Life cycle assessment of the carbon intensity of deep geothermal heat systems: a case study from Scotland

Alistair T. McCay, Michael E.J. Feliks, Jennifer J. Roberts

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Deep geothermal energy is widely recognised as a source of low carbon heat. However, to date there have been no specific assessment of the carbon intensity of low-enthalpy deep geothermal; previous studies focussed on geothermal power or higher enthalpy heat. As such, there is no established method for assessing the CO2 emissions from implementing a deep geothermal heating scheme. Here we address these gaps. We perform a life cycle assessment of greenhouse gas emissions relating to a deep geothermal heat system to (i) calculate the carbon intensity of geothermal heat; (ii) identify key factors affecting these values; (iii) consider the carbon abated if geothermal heat substitutes conventional heating; and (iv) present information that future projects can apply to assess the carbon emissions reduction offered by geothermal heat development. Our work is informed by parameters from a feasibility study for a proposed geothermal heat system in Banchory, Scotland. The project planned a 2.5 MWth geothermal plant extracting heat from the Hill of Fare granite via two boreholes, one injection and one production. We find that the majority of the emissions are associated with site construction, and sensitive to site and materials specific factors, for example the depth of the drilled boreholes and type and quantities of steel and cement used to seal them, or soils disturbed for laying pipelines and constructing access roads. During operation the carbon intensity of the electricity grid used to power hydraulic pumps largely determines the carbon intensity of the produced heat. We calculate that the carbon intensity of the heat produced is 9.7–14.0 kg(CO2e) MWhth which is 4.9–7.3% of the emissions from heat from natural gas. These values are compatible with Scotland's plans for long term decarbonisation of heat in line with national emission reduction obligations and would likely be compatible with any country's decarbonisation goals.
LanguageEnglish
Pages208-219
Number of pages12
JournalScience of the Total Environment
Volume685
Early online date22 May 2019
DOIs
Publication statusPublished - 1 Oct 2019

Fingerprint

Life cycle
Carbon
life cycle
carbon
enthalpy
Decarbonization
borehole
heating
Boreholes
geothermal power
geothermal energy
Enthalpy
carbon emission
feasibility study
Pipeline laying
Hot Temperature
Deep-Heat
Geothermal heating
natural gas
electricity

Keywords

  • geothermal
  • Scotland
  • energy
  • heat
  • case study

Cite this

@article{bc4e2a08592e45709bbfe8970997d1fc,
title = "Life cycle assessment of the carbon intensity of deep geothermal heat systems: a case study from Scotland",
abstract = "Deep geothermal energy is widely recognised as a source of low carbon heat. However, to date there have been no specific assessment of the carbon intensity of low-enthalpy deep geothermal; previous studies focussed on geothermal power or higher enthalpy heat. As such, there is no established method for assessing the CO2 emissions from implementing a deep geothermal heating scheme. Here we address these gaps. We perform a life cycle assessment of greenhouse gas emissions relating to a deep geothermal heat system to (i) calculate the carbon intensity of geothermal heat; (ii) identify key factors affecting these values; (iii) consider the carbon abated if geothermal heat substitutes conventional heating; and (iv) present information that future projects can apply to assess the carbon emissions reduction offered by geothermal heat development. Our work is informed by parameters from a feasibility study for a proposed geothermal heat system in Banchory, Scotland. The project planned a 2.5 MWth geothermal plant extracting heat from the Hill of Fare granite via two boreholes, one injection and one production. We find that the majority of the emissions are associated with site construction, and sensitive to site and materials specific factors, for example the depth of the drilled boreholes and type and quantities of steel and cement used to seal them, or soils disturbed for laying pipelines and constructing access roads. During operation the carbon intensity of the electricity grid used to power hydraulic pumps largely determines the carbon intensity of the produced heat. We calculate that the carbon intensity of the heat produced is 9.7–14.0 kg(CO2e) MWhth which is 4.9–7.3{\%} of the emissions from heat from natural gas. These values are compatible with Scotland's plans for long term decarbonisation of heat in line with national emission reduction obligations and would likely be compatible with any country's decarbonisation goals.",
keywords = "geothermal, Scotland, energy, heat, case study",
author = "McCay, {Alistair T.} and Feliks, {Michael E.J.} and Roberts, {Jennifer J.}",
year = "2019",
month = "10",
day = "1",
doi = "10.1016/j.scitotenv.2019.05.311",
language = "English",
volume = "685",
pages = "208--219",
journal = "Science of the Total Environment",
issn = "0048-9697",
publisher = "Elsevier",

}

Life cycle assessment of the carbon intensity of deep geothermal heat systems : a case study from Scotland. / McCay, Alistair T.; Feliks, Michael E.J.; Roberts, Jennifer J.

In: Science of the Total Environment, Vol. 685, 01.10.2019, p. 208-219.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Life cycle assessment of the carbon intensity of deep geothermal heat systems

T2 - Science of the Total Environment

AU - McCay, Alistair T.

AU - Feliks, Michael E.J.

AU - Roberts, Jennifer J.

PY - 2019/10/1

Y1 - 2019/10/1

N2 - Deep geothermal energy is widely recognised as a source of low carbon heat. However, to date there have been no specific assessment of the carbon intensity of low-enthalpy deep geothermal; previous studies focussed on geothermal power or higher enthalpy heat. As such, there is no established method for assessing the CO2 emissions from implementing a deep geothermal heating scheme. Here we address these gaps. We perform a life cycle assessment of greenhouse gas emissions relating to a deep geothermal heat system to (i) calculate the carbon intensity of geothermal heat; (ii) identify key factors affecting these values; (iii) consider the carbon abated if geothermal heat substitutes conventional heating; and (iv) present information that future projects can apply to assess the carbon emissions reduction offered by geothermal heat development. Our work is informed by parameters from a feasibility study for a proposed geothermal heat system in Banchory, Scotland. The project planned a 2.5 MWth geothermal plant extracting heat from the Hill of Fare granite via two boreholes, one injection and one production. We find that the majority of the emissions are associated with site construction, and sensitive to site and materials specific factors, for example the depth of the drilled boreholes and type and quantities of steel and cement used to seal them, or soils disturbed for laying pipelines and constructing access roads. During operation the carbon intensity of the electricity grid used to power hydraulic pumps largely determines the carbon intensity of the produced heat. We calculate that the carbon intensity of the heat produced is 9.7–14.0 kg(CO2e) MWhth which is 4.9–7.3% of the emissions from heat from natural gas. These values are compatible with Scotland's plans for long term decarbonisation of heat in line with national emission reduction obligations and would likely be compatible with any country's decarbonisation goals.

AB - Deep geothermal energy is widely recognised as a source of low carbon heat. However, to date there have been no specific assessment of the carbon intensity of low-enthalpy deep geothermal; previous studies focussed on geothermal power or higher enthalpy heat. As such, there is no established method for assessing the CO2 emissions from implementing a deep geothermal heating scheme. Here we address these gaps. We perform a life cycle assessment of greenhouse gas emissions relating to a deep geothermal heat system to (i) calculate the carbon intensity of geothermal heat; (ii) identify key factors affecting these values; (iii) consider the carbon abated if geothermal heat substitutes conventional heating; and (iv) present information that future projects can apply to assess the carbon emissions reduction offered by geothermal heat development. Our work is informed by parameters from a feasibility study for a proposed geothermal heat system in Banchory, Scotland. The project planned a 2.5 MWth geothermal plant extracting heat from the Hill of Fare granite via two boreholes, one injection and one production. We find that the majority of the emissions are associated with site construction, and sensitive to site and materials specific factors, for example the depth of the drilled boreholes and type and quantities of steel and cement used to seal them, or soils disturbed for laying pipelines and constructing access roads. During operation the carbon intensity of the electricity grid used to power hydraulic pumps largely determines the carbon intensity of the produced heat. We calculate that the carbon intensity of the heat produced is 9.7–14.0 kg(CO2e) MWhth which is 4.9–7.3% of the emissions from heat from natural gas. These values are compatible with Scotland's plans for long term decarbonisation of heat in line with national emission reduction obligations and would likely be compatible with any country's decarbonisation goals.

KW - geothermal

KW - Scotland

KW - energy

KW - heat

KW - case study

UR - https://www.sciencedirect.com/journal/science-of-the-total-environment

U2 - 10.1016/j.scitotenv.2019.05.311

DO - 10.1016/j.scitotenv.2019.05.311

M3 - Article

VL - 685

SP - 208

EP - 219

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

ER -