Waste management

The major environmental and social impacts of materials, products and processes are now widely recognised. The focus of my research is on sustainable use of materials, waste management and what is increasingly known as resource efficiency. This is an absolutely key area if we are to achieve more sustainable development and provides significant opportunities for innovation.

Waste management research has developed significantly over recent years. The main emphasis has changed from safe disposal to beneficial reuse of materials and wastes as resources. This type of interdisciplinary research falls between the more traditional fields of environmental engineering, materials processing, waste recycling and civil engineering and therefore involves high levels of collaboration with both industry and other researchers at Imperial and beyond.

1. Carbon Neutral Construction Products Using Novel Cements
Funding: TSB Technology Programme
Total value of project: £ 1.5M (Lead partner is Novacem)
Co-investigator at Imperial: Dr Nikolaos Vlasopoulos
The project supports two Post Doctoral Researchers
Industrial collaborators: Rio Tinto Minerals, Laing O'Rourke and WSP Group

2. Sustainable Innovative Lightweight Expanded Clay-Glass('SILEC-G')
Funding: TSB Technology Programme
Total value of project: £ 985K (Lead partner Claylite Aggregates)
Co-investigator at Imperial: Professor Boccaccini, Materials Department
This project supports one Post Doctoral researcher (to be appointed)
Industrial Collaborators: Claylite Aggregates, Castle Aggregates

3. Integrated Solution For Air Pollution Control Residues Using Dc Plasma Tech
Funding: DTI Technology Programme
Total value of project: £ 2.37 M (Lead partner is Tetronics Ltd)
Co-investigators at Imperial: Professor Boccaccini, Materials Department
Industrial collaborators: Tetronics Limited, Enviros Consulting Limited, Veolia ES Selchp Limited, Grundon Waste Management Limited, Pfizer Limited, Hampshire County Council, Ballast Phoenix Limited and Akristos Limited

4. Process Envelopes For Cement-Based Stabilisation/Solidification (ProCeSS)
Funding: DTI Technogy Programme
Total value of project: £ 867,740 (Lead partner is UCL)
Industrial collaborators: British Cement Association, Quarry Products Association Ltd,
Civil & Marine (Holdings) Ltd, Corus UK Ltd, Elkem Materials Ltd, Surface Engineering Association, United Kingdom Quality Ash Association, Scott Wilson, Construction Industry Research and Information Association, The Concrete Centre, Veolia Environmental Services plc, May Gurney Ltd., SITA UK Limited, White Young Green Environmental Ltd, WRc plc
Academic collaborators: University Colege London, Birkbeck College, Surrey University and Cambridge University

5. Development Of Carbon Negative Construction Products Using Novel MgO Based Binders
Funding: EPSRC Follow-on-Fund
Total value of project: £ 120k
This project supports Dr Nikolaos Vlasopoulos
Industrial collaborator: Novacem

6. New Technologies To Allow Beneficial Reuse Of Silt From Construction And Demolition Waste Recycling Washing Plant
Funding: DEFRA Waste and Resources R&D Programme
Total value of project: £ 201,742
Co-investigators at Imperial: Dr M Tyrer, Materials Department, Dr Bill Dudeney (Earth Science and Engineering), Dr Nick Voulvoulis (Centre for Energy Policy and Technology), Dr Neil Tsang (Civil and Environmental Engineering)
Industrial collaborators: Winkworth Machinery Ltd, Powerscreen Ltd (now Duo (Europe) plc)
Completed March 2008

7. Production Of Lightweight Aggregates From Problematic Waste Ashes Using The Lytag Process
Funding: EPSRC Industrial Case Award with Lytag, now CEMEX Lytag
Co-investigator: Dr Aldo Boccaccini (Materials Department)
Completed March 2007

8. Development of Novel Glass-Ceramics from Problematic UK Wastes using Borates and Borate Containing Wastes
Funding: EPSRC Industrial Case Award with Borax Europe, now Rio Tinto Minerals
Co-investigator: Dr Aldo Boccaccini (Materials Department)

9. Development Low Embodied Energy Construction Products from Sewage Sludge Ash
Funding: EPSRC Industrial Case Award with Akristos Ltd.

10. Development of Hazardous Waste Treatment Technologies for Alexandria, Egypt
Funding: Egyptian Government
Co-investigator: Dr Geoff Fowler
Winner of the Imperial Innovations Student Innovations Competition 2008
Prize winner in GSEPS Research Symposium Poster Competition 2008

11. Reuse of Oil Drill Cuttings in the Oil and Gas Industry in Nigeria
Funding: Petroleum Technology Development Fund, Nigeria

12. Sustainable use of Waste Solid Products from Bioleaching Processes
Funding: EU Sixth Framework project (BioMinE)
Co-investigator: Dr Bill Dudeney (Earth Science and Engineering)
This project supports one co-supervised PhD student (Steve Bouzalakos)
Project collaborators include 13 universities and 17 industrial organisations
Completed June 2008

13. Production of Water Adsorbent Granules from Wastes
Funding: Bob Martin Ltd/IC Innovations/ICON
Total value of project to date: £ 75K

14. Nuclear Waste Encapsulation
Funding: EPSRC through the DIAMOND project
This is supporting two PhD projects, (geopolymers and alternative cement systems containing MgO). The DIAMOND Project involves collaboration between Imperial and Leeds, Sheffield, Loughborough, UCL and Manchester Universities. Collaboration at Imperial involves the Materials Department (Vandeperre and Boccaccini)

15. Novel Cementing Materials Manufactured from Waste Incineration Ashes
Funding: Royal Society/BP International Incoming Fellowship
Dr X.C.Qiao
Academic collaborators: Hong Kong Polytechnic University
Completed June 2006

16. Waste Management in Developing Countries
Co-investigator: Visiting Professor David Wilson
Ongoing research through a series of MSc projects

Bioconversion of biodegradable wastes

A semi-industrial scale investigation of the factors controlling the bioconversion of biodegradable wastes into a consistent solid recovered fuel (SRF) product for use as an auxiliary energy source by the cement industry

This 3 year project is funded by the Cyprus Research Promotion Foundation. Dr Stephen Smith is the academic supervisor and the PhD student is Iakovos Skourides. The host organization in Cyprus is Isotech Ltd and the other participants are Peter Hood, Future Fuels International Ltd and Vassiliko Cement Works Ltd.

European Landfill Directive requires the phased reduction of biodegradable municipal waste (BMW) disposed to landfill by EU Member States to ultimately achieve 35% of the quantity disposed in 1995 by 2016. Composting and mass burn incineration are the two most widespread techniques for diverting BMW from Landfills. However, there are important constraints and barriers impacting these techniques. Incineration is an expensive, complex technology and receives poor public acceptance in the UK. The economic and practical viability of composting depends on producing a high quality end-product and the availability of markets, which requires the separate collection of BMW and establishment of end-uses for the material. Residual compost is an intrinsically low value soil conditioning material relative to the cost of production and there is strong competition for markets from other organic waste derived materials.

Mechanical biological treatment (MBT) is an alternative approach to incineration and composting for managing municipal solid waste (MSW) and diverting BMW fromlandfill disposal; it is a well established practice in Europe and is likely to expand in the UK. The process includes the treatment of the biodegradable fraction to produce compost-like output (CLO) or a stabilised residue destined for landfill disposal.

Aerobic biological processes can also be configured to utilise metabolically generated heat to dry the putrescible organic fraction to produce a solid recovered fuel (SRF) with significant value as an alternative energy source to conventional fossil fuels in industrial situations, such as cement manufacture, thus contributing to the reduction of greenhouse gas emissions. Critical industrial processes demand a high specification and consistent calorific value which places major demands on the MBT system. However, there are no published data in the scientific literature on the thermokinetics or operational efficiency of technologies for biodrying BMW for fuel manufacture.

The majority of available MBT technologies rely on conventional static aeration methods for treating the biodegradable fraction. However, continuous or semi-continuous agitation and controlled aeration within a rotary drum, specifically configured and optimised for biodrying, may provide an alternative approach and significant advantages compared to the conventional methods of MBT. This may enable microbial activity and heat generation to be maximised at limiting moisture contents, reduced process retention times, enhanced particle size reduction and improvied homogeneity of the treated end product for use as a fuel.

Project Description, Objectives and Results

The main objective of the research is to quantify the factors controlling bio-drying and the quality of SRF using a semi-industrial scale rotary drum bio-reactor. The project also aims to optimise the bio-drying process and the quality of the end product and also assess the effect of using SRF in cement production on the quality of cement.

Bio-drying experiments are being conducted using a thermally insulated, semiindustrial cale rotary drum bio-dryer at Vassiliko Cement Works Ltd in Cyprus. The capacity of the bio-dryer is equivalent to approximately 9 m3 with dimensions: 2 m diameter x 3 m length; it is fitted with load cells and weight, temperature and humidity data are continuously recorded by a programmable logic controller (PLC), which also controls the drum aeration and rotation rate.

Entertic pathogen survival

Entertic pathogen survival and nutrient transformations in sewage sludge-amended agricultural soil

This research project is supported by UKWIR, DEFRA, Thames Water, Yorkshire Water, Anglian Water, Scottish Water and EPSRC. The principal investigator on this project is Professor Stephen Smith. The post doctoral research assistant is Dr Michael Rogers, and the PhD students are James Cass, Felipe Perez-Viana and Hannah Rigby.


Application of sewage sludge to agricultural soils is a widespread beneficial practice. A multiple barrier approach is employed to protect human health from infectious diseases caused by residual numbers of pathogenic organisms that may be present in sludge. This includes the treatment of sludge to reduce pathogen numbers and also the placing of time constraints on cropping, to allow effective decay of enteric microorganisms in the soil environment. However, there is a lack of data, particularly pertaining to temperate soils, regarding decay kinetics in soil for enteric microorganisms originating from application of sewage sludge.


The aim of this project is to increase understanding of the fundamental ecological processes involved in the decay of enteric microorganisms in sludge-amended agricultural soil. Through extensive field trials, it is intended to focus the research on quantifying the intrinsic ecological dynamics that exist in the soil environment that are directly or indirectly responsible for the suppression of enteric microorganisms added to soil in sludge. The field experiments are also supporting investigations to determine the microbiological controls on nitrogen release from different types of conventional and enhanced-treated biosolids to provide a sound scientific basis to support the agronomic use of these products, thus maximising efficient use of nutrient resources in the biosolids.


The experimental work is principally field based and the first field trial began on 19 April 2005 and continued for 108 days. Soil sampling and enumeration of E. coli, the indicator organism, was carried out at regular intervals during this time. Several replicate plots were amended with a variety of conventional and enhanced treated biosolids, along with animal wastes. The field trials were established on two field sites of contrasting soil type, at the Imperial College Wye campus farm in Kent.

Microbiological analyses of untreated plots indicated that E. coli was present in unamended control soil, as previously reported by our research group. This background population meant that enhanced biosolids, which are treated to eliminate pathogens, had little microbiological impact when added to soil - E. coli populations in these substrates were similar to those found in amended soil. Conventional biosolids, treated by mesophilic anaerobic digestion, contained high E. coli populations and, when added to soil, E. coli populations initially increased.

Over the course of the field trial, populations of E. coli in these amendments showed evidence of decay. While they did not reach the relatively low levels seen in the control soils after 108 days, the difference in numbers between the control and the amended plots were very small and were detected due to the sensitivity of the enumeration methods employed. Certain amended plots, along with the control plots, were sampled again after 152 days.

There was no statistically significant difference between the control and amended plots at one site, but due to the lower background seen in control plots at the other site, there were small, albeit significant, increase in E. coli numbers for the sludge-amended soil compared to the control. The sizes of the E. coli populations in soils following amendment, however, were extremely small when considered as a proportion of the total bacterial population in soil.

Soil microbial biomass concentrations were also recorded over the course of the field trial, and were shown to be related to organic matter (OM) content of the soils, increasing with the amount of OM in soil. The soil properties had a profound influence on microbial response to the applied biosolids. No effect of the amendments was apparent in the high OM soil, while the effect in low OM soil depended on the biomass content of the added material and substrate availability. The largest increase was observed in the plots amended with conventionally-treated sludges.

Nitrogen mineralisation investigations were also carried out over the course of the field trials. These also showed an apparent influence of soil ecological dynamics on the extent of N release from the sludges. Thus, the rate of N mineralization was lower in soil with low OM status, compared to the soil with high OM. This could be due to increased retention of N by the microbial biomass in low nutrient conditions.

A second field trial began on 18 September and is currently ongoing - this will again provide data concerning E. coli decay and soil microbial biomass over several months, this time over late autumn and winter, to compare data with spring. The photographs show the field trials being set up at the Imperial College farm in Kent.