A conceptual framework for the recycling of aggregates and other wastes

A conceptual framework for the understanding of recycled aggregate applications is presented. The framework is described in terms of the environmental and economic utility (or value) of the application, and the utility relative to the original application. The determination of utility considers production factors (energy consumption, financial cost, amount of pollution and waste generated) and factors such as the market value of the product and ‘renewability’ of the primary resource. Examples for each category of utility and relative utility are given. Estimates of the level of aggregate recycling at each level of environmental and economic utility in Scotland are given for 1999. These illustrate the use of the framework as an aid to the interpretation of data for the quantities of aggregates recycled. Although the framework was developed specifically for recycled aggregates it is equally applicable to other material categories and examples are given where appropriate, particularly in relation to relative utility. The concept of utility is considered suitable for both project-level comparisons of different applications for recycled aggregates and also for strategic evaluations at a national level. The concept of relative utility is considered suitable for project-level evaluations of recycled aggregate applications, but not for strategic evaluations.