Environment

New technique uses plastic waste to capture CO2 emissions

New technique uses plastic was...
Graduate student Paul Savas feeds raw plastic into a crusher to prepare it for pyrolysis
Graduate student Paul Savas feeds raw plastic into a crusher to prepare it for pyrolysis
View 2 Images
Graduate student Paul Savas feeds raw plastic into a crusher to prepare it for pyrolysis
1/2
Graduate student Paul Savas feeds raw plastic into a crusher to prepare it for pyrolysis
Most of the pores in each particle are about 0.7 nanometers wide
2/2
Most of the pores in each particle are about 0.7 nanometers wide

Two of our biggest environmental problems are the tons of unusable plastic waste, and the tons of carbon dioxide (CO2) which are released into the atmosphere in smokestack emissions. A new process is claimed to use the former to trap the latter.

Currently being developed by a team at Rice University, the technique is a variation on an existing pyrolysis-based plastic-recycling process – pyrolysis is defined as the thermal decomposition of materials at elevated temperatures in an inert atmosphere.

The procedure begins with plastic waste being ground into a powder, after which it's mixed with potassium acetate – that's the unique part – and then heated at 600 ºC (1,112 ºF) for 45 minutes. Doing so renders the plastic powder into sorbent particles filled with nanoscale pores, which are very effective at trapping airborne carbon dioxide molecules.

Most of the pores in each particle are about 0.7 nanometers wide
Most of the pores in each particle are about 0.7 nanometers wide

Each particle can indefinitely store up 18 percent of its own weight in CO2 at room temperature. When heated to around 75 ºC (167 ºF), though, it releases the trapped carbon dioxide, which could conceivably be used in the production of products like fuels or building materials. The sorbent particle can then be reused, since approximately 90 percent of its pores are reopened as the CO2 is released.

As an added bonus, when the particles are initially created, a wax byproduct is also produced, which could be utilized in detergents or lubricants. And importantly, while commonly used plastics such as polypropylene or high- and low-density polyethylene are typically difficult to chemically recycle, they're ideal for conversion to the CO2-capturing particles.

The scientists estimate that the cost of using filters made of the sorbent to remove CO2 from flue gas streams would be about US$21 a ton. By contrast, an existing process which utilizes compounds known as amines to remove CO2 from natural gas streams reportedly costs $80 to $160 per ton. What's more, it is believed that the sorbent should last longer than the amines.

"Point sources of CO2 emissions like power plant exhaust stacks can be fitted with this waste-plastic-derived material to remove enormous amounts of CO2 that would normally fill the atmosphere," said Prof. James Tour, co-lead author of the study along with Wala Algozeeb, Paul Savas and Zhe Yuan. "It is a great way to have one problem, plastic waste, address another problem, CO2 emissions."

A paper on the research was recently published in the journal ACS Nano.

Source: Rice University

5 comments
5 comments
Peter Forte
This does not remove the need to reduce or eliminate our reliance on and use of plastics.
DaveWesely
Yeah, yeah, that's the ticket! We will pull the CO2 from the exhaust gas of smokestacks so it doesn't reach the atmosphere, and then we can turn it into fuel. Yeah, yeah, then we can burn it and turn it into CO2 for the atmosphere. (Hat tip to Jon Lovitz.)
I've got a better idea. Speed up production of wind turbines and solar panels. Create more demand for them with financing incentives.
Put the plastic in landfills (It's called carbon sequestration.).
Incentivize the pyrolysis of crop and wood residue so that 50% of the carbon content becomes inert, instead of the 2% if it were left to decay on its own. As part of the organic matter pyrolysis, add CO2 (from the exhaust created to start pyrolysis) and ammonia (NH3). This opens up nanoscale pores in the carbon and creates stable spaces for NH3. Add this to the soil instead of directly injecting NH3. Then instead of 40% of the nitrogen being lost to the atmosphere before the crops can use it, the inert carbon compounds hold it in place. Carbon sequestration AND better soil. But that means carbon credits (money) goes to farmers, instead of back to the oil industry with these carbon capture schemes.
Catweazle
Concerning the"problem" with CO2 it is instructive to plug "Greening of the Earth and its drivers" into a search engine.
Particularly interesting is the paper "Nature Climate Change volume 6, pages791–795 (2016)"
guzmanchinky
Amazing approach! I hope it pans out.
Malcolm Jacks
Its about time they found a better alternative for car exhaust instead of the old system i.e. catalytic converters which are very expensive and not very efficient. Maybe this could be the answer to?