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The Dangers Of Negative Emissions Technologies | Earth Wise

September 28, 2020 By EarthWise Leave a Comment

Reducing carbon emissions is not easy and there are plenty of people who don’t even want to try for various reasons, generally related to their perceived economic interests and convenience. As a result, there is a great deal of interest in so-called negative emissions technologies or NETs. These are methods for removing carbon dioxide from the atmosphere. Even the UN Intergovernmental Panel on Climate Change assumes that NETs will play a role in mitigating the effects of climate change and meeting international goals.

The most widely studied approaches to negative emissions technology are bioenergy with carbon capture and storage – which entails growing crops for fuel, and then capturing and burying the CO2 produced from burning the fuel; planting more forests; and direct air capture, which involves actually pulling CO2 out of the air and storing it – probably underground.

A new study published in Nature Climate Change points out that none of these technologies has even been tried at the demonstration scale, much less at the massive levels required to make a dent in current CO2 emissions.

Their analysis of the biofuel and reforestation strategies show that each would take up vast land and water resources already needed for agriculture and nature. Air capture uses less water than the other two approaches, but still uses quite a bit and even more energy, which if supplied by fossil fuels, would offset the benefits of carbon capture.

Negative emissions technologies may well play an important role in combating climate change, but it is essential that we understand what the consequences will be from implementing them. We need to know the pitfalls that could arise. It would be a major mistake to simply count on NETs to be some kind of silver bullet.

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Remove CO2 from the air? Don’t bet on it before examining costs, researchers say

Photo, posted January 11, 2008, courtesy of Al Pavangkanan via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Storing CO2 Underground | Earth Wise

February 19, 2020 By EarthWise Leave a Comment

Capturing the carbon dioxide emitted from power plants and factories and safely storing it so it can’t enter the atmosphere has long been an attractive and desirable goal. Even though the use of renewable energy sources has been expanding rapidly, it will still be a long time before fossil fuel plants go away entirely.

The most widely considered method of carbon capture and storage is underground storage. The idea is to send the carbon dioxide through a pipeline to a place where underground rock formations can store it safely and permanently. Typically, it would be pumped deep underground – often more than half a mile down – and the site would be monitored to make sure the CO2 doesn’t leak back up to the atmosphere or into the water table.

A new study looked at how much carbon dioxide the suitable geological formations on Earth can store. The conclusion of the study is that drilling about 12,000 carbon storage wells globally could provide enough capacity to store 6 to 7 billion tons of CO2 a year by 2050. That is about 13% of global emissions.

Drilling 12,000 wells is equivalent to the amount of oil and gas drilling that has taken place just in the Gulf of Mexico over the last 70 years. The study identified locations worldwide that could handle the pressures associated with storing injected carbon dioxide.

So far, less than two dozen projects exist that capture and store carbon dioxide from fossil fuel plants. In total, these plants can capture about 36 million tons a year, which is far less than what is needed. But the new study at least shows that finding places to put captured carbon is not a problem.

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Ample Geological Capacity Exists to Store Large Quantities of Captured CO2

Photo courtesy of Equinor.

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.

Growing Rocks To Store Carbon

April 24, 2019 By EarthWise Leave a Comment

The US Geological Survey recently published a comprehensive review of geological carbon storage in sedimentary rocks through carbon mineralization. That is the process by which carbon dioxide becomes a solid mineral, such as a form of carbonate. Certain rocks undergo a chemical reaction when exposed to carbon dioxide and turn into different minerals as a result.

The idea is to use carbon mineralization as a way to permanently store carbon dioxide that has been captured from power plant emissions, other industrial activities, or even directly from the atmosphere.

Two basic approaches are injecting the CO2 deep underground or exposing it to crushed rocks at the surface. The two types of rock best suited for mineralization through injection are basalt and various ultramafic rocks. Pilot studies have shown that injection into basalt can lead to mineralization in under two years.

Exposing carbon dioxide to crushed rock at the surface generally makes use of crushed mining waste. Mineralization can be much faster in this case because there is more surface area on the crushed rock where mineralization occurs. (However, the quantities of rock available at the surface are much less than what exists deep underground).

Like all carbon capture and storage approaches, the key consideration is cost. The USGS study estimates that underground injection would cost around $30 per metric ton of CO2. The crushed rock approach might only cost $8 per metric ton, but that assumes the crushed rock is already available. If it must be newly mined, the costs would obviously go up significantly. To put this into perspective, a typical car produces around 4 metric tons of CO2₂ per year. So, it would cost somewhere between $30 and $120 a year to eliminate the emissions from one car. Perhaps that is a price we need to pay until we ditch gasoline cars.

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How Growing Rocks Can Help Reduce Carbon Emissions

Photo, posted October 17, 2011, courtesy of Glen Bledsoe via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Making Coal To Fight Climate Change

April 19, 2019 By EarthWise Leave a Comment

Coal is the most harmful fossil fuel for the environment and, furthermore, for human health. Its use has stubbornly persisted because it is so plentiful and, therefore, cheap. As a result, a big part of efforts to fight climate change is finding a way to remove the carbon dioxide dumped into the atmosphere by the combustion of coal.

Researchers at the Royal Melbourne Institute of Technology in Australia have developed a remarkable technology that in effect reverses the process that has led to soaring CO2 levels in the atmosphere. They have found a way to pull carbon dioxide from the atmosphere and turn it into coal, after which it can be stored cheaply and safely underground.

Most previous carbon capture and storage technologies have focused on compressing carbon dioxide gas into a liquid form and then pumping it into rock formations. Such techniques are rather expensive, require lots of energy, and pose risks that the liquid CO2 could escape from its underground storage sites. More recently, research on solid metal catalysts has led to the possibility of turning CO2 into solid carbon, but most of these reactions require very high temperatures and use a lot of energy.

The new technique developed at RMIT uses a new class of catalysts based on metal alloys. With a small jolt of electricity applied at room temperature, CO2 can be converted into solid carbon – basically, coal.

If this technique can be industrialized economically, it would be like turning back the clock by taking carbon dioxide that entered the atmosphere by the combustion of coal and turning it back into coal and putting it back underground. It seems like excellent environmental justice.

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