The climate footprint of imports of combustible waste in systems with high shares of district heating and variable renewable energy

Waste LCA and the future

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 systems will soon be challenged by profound changes necessary in our societies and sectors to meet sustainable development goals. Foreseen changes in energy, material, and nutrient provision will directly and indirectly affect waste management in terms of its operation and goals. This study reflects on anticipated changes in society and industrial sectors and how these changes may affect waste management and LCA modelling of waste management systems in terms of waste input, the modelling of technologies and systems and exchanges of energy, materials, and nutrients, as well as how it may affect impact assessment and the interpretation of results. The study provides practical recommendations for LCA modelling of future waste management systems, which will hopefully lead to robust assessments that can support decision-making in an evolving society subject to great changes.

The impact of incineration phase-out on municipal solid waste landfilling and life cycle environmental performance: Case study of Madrid, Spain

Reducing the amount of municipal solid waste (MSW) fed to incineration while enhancing source separation and biological treatments is being considered a mean to protect the environment and human health and promote recycling. However, such a strategy can compromises the landfill reduction targets while the associated environmental benefits remain so far unexplored and, in any case, any potential benefit should be evaluated for specific situations. In this study we applied material flow analysis (MFA) and life cycle assessment (LCA) to quantitatively evaluate the potential impact of phasing-out incineration in Madrid, Spain. The current MSW management system was assessed against future scenarios that describe the elimination of incineration as well as the increase of source separation, recycling, composting, and anaerobic digestion. The results revealed that incineration phase-out jeopardizes landfill reduction. However, phasing-out incineration can reduce the impact on acidification, terrestrial and marine eutrophication, photochemical ozone formation, human toxicity cancer effects, and ecotoxicity. The climate impact ranges from irrelevant to largely beneficial depending on how the biogenic carbon is considered. The transition towards a renewable electricity mix and the increase in source separation of biodegradable waste seriously compromise the climate benefits of incineration over landfilling. Overall, actions are required in order to align incineration phase-out with the landfill reduction objective, namely upgrading material recovery facilities to reduce rejects and seeking alternative pathways for the rejects that will always exist.

A Conceptual Review on Using Consequential Life Cycle Assessment Methodology for the Energy Sector

Energy is engaged in the supply chain of many economic sectors; therefore, the environmental impacts of the energy sector are indirectly linked to those of other sectors. Consequential life cycle assessment (CLCA) is an appropriate methodology to examine the direct and indirect environmental impacts of a product due to technological, economic or social changes. To date, different methodological approaches are proposed, combining economic and environmental models. This paper reviews the basic concept of CLCA and the coupling of economic and environmental models for performing CLCA in the energy sector during the period 2006–2020, with the aim to provide a description of the different tools, highlighting their strengths and limitations. From the review, it emerges that economic modelling tools are frequently used in combination with environmental data for CLCA in the energy sector, including equilibrium, input-output, and dynamic models. Out of these, the equilibrium model is the most widely used, showing some strengths in availability of data and energy system modelling tools. The input-output model allows for describing both direct and indirect effects due to changes in the energy sector, by using publicly available data. The dynamic model is less frequently applied due to its limitation in availability of data and modelling tools, but has recently attracted more attention due to the ability in modelling quantitative and qualitative indicators of sustainability.

The economic value of imports of combustible waste in systems with high shares of district heating and variable renewable energy

This study analyses the socio-economic value of trade of combustible waste, taking Denmark as an example for importing countries with large district heating networks and already high shares of variable renewable energy. An integrated systems analysis framework allowed to assess under which circumstances import of wastes leads to less expensive waste management and energy, accounting for increasing ambitions for a circular economy and renewable energy. The dynamics of both systems are captured through two optimization models, which are solved simultaneously. OptiFlow optimizes Danish waste management and transport, and Balmorel, the Northern European energy system. Results show that waste import to cover the existing Danish incineration overcapacity during wintertime has definite economic value. Conversely, summertime import can have negative value unless a gate fee is received, with the exception of imports of waste with high calorific content (>16.2 GJ/t). In some cases, mothballing of up to 14% of the existing incineration plants is a cost-efficient alternative to decrease the level of over-capacity. In the longer term, results show a socio-economic value of importing waste, being mainly sensitive to assumptions regarding biomass prices and wind power cost, as the technologies would compete with incineration plants. The present methodology can be applied to other countries where waste-to-energy participates in district heating, and where variable renewable electricity and constraints on biomass resources are becoming important. A pan-regional approach regarding waste management planning to maximize the value from combustible waste might be desired, along with a coherent taxation to avoid competition based on tax differences.