CO2 Scrubber / Carbon Dioxide removal

Whatever the positions on global warming and climate change, all can agree that the health of both humanity and the natural world is enhanced with less carbon dioxide (CO2) in the atmosphere. The push for renewable fuels and energy sources reflects this reality; research and development are ongoing with many alternatives to fossil fuels coming online and proving promising. At the same time, technology makes great strides in terms of making the burning of oil, coal and natural gas less detrimental to the environment. Scientists have conceived of ways to separate and capture the CO2 — or much of it — before it is released into the air.

What Makes Air Clean?

For the most part, air is comprised of gas or, more precisely, a number of gases. The largest proportion of what we breathe is nitrogen — a whopping 78 percent. After that, oxygen composes 21 percent of air. The remaining one percent consists of a smattering of other gaseous elements and compounds, including CO2, hydrogen and neon. In addition to gases, there are tiny particles — known as aerosols — that pervade the atmosphere. These can emanate from nature, as with pollen, or from human creations, e.g. car exhaust. More aerosols indicate greater atmospheric impurity; fewer mean cleaner air. What, though, about the gases?

Why Is CO2 So Dangerous?

It would seem that the modest presence of CO2 (0.04 percent) poses little danger to anything. Yet numbers can be deceiving. After all, only a small amount of cyanide can taint an entire reservoir. In the case of carbon dioxide, the innate power of this gaseous compound to trap the earth’s heat and prevent it from ascending into space makes it a particularly hazardous substance even in a limited presence. To be sure, CO2 is an important atmospheric constituent for the purpose of floral photosynthesis. Moreover, retaining heat in the optimal amount keeps winters from being globally lethal.

Still, the more CO2 is concentrated, the greater its capacity to prevent heat from ascending above the atmosphere. If uninhibited, CO2 could rise to 0.1 percent of its share of the atmosphere. This is how CO2 becomes a problem for the earth’s climate. It also explains why carbon dioxide removal is essential for the purpose of maintaining ecological balance.The immediate challenge for humanity is the prevention of this compound’s accumulation in the troposphere. It musts be attacked at the source, i.e. the very point where fossil fuel combustion takes place.

Enter the CO2 scrubber.

How Do Production Facilities Mitigate CO2 Emissions?

Many know of the dangers of a surplus in carbon dioxide emissions. Yet they are frustrated with the pace of alternative energy research and development, especially when it comes to cost-effectiveness. As of right now, fossil fuels deliver the most powerful bang for the buck. While scientific advancements can switch this edge in favor of renewables, it has yet to reach that point. In the interim, we look to technology that intercepts this gas before it makes contact with the air we breathe.

Most homes, for example, are powered by electricity which is generated by a power plant. Under the management of a public utility, the power plant burns coal or some other fossil-based fuel to produce steam which, in turn, creates the impetus to move a turbine. Subsequently, the mechanical energy produced from the rotating shaft of the turbine is received by a generator. This generator converts mechanical energy into electricity by means of internal magnets. So, from coal mined from the earth comes the power to light houses, streets and cities.

Back to the steam: noted above is the fact that the first manifestation of power in the plant is steam that results from the combustion of the fossil fuel. Steam, though, is not the only fruit of this combustion. Certain by-products are yielded as well, namely carbon dioxide, nitrogen oxides and a smattering of other gases. Formerly, the CO2 would travel up and out of the flue-gas stack to do its heat-holding work in the atmosphere unimpeded. With the advent of CO2 scrubbers, much of that “greenhouse gas” is sequestered prior to ever escaping the confines of the power plant.

The CO2 scrubbers serve as a CO2 removal system within a power facility or in other industrial settings. In a process known as post-combustion carbon capture, the gaseous elements released are gathered and cooled. A solvent — either aqueous ammonia or monoethanolamine (MEA) — is applied to the gaseous mix, absorbing the CO2 and forming a new compound. In so doing, it creates a solid that separates from the other gases that are then released. The solid is re-heated, releasing the CO2 for storage. The solvents are frequently recycled for later use. It is estimated that 80 to 90 percent of CO2 is sequestered by an industrial carbon dioxide scrubber.

Other Ways to Mitigate Atmospheric CO2

A carbon dioxide scrubber need not make use of solvents. Pressure swing adsorption CO2 removal involves the use of high pressure and solid surfaces. Under intense chamber pressure, different gases are drawn to distinct surfaces thereby affecting carbon dioxide removal. Another carbon dioxide scrubber method involves a specially treated CO2 removal membrane that filters the CO2 while allowing other components to pass through.

Interestingly, research is ongoing relative to a carbon dioxide removal machine that can act as a CO2 air scrubber, i.e. removing the gas from the open atmosphere. There is now a prototype for CO2 scrubbing plants that can act on the gas that is emitted by smaller agents, e.g. cars, homes and ranches. In addition to the carbon dioxide air scrubber, a CO2 scrubber for biogas — from organic matter — is already operational. Storage techniques vary as well. An oxygen not included CO2 scrubber traps the compound in already polluted water. Clearly, CO2 scrubbing plants employ an array of means to reduce emissions. Still, as a rule, the industrial CO2 scrubber represents significant progress in keeping carbon dioxide at bay.

A Final Thought: Drawbacks?

The fight against excess carbon dioxide has run on parallel tracks. On the one hand, there is the development of alternative sources: wind, solar, hydro-power, biomass and geo-thermal, to name a few. On the other track is CO2 reduction at the source of fossil fuel combustion, i.e. scrubbing. The latter makes a tremendous difference but the cost is high, in terms of both financial and energy expenditures. For all the cost-effectiveness of fossil fuels in an absolute sense, when the price of scrubbing is included, other sources should not be excluded.


AirFacts Magazine