A simulation model, ORWARE (ORganic WAste REsearch) is described. The model is mainly used as a tool for researchers in environmental systems analysis of waste management. It is a computer-based model for calculation of substance flows, environmental impacts, and costs of waste management. The model covers, despite the name, both organic and inorganic fractions in municipal waste. The model consists of a number of separate submodels, which describes a process in a real waste management system. The submodels may be combined to design a complete waste management system. Based on principles from life cycle assessment the model also comprises compensatory processes for conventional production of e.g. electricity, district heating and fertiliser. The compensatory system is included in order to fulfil the functional units, i.e. benefits from the waste management that are kept constant in the evaluation of different scenarios. ORWARE generates data on emissions, which are aggregated into different environmental impact categories, e.g. the greenhouse effect, acidification and eutrophication. Throughout the model all physical flows are described by the same variable vector, consisting of up to 50 substances. The extensive vector facilitates a thorough analysis of the results, but involves some difficulties in acquiring relevant data. Scientists have used ORWARE for 8 years in different case studies for model testing and practical application in the society. The aims have e.g. been to evaluate waste management plans and to optimise energy recovery from waste.

Different waste treatment options for municipal solid waste have been studied in a systems analysis. Different combinations of incineration, materials recycling of separated plastic and cardboard containers, and biological treatment (anaerobic digestion and composting) of biodegradable waste, were studied and compared to landfilling. The evaluation covered use of energy resources, environmental impact and financial and environmental costs. In the study, a calculation model ( ) based on methodology from life cycle assessment (LCA) was used. Case studies were performed in three Swedish municipalities: Uppsala, Stockholm, and Älvdalen.

The study shows that reduced landfilling in favour of increased recycling of energy and materials lead to lower environmental impact, lower consumption of energy resources, and lower economic costs. Landfilling of energy-rich waste should be avoided as far as possible, partly because of the negative environmental impacts from landfilling, but mainly because of the low recovery of resources when landfilling.

Differences between materials recycling, nutrient recycling and incineration are small but in general recycling of plastic is somewhat better than incineration and biological treatment somewhat worse.

When planning waste management, it is important to know that the choice of waste treatment method affects processes outside the waste management system, such as generation of district heating, electricity, vehicle fuel, plastic, cardboard, and fertiliser.

Life cycle assessment (LCA) and life cycle costing (LCC) are well-established methods used for many years in many countries for system analysis of waste management. According to standard LCA procedure the assessment should include improvement analysis, in many cases this is performed by simple sensitivity analyses. An obstacle to perform more thorough sensitivity analyses is that it is hard to distinguish input data important to the results, i.e. key parameters. This paper further elaborates sensitivity analyses performed in an environmental system analysis fora hypothetical Swedish municipality. In this paper, the method to identify and test input data that can be categorised as potential key parameters is described. The method and the results from computer simulations of the identified parameters are presented, and some conclusions are drawn regarding the robustness of the results for environmental impact from municipal solid waste management. The major conclusion is that the results are robust. Changes in results, when changing the preconditions, are often small and the changes observed do not lead to new conclusions; i.e., a change of ranking order between treatment options.

This article discusses the ORWARE tool, a model originally developed for environmental systems analysis of waste management systems, and shows its prospect as a tool for environmental technology chain assessment. Different concepts of technology assessment are presented to put ORWARE into context in the discussion that has been going for more than two decades since the establishment of the US Congressional Office of Technology Assessment (OTA). An even-handed assessment is important in different ways such as reproducibility, reliability, credibility, etc. Conventional technology assessment (TA) relied on the judgements and intuition of the assessors. A computer-based tool such as ORWARE provides a basis for transparency and a structured management of input and output data that cover ecological and economic parameters. This permits consistent and coherent technology assessments. Using quantitative analysis as in ORWARE makes comparison and addition of values across chain of technologies easier. We illustrate the application of the model in environmental technology chain assessment through a study of alternative technical systems linking waste management to vehicle fuel production and use. The principles of material and substance flow modelling, life cycle perspective, and graphical modelling featured in ORWARE offer a generic structure for environmentally focused TA of chains and networks of technical processes.

A technology assessment of thermal treatment technologies for wastes was performed in the form of scenarios of chains of technologies. The Swedish assessment tool, ORWARE, was used for the assessment. The scenarios of chains of thermal technologies assessed were gasification with catalytic combustion, gasification with flame combustion, incineration and landfilling. The landfilling scenario was used as a reference for comparison. The technologies were assessed from ecological and economic points of view.

The results are presented in terms of global warming potential, acidification potential, eutrophication potential, consumption of primary energy carriers and welfare costs. From the simulations, gasification followed by catalytic combustion with energy recovery in a combined cycle appeared to be the most competitive technology from an ecological point of view. On the other hand, this alternative was more expensive than incineration. A sensitivity analysis was done regarding electricity prices to show which technology wins at what value of the unit price of electricity (SEK/kW h).

Within this study, it was possible to make a comparison both between a combined cycle and a Rankine cycle (a system pair) and at the same time between flame combustion and catalytic combustion (a technology pair). To use gasification just as a treatment technology is not more appealing than incineration, but the possibility of combining gasification with a combined cycle is attractive in terms of electricity production.

This research was done in connection with an empirical R&D work on both gasification of waste and catalytic combustion of the gasified waste at the Division of Chemical Technology, Royal Institute of Technology (KTH), Sweden.