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

An embodied energy and carbon assessment tool using a hybrid energy inputoutput
methodology
Mark McCaffrey 1 ; Dr. Jamie Goggins 2 ; Dr. Gordon Baylor 3
College of Engineering & Informatics; Ryan Institute for Environmental, Marine and Energy
Research; Informatics Research Unit for Sustainable Engineering (IRUSE).
1) m.mccaffrey1@nuigalway.ie 2) jamie.goggins@nuiglway.ie 3) gordonbaylor@hotmail.com
Abstract
In the aftermath of the Kyoto protocol [1] the
‘carbon market’ has incentivised industries to become
more sustainable and change their outlook. The energy
intensity of every sector of the Irish economy is being
scrutinised, but very little attention has been paid to
embodied energy (EE) and embodied carbon (EC) in
our products and systems. It is critical that EE/EC can
be assessed, as previous studies have emphasised just
how important it is. In reference to the built
environment: the EE of a multi storey building can
represent up to 67% of the operational energy (OE) for
a 25 year LC [2]; for a low energy house the EE can
account for up to 50% of the OE over a 60 year LC [3].
EE may be expressed as megajoules (MJ) per unit
weight (kg) or unit area (m 2 ). The EC is measured in
carbon dioxide equivalent (CO2e). This research focuses
on the development of a framework, by the authors,
enabling the quantification of EE/EC in an Irish context
using a hybrid Input-Output (I-O) methodology. An
initial study applies the framework to cement, which is
a material high in EE/EC and consequently a material
included in the European Union-Emissions trading
scheme (EU-ETS).
1. Introduction
The energy I-O methodology tracks energy flows
through sectors of an economy. It was born out of the
U.S. oil crisis in the 1970s. The novel concept of the
methodology is that it can be further utilised in a hybrid
I-O energy analysis. The hybrid I-O EE and EC values
for a product being assessed can then be utilised to
compile a life cycle inventory (LCI), as part of a life
cycle assessment (LCA). Indirect energy and
subsequent indirect combustion emissions are then
inclusive in the LCA. Commonly used simple process
analysis does not account for both indirect energy and
emissions [4]. This research develops the energy I-O
methodology for use in Ireland; using the Central
Statistics Office (CSO) “I-O tables”, the Sustainable
Energy Authority of Ireland (SEAI) “energy balance”,
and pricing data from the CSO and Economic and
Social Research Institute (ESRI). Two unrelated
specialist areas (economics and energy) are required to
calculate average energy tariffs and disaggregation
constants to convert the energy sectors of the national I-
O tables from monetary flows (€/€) to energy flows
(GJ/€) and subsequently to CO2e flows (kgCO2e/€)
using the Intergovernmental Panel on Climate Change
(IPCC) combustion emission factors.
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2. Assessment of cement manufacture
Cement is the largest contributing factor to the EE/EC
of concrete equating to 5% of total Irish CO2e emissions
in 2005 [5]. In order to investigate the validity of the
hybrid I-O energy analysis methodology for calculating
the EE and EC of a product or system, as part of an
LCA and also as part of the EU-ETS, cement was
chosen as a product for assessment. The IPCC
guidelines and the ISO EN 14044 standards [6] were
accorded to for EU-ETS and LCA calculations,
respectively. The I-O energy and carbon intensities of
the non-metallic mineral sector, which includes cement
manufacture, results in total energy and carbon
intensities of 4.41 MJ/€ and 0.33 kgCO2e/€,
respectively. The hybrid I-O energy and carbon
emissions intensities, for cement produced in Ireland in
2005, were found to be 3.32 MJ/kg and 0.86 kgCO2e/kg.
3. Conclusion
This research demonstrates how the I-O energy
analysis methodology can account comprehensively for
energy and emissions throughout the economy at both a
sectoral level and in respect to the products and systems
therein. The results can be utilised in LCAs of buildings
to calculate the OE versus the EE and EC or on
renewable energy technologies, to calculate the payback
period in terms of energy and carbon. Conversely, as
energy and CO2e emissions associated with the Irish
electricity generation sector reduces, EE and EC will
become larger over a complete LC. Hence, there is a
need for robust and complete analysis, which takes both
direct and indirect energy and carbon into account.
References:
[1] UNFCCC, Kyoto protocol to the United Nations
framework convention on climate change. 1998, UNFCCC:
[2] Cole R.J. and Kernan P.C., Life-cycle energy use in office
buildings. Building and Environment, 1996. 31(4).
[3] Daly P., A zero energy demonstration house in Ireland, in
Conference on Passive and Low Energy Architecture.
2008: Dublin.
[4] McCaffrey M., Goggins J., and Baylor G., The use of
embodied energy and carbon as indicators of the
environmental impact of reinforced concrete structures in
Ireland, in The Bridge and Concrete Research Institute.
2010: Cork.
[5] SEAI, Ireland’s Low-Carbon Opportunity, in An analysis
of the costs and benefits of reducing greenhouse gas
emissions Technical Appendix. 2009a, SEAI.
[6] ISO 14044, Environmental management - in Life cycle
assessment - Requirements and guidelines. 2006, BSI EN.