caverns

Storing carbon in buildings

February 4, 2025 By EarthWise Leave a Comment

According to a new study by researchers at the University of California, Davis and Stanford University, construction materials used in buildings have the potential to lock away billions of tons of carbon dioxide. The study, published in Science, shows that storing CO2 in buildings could be a major contributor to efforts to reduce greenhouse gas emissions.

Overall efforts in carbon sequestration take carbon dioxide – either as it’s being produced or once it’s already in the atmosphere – and store it away. Storing it might involve injecting it into underground caverns or deep in the ocean. Alternatively, storing it might involve converting it into a stable form using chemical reactions. These various strategies involve both practical challenges and potential environmental risks.

The new study suggests that many materials that are already produced in large quantities have the potential to store carbon dioxide. These include concrete, asphalt, plastics, wood, and brick. More than 30 billion tons of these materials are produced worldwide every year.

Ways to accomplish carbon storage include adding biochar into concrete, using artificial rocks loaded with carbon as concrete and asphalt aggregates, plastic and asphalt binders based on biomass instead of petroleum, and including biomass fiber into bricks.

The largest potential is using carbonated aggregates to make concrete. Concrete is by far the world’s most popular building material with more than 20 billion tons being produced each year.

The feedstocks for these ways to store carbon in building materials are mostly low-value waste materials, so the economics of implementing these carbon sequestering strategies are likely to be quite favorable.

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Storing Carbon in Buildings Could Help Address Climate Change

Photo, posted October 19, 2022, courtesy of Alexandre Prevot via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Giant batteries in the Earth

December 23, 2024 By EarthWise 1 Comment

The wind and the sun are inexhaustible sources of energy, and we are tapping into them to produce electricity at a growing rate around the world. But neither of them is always available when we need them. When the sun isn’t shining and the wind isn’t blowing, they don’t work.

An opposite problem also exists. When our energy needs are low, but it is sunny or windy, solar and wind power are all dressed up with nowhere to go. Energy storage is the answer to both of these problems. When there is excess generation, store the energy for later use. When there is need for energy and not enough is being generated, tap into the energy that is stored.

Giant banks of lithium-ion batteries are the rapidly growing form of energy storage, and they are increasingly providing resilience in the electric grid. But battery storage is short-term energy storage. Even the largest battery banks can only provide a few hours of electricity.

So, there is a real need for “long-duration energy storage” – systems that provide at least 10 hours of backup power and sometimes much more – for the grid to be fully reliable.

Pumped hydro storage, which uses water from elevated reservoirs to drive turbines, has been around for a long time. Historically, this is the largest form of energy storage in the world. Other methods include pumping compressed air into underground caverns or lifting massive blocks into elevated positions. All of these techniques use excess electricity to place things like water, air, or cement into a position where they can be used to drive electrical generators.

The grid of tomorrow will store energy in giant battery banks, but also in the ground, in reservoirs, and in large structures.

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How giant ‘batteries’ in the Earth could slash your electricity bills

Photo, posted March 21, 2024, courtesy of Sandra Uecker/USFWS via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A giant underground battery

February 5, 2024 By EarthWise Leave a Comment

Two up-and-coming energy technologies are coming together near a tiny town in central Utah. Outside of the town of Delta, population 3,600, two caverns, each as deep as the Empire State Building, are being created from an underground salt formation to be used to store hydrogen gas. The gas will be used as a fuel in a new electricity generation plant.

The plant will replace an aging local coal-fired power plant. The new plant will burn a mixture of natural gas and hydrogen – green hydrogen produced without emitting greenhouse gases. To produce the hydrogen, the facility will operate 40 giant electrolyzers that will use excess solar and wind power generated at times of low demand to split water molecules into hydrogen and oxygen.

The caverns were created by a process called solution mining in which high-pressure water is pumped down into salt deposits that are dissolved. The resulting caverns are 200 feet in diameter and 1,200 deep and lie 3,000 to 4,000 feet below the surface. Hydrogen cannot escape through the thick salt layers.

The amount of energy that can be stored in the form of hydrogen fuel in these caverns is massive – far more than all the battery storage installed in the U.S. to date. Chevron has a majority stake in one of the projects and will supply the natural gas. The facility is expected to go online in 2025.

While this will produce far fewer emissions than existing coal plants, it is not carbon-free. Currently, turbine technology cannot operate with pure hydrogen fuel. The Delta plant will run on only 30% hydrogen. The hope is that turbine technology will improve in the future and permit operation on pure hydrogen.

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A Huge Underground Battery Is Coming to a Tiny Utah Town

Photo, posted September 9, 2013, courtesy of Scott via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Pulling Carbon Dioxide Out Of Seawater | Earth Wise

April 17, 2023 By EarthWise Leave a Comment

The world’s largest sink for carbon dioxide from the atmosphere is the ocean. The world’s oceans soak up 30-40% of all the gas produced by human activities. Dissolving carbon dioxide in water produces carbonic acid. This is the reason that oceans are becoming increasingly acidic, which is causing serious damage to ocean ecosystems.

There are many efforts underway aimed at directly removing carbon dioxide from the air as a way to mitigate the effects of ongoing emissions. But another possibility is to remove CO2 directly from ocean water. Existing methods for doing it involve the use of expensive membranes and complex chemicals. The economics of such methods are quite unfavorable.

Recently, a team of researchers at MIT has identified what they claim is a truly efficient and inexpensive removal mechanism. It involves a reversible process based on membrane-free electrochemical cells. Electrodes in the cells release protons that are introduced to seawater which drive the release of carbon dioxide dissolved in the water. The carbon dioxide can be collected and the processed water ends up being alkaline.

Running this process at a site that is already collecting seawater – such as at a desalination plant – would be an effective way to collect carbon dioxide as well as help mitigate ocean acidification.

Once the carbon dioxide is removed from the water, it still needs to be disposed of, just as is the case for other carbon removal processes. It could be turned into useful chemicals or it could be stored in underground caverns. But this approach is fairly unique in that the carbon dioxide has already been captured by the ocean. The issue remains what to do with it.

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How to pull carbon dioxide out of seawater

Photo, posted January 19, 2016, courtesy of Judy Dean via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Turning Carbon Into Stone | Earth Wise

January 31, 2023 By EarthWise Leave a Comment

A start-up company in Oman called 44.01 was recently awarded a $1.2 million Earthshot Prize by Prince William of the U.K. The company, whose name corresponds to the molecular weight of carbon dioxide, is working on speeding up natural chemical reactions that take carbon from the air and lock it into solid mineral form.

The company’s location in Oman is no random occurrence. The mountains of northern Oman and along the coast of the United Arab Emirates are the site of a huge block of oceanic crust and upper mantle that was thrust upward some 96 million years ago. The tilted mass of rock is over 200 miles long and is the largest surface exposure of the Earth’s mantle in the world.

This type of rock, called peridotite, is rich in olivine and pyroxene, which react with water and carbon dioxide to form calcium-based minerals like serpentine and calcite that permanently lock in carbon. Other kinds of rock also are capable of carbon-storing mineralization, but this mantle rock is the most effective for the purpose. It only exists at the Earth’s surface in a few places, including Papua New Guinea and some spots in California and Oregon.

The 44.1 company is planning to use solar-powered direct air capture devices to remove CO₂ from the air, use it to produce carbonated water, and inject the water into the reactive rocks. The company will operate a couple of pilot systems during 2023. Ultimately, the company believes it can scale up the process to be able to permanently sequester as much as a billion tons of CO₂ a year by the year 2040 without needing to inject the gas into deep caverns or find other places to store it.

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With Major Prize, a Project to Turn Carbon Emissions to Stone Gains Momentum

Photo, posted August 10, 2018, courtesy of JM McBeth via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Compressed Air Energy Storage

October 23, 2019 By EarthWise Leave a Comment

The increasing use of solar and wind power has created a growing need for technology to store up the energy they generate for use when it is most needed.

Historically, pumped hydropower has provided the largest amount of storage capacity, but it is limited to only certain geographic locations. Battery energy storage has been growing rapidly, with the technology becoming better and cheaper over time. But there are various other ways to store energy that have potential and may well find their place in the changing energy infrastructure.

One of these is compressed air energy storage, which has been around for more than a century. It has been used as a backup method for restarting power plants. But to date, the economic viability of using it at a large scale has been lacking.

A Canadian startup company called Hydrostor is developing compressed air energy storage technology that it believes can be used on a utility scale.

The way it works is excess renewable energy is used to run compressors that compress air. Compressing the air heats it up and the heat is captured and stored in insulated hot water tanks. The compressed gas is then injected into underground caverns. When energy is needed, the compressed air is released, the stored heat is added, and the warmed gas is run through turbines to generate electricity. Additional features improve the system’s efficiency.

Hydrostore has built a 1 MW pilot project in Ontario, Canada and is now commissioning a 2MW system as well. It is funded to build a 5 MW system in Australia next year and it is bidding for 300 MW and 500 MW systems in North America. The company has received equity funding from Baker Hughes, a large oil-and-gas services and equipment company.

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Storing energy in compressed air could finally become cheap enough for the big time

Photo courtesy of Hydrostor.

Earth Wise is a production of WAMC Northeast Public Radio.