Simone Manfredi

Landfilling of waste: accounting of greenhouse gases and global warming contributions

Accounting of greenhouse gas (GHG) emissions from waste landfilling is summarized with the focus on processes and technical data for a number of different landfilling technologies: open dump (which was included as the worst-case-scenario), conventional landfills with flares and with energy recovery, and landfills receiving low-organic-carbon waste. The results showed that direct emissions of GHG from the landfill systems (primarily dispersive release of methane) are the major contributions to the GHG accounting, up to about 1000 kg CO2-eq. tonne —1 for the open dump, 300 kg CO2-eq. tonne —1 for conventional landfilling of mixed waste and 70 kg CO2-eq. tonne—1 for low-organic-carbon waste landfills. The load caused by indirect, upstream emissions from provision of energy and materials to the landfill was low, here estimated to be up to 16 kg CO2-eq. tonne—1. On the other hand, utilization of landfill gas for electricity generation contributed to major savings, in most cases, corresponding to about half of the load caused by direct GHG emission from the landfill. However, this saving can vary significantly depending on what the generated electricity substitutes for. Significant amounts of biogenic carbon may still be stored within the landfill body after 100 years, which here is counted as a saved GHG emission. With respect to landfilling of mixed waste with energy recovery, the net, average GHG accounting ranged from about —70 to 30 kg CO2-eq. tonne— 1, obtained by summing the direct and indirect (upstream and downstream) emissions and accounting for stored biogenic carbon as a saving. However, if binding of biogenic carbon was not accounted for, the overall GHG load would be in the range of 60 to 300 kg CO2-eq. tonne —1. This paper clearly shows that electricity generation as well as accounting of stored biogenic carbon are crucial to the accounting of GHG of waste landfilling.

Experience with the use of LCA-modelling (EASEWASTE) in waste management:

Life-cycle assessment (LCA) models are becoming the principal decision support tools of waste management systems. This paper describes our experience with the use of EASEWASTE (Environmental Assessment of Solid Waste Systems and Technologies), a new computerized LCA-based model for integrated waste management. Our findings provide a quantitative understanding of waste management systems and may reveal consistent approaches to improve their environmental performances. EASEWASTE provides a versatile system modelling facility combined with a complete life-cycle impact assessment and in addition to the traditional impact categories addresses toxicity-related categories. New categories dealing with stored ecotoxicity and spoiled groundwater resources have been introduced. EASEWASTE has been applied in several studies, including full-scale assessments of waste management in Danish municipalities. These studies led to numerous modelling issues: the need of combining process-specific and input-specific emissions, the choice of a meaningful time horizon, the way of accounting for biological carbon emissions, the problem of stored ecotoxicity and aspects of crediting the waste management system with the savings inherent in avoided production of energy and materials. Interpretation of results showed that waste management systems can be designed in an environmentally sustainable manner where energy recovery processes lead to substantial avoidance of emissions and savings of resources.

LCA and economic evaluation of landfill leachate and gas technologies

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 controls may include bottom liners and leachate collection systems as well as leachate treatment prior to discharge to surface water. Gas controls may include oxidizing top covers, gas collection systems with flares or gas utilization systems for production of electricity and heat. The importance of leachate and gas control measures in reducing the overall environmental impact from a conventional landfill was assessed by life-cycle-assessment (LCA). The direct cost for the measures were also estimated providing a basis for assessing which measures are the most cost-effective in reducing the impact from a conventional landfill. This was done by modeling landfills ranging from a simple open dump to highly engineered conventional landfills with energy recovery in form of heat or electricity. The modeling was done in the waste LCA model EASEWASTE. The results showed drastic improvements for most impact categories. Global warming went from an impact of 0.1 person equivalent (PE) for the dump to -0.05 PE for the best design. Similar improvements were found for photochemical ozone formation (0.02 PE to 0.002 PE) and stratospheric ozone formation (0.04 PE to 0.001 PE). For the toxic and spoiled groundwater impact categories the trend is not as clear. The reason for this was that the load to the environment shifted as more technologies were used. For the dump landfill the main impacts were impacts for spoiled groundwater due to lack of leachate collection, 2.3 PE down to 0.4 PE when leachate is collected. However, at the same time, leachate collection causes a slight increase in eco-toxicity and human toxicity via water (0.007 E to 0.013 PE and 0.002 to 0.003 PE respectively). The reason for this is that even if the leachate is treated, slight amounts of contaminants are released through emissions of treated wastewater to surface waters. The largest environmental improvement with regard to the direct cost of the landfill was the capping and leachate treatment system. The capping, though very cheap to establish, gave a huge benefit in lowered impacts, the leachate collection system though expensive gave large benefits as well. The other gas measures were found to give further improvements, for a minor increase in cost.

Contribution of individual waste fractions to the environmental impacts from landfilling of municipal solid waste.

A number of LCA-based studies have reported on the environmental performance of landfilling of mixed waste, but little is known about the relative contributions of individual waste fractions to the overall impact potentials estimated for the mixed waste. In this paper, an empirical model has been used to estimate the emissions to the environment from landfilling of individual waste fractions. By means of the LCA-model EASEWASTE, the emissions estimated have been used to quantify how much of the overall impact potential for each impact category is to be attributed to the individual waste fractions. Impact potentials are estimated for 1 tonne of mixed waste disposed off in a conventional landfill with bottom liner, leachate collection and treatment and gas collection and utilization for electricity generation. All the environmental aspects are accounted for 100 years after disposal and several impact categories have been considered, including standard categories, toxicity-related categories and groundwater contamination. Amongst the standard and toxicity-related categories, the highest potential impact is estimated for human toxicity via soil (HTs; 12 mPE/tonne). This is mostly caused by leaching of heavy metals from ashes (e.g. residues from roads cleaning and vacuum cleaning bags), batteries, paper and metals. On the other hand, substantial net environmental savings are estimated for the categories Global Warming (GW; -31 mPE/tonne) and Eco-Toxicity in water chronic (ETwc; -53 mPE/tonne). These savings are mostly determined by the waste fractions characterized by a high content of biogenic carbon (paper, organics, other combustible waste). These savings are due to emissions from energy generation avoided by landfill gas utilization, and by the storage of biogenic carbon in the landfill due to incomplete waste degradation.

Environmental assessment of low-organic waste landfill scenarios by means of life-cycle assessment modelling (EASEWASTE)

The environmental performance of two low-organic waste landfill scenarios (‘low-organic-energy’ and ‘low-organic-flare’) was developed and compared with two household waste landfill scenarios (‘household-energy’ and ‘household-flare’) by means of LCA-modelling. The LCA-modelling was made for 1 tonne of wet waste landfilled and the environmental aspects were evaluated for a 100-year period after disposal. The data utilized in the LCA-calculations to model the first 10—20 years of landfilling of the two low-organic waste scenarios make extensive use of site-specific data from the Nauerna Landfill (The Netherlands), but average data from other comparable, existing landfills were used too. As data from full-scale landfills do not cover more than 30—40 years of landfilling, data from laboratory simulations and accelerated tests of limited scale were also utilized. The life-cycle impact assessments show that the low-organic waste scenarios achieved better environmental performance than the household waste scenarios with regard to both ordinary and toxicity-related environmental impact categories. This indicates that the reduction of organic matter accepted at landfills (as prescribed by the European Union Landfill Directive: Council Directive 1999/31/EC, EU, Brussels, 1999) can be a successful approach to decrease the environmental loads in several impact categories in comparison with landfilling of waste with significant organic content. However, when utilization of landfill gas is accounted for in the life-cycle impact assessment calculation, the small gas generation in low-organic waste landfills reduced the actual potential for energy generation and therefore the environmental savings obtained were reduced proportionally. Groundwater pollution from input of leachate was also evaluated and the WHO (Guidelines for Drinking-water Quality; WHO, Geneva, 2006) guideline for drinking water quality was assumed as reference. The results show that low-organic waste landfills pose a smaller risk of groundwater contamination, but the impact potentials estimated still remain a lot higher than estimated in other categories.

Environmental assessment of Ämmässuo Landfill (Finland) by means of LCA-modelling (EASEWASTE)

The Old Ämmässuo Landfill (Espoo, Finland) covers an area of 52 hectares and contains about 10 million tonnes of waste that was landfilled between 1987 and 2007. The majority of this waste was mixed, of which about 57% originated from households. This paper aims at describing the management of the Old Ämmässuo Landfill throughout its operational lifetime (1987—2007), and at developing an environmental evaluation based on life-cycle assessment (LCA) using the EASEWASTE-model. The assessment criteria evaluate specific categories of impact, including standard impact categories, toxicity-related impact categories and an impact categorized as spoiled groundwater resources (SGR). With respect to standard and toxicity-related impact categories, the LCA results show that substantial impact potentials are estimated for global warming (GW), ozone depletion (OD), human toxicity via soil (HTs) and ecotoxicity in water chronic (ETwc). The largest impact potential was found for SGR and amounted to 57.6 person equivalent (PE) per tonne of landfilled waste. However, the SGR impact may not be viewed as a significant issue in Finland as the drinking water is mostly supplied from surface water bodies. Overall, the results demonstrate that gas management has great importance to the environmental performance of the Old Ämmässuo Landfill. However, several chemicals related to gas composition (especially trace compounds) and specific emissions from on-site operations were not available or were not measured and were therefore taken from the literature. Measurement campaigns and field investigations should be undertaken in order to obtain a more robust and comprehensive dataset that can be used in the LCA-modelling, before major improvements regarding landfill management are finalized.

Environmental assessment of gas management options at the Old Ämmässuo landfill (Finland) by means of LCA-modeling (EASEWASTE)

The current landfill gas (LFG) management (based on flaring and utilization for heat generation of the collected gas) and three potential future gas management options (LFG flaring, heat generation and combined heat and power generation) for the Old Ammässuo landfill (Espoo, Finland) were evaluated by life-cycle assessment modeling. The evaluation accounts for all resource utilization and emissions to the environment related to the gas generation and management for a life-cycle time horizon of 100 yr. The assessment criteria comprise standard impact categories (global warming, photo-chemical ozone formation, stratospheric ozone depletion, acidification and nutrient enrichment) and toxicity-related impact categories (human toxicity via soil, via water and via air, eco-toxicity in soil and in water chronic). The results of the life-cycle impact assessment show that disperse emissions of LFG from the landfill surface determine the highest potential impacts in terms of global warming, stratospheric ozone depletion, and human toxicity via soil. Conversely, the impact potentials estimated for other categories are numerically-negative when the collected LFG is utilized for energy generation, demonstrating that net environmental savings can be obtained. Such savings are proportional to the amount of gas utilized for energy generation and the gas energy recovery efficiency achieved, which thus have to be regarded as key parameters. As a result, the overall best performance is found for the heat generation option - as it has the highest LFG utilization/energy recovery rates - whereas the worst performance is estimated for the LFG flaring option, as no LFG is here utilized for energy generation. Therefore, to reduce the environmental burdens caused by the current gas management strategy, more LFG should be used for energy generation. This inherently requires a superior LFG capture rate that, in addition, would reduce fugitive emissions of LFG from the landfill surface, bringing further environmental benefits.

Prioritizing and optimizing sustainable measures for food waste prevention and management

Highlights • The waste hierarchy is not enough for prioritizing food waste prevention measures.• The methodology proposed prioritizes measures using LCA and mathematical programming.• The methodology identifies quick wins – actions with low cost and high impact avoided.• The relevance of the weighting set used in the prioritization is limited.• Targets for food waste prevention must be set at the level of environmental impact.

Towards more sustainable management of European food waste: Methodological approach and numerical application

Trying to respond to the latest policy needs, the work presented in this article aims at developing a life-cycle based framework methodology to quantitatively evaluate the environmental and economic sustainability of European food waste management options. The methodology is structured into six steps aimed at defining boundaries and scope of the evaluation, evaluating environmental and economic impacts and identifying best performing options. The methodology is able to accommodate additional assessment criteria, for example the social dimension of sustainability, thus moving towards a comprehensive sustainability assessment framework. A numerical case study is also developed to provide an example of application of the proposed methodology to an average European context. Different options for food waste treatment are compared, including landfilling, composting, anaerobic digestion and incineration. The environmental dimension is evaluated with the software EASETECH, while the economic assessment is conducted based on different indicators expressing the costs associated with food waste management. Results show that the proposed methodology allows for a straightforward identification of the most sustainable options for food waste, thus can provide factual support to decision/policy making. However, it was also observed that results markedly depend on a number of user-defined assumptions, for example on the choice of the indicators to express the environmental and economic performance.