip-based functional unit seems the most appropriate for accounting of the function of the pallets, as its purpose is to carry goods and facilitate the transportation of cargo. A significant amount of primary inventory data on the production and repair of wooden and plastic pallets are available, yet there are significant variations in the data. Data on pallets made of wood–polymer composites was largely missing

Environmental impacts of wooden, plastic, and wood-polymer composite pallet: a life cycle assessment approach

Purpose Waste recycling is one of the essential tools for the European Union’s transition towards a circular economy. One of the possibilities for recycling wood and plastic waste is to utilise it to produce composite product. This study analyses the environmental impacts of producing composite pallets made of wood and plastic waste from construction and demolition activities in Finland. It also compares these impacts with conventional wooden and plastic pallets made of virgin materials. Methods Two different life cycle assessment methods were used: attributional life cycle assessment and consequential life cycle assessment. In both of the life cycle assessment studies, 1000 trips were considered as the functional unit. Furthermore, end-of-life allocation formula such as 0:100 with a credit system had been used in this study. This study also used sensitivity analysis and normalisation calculation to determine the best performing pallet. Result and discussion In the attributional cradle-to-grave life cycle assessment, wood-polymer composite pallets had the lowest environmental impact in abiotic depletion potential (fossil), acidification potential, eutrophication potential, global warming potential (including biogenic carbon), global warming potential (including biogenic carbon) with indirect land-use change, and ozone depletion potential. In contrast, wooden pallets showed the lowest impact on global warming potential (excluding biogenic carbon). In the consequential life cycle assessment, wood-polymer composite pallets showed the best environmental impact in all impact categories. In both attributional and consequential life cycle assessments, plastic pallet had the maximum impact. The sensitivity analysis and normalisation calculation showed that wood-polymer composite pallets can be a better choice over plastic and wooden pallet. Conclusions The overall results of the pallets depends on the methodological approach of the LCA. However, it can be concluded that the wood-polymer composite pallet can be a better choice over the plastic pallet and, in most cases, over the wooden pallet. This study will be of use to the pallet industry and relevant stakeholders.Publishers versio

Wooden and Plastic Pallets: A Review of Life Cycle Assessment (LCA) Studies

Pallets are the tiny cogs in the machine that drive transportation in the global economy. The profusion of pallets in today’s supply chain warrants the investigation and discussion of their respective environmental impacts. This paper reviews the life cycle assessment studies analyzing the environmental impacts of pallets with the intent of providing insights into the methodological choices made, as well as compiling the inventory data from the studies reviewed. The study is a meta-analysis of eleven scientific articles, two conference articles, two peer-reviewed reports, and one thesis. The review was implemented to identify the key methodological choices made in those studies, such as their goals, functional units, system boundaries, inventory data, life cycle impact assessment (LCIA) procedures, and results. The 16 studies reviewed cumulatively analyzed 43 pallets. Mostly pooled (n = 22/43), block-type (n = 13/43), and wooden (n = 32/43) pallets with dimensions of 1219 mm × 1016 mm or 48 in. × 40 in. (n = 15/43) were studied. Most of the studies represented pallet markets in the United States (n = 9/16). Load-based (e.g., 1000 kg of products delivered), trip-based (e.g., 1000 trips), and pallet-based (e.g., one pallet) functional units were declared. A trip-based functional unit seems the most appropriate for accounting of the function of the pallets, as its purpose is to carry goods and facilitate the transportation of cargo. A significant amount of primary inventory data on the production and repair of wooden and plastic pallets are available, yet there are significant variations in the data. Data on pallets made of wood–polymer composites was largely missing

Life cycle assessment of the existing and proposed municipal solid waste management system in Moscow, Russia

This study provides the first life cycle assessment (LCA) for municipal solid waste waste management system in one of the largest cities in Europe, Moscow. Its significance stems from recent important changes in the waste management system, the introduction of limited source separate collection in 2020, and the first examination of sorted municipal solid waste (MSW) composition. Moscow city generates 8.1 million tonnes of MSW per year, most of which is still mainly disposed of in landfill sites. The study assesses the current situation, the waste management system planned to be operational by 2024 and proposes improvements to separate collection and treatment of organic waste that could be adopted in the future. In this context, 6 scenarios are compared using LCA based approach. The impacts are presented as global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP). The results show that the existing MSW management system has the highest GWP and AP. Planned changes to the system by 2024 will reduce impacts in all categories. The largest emissions reduction potential is found for refuse-derived fuel (RDF) production and its use in cement kilns as a replacement for coal, which reduces emissions by 1.1 kg CO2-eq/kgRDF and results in a negative AP. The change in EP remains negligible. Separate collection and treatment of biowaste is also beneficial, with anaerobic digestion being the most advantageous treatment method. Nevertheless, even after the implementation of all initiatives, landfill still represents about 53% of direct emissions in GWP. Sensitivity analysis estimated that flaring of landfill gas can reduce GWP from landfill sites by a factor greater than two. With these changes, the total emissions of the system approach zero. Energy recovery at MSW incineration plants and substitution to the grid gives reductions in GWP and EP in the range of 35% and provides especially significant reductions in AP. The waste management system in Moscow accounts for 3% of residents’ carbon footprint, which might drop to 1% if appropriate changes to the system are implemented.Post-print / Final draf

Optimal Recycling Combination of Ash in South-East Finland

The present world energy production is heavily relying on the combustion of solid fuels like coals, peat, biomass, municipal solid waste, whereas the share of renewable fuels is anticipated to increase in the future to mitigate climate change. In Finland, peat and wood are widely used for energy production. In any case, the combustion of solid fuels results in generation of several types of thermal conversion residues, such as bottom ash, fly ash, and boiler slag. The predominant residue type is determined by the incineration technology applied, while its composition is primarily relevant to the composition of fuels combusted. An extensive research has been conducted on technical suitability of ash for multiple recycling methods. Most of attention was drawn to the recycling of the coal combustion residues, as coal is the primary solid fuel consumed globally. The recycling methods of coal residues include utilization in a cement industry, in concrete manufacturing, and mine backfilling, to name few. Biomass combustion residues were also studied to some extent with forest fertilization, road construction, and road stabilization being the predominant utilization options. Lastly, residues form municipal solid waste incineration attracted more attention recently following the growing number of waste incineration plants globally. The recycling methods of waste incineration residues are the most limited due to its hazardous nature and varying composition, and include, among others, landfill construction, road construction, mine backfilling. In the study, environmental and economic aspects of multiple recycling options of thermal conversion residues generated within a case-study area were studied. The case-study area was South-East Finland. The environmental analysis was performed using an internationally recognized methodology — life cycle assessment. Economic assessment was conducted applying a widely used methodology — cost-benefit analysis. Finally, the results of the analyses were combined to enable easier comparison of the recycling methods. The recycling methods included the use of ash in forest fertilization, road construction, road stabilization, and landfill construction. Ash landfilling was set as a baseline scenario. Quantitative data about the amounts of ash generated and its composition was obtained from companies, their environmental reports, technical reports and other previously published literature. Overall, the amount of ash in the case-study area was 101 700 t. However, the data about 58 400 t of fly ash and 35 100 t of bottom ash and boiler slag were included in the study due to lack of data about leaching of heavy metals in some cases. The recycling methods were modelled according to the scientific studies published previously. Overall, the results of the study indicated that ash utilization for fertilization and neutralization of 17 600 ha of forest was the most economically beneficial method, which resulted in the net present value increase by 58% compared to ash landfilling. Regarding the environmental impact, the use of ash in the construction of 11 km of roads was the most attractive method with decreased environmental impact of 13% compared to ash landfilling. The least preferred method was the use of ash for landfill construction since it only enabled 11% increase of net present value, while inducing additional 1% of negative impact on the environment. Therefore, a following recycling route was proposed in the study. Where possible and legally acceptable, recycle fly and bottom ash for forest fertilization, which has strictest requirements out of all studied methods. If the quality of fly ash is not suitable for forest fertilization, then it should be utilized, first, in paved road construction, second, in road stabilization. Bottom ash not suitable for forest fertilization, as well as boiler slag, should be used in landfill construction. Landfilling should only be practiced when recycling by either of the methods is not possible due to legal requirements or there is not enough demand on the market. Current demand on ash and possible changes in the future were assessed in the study. Currently, the area of forest fertilized in the case-study are is only 451 ha, whereas about 17 600 ha of forest could be fertilized with ash generated in the region. Provided that the average forest fertilizing values in Finland are higher and the area treated with fellings is about 40 000 ha, the amount of ash utilized in forest fertilization could be increased. Regarding road construction, no new projects launched by the Center of Economic Development, Transport and the Environment in the case-study area were identified. A potential application can be found in the construction of private roads. However, no centralized data about such projects is available. The use of ash in stabilization of forest roads is not expected to increased in the future with a current downwards trend in the length of forest roads built. Finally, the use of ash in landfill construction is not a promising option due to the reducing number of landfills in operation in Finland.Publishers versio