Thomas H Christensen

• Technical University of Denmark

Biodegradable plastics are often promoted as sustainable alternatives to conventional plastics. Nevertheless, significant knowledge gaps exist regarding their degradation under relevant conditions, particularly when compounded into commercial products. To this end, the present research investigates the disintegration of ten commercially available b...

The liquid fraction of digestate (LFD) from anaerobic digestion of food waste contains high nitrogen concentrations, and in some countries, the LFD is treated as wastewater. We modelled alternative LFD treatments, including pretreatment with the partial nitritation Anammox (PNA) process. The PNA effluent is discharged to the sewers to undergo furth...

Life cycle assessment (LCA) models quantifying the environmental aspects of waste management have become an integral part of waste management decision-making over the last two decades and have provided ample knowledge on both environmental benefits and drawbacks in the way we handle waste. Waste management and LCA modelling of waste management syst...

Sewage sludge (SS) management remains a challenge across the world. We quantified the potential climate change impacts of eight conventional technology configurations (TCs) for SS treatment and disposal by considering four different energy exchanges and using a life cycle assessment (LCA) model that employed uncertainty distributions for 104 model...

The biological treatment of municipal sewage sludge, including anaerobic digestion and composting, was reviewed with the purpose of establishing inventory data to address all the inputs and outputs related to sludge treatment. We identified 193 scientific papers, resulting in 64 datasets on anaerobic digestion and 35 datasets on composting. For ana...

Biogas from anaerobic digestion is an important renewable energy source. Combining its utilisation with carbon capture and storage (CCS) or carbon capture and utilisation (CCU) may improve climate change performance. This study uses life cycle assessment to evaluate the environmental impacts of 17 biogas management technology configurations (TCs)....

Technological comparison and system modelling of sewage sludge treatment are important in terms of sustainable development and climate change mitigation. Dewatering and drying are important processes for reducing volume for transportation and often a requirement for further sludge treatment. Inventory data on mass transfers and material and energy...

System modelling of sewage sludge (SS) treatment attracts a growing interest for better comparison and optimisation of technologies. However, SS parameters need to be generalised to be used in holistic assessments, since scattered data may inhibit the development and interpretation of system models. A review of the literature on SS parameters relev...

One of the important tasks of the environmental policy of the Russian Federation is to implement an integrated regional waste management system through the active involvement of production and consumption waste in the economic turnover, the use of environmentally sound recycling methods, the solution of environmental problems related to waste manag...

The thermal treatment of sewage sludge has gained much interest in recent years, as exemplified by the 269 papers found in the scientific literature for the period 2010–2021. We identified 140 datasets in 57 papers presenting inventory data related to mass flows, energy and emissions for the incineration, gasification and pyrolysis of sewage sludge...

The potential climate change impacts of the development in Chinese household waste management, with less landfilling, more incineration with energy recovery, and source-separated food waste treated in biorefineries, were assessed through a life cycle assessment. When the waste management system interacts with a fossil-based energy system, landfilli...

Purpose Future scenarios and life cycle assessment (LCA) are powerful tools that can provide early sustainability assessments of novel products, technologies and systems. The combination of the two methods involves practical and conceptual challenges, but formal guidance and consensus on a rigorous approach are currently missing. This study provide...

Amending municipal solid waste incineration with carbon capture and storage (CCS) is a new approach that can reduce the climate change impacts of waste incineration. This study provides a detailed analysis of the consequences of amending the new Amager Bakke incinerator in Copenhagen (capacity: 600,000 tonnes waste per year) with CCS as a post-comb...

Biorefining of Chinese food waste (FW) into transport fuels was assessed in terms of amount of fuel produced and over all Global Warming Potential (GWP) for six different scenarios including biogas, biomethane, bioethanol and biodiesel in different combinations. The life-cycle perspective used included GWP aspects of material and energy use, emissi...

The effects of amending municipal solid waste incineration (MSWI) with carbon capture and storage (CCS) via MEA (Monoethanolamine) technology differ according to the air pollution control technologies and energy recovery systems. Electricity output reduces by one-third for power-only plants and halves for combined heat-and-power plants, while varia...

Amending municipal solid waste incineration (MSWI) with carbon capture and utilisation (CCU) can simultaneously lower the climate change impacts of incineration and supply carbon for a range of uses. However, life cycle assessment (LCA) shows that technology choices and the benefits of CCU applied to MSWI depend on the energy system in which the MS...

Life cycle assessment (LCA) has been used in waste management for the last two decades and hundreds of journal papers have been published. The use of LCA in waste management has provided a much-improved holistic view of waste management including waste flows and potential environmental impacts. Although much knowledge has been obtained from LCA stu...

The environmental impact potentials of producing bioethanol from corn stover were systematically assessed by life cycle assessment using datasets reported in the literature. The 15% best datasets with respect to global warming potential for seven different technological configurations were extracted from a published database reviewing 474 publicati...

Bioethanol from residual corn stover could contribute to lowering CO 2 loads within the transport sector, if used as an amendment to gasoline. We modelled by life cycle assessment and Monte Carlo simulation seven different technological configurations for producing bioethanol from corn stover based on consistent mass flows and estimated ethanol pro...

Consistent material and substance flow diagrams for five alternative biorefinery scenarios for treating Chinese food waste were obtained by combining reported experimental research data and material flow analysis. The biorefinery alternatives produced biogas, biomethane, bioethanol and biodiesel in various combinations. The compiled statistical dat...

A life cycle assessment (LCA) was performed on five garden waste treatment practices: the production of mature compost including the woody fraction (MCIW), the production of mature compost without the woody fraction (MCWW), the production of immature compost without the woody fraction (ICWW), fresh garden waste including the woody fraction (GWIW) a...

The amount of waste which is being recycled is increasing in Europe. Garden waste is increasingly composted and land applied. However, composting to full maturity requires resources in terms of space, equipment and labour. Alternatives could include a simple shredding, or composting for a shorter time. Finally, an option could be to remove trunks a...

The current waste management system, handling around 500,000 t of household, commercial, and institutional waste annually in the Irkutsk region, Siberia, is based on landfilling in an old landfill with no controls of leachate and gas. Life-cycle assessment modelling of the current system shows that it is a major load on the environment, while the s...

A life cycle assessment (LCA) was performed on five commonly applied sewage sludge treatment practices: dewatering of mixed sludge (DMS), lime stabilisation of dewatered sludge (LIMS), anaerobic digestion of mixed sludge (ADS), dewatering of anaerobically-digested sludge (DADS) and incineration of dewatered anaerobically-digested sludge (INC). In t...

An attributional life cycle assessment (LCA) of the management of 1 ton of household waste was conducted in accordance with ISO 14044:2006 and the ILCD Handbook for seven European countries, namely Germany, Denmark, France, UK, Italy, Poland and Greece, representing different household waste compositions, waste management practices, technologies, a...

The contribution of misplaced special waste (sWEEE, lamps, CRT, batteries, ink cartridges and cables) to environmental impacts from incineration of residual household waste was quantified through life cycle assessment (LCA)-modelling. Misplaced special waste was quantified to constitute less than 1% of the net impact for most environmental impact c...

The composition of waste materials has fundamental influence on environmental emissions associated with waste treatment, recycling and disposal, and may play an important role also for the Life Cycle Assessment (LCA) of waste management solutions. However, very few assessments include effects of the waste composition and waste LCAs often rely on po...

The environmental importance of capital goods (trucks, buildings, equipment, etc.) was quantified by LCA modelling 1 tonne of waste treated in five different waste management scenarios. The scenarios involved a 240 L collection bin, a 16 m3 collection truck, a composting plant, an anaerobic digestion plant, an incinerator and a landfill site. The c...

Land application of sewage sludge has a number of advantages over other alternatives, but is also associated with environmental impacts. To make proper assessments of different sludge treatments, it is crucial to have reliable estimates of emissions after the application of different sludge types. However, because of the complexity of the agricultu...

Purpose Identification of key inputs and their effect on results from Life Cycle Assessment (LCA) models is fundamental. Because parameter importance varies greatly between cases due to the interaction of sensitivity and uncertainty, these features should never be defined a priori. However, exhaustive parametrical uncertainty analyses may potential...

Available @: http://www.dtu.dk/-/media/DTUdk/Samarbejde/Skifergas_udredning/videnskabelig_udredning_af_international_viden_om_skifergas_relateret_til_en_dansk_kontekst.ashx?la=da Indvinding af skifergas har i de senere år påkaldt sig stigende interesse internationalt og i Danmark. På den baggrund har Miljø- og Fødevareministeriet bedt DTU, GEUS og...

The agro-ecosystem model Daisy was used to explore the long-term fate of nitrogen (N) after land application of compost and digestate (based on source separated organic municipal solid waste (MSW)). The cumulative crop N yield response and emissions for mineral fertilizer (MF), anaerobically digested organic waste (MSW-D), and composted organic was...

Life cycle assessment (LCA) modelling of construction and demolition waste (C&DW) management was carried out. The functional unit was management of 1 Mg mineral, source separated C&DW, which is either utilised in road construction as a substitute for natural aggregates, or landfilled. The assessed environmental impacts included both non-toxic and t...

Five samples of construction and demolition waste (C&DW) were investigated in order to quantify leaching of inorganic elements under percolation conditions according to two different experimental setups: standardised up-flow saturated columns (<4mm particle size) and unsaturated, intermittent down-flow lysimeters (<40mm particle size). While standa...

Application of sewage sludge on agricultural land becomes more and more common in many parts of the world in order to recycle the nutrients from the sludge. A range of sewage sludge stabilization techniques are available to make the sludge more stable prior to storage, transportation, and application. These stabilization techniques include dewateri...

Materials and energy used for construction of anaerobic digestion (AD) and windrow composting plants were quantified in detail. The two technologies were quantified in collaboration with consultants and producers of the parts used to construct the plants. The composting plants were quantified based on the different sizes for the three different typ...

A new model for the environmental assessment of environmental technologies, EASETECH, has been developed. The primary aim of EASETECH is to perform life-cycle assessment (LCA) of complex systems handling heterogeneous material flows. The objectives of this paper are to describe the EASETECH framework and the calculation structure. The main noveltie...

A Life Cycle Assessment (LCA) of a municipal wastewater treatment plant (WWTP) was conducted to illustrate the effect of an emission inventory data collection scheme on the outcomes of an environmental impact assessment. Due to their burden in respect to data collection, LCAs often rely heavily on existing emission and operational data, which are g...

This paper reviews databases on material recycling (primary as well as secondary production) used in life cycle assessments (LCA) of waste management systems. A total of 366 datasets, from 1980 to 2010 and covering 14 materials, were collected from databases and reports. Totals for CO2-equivalent emissions were compared to illustrate variations in...

The management of the plastic fraction is one of the most debated issues in the discussion on integrated municipal solid waste systems. Both material and energy recovery can be performed on such a waste stream, and different separate collection schemes can be implemented. The aim of the paper is to contribute to the debate, based on the analysis of...

The municipal waste management system of the region of Irkutsk is described and a life cycle assessment (LCA) performed to assess the environmental performance of the system. Annually about 500 000 tons of waste are managed. The waste originates from three sources: household waste (27%), commercial waste (23%) and office & institutional waste (44%)...

The continuously increasing solid waste generation worldwide calls for management strategies that integrate concerns for environmental sustainability. By quantifying environmental impacts of systems, life cycle assessment (LCA) is a tool, which can contribute to answer that call. But how, where and to which extent has it been applied to solid waste...

Life cycle assessment (LCA) is increasingly used in waste management to identify strategies that prevent or minimise negative impacts on ecosystems, human health or natural resources. However, the quality of the provided support to decision- and policy-makers is strongly dependent on a proper conduct of the LCA. How has LCA been applied until now?...

The fate of total organic carbon, 32 elements (Al, Ag, As, Ba, Be, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, N, Na, Ni, P, Pb, S, Sb, Se, Sn, Sr, Ti, V, and Zn) and 4 groups of organic pollutants (linear alkylbenzene sulfonates, bis(2-ethylhexyl)phthalate, polychlorinated biphenyl and polycyclic aromatic hydrocarbons) in a conventional...

Landfills with solid waste are abundant sources of groundwater pollution all over the world. Old uncontrolled municipal landfills are often large, heterogeneous sources with demolition waste, minor fractions of commercial or industrial waste, and organic waste from households. Strongly anaerobic leachate with a high content of dissolved organic car...

As compost use in agriculture increases, there is an urgent need to evaluate the specific environmental benefits and impacts as compared with other types of fertilizers and soil amendments. While the environmental impacts associated with compost production have been successfully assessed in previous studies, the assessment of the benefits of compos...

In this article, 35 published studies on life cycle assessment (LCA) of sewage sludge were reviewed for their methodological and technological assumptions. Overall, LCA has been providing a flexible framework to quantify environmental impacts of wastewater and sewage sludge treatment and disposal processes for multiple scales, ranging from process...

Purpose When performing uncertainty propagation, most LCA practitioners choose to represent uncertainties by single probability distributions and to propagate them using stochastic methods. However, the selection of single probability distributions appears often arbitrary when faced with scarce information or expert judgement (epistemic uncertainty...

A total of 26.1Mg of residual waste from 3129 households in 12 Danish municipalities was analysed and revealed that 89.6kg of Waste Electrical and Electronic Equipment (WEEE), 11kg of batteries, 2.2kg of toners and 16kg of cables had been wrongfully discarded. This corresponds to a Danish household discarding 29g of WEEE (7 items per year), 4g of b...

Materials and energy used for the construction of modern waste incineration plants were quantified. The data was collected from five incineration plants (72,000-240,000tonnes per year) built in Scandinavia (Norway, Finland and Denmark) between 2006 and 2012. Concrete for the buildings was the main material used amounting to 19,000-26,000tonnes per...

The majority of the waste in Greenland is disposed of in open dumps or incinerated in simple small-scale incinerators. There are relatively few environmental regulations that control the emissions of leachate, landfill gas and/or flue gases from incineration. Only some scrap metal and hazardous waste are collected separately and exported to Europe....

Materials and energy used for construction of a hill-type landfill of 4 million m(3) were quantified in detail. The landfill is engineered with a liner and leachate collections system, as well as a gas collection and control system. Gravel and clay were the most common materials used, amounting to approximately 260 kg per tonne of waste landfilled....

Due to increasing compost use in agriculture, there is an urgent need to evaluate compost benefits and impacts versus other fertilizers. Here we review the recent progress made in the quantification of positive effects associated with compost use on land using life cycle assessment (LCA), an internationally recognised environmental tool. Nine envir...

The capital goods for collection and transport of waste were quantified for different types of containers (plastic containers, cubes and steel containers) and an 18-tonnes compacting collection truck. The data were collected from producers and vendors of the bins and the truck. The service lifetime and the capacity of the goods were also assessed....

In some arid regions where landfill produces minimal amount of leachate, leachate recirculation is suggested as a cost-effective option. However, its long-term impacts to environment remain disputed. For the purpose of revealing the environmental impacts of leachate recirculation in landfill, four scenarios were modeled using EASEWASTE, comparing t...

Biomass and waste are expected to play a key role in future energy systems based on large shares of renewable energy resources. The LCA model EASETECH Energy was developed specifically for modelling large and complex energy systems including various technologies and several processing steps. The model allows simultaneous balancing of mass and energ...

Uncertainty analysis in LCA studies has been subject to major progress over the last years. In the context of waste management, various methods have been implemented but a systematic method for uncertainty analysis of waste-LCA studies is lacking. The objective of this paper is (1) to present the sources of uncertainty specifically inherent to wast...

The environmental impacts of waste incineration with auxiliary coal were investigated using the life-cycle-based software, EASEWASTE, based on the municipal solid waste (MSW) management system in Shuozhou City. In the current system, MSW is collected, transported, and incinerated with 250kg of coal per ton of waste. Based on observed environmental...

In Africa the majority of solid waste data is for big cities. Small and rural towns are generally neglected and waste data from these areas are often unavailable, which makes planning a proper solid waste management difficult. This paper presents the results from two waste characterization projects conducted in Kétao, a rural town in Togo during th...

An environmental assessment of the management of organic household waste (OHW) was performed from a life cycle perspective by means of the waste-life cycle assessment (LCA) model EASEWASTE. The focus was on home composting of OHW in Denmark and six different home composting units (with different input and different mixing frequencies) were modelled...

Recycling of materials from municipal solid waste is commonly considered to be superior to any other waste treatment alternative. For the material fractions with a significant energy content this might not be the case if the treatment alternative is a waste-to-energy plant with high energy recovery rates. The environmental impacts from recycling an...

Management of sewage sludge is one of the biggest challenges for water utilities; it dictates the efficiency of material recovery in the city and fate of pollutants and pathogens in wastewater. An incubation study is conducted to estimate the impact of stabilization technique to greenhouse gas (GHG) emission after land application. Anaerobic digest...

Based on available data in the literature the recovery of aluminium, copper, gold, iron, nickel, palladium and silver from high-grade WEEE was modeled by LCA. The pre-treatment of WEEE included manual sorting, shredding, magnetic sorting, Eddy-current sorting, air classification and optical sorting. The modeled metallurgical treatment facility incl...

Waste prevention has been addressed in the literature in terms of the social and behavioural aspects, but very little quantitative assessment exists of the environmental benefits. Our study evaluates the environmental consequences of waste prevention on waste management systems and on the wider society, using life-cycle thinking. The partial preven...

Bulky waste is a significant and increasing waste stream in Denmark. However, only little research has been done on its composition and treatment. In the present study, data about collection methods, waste quantities and treatment methods for bulky waste were obtained from two municipalities. In addition a sorting analysis was conducted on combusti...

Several alternatives exist for handling of individual waste fractions, including recycling, incineration and landfilling. From an environmental point of view, the latter is commonly considered as the least desirable option. Many studies based on life-cycle assessment (LCA) highlight the environmental benefits offered by incineration and especially...

A comprehensive experimental setup with six single-family home composting units was monitored during 1 year. The composting units were fed with 2.6-3.5 kg organic household waste (OHW) per unit per week. All relevant consumptions and emissions of environmental relevance were addressed and a full life-cycle inventory (LCI) was established for the si...

Selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator was investigated using LCA. The relationship between NO(x)-cleaning and ammonia dosage was measured at the plant. Un-reacted ammonia - the ammonia slip - leaving the flue-gas cleaning system adsorbed to fly-ash or in the effluent of the acid...

The environmental impacts of municipal solid waste management in Beijing City were evaluated using a life-cycle-based model, EASEWASTE, to take into account waste generation, collection, transportation, treatment/disposal technologies, and savings obtained by energy and material recovery. The current system, mainly involving the use of landfills, h...

The waste-LCA model EASEWASTE quantifies potential environmental effects from biological treatment of organic waste, based on mass and energy flows, emissions to air, water, soil and groundwater as well as effects from upstream and downstream processes. Default technologies for composting, anaerobic digestion and combinations hereof are available i...

Waste management in Greenland (56,000 inhabitants) is characterized by landfilling, incineration and export to Denmark of small quantities of metals and hazardous waste. The annual amount of waste is estimated to about 50,000 tons but actual data are scarce. Data on the waste composition is basically lacking. The scattered small towns and settlemen...

The composition of household waste in Greenland was investigated for the first time. About 2tonnes of household waste was sampled as every 7th bag collected during 1 week along the scheduled collection routes in Sisimiut, the second largest town in Greenland with about 5400 inhabitants. The collection bags were sorted manually into 10 material frac...

Landfills receiving a mix of waste, including organics, have developed dramatically over the last 3–4 decades; from open dumps to engineered facilities with extensive controls on leachate and gas. The conventional municipal landfill will in most climates produce a highly contaminated leachate and a significant amount of landfill gas. Leachate contr...

An environmental assessment of six scenarios for handling of garden waste in the Municipality of Aarhus (Denmark) was performed from a life cycle perspective by means of the LCA-model EASEWASTE. In the first (baseline) scenario, the current garden waste management system based on windrow composting was assessed, while in the other five scenarios al...

C&D Waste: BuildingsC&D Waste: Roads and PavementsC&D Waste: ExcavationsReferences

A number of waste life cycle assessment (LCA) models have been gradually developed since the early 1990 s, in a number of countries, usually independently from each other. Large discrepancies in results have been observed among different waste LCA models, although it has also been shown that results from different LCA studies can be consistent. Thi...

The emission of greenhouse gases (GHGs) is a potential environmental disadvantage of home composting. Because of a lack of reliable GHG emission data, a comprehensive experimental home composting system was set up. The system consisted of six composting units, and a static flux chamber method was used to measure and quantify the GHG emissions for o...