Carbon-Scrubbing Technology: the Need of the Hour

With the concentration of carbon dioxide (CO₂) steadily rising, the world seems to be sitting on a time bomb. Studies suggest, from approximately 315 ppm (parts per million) in 1959 to the present atmospheric average of approximately 385 ppm, the CO₂ concentration in the atmosphere is increasing at an alarming rate[s1]. According to a report by IPCC, the world is hurtling towards an era when the global CO₂ concentrations will rise to as much as 500–1000 ppm by the year 2100[s2].

With startling data like that, it is pretty clear that humans may have to make some really strict decisions regarding their energy consumption. They will have to think of ways to reduce CO₂ concentration in the atmosphere. To keep the global temperature from rising, merely shifting to a low-carbon economy will simply not be enough. We need to remove carbon from the atmosphere, either by planting more forests or using more advanced technology, like CO₂ scrubbing. The revolutionary technology is said to purify the air and could counteract the rise in CO₂. This article details the carbon scrubbing technology and discusses how it could potentially ‘save the planet’.

What is CO₂ scrubbing?

To produce energy, most power plants burn fossil fuel. This releases many greenhouse gases that contribute to global warming. One of the main greenhouse gases is carbon dioxide (CO₂), which contributes to 60 percent of the greenhouse gas effect (global warming). CO₂ scrubbing is a range of technologies that involves capturing carbon dioxide emissions from power stations and industrial sites and then storing it for future use. Hence, it is also known as Carbon capture and storage (CCS). It involves collecting, transporting and burying the gas.

The good thing is the technology can work with any kind of power plant that runs on fossil fuel and can be retrofitted to existing facilities.

How does it work?

Carbon capture and storage involves three main steps:

Step 1. Carbon dioxide is isolated from the other flue gases (the gases released after the combustion of fossil fuels) using a liquid solvent to bind with the CO₂.

Step 2. Once the flue gases have been removed or scrubbed of CO₂, they’re released into the atmosphere.

Step 3. After the CO₂ has been captured, it is liquefied, transported and buried, either in deep underground saline aquifers, suitable geological formations or disused oil fields.

What are the technologies for it?

There are three main technologies for carbon dioxide scrubbing:

1. The post-combustion process, which involves scrubbing the power plant’s exhaust gas using chemicals.
2. Pre-combustion CCS, which involves converting fossil fuel into a clean-burning gas and stripping out the CO₂ released in the process. This takes place even before the fuel is placed in the furnace.
3. The third method involves burning fossil fuel in an atmosphere with a higher concentration of pure oxygen; this process produces an exhaust gas that is almost pure CO₂. It is also known as ‘oxyfuel’.

Is CO₂ scrubbing a new technology?

No, CO₂ scrubbing is not a new technology; it has been around for decades and applied in many cases, mainly submarines and spacecraft. In spacecraft, for example, the carbon dioxide is removed from the cabin air through chemical processes.

What is the energy cost involved in the process?

The technology is not cheap.  It could use up to 40% of a power station’s energy. Apart from this, pipes to transport the CO₂ to the burial sites can also cost a lot of money.

Renewable energy for CO₂ scrubbing – a cost-effective and eco-friendly option

To reduce the energy costs involved in CO₂ scrubbing, renewable energy options, like solar power are being considered. Chemical engineers from Indiana University, U.S. have created a molecule that uses solar energy for conversion of atmospheric CO₂ into greenhouse-neutral fuels, like carbon monoxide, which can then be stored or used for power generation. This study is a major leap in that direction of energy and cost saving.

Fuel cell carbon capture and storage-future of the carbon scrubbing technology

To address the problems related to the present carbon scrubbing technology, a new CCS technology is being developed which is called ‘Fuel cell carbon capture and storage’. Here’s how it works:

1. Fuel cells function like purification membranes that pull carbon dioxide out of the flue gases; into a fuel exhaust stream.
2. Once CO₂ enters the fuel exhaust stream, CO₂ can be easily and cost-effectively captured.
3. Once captured, the CO₂ is chilled, compressed and utilized for industrial use or more power generation.

Emerging markets in the Third World will require fossil fuels to grow their economies. That’s a necessity until we come up with more affordable carbon scrubbing technology that can be accessed by the developing nations as well. We believe though the technology is still in its infancy, consistent improvements will eventually bring down the cost of capturing CO₂ waste.

[s1](Keeling et al.,2009).

[s2]IPCC 2007).

by Ajay Narayan