Modelling of environmental impacts from the application of treated organic municipal solid waste (MSW) in agriculture differs widely between different models for environmental assessment of waste systems. In this comparative study five models were examined concerning quantification and impact assessment of environmental effects from land application of treated organic MSW: DST (Decision Support Tool, USA), IWM (Integrated Waste Management, U.K.), THE IFEU PROJECT (Germany), ORWARE (ORganic WAste REsearch, Sweden) and EASEWASTE (Environmental Assessment of Solid Waste Systems and Technologies, Denmark). DST and IWM are life cycle inventory (LCI) models, thus not performing actual impact assessment. The DST model includes only one water emission (biological oxygen demand) from compost leaching in the results and IWM considers only air emissions from avoided production of commercial fertilizers. THE IFEU PROJECT, ORWARE and EASEWASTE are life cycle assessment (LCA) models containing more detailed land application modules. A case study estimating the environmental impacts from land application of 1 ton of composted source sorted organic household waste was performed to compare the results from the different models and investigate the origin of any difference in type or magnitude of the results. The contributions from the LCI models were limited and did not depend on waste composition or local agricultural conditions. The three LCA models use the same overall approach for quantifying the impacts of the system. However, due to slightly different assumptions, quantification methods and environmental impact assessment, the obtained results varied clearly between the models. Furthermore, local conditions (e.g. soil type, farm type, climate and legal regulation) and waste composition strongly influenced the results of the environmental assessment.

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Summary This article presents an integrative approach to calculating the weight of potential biowaste and collected biowaste materials, as the basis for a life‐cycle assessment (LCA) of biowaste management. Biowaste contains kitchen and garden (yard) waste of households. This approach could be used for waste management planning and for the implementation of biowaste schemes. Case studies and examples in the literature are analyzed to model the mass of the flow of biowaste. This article defines relevant operands, presents the main assumptions, and describes the calculation principles. Spatial aspects and the uncertainties related to the inclusion of this aspect are explicitly considered in the calculation of the weight of the potential biowaste. We also present the calculation principles for obtaining the weight of (1) biowaste used in home composting, (2) the organic portion of residual waste, (3) biowaste separately collected by a bring system, and (4) biowaste separately collected by curbside collection (known in some areas as kerbside collection). By choosing the biowaste potential in kilograms per capita year (kg/cap yr) as the functional unit, previously ignored options within the biowaste system could be assessed. For example, widening the system boundaries allows LCA studies to assess the contribution of private and public transport of waste to ecological impact categories. It allows examining the effects of supporting home composting through financial incentives and the introduction of a separate collection system. This study focuses on the comparison of different collection types and on the characteristics of the area under investigation. It also incorporates the behavior of the inhabitants of households and includes a sensitivity analysis of relevant operands. This approach is being included in an LCA assessing biowaste management options.