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Making geothermal energy truly sustainable

09 September 2022
With more than $6 million in new MBIE funding, University of 免费色情视频 researchers are working to reduce the greenhouse gas emissions of geothermal energy.

Geothermal energy has a reputation for being green 鈥 but though it鈥檚 much cleaner than fossil fuels, it does produce some greenhouse gas emissions. With more than $6 million in newly announced funding from the Ministry of Business, Innovation and Employment, researchers at Waipapa Taumata Rau, University of 免费色情视频, are working to change that.

Associate Professor , co-director of the at the Department of Engineering Science, is leading a team aiming to turn the greenhouses gases that geothermal plants currently emit into rock, trapping it permanently underground. 

鈥溍夥焉槭悠 is a world leader in geothermal energy technology and many countries implement our research,鈥 says Research Fellow , a member of the team. 鈥淭his could transform the industry, bringing it from low to no emissions.鈥

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Dr Eylem Kaya, Associate Professor Sadiq Zarrouk, Minister for Research, Science and Innovation Ayesha Verrall, Vice-Chancellor Dawn Freshwater and Deputy Vice-Chancellor Research Jim Metson

And while geothermal plants are the first target, the process has the potential to be applied to other industries, including fossil fuel power plants. If widely applied around the world, it could take a significant chunk out of global emissions, says Zarrouk.

鈥淲e don鈥檛 claim we鈥檒l be able to eliminate all global emissions but we鈥檙e going to help reduce them, starting with geothermal energy and going beyond.鈥

Geothermal energy: A primer

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Current geothermal plant design

Geothermal energy is a result of the heat at the Earth鈥檚 core, which unlike solar and wind, is always reliable. Aotearoa 免费色情视频鈥檚 volcanic fields make the country a great place for geothermal power 鈥 it produces the fifth most geothermal energy in the world.

In a geothermal power plant, wells are drilled deep under the surface to reach hot groundwater. As the hot water rises to the surface, some of it turns to steam. This steam powers turbines that produce electricity. The wastewater is then pumped back underground to maintain the system鈥檚 pressure.

On average, geothermal plants produce far less greenhouse gas than fossil fuel plants. However, they do produce some, mainly carbon dioxide (CO2), as well as hydrogen sulphide (H2S) and other gases, because these gases naturally exist underground and some of it comes to the surface along with the hot water.

The exact amount of emissions varies, mostly due to the natural conditions under the surface, but in 免费色情视频, some plants emit enough that the carbon price they pay is significant, with the price expected to go up as the country moves towards the goal of net-zero emissions by 2050. This is part of what鈥檚 motivating the industry to cut emissions.

That鈥檚 not all. The Climate Change Commission has recommended closing several high-emitting geothermal fields by 2030 despite the billions the infrastructure cost to build. For the industry to survive, it鈥檚 going to have to lower emissions quickly. 

Geothermal power currently supplies 18.1 percent of 免费色情视频鈥檚 electricity. However, if the country鈥檚 full geothermal potential were realised, it could supply significantly more of the electricity demand. If geothermal energy were made carbon neutral and scaled up, it would be a big step towards net zero.

Turning gas into rock

Scientists are already working on ways to re-dissolve greenhouse gases in water before the liquid is injected back underground. From there, however, the gases can again escape, whether by naturally bubbling up or through geothermal energy production. That鈥檚 why Zarrouk and his team are working on a second step: turning the dissolved gases into rock. 

It may sound like science fiction 鈥 but the process of turning carbon into rock exists in nature. It鈥檚 why fossils exist. Of course, geothermal engineers aren鈥檛 interested in waiting millennia. They鈥檙e working on ways to mineralise CO2 much faster. 

In Iceland, scientists are capturing carbon by injecting it underground into the local basaltic rock, which has the right structure and chemical composition to trap CO2 and petrify it into calcite. However, 免费色情视频 rock isn鈥檛 as naturally suited for this as Iceland鈥檚. 

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Researchers' new geothermal plant design
鈥淥nce the gas is mineralised, it鈥檚 stable, harmless and risk-free. Even if there is a seismic event, it remains as rock.鈥
Dr Eylem Kaya

Zarrouk鈥檚 team鈥檚 big idea is to introduce the ions that can trap CO2 and H2S and inject them underground along with the dissolved gases. The result will be that even in areas with non-basaltic rock, greenhouse gases can be solidified underground. The CO2 will petrify into calcite and the H2S into pyrite (fool鈥檚 gold) 鈥 both non-toxic, common minerals.

鈥淥nce the gas is mineralised, it鈥檚 stable, harmless and risk-free,鈥 says Kaya. 鈥淓ven if there is a seismic event, it remains as rock.鈥

The scientists will nonetheless implement a long-term monitoring programme to watch for any problems such as gas escape.

Broad and deep partnerships

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The team is working with a range of partners across Aotearoa and internationally. Its relationship with tangata whenua is key to its work.

鈥淢膩ori are the owners of the resources and land, so they want to make sure their resources remain safe and that mana whenua have a clear voice in their management,鈥 says Zarrouk. 鈥淚f this project is commercialised, mana whenua will be part of the business side as well.鈥

Principles of management for the project will include embedding M膩tauranga M膩ori in decision making, reciprocity and prioritisation of uses of geothermal resources for the benefit of the community.

鈥淢膩ori use geothermal resources in a very sustainable way,鈥 says Kaya. 鈥淲e have a lot to learn from them.鈥

The team aims to develop community capacity by recruiting M膩ori PhD students. It also aims to spark interest in the field through outreach to high school students.

The team is also working closely with industry partners in 免费色情视频 and abroad. Both Zarrouk and Kaya have been involved with the board of the International Geothermal Association so they are well connected internationally.

鈥淚n 免费色情视频, every geothermal power generation company is supporting this project,鈥 says Kaya. 鈥淲e also have close collaborators in Indonesia, the Philippines, the U.S., Turkey, Italy, Japan and other countries.鈥

Reducing emissions worldwide

The team plans to take its technology from the lab to the field within a few years. After the technology is proven, the team plans to commercialise it, whether through licensing, consultancy or by starting a company. In addition to helping advance the team鈥檚 research, UniServices is providing early advice on moving from research to commercialisation.

If every existing 免费色情视频 geothermal plant adopted the technology, emissions would be reduced by 560 kilotonnes a year 鈥 worth $42.3 million under current carbon pricing. If the technology were applied to other industries, such as dairy 鈥 milk plants often use fossil fuels for purposes such as milk drying 鈥 emissions would decline still further.

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If fossil fuel plants internationally were to use the team鈥檚 process to capture emissions and pump them underground to mineralise, the technology would go from carbon neutral to carbon negative, say the researchers. While there would be a cost to bring in the technology, this would be more than offset by the savings in carbon pricing.

鈥淚f this technology is taken up around the world, it will make a real dent in emissions,鈥 says Zarrouk. 鈥淥thers are also doing their bit, working on the electrification of cars, switching to hydrogen, etc. 鈥 this work is part of the big jigsaw to help solve the problem of climate change.鈥

鈥淚f this technology is taken up around the world, it will make a real dent in emissions.鈥
Associate Professor Sadiq Zarrouk
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