Emmanuel Gentil

Review of LCA studies of solid waste management systems - Part I: Lessons learned and perspectives

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 management systems (SWMSs) until now, and which lessons can be learnt from the findings of these LCA applications? To address these questions, we performed a critical review of 222 published LCA studies of SWMS. We first analysed the geographic distribution and found that the published studies have primarily been concentrated in Europe with little application in developing countries. In terms of technological coverage, they have largely overlooked application of LCA to waste prevention activities and to relevant waste types apart from household waste, e.g. construction and demolition waste. Waste management practitioners are thus encouraged to abridge these gaps in future applications of LCA. In addition to this contextual analysis, we also evaluated the findings of selected studies of good quality and found that there is little agreement in the conclusions among them. The strong dependence of each SWMS on local conditions, such as waste composition or energy system, prevents a meaningful generalisation of the LCA results as we find it in the waste hierarchy. We therefore recommend stakeholders in solid waste management to regard LCA as a tool, which, by its ability of capturing the local specific conditions in the modelling of environmental impacts and benefits of a SWMS, allows identifying critical problems and proposing improvement options adapted to the local specificities.

Review of LCA studies of solid waste management systems Part II: Methodological guidance for a better practice

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? Are there any inconsistencies in the past practice? To answer these questions, we draw on a critical review of 222 published LCA studies of solid waste management systems. We analyse the past practice against the ISO standard requirements and the ILCD Handbook guidelines for each major step within the goal definition, scope definition, inventory analysis, impact assessment, and interpretation phases of the methodology. Results show that malpractices exist in several aspects of the LCA with large differences across studies. Examples are a frequent neglect of the goal definition, a frequent lack of transparency and precision in the definition of the scope of the study, e.g. an unclear delimitation of the system boundaries, a truncated impact coverage, difficulties in capturing influential local specificities such as representative waste compositions into the inventory, and a frequent lack of essential sensitivity and uncertainty analyses. Many of these aspects are important for the reliability of the results. For each of them, we therefore provide detailed recommendations to practitioners of waste management LCAs.

C balance, carbon dioxide emissions and global warming potentials in LCA-modelling of waste management systems

Global warming potential (GWP) is an important impact category in life-cycle-assessment modelling of waste management systems. However, accounting of biogenic CO2 emissions and sequestered biogenic carbon in landfills and in soils, amended with compost, is carried out in different ways in reported studies. A simplified model of carbon flows is presented for the waste management system and the surrounding industries, represented by the pulp and paper manufacturing industry, the forestry industry and the energy industry. The model calculated the load of C to the atmosphere, under ideal conditions, for 14 different waste management scenarios under a range of system boundary conditions and a constant consumption of C-product (here assumed to be paper) and energy production within the combined system. Five sets of criteria for assigning GWP indices to waste management systems were applied to the same 14 scenarios and tested for their ability to rank the waste management alternatives reflecting the resulting CO2 load to the atmosphere. Two complete criteria sets were identified yielding fully consistent results; one set considers biogenic CO2 as neutral, the other one did not. The results showed that criteria for assigning global warming contributions are partly linked to the system boundary conditions. While the boundary to the paper industry and the energy industry usually is specified in LCA studies, the boundary to the forestry industry and the interaction between forestry and the energy industry should also be specified and accounted for.

Models for waste life cycle assessment : Review of technical assumptions

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. This paper is an attempt to identify, review and analyse methodologies and technical assumptions used in various parts of selected waste LCA models. Several criteria were identified, which could have significant impacts on the results, such as the functional unit, system boundaries, waste composition and energy modelling. The modelling assumptions of waste management processes, ranging from collection, transportation, intermediate facilities, recycling, thermal treatment, biological treatment, and landfilling, are obviously critical when comparing waste LCA models. This review infers that some of the differences in waste LCA models are inherent to the time they were developed. It is expected that models developed later, benefit from past modelling assumptions and knowledge and issues. Models developed in different countries furthermore rely on geographic specificities that have an impact on the results of waste LCA models. The review concludes that more effort should be employed to harmonise and validate non-geographic assumptions to strengthen waste LCA modelling.

Greenhouse gas accounting and waste management

Accounting of emissions of greenhouse gas (GHG) is a major focus within waste management. This paper analyses and compares the four main types of GHG accounting in waste management including their special features and approaches: the national accounting, with reference to the Intergovernmental Panel on Climate Change (IPCC), the corporate level, as part of the annual reporting on environmental issues and social responsibility, life-cycle assessment (LCA), as an environmental basis for assessing waste management systems and technologies, and finally, the carbon trading methodology, and more specifically, the clean development mechanism (CDM) methodology, introduced to support cost-effective reduction in GHG emissions. These types of GHG accounting, in principle, have a common starting point in technical data on GHG emissions from specific waste technologies and plants, but the limited availability of data and, moreover, the different scopes of the accounting lead to many ways of quantifying emissions and producing the accounts. The importance of transparency in GHG accounting is emphasised regarding waste type, waste composition, time period considered, GHGs included, global warming potential (GWP) assigned to the GHGs, counting of biogenic carbon dioxide, choice of system boundaries, interactions with the energy system, and generic emissions factors. In order to enhance transparency and consistency, a format called the upstream-operating-downstream framework (UOD) is proposed for reporting basic technology-related data regarding GHG issues including a clear distinction between direct emissions from waste management technologies, indirect upstream (use of energy and materials) and indirect downstream (production of energy, delivery of secondary materials) activities.

Global warming factor of municipal solid waste management in Europe

The global warming factor (GWF; CO2-eq. tonne—1 waste) performance of municipal waste management has been investigated for six representative European Member States: Denmark, France, Germany, Greece, Poland and the United Kingdom. The study integrated European waste statistical data for 2007 in a life-cycle assessment modelling perspective. It is shown that significant GWF benefit was achieved due to the high level of energy and material recovery substituting fossil energy and raw materials production, especially in Denmark and Germany. The study showed that, despite strong regulation of waste management at European level, there are major differences in GWF performance among the member states, due to the relative differences of waste composition, type of waste management technologies available nationally, and the average performance of these technologies. It has been demonstrated through a number of sensitivity analyses that, within the national framework, key waste management technology parameters can influence drastically the national GWF performance of waste management.

Greenhouse gases, radiative forcing, global warming potential and waste management — an introduction

Management of post-consumer solid waste contributes to emission of greenhouse gases (GHGs) representing about 3% of global anthropogenic GHG emissions. Most GHG reporting initiatives around the world utilize two metrics proposed by the Intergovernmental Panel on Climate Change (IPCC): radiative forcing (RF) and global warming potential (GWP). This paper provides a general introduction of the factors that define a GHG and explains the scientific background for estimating RF and GWP, thereby exposing the lay reader to a brief overview of the methods for calculating the effects of GHGs on climate change. An objective of this paper is to increase awareness that the GWP of GHGs has been re-adjusted as the concentration and relative proportion of these GHGs has changed with time (e.g., the GWP of methane has changed from 21 to 25 CO2-eq). Improved understanding of the indirect effects of GHGs has also led to a modification in the methodology for calculating GWP. Following a presentation of theory behind GHG, RF and GWP concepts, the paper briefly describes the most important GHG sources and sinks in the context of the waste management industry. The paper serves as a primer for more detailed research publications presented in this special issue of Waste Management & Research providing a technology-based assessment of quantitative GHG emissions from different waste management technologies.

To waste or not to waste – food?

In our relatively affluent European region, we (as private residents) throw away about a third of the food we purchase. About 60% of residential food waste (by weight) is considered avoidable (it is edible), 20% is potentially avoidable (such as leftover breadcrumbs) and 20% is considered unavoidable (such as bones and peelings). Considering the food production life cycle from ‘field to fork’, encompassing agriculture, industry, distribution, retailers, restaurants, catering services, and private households, food wastage could account for up to 50% of production. These are, to any standard, very high numbers that should be reduced for economic, environmental and ethical reasons. Of course food wasting varies with geographical location in response to culture, standard of living, level of urbanization, local climate, etc. Quantification and characterization of food waste is therefore, uncertain and overall environmental impacts of food waste treatment are difficult to assess. Eurostat data indicates that in 2008, about 116 million tonnes of food waste was generated by the EU27 countries across all sectors, corresponding to 4% of total waste production, or 232 kg capita−1 year−1. Households alone waste about 48 kg capita−1 year−1, corresponding to about 21% of total food waste generation across all sectors. In 2008, Eurostat reported food wasting in Denmark of 160 000 tonnes (30 kg capita−1 year−1) generated across all sectors, including 37 000 tonnes (7 kg capita−1 year−1) directly from households. An assessment of Danish food waste generation performed in 2011, by the University of Aarhus and the University of Copenhagen, showed that about 1 million tonnes, or 285 kg capita−1 year−1, of food waste was generated across all sectors. This included 237 000 tonnes from households (103 kg capita−1 year−1). The relatively large discrepancy between these numbers stems from different methods for collecting data about waste generation and illustrates the difficulty in obtaining reliably accurate figures for food waste generation. Both in Europe and globally, food waste has been, and to a large degree still is, disposed of at landfills or uncontrolled dumps. Several countries, including Japan, Denmark, Sweden and Switzerland incinerate food waste together with other municipal wastes for energy recovery. During the previous 20 years, anaerobic digestion for methane production and energy recovery have gained increased interest for treatment of especially industrial food wastes, including a large part of the non-edible fraction. Composting of food waste with the aim of reducing volume and recovering nutrients has also gained increased interest, although the waste quantities treated using this technology, are relatively small compared to other technologies. Food production generally results in a net CO2 emission, whereas food waste management measures may result in either a net CO2 emission or a net CO2 saving, depending on the treatment processes applied. It may be assumed that if food wastage is reduced, the associated impacts on the CO2 balance from both food production and food waste treatment are minimized. To illustrate the potential reduction in carbon footprint per capita, by non-wasting food, a simple estimate of the net change in carbon footprint of the food production and food waste treatment systems was made. The estimate was based on Danish conditions where about 109 kg of edible food waste is generated per person per year with 26, 21, 13 and 40% produced in agriculture, food processing, retail and households, respectively, and where the food waste composition is about 76% vegetable and 24% animal waste. It was further assumed that the edible food waste from agriculture, retail and households was co-incinerated with residual municipal waste, whereas edible vegetable and meat waste from the food industry was digested or incinerated, respectively. The estimate shows that, if the 109 kg of edible food waste is avoided, it will result in a net savings of about 240 kg CO2-eq capita−1 year−1 throughout the whole food supply and food waste management chain. In comparison, studies have shown that the current treatment of organic municipal waste (sewage sludge, organic household waste, yard and park waste, and organic waste from small businesses) yields a net savings of about 210 kg CO2-eq capita−1 year−1. In this context, edible food waste prevention provides a significant CO2 savings. An estimate of the current municipal waste management in Scandinavia indicates a potential net savings of about 1580 kg CO2-eq capita−1 year−1, thus, if an efficient scheme for reducing food waste is implemented, the potential savings could reach 1820 kg CO2-eq capita−1 year−1. This is equivalent to about 20% of the carbon footprint of the average EU citizen and clearly shows that improvements in the waste sector can lead to a significant reduction in greenhouse gas emissions. The above estimates suggest that significant reductions in greenhouse gas emissions might be achieved by reducing the generation of other types of wastes in addition to food wastes. Moreover, there may also be a significant economic gain. Instead of investing heavily in infrastructure and technology for waste handling and treatment, money may be better spent on waste prevention. Of course there will always be waste that cannot be avoided, however, significant economic and environmental benefits are likely achievable if waste generation is prevented whenever possible. To waste or not to waste – food? 445544WMR30510.1177/0734242X12445544GentilWaste Management & Research 2012

LCA of Solid Waste Management Systems

The chapter explores the application of LCA to solid waste management systems through the review of published studies on the subject. The environmental implications of choices involved in the modelling setup of waste management systems are increasingly in the spotlight, due to public health concerns and new legislation addressing the impacts from managing our waste. The application of LCA to solid waste management systems, sometimes called “waste LCA”, is distinctive in that system boundaries are rigorously defined to exclude all life cycle stages except from the end-of-life. Moreover, specific methodological challenges arise when investigating waste systems, such as the allocation of impacts and the consideration of long-term emissions. The complexity of waste LCAs is mainly derived from the variability of the object under study (waste) which is made of different materials that may require different treatments. This chapter attempts to address these challenges by identifying common misconceptions and by providing methodological guidance for alleviating the associated uncertainty. Readers are also provided with the list of studies reviewed and key sources for reference to implement LCA on solid waste systems.