Geothermal "mining" waste in Iceland -disposal and value creation

Sveinborg Hlíf Gunnarsdóttir1, Hjalti Franzson1, Vigdís

Harðardóttir1 and Bryndís G. Róbertsdóttir2.

1. ÍSOR, Iceland geosurvey

2. National energy authority

Introduction

− Geological context

− Geothermal mining waste in Iceland

− Waste water, gas and precipitates from geothermal power production.

− Some examples of disposal and value creation

Iceland‘s geological setting

Geological setting

Central volcanoes

Prospect areas and gold anomalies in Iceland

Formation of epithermal ore

The Þormóðsdalur prospect

− Quartz-adularia vein system with Au enrichment from <0.5 ppm to a maximum of 415 ppm.

− 3000 m from 41 cored wells.

− Mining would be underground.

− Mining waste would have to be taken good care of due to proximity to a river and a lake. Fortunately base metal concentrations are very low.

− ÍSOR is a part of the NORDMIN project WASCIOUS, Water conscious mining.

Mining waste in Iceland

− Waste from the use of our geothermal resources is our mining waste

− Three types of geothermal mining waste

− Waste water

− Gases

− Mineral precipitations from geothermal fluids

Waste water- Disposal and value creation

Blue lagoon - Svartsengi Gray lagoon - Reykjanes

Pictures: ÍSOR

Waste water - Reinjection

Picture: http://www.bgs.ac.uk/research/energy/geothermal/

Hellisheidi power plant

Electricity production 300 MW CO2 emission 40 000 t/yr Waste water 700kg/s

Thermal capacity 400 MWth H2S emission 12 000 t/yr Waste water 22 Mt/yr

Waste gas – Carbfix/Sulfix pilot project at Hellisheiði

− Goal of the project: Reduce CO2

and H2S emissions from the geothermal power plant

− CO2 and H2S separated from gas emissions and reinjected with waste water into the system to precipitate in the basaltic rocks as carbonates and sulfides.

Picture: Clark et al., 2016 in prep.

Basic theory of Carbfix/sulfix

Waste gases

• Carbon Recycling International• Operating next to the Svartsengi power plant.• Turning C02 into methanol fuel

Picture: http://www.carbonrecycling.is

Precipitation of minerals from geothermal fluids-

Scaling in Reykjanes

Wellhead RN9

Orifice plate

Gray Lagoon

Vent

house Separation

station

19 m

Upstream

Downstream

G.O.Fridleifsson

Precipitation of minerals from geothermal fluids-Scaling in Reykjanes

RN12, 314°C max in well, at wellhead

247°C; ΔP 15 bars, CuS

5µ

m

Cc

Bornite, sphalerite,

galena, chalcopyrite,

covellite

RN-12

Zn = 20%

Fe = 9%

Cu = 23%

Pb = 15%

S = 22%

570 ppm Au

9200 ppm Ag

Medium-pressure wells

Precipitation of minerals from geothermal fluids-Scaling in Reykjanes

Borehole – clogging – surface pipeline

330°C

260°C

267°C Sph, cpy, gn,

(bn, cv, py, Am

SiO2)

Zn: 48-43 wt%

Cu: 11-18 %

Fe: 3-4 %

Pb: 0.3-1%

SiO2: 3-2%

S: 30-28%

Ag: 890-

3500ppm

Au:110-80 ppm

Precipitation of minerals from geothermal fluid

The National Planning Agency

− State authority, under the Ministry for the Environment and Natural Resources

− Responsible for the administration and implementation of the Planning Act, the Environmental Impact Assessment Act (EIA) and the Strategic Environmental Assessment Act (SEA).

Final comments

− Iceland is a living example of the geological environment and processes which created some of the metallogenic provinces now hosting deposits which are being mined.

− There are no mines in Iceland but still we have to take care of the mining waste.

− Innovative solutions regarding waste water and gases might have some implications in a broader perspective of the mining industry.

− Need for expertise in Iceland if future gold mining prospect will be exploited.

− Nordmin is a great collaboration, learning and networking platform for Icelandic scientists and consultants.