NUI Galway – UL Alliance First Annual ENGINEERING AND - ARAN ...

Building with our waste: Incinerator Ash as a Construction Material in
Ireland
Researcher: Murrough P. O’Brien
Supervisor: Dr. Declan T. Phillips
Department of Civil Engineering and Materials Science, University of Limerick
E-mail: murrough.obrien@ul.ie
Abstract:
This research considers the potential of Irish
municipal Incinerator Bottom Ash (IBA) serving as
a useful construction aggregate. In this research,
IBA is studied from three separate aspects;
mechanical characteristics, environmental safety
and economic viability. Knowledge of these
properties is essential if this material is to be put to
use in construction. An estimation of the cost of
producing such a material will be provided. A
successful outcome will result in IBA which would
otherwise be land-filled being applied to
constructive applications thus improving the nature
of waste management in Ireland.
Introduction:
Municipal waste management in Ireland is
facing a major change with the arrival of Waste to
Energy (WtE) incineration facilities. Our first
facility is approaching completion in Meath while
others are proposed in Dublin and Cork. These
plants will significantly reduce our dependence on
landfill with the combined benefits of producing
electricity and hot water from our waste.
Although incineration considerably reduces the
waste bulk, it does not eliminate it. For every tonne
of waste burnt 240 kg of ash will remain on the
grate in the form of Incinerator Bottom Ash (IBA).
It is expected that by the end of 2012 the Meath
facility alone will produce 50,000 tonnes of IBA
per year. Currently it is planned to dispose of this
by landfill. The Irish WtE operators have cited a
lack of scientific data of Irish IBA as the main
reason for not using it beneficially.
This project aims to investigate Irish IBA as an
environmentally safe and reliable construction
material. If successful, landfill of IBA will be
eliminated. This will drastically improve the WtE
system for sustainably managing our waste.
What is Incinerator Bottom Ash (IBA)?
IBA is an aggregate like material which consists
of glass, ceramics, metal, and fine ash components
(Wiles, 1996). IBA aggregate has been used as
construction fill in Denmark since 1903. Since then
it has been used across the globe in applications
ranging from cement production to aggregate in
bituminous mixes, but mainly as an unbound road
foundation material.
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My Project:
I have assembled a statistically representative
sample of Irish waste. This will be incinerated at
850° C before testing the quality of the resultant
ash. It is also my aim to assess the economic
viability of IBA.
Mechanical Characteristics:
To meet industry standards IBA must have the
strength demanded of it to support and distribute its
design loads as well as the durability to sustain
long term usage. A range of critical properties such
as; gradation, shear strength, durability, toughness,
compaction and specific gravity will be assessed in
the laboratory. Constructability will be assessed on
a trial road foundation constructed from IBA.
Environmental Safety:
The main concern surrounding the use of IBA in
an unbound form is the fear that it will leach toxic
heavy metals when it is placed against the natural
soil. A leachate testing and analysis programme
using Atomic Absorption Spectrometry has been
designed to assess the safety of the material. This
includes availability, compliance, column, tank and
lysimeter leachate tests.
Economic Analysis:
IBA usage provides a number of financial
advantages. It saves a considerable landfill cost and
it does not require the same intensity of quarry
processes as crushed rock. Against this it does
require more quality control, the extent of which
will be known on completion of the quality tests.
Conclusion:
If Irish IBA aggregate can be used, we will
reduce our landfill and rock extraction volumes,
while making our infrastructure more sustainable.
This will cause waste to be viewed as a raw
material rather than an inconvienance.
References:
Wiles C.C. (1996) ’Municipal Solid Waste
Combustion Ash: State-of-The-Knowledge, Journal
of Hazardous Materials, 47, pp 325 – 344.