February 20081

Carb-Fix (CO2 fixation into basalt)

Experiment at Hellisheiði Geothermal Plant, Iceland

by

Hólmfríður Sigurðardóttir

Project Manager

Reykjavik Energy

Contact: holmfridur.sigurdardottir@or.is

February 20082

The Beginning

• Jan 2006 Wally Broecker invited by President of Iceland to give a lecture on climate change”

• Workshop in Reykjavík January 16th -17th 2006

• Cooperation – University of Iceland - www.raunvis.hi.is– Columbia University - www.ldeo.columbia.edu– CNRS in France - www.cnrs.fr– Reykjavík Energy – www.or.is

The Future• CO2 strapped from the atmosphere

February 20084 Ingvar Sigurðsson

• Basalt is igneous rock formed during volcanic eruptions

• Can be glassy and/or crystalline• Basalt contains about 10 weight% CaO

which can be used for carbon fixation

Mineral name Potential CO2 fixed,kg/m³ mineral

Plagioclase 436

Olivine 2015-1896

Pyroxene 1404

Serpentine 1233

Mica group 62

Clay Minerals 161

February 20085

Why Iceland?

• Bedrock > 90% basaltic• Excellent infrastructure for experiment at Hellisheiði

plant• Ample supply of fresh water, CO2 gas and dissolvable

basalts• Group of scientist, engineers and craftsmen

– Fundamental equations describing rate of basalt dissolution – Study may prove the feasibility of CO2 fixation projects

elsewhere

Basalt

Sigfús Már Pétursson Guðmundur LárussonSigfús Már Pétursson

February 20086

Iceland - CO2 Emission

• Icelanders ~3.7 Mt CO2 /yr (figures from 2004)• Energy from fossil fuel 52%• Industrial processes 25%• Agriculture 14%• Waste 5%• Geothermal energy 4%

• Geothermal power plants (450 MW):• 20-40 g CO2/kWh

– Comparison of CO2 emission from different energy sources in the USA (Bloomfield et al. 2003)

• Natural gas: 599 g CO2/kWh

• Oil: 893 g CO2/kWh

• Coal: 955 g CO2/kWh

• Magma: ~ 2 Mt CO2 /yr Sigurður R Gíslason

Sigfús Már Pétursson

February 20087

Natural Processes

Recharge by cold ground-

water

Solidifying magma

Heat conductionand naturalCO2 release

Heat conductionand naturalCO2 release

Supercritical convection

Upflow zone280-320 °C

Deep inflow zone

FumarolesHot spring areas, fumaroles

350-400 °C

600-1000 °C

Outer boundary: 100 °C/km and constant pressure

Alteration cap

Lateral outflow zone, 220-280 °C

February 20088

CO2 Captured Naturally in

Hellisheiði

Dep

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ab

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eve

l)

February 20089

Solidifying magma

Heat conductionand natural

CO2 release

Heat conductionand natural

CO2 release

CO2 in geothermal steam from wells at Hellisheiði

Alteration cap

CO2 fully dissolved in fresh water and injected down to 400-800 m

Add calcite to the alteration cap

Gretar Ívarsson

February 200810

1 kg/s of CO2 fromcondensers

1 kg/s of CO2 fromcondensers

400 kg/s of steam, gas and water from deep and hot (>240 °C) geothermal wells400 kg/s of steam, gas and water from

deep and hot (>240 °C) geothermal wells Hellisheiði geothermal power plant

Hellisheiði geothermal power plant

Target zone for CO2 sequestration identified

at 400-800 m depth

Target zone for CO2 sequestration identified

at 400-800 m depth

Groundwater

Groundwater

Gas injected fullydissolved in water

into target zone

Gas injected fullydissolved in water

into target zone

Sigfús Már Pétursson

February 200812Sigfús Már Pétursson

The gas mixture: 0,5 % of the steam is geothermal gasGas mass%CO2 83 H2S 16CH4 N2 ~1 H2

~ 13 l/s of water to dissolve 1 kg/s CO2 at 25°C and 40 bar

~ 10 kg basalt to react with 1 kg/s CO2

February 200813

Tracer Tests

• An initial tracer test at the target zone for CO2-injection– Nature of the groundwater system– Flow-patterns and flow-rates

• Large dispersion• Matrix permeability – not through fractures• Large surface area for chemical reactions • Ensure that a potentially leaky site is not selected

Gretar ÍvarssonGuðmundur Lárusson

February 200814

CO2 Separated from the Gas Mixture

Compression, refrigeration and distillation: – 98% CO2 and 2% H2S as a liquid

– H2 ,possibly applicable as fuel

• Estimated cost:– 1MW/yr of electricity needed for

the process and injection– 1% of the electricity production

at Hellisheiði geothermal plant

Sigurður R Gíslason

February 200815

Bedrock and BoreholesHN-4

HK-31

Casing

Flow direction

Lavaflows

Hyaloclastite formations

Upper level of alteration minerals

Bedrock temperature

CO2 injection well - HN-2Fresh water - HN-1

February 200817

The ProcessInjection well: CO2 fully dissolved in fresh water

Low pH: 3-4

Dissolution of basalt release of Ca2+ and other ionsPrecipitation of calcite

pH increases

• Reservoir may gradually clog up with calcite scaling

• Natural process in high-temperature systems

February 200819

Regulatory Frameworks

• Law and regulations – Prevention of contaminating groundwater– Health and safety– Planning act, Nature conservation law – Operating permits

• Environmental impacts– Surface: Perturbation of pristine areas, visual impacts, suffocation

etc.– Subsurface: Metal mobilization, groundwater contamination etc.– Air: Leakage of CO2 back to the atmosphere

• Site monitoring and verification

Reykjavik Energy

February 200820

Site Monitoring

• Soil CO2 flux – before and after injection

• Tracers and chemical analysis• Geophysical signals

– Resistivity– Gravity

National Energy Authority

February 200821

Global Significance

• Extensive basalt shields worldwide

February 200822

Global Significance

• Extensive basalt shields worldwide

• Mineral stable for thousands or millions of years

• The experiment will address whether mineral storage of CO2 in basalts is a global alternative

• The project may demonstrate that “zero emission” geothermal power plants are possible

• New technology for strapping CO2 from the atmosphere – sequestration projects can be operated at “best” geological conditions

February 200823