Good quality waste characterisation data are fundamental to Defra’s policies and strategies to manage environmental challenges, yet the UK dataset for the new inorganic and organic wastes generated in response to waste legislation was poor. This project aimed to fill some of the gaps in understanding the characteristics of residues from the treatment of municipal solid waste and industrial process wastes.
Policy development to minimise landfilling, recover value from discarded materials and limit environmentally challenging emissions depends on an evidence-base comprising the basic characteristics of those materials before and after treatment and predictions of their impacts in the disposal/reuse scenario. The project aimed to identify and characterise priority wastes, report implications for their landfill disposal/diversion and resource recovery and make data accessible to researchers and policy developers.
An overview of how this work relates to other research is summarised below.
The dataset provides information on characteristics needed to assess acceptance for landfill disposal and treatment, as well as potential resource recovery (e.g. energy, secondary materials and organic matter). It also supplies information on nitrogen, carbon, sulphur and phosphorus that have implications for gas emissions and/or nutrient value, in addition to other parameters that enable risk assessments to be made of potential emissions to air, land and water.
Organic wastes come from diverse sources and may contain different biochemical compositions in terms of fats, carbohydrate, protein and lignin contents. The current practice is to reduce disposal of raw organic wastes and to either pre-treat them prior to disposal or recycle them to land.
Prediction of the behaviour and environmental impacts of organic wastes in treatment processes, such as composting and anaerobic digestion, and of the fate of such materials when either landfilled or recycled to land may differ for specific wastes. The project aimed to provide a detailed characterisation of selected organic wastes, including biodegradability, and determine whether the results of such tests can provide a prediction of the behaviour of organic wastes if landfilled or recycled to land. This builds on the work currently undertaken for the Environment Agency to evaluate biodegradability test methods and to identify those factors that may enable sustainable landfilling.
For inorganic wastes, a limited comprehensive dataset exists for currently produced industrial wastes but a new generation of treatment residues including stable, non-reactive hazardous wastes and monolithic wastes was generated. Their characteristics were assessed and information made accessible to researchers and regulatory agencies.
The overall objectives were to:
a)provide “state of the art” data and information on the characteristics of pre/post-treatment wastes;
b)provide a UK-wide data resource focusing on composition and leachability (through UK support to LeachXS©);
c)review the UK landfill waste acceptance criteria for monolithic wastes.
In outline, the sampling and testing programme included the following stages:
1.identify and select candidate waste streams for testing;
2.design sampling plans to generate appropriate samples of UK waste streams;
3.collect organic and inorganic residues from waste processes;
4.characterize the residues including: chemical composition, biodegradability and/or leaching behaviour;
5.export data to the UK satellite database of LeachXS©, the leaching expert system developed by ECN (Energy Research Centre, Netherlands), DHI (Denmark) and Vanderbilt University (US); and
6.review UK waste acceptance criteria for monolithic wastes based on the assessment of stabilized waste data and comment from European experts.