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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., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This work addressed the role of waste-to-energy (WtE) within the growing paradigm of the circular economy (CE), by combining long-term co-optimization of waste management and energy systems, to determine possible economic and climate impact consequences of future WtE capacity utilization. Co-optimization was realized by integration of a network optimization model for the waste sector, OptiFlow, with the partial equilibrium energy systems model Balmorel. The modelling framework allows to determine the effects of waste-derived energy production within energy systems, including induced and avoided energy (production and long-term investments). The article documents the application of this framework to an analysis of waste trade for WtE between European countries in the base year 2014 and prospectively until 2035, taking Denmark as example for an importing country. Results indicating present and long-term economic benefits for waste trade, under socio-economic conditions, were documented in a concurrent publication. Here, a broader consequential LCA approach was employed to appraise climate change impact potential in a variety of foreground and background conditions. We find that in 2014, trade of residual combustible waste was mostly beneficial from a climate perspective, as the Danish energy system still relies partly on fossil fuels. Towards 2035, climate advantages are uncertain and dependent on avoidance of higher impact waste management (i.e. sanitary landfilling), the differences in the energy carbon-intensity of importing and exporting countries, impact of global biomass supply, and the type and quantity of traded waste. In general, benefits from waste-derived energy production will be offset by direct combustion emissions as background systems decarbonize. Waste transport played only a minor role in the outcome. The study showcases integration of ESA in waste LCA to better account for affected (often referred as marginal) energy production., (Copyright © 2018 Elsevier Ltd. All rights reserved.)