A revolutionary new carbon dioxide filtering device that can work on gases of any concentration could be a vital tool for combating climate change.

The ‘paradigm shifting’ approach can capture carbon out of everything from power plant emissions to open air with concentrations of just 400 parts per million.

Existing carbon dioxide extractors have mostly only worked on the high concentrations found in power plant exhausts.

Previous approaches that work on the low concentrations of the greenhouse gases found in the atmosphere, in contrast, had been expensive and energy-intensive.   

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A revolutionary new carbon dioxide filtering device that can work on gases of any concentration could be a vital tool for combating climate change. Pictured, the device in operation. During the charging cycle, bottom, CO2 (red) is captured on the electrodes, leaving filtered oxygen (blue) to pass out of the device. When discharged, top, pure CO2 is released

A revolutionary new carbon dioxide filtering device that can work on gases of any concentration could be a vital tool for combating climate change. Pictured, the device in operation. During the charging cycle, bottom, CO2 (red) is captured on the electrodes, leaving filtered oxygen (blue) to pass out of the device. When discharged, top, pure CO2 is released

Chemical engineers Sahag Voskian and T. Alan Hatton of the Massachussets Institute of Technology developed the carbon capture approach, which works by passing the air to be filtered through a stack of special charged plates.

In its operating principle, the device is somewhat like a battery — but one that absorbs carbon dioxide passing over its electrodes as it charges and subsequently releases the collected greenhouse gas as it discharges.

During the charging cycle, carbon dioxide from the gas intake readily reacts with the device’s electrodes, each of which is coated with a carbon nanotubes coupled with a compound called polyanthraquinone.

When the battery discharges — releasing power that helps to run the whole system — the reaction runs in reverse, releasing a stream of carbon dioxide.

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In practice, multiple devices could be run in complementary charge/discharge cycles, with the carbon dioxide output free to be recycled for such applications as carbonating fizzy drinks, or feeding plants grown in greenhouses. 

Alternatively, the collected greenhouse gas could sequestered underground, or converted into a new fuel source as desired. 

IS CARBON CAPTURE A GOOD IDEA? 

The appeal of carbon capture solutions is that they may help to preserve business-as-usual activities while simultaneously lowering greenhouse gas emissions.

However, some experts have argued that these concepts may do more harm overall than good.

For these critics, cutting down on emissions overall is more important. 

‘Even if you have 100% capture from the capture equipment, it is still worse, from a social cost perspective, than replacing a coal or gas plant with a wind farm,’ Stanford University environmental engineer Mark Z. Jacobson told Futurity.

‘Carbon capture never reduces air pollution and always has a capture equipment cost. 

‘Wind replacing fossil fuels always reduces air pollution and never has a capture equipment cost.’ 

‘The greatest advantage of this technology over most other carbon capture or carbon absorbing technologies is the binary nature of the adsorbent’s affinity to carbon dioxide,’ said Dr Voskian. 

This means that the plates either react really strongly with the greenhouse gas or not at all, depending on the  whether the battery is being charged or discharged. 

‘This binary affinity allows capture of carbon dioxide from any concentration, including 400 parts per million, and allows its release into any carrier stream, including 100 percent CO2,’ Dr Voskian said. 

‘All of this is at ambient conditions — there’s no need for thermal, pressure, or chemical input. It’s just these very thin sheets, with both surfaces active, that can be stacked in a box and connected to a source of electricity.’

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‘This carbon dioxide capture technology is a clear demonstration of the power of electrochemical approaches that require only small swings in voltage to drive the separations,’ added Professor Hatton.

The device only uses one gigajoule of energy for every ton of carbon dioxide captured, making it energy efficient in comparison with the 1–10 gigajoules  — depending on the intake concentration — used by alternative approaches. 

The 'paradigm shifting' approach can capture carbon out of everything from power plant emissions, pictured, to open air with concentrations of just 400 parts per million

The ‘paradigm shifting’ approach can capture carbon out of everything from power plant emissions, pictured, to open air with concentrations of just 400 parts per million

In their laboratory, the duo have demonstrated that the device can endure more than 7,000 charging–discharging cycles with only a 30 per cent loss in efficiency.

The researchers are optimistic, furthermore, that they can improve the lifetime of the electrodes to cover around 20,000–50,000 cycles. 

Having completed their initial study, the researchers establish a company — dubbed Verdox — through which they intend to commercialise the process. 

The firm aims to have a pilot-scale plant within the new few years, said Dr Voskian.

He added: ‘If you want more capacity, you just need to make more electrodes.’

The full findings of the study were published in the journal Energy and Environmental Science.

WHAT IS CARBON CAPTURING AND HOW DOES IT WORK?

Carbon Capture and Storage (CCS) captures emissions produced from the use of fossil fuels in electricity generation and industrial processes.

It aims to prevent the carbon dioxide from entering the atmosphere and is able to capture up to 90 per cent of the carbon dioxide (CO2) they emit.

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The use of CCS with renewable biomass is one of the few carbon abatement technolo­gies that can be used in a ‘carbon-negative’ mode ­– actually taking carbon dioxide out of the atmosphere.

The process consists of three parts – capturing the carbon dioxide; transporting the carbon dioxide; and securely storing the carbon dioxide emissions.

These can be stored underground in depleted oil and gas fields or deep saline aquifer formations.

Carbon capture technologies allow the separation of carbon dioxide from gases produced in electricity generation and industrial processes by one of three methods: pre-combustion capture; post-combustion capture; and oxyfuel com­bustion.

Carbon dioxide is then transported by pipeline or by ship for safe storage. Millions of tonnes of carbon dioxide are already transported annually for commercial purposes by road tanker, ship and pipelines. 

The carbon dioxide is then stored in carefully selected geological rock formation that are typically located several miles below the earth’s surface.



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