Ask Eartha: Clean coal and the transition to a zero-emissions energy grid
January 27, 2017
I've heard a lot of talk about "clean coal" lately. What is it, how does it work and is it really clean?
Thanks for a great question this week, Katelyn. You're not kidding — coal has been in the news a lot lately, and clean coal is a renewed topic of interest. The name implies that it's an environmentally benign technology, but there's more to the story than that. Before we dive in, here's some history about coal.
When we burn coal, we're actually burning the remains of plants and animals that lived and died near swamps and inland seas millions of years ago. As this material accumulated and decomposed, it formed a substance called peat. Over millions of years, layers of peat were covered by other deposits and buried below the Earth's surface. Compacted under pressure, the moisture was squeezed out of the peat, and heat from the Earth's core baked it, turning it into coal. Peat needs moist conditions to form, which is why we don't find coal everywhere. However, the U.S. won the coal lottery. With 25 percent of the world's coal deposits, coal is found in 38 states, lying beneath 13 percent of our land area. Not surprisingly, in 2015 coal accounted for 33 percent of our energy production.
Because coal is essentially concentrated carbon, burning it releases carbon dioxide — more than any other fossil fuel. In fact, it's the single-largest source of man-made carbon dioxide emissions in the world. This is where clean coal comes in. The basic premise of clean coal is using technology to burn coal without emitting pollutants. There are a few technologies that fall under the clean coal umbrella, but by and large, when you hear people talk about clean coal, they're talking about Carbon Capture and Storage.
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CCS technology does just what you'd think: It prevents carbon dioxide emissions from entering the atmosphere by filtering it out from the emissions produced by power plants. The International Energy Agency estimates that CCS can reduce carbon emissions produced by power plants by 85 to 95 percent. Once captured, the carbon dioxide is compressed and transported through a pipeline to storage in underground geological formations more than a mile below the Earth's surface, like spent oil and gas fields or salt water reservoirs. It can also be injected into permeable rock.
The technology is proven to work, and some energy experts, including former U.S. Secretary of Energy Steven Chu, argue that it's necessary to use clean coal technology to slow climate change as we transition to a zero-emissions energy grid. In fact, the Natural Resources Defense Council reports that CCS could contribute 15 to 55 percent of global reduction in carbon emissions by 2100. So why isn't clean coal widespread? For one, it costs a lot of money. Until recently, no one has been able to implement a CCS project that is cost-effective enough for widespread adoption, and most North American pilot projects have been plagued by delays and cost over-runs. That said, China is investing heavily in researching and developing commercial-scale CCS facilities, including its $1 billion GreenGen power plant which is scheduled to start capturing carbon dioxide emissions around 2020. And late last year, the Petra Nova project in Houston went online. Completed on-schedule and on-budget, Petra Nova is currently the world's largest carbon capture facility, and it's capable of removing over 90 percent of carbon dioxide from its emissions. Nevertheless, recent analyses suggest that the cost of CCS coal plants could still be two to three times higher than costs for onshore wind, utility scale solar, geothermal and hydropower projects. Many experts now believe that natural gas and biomass plants with CCS are much better options. In the meantime, costs for renewable energy are steadily dropping, and a study from the Department of Energy's National Renewable Energy Laboratory demonstrates that the U.S. can generate 80 percent of its electricity from renewables by 2050.
While clean coal might be a bridge to a carbon-free energy grid, it is not a silver bullet. It takes a lot of energy to remove carbon dioxide from power plant emissions, which means these facilities must burn even more coal to do so. And even with the carbon dioxide removed, coal still carries a heavy toll: Extracting it causes extensive environmental damage, such as destruction of wildlife habitat and contamination of ground water; mining also leads to health problems such as asthma and lung disease; and burning it releases a cocktail of chemicals in addition to carbon dioxide that not only contribute to climate change, but also acid rain, smog, mercury build-up in fish and asthma and lung disease in humans. Coal mining also produces hazardous waste which can contaminate ground water. Mining also destroys wildlife habitat and negatively impacts the healthy functioning of ecosystems. So while we can clean up the emissions from coal-fired power plants, we can't clean up the entire process. Coal is still dirty, even if it's "clean."
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