Spruce Cone Material Could Scrub CO2 Emissions | Chemical & Engineering News
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Web Date: January 22, 2016

Spruce Cone Material Could Scrub CO2 Emissions

Sustainability: Scientists carbonize spruce cones to create a renewable, nanoporous adsorbent
Department: Science & Technology
News Channels: Biological SCENE, Environmental SCENE, Nano SCENE, Organic SCENE
Keywords: carbon capture, pinecones, bio-waste, nanoporous carbon adsorbent, CO2
Spruce cones can be carbonized into a material with nanoscale pores that effectively soak up CO2 molecules.
Credit: ACS Sustainable Chem. Eng.
Photograph of a Norway spruce cone and a scanning electron micrograph of a carbonized scale from a Norway spruce cone.
Spruce cones can be carbonized into a material with nanoscale pores that effectively soak up CO2 molecules.
Credit: ACS Sustainable Chem. Eng.

Spruce cones could yield a material for capturing and storing carbon dioxide emissions that outperforms other solid sorbents, says a new study (ACS Sustainable Chem. Eng., DOI: 10.1021/acssuschemeng.5b01113).

Carbon capture and storage—plucking CO2 molecules out of smokestacks and injecting them underground—is necessary to tame climate change, experts say. But the prohibitive cost of the standard capture process, which uses aqueous amines, has scientists investigating less costly methods.

Porous, carbon-based sorbents derived from metal organic frameworks (MOFs) have a high capacity for CO2, but MOFs are costly to synthesize and are made from petrochemicals, an unsustainable resource. So Zhengxiao Guo at University College London and colleagues wondered if they could turn biowastes into a CO2 sorbent. Other researchers have used cones to produce activated carbon for water cleanup, so the team tried cones from a Norway spruce (Picea abies). They carbonized spruce cone scales in a furnace, ground them into particles, and activated them with potassium hydroxide. The KOH treatment helped generate nanosized pores that increase the particles’ surface area. The scientists exposed the sorbent to the same CO2 concentration found in flue gas—15% CO2 by weight—and found that the sorbent had adsorbed 21% CO2 by weight. “This capacity to adsorb CO2 is similar to that of MOFs, but MOFs are not as selective for CO2 and are more expensive to produce than the pinecone adsorbent,” Guo says. X-ray photoelectron spectrometry revealed that nitrogen and calcium naturally present in the cones remains in the nanoporous material, boosting CO2 uptake by introducing active sites on the sorbent surface.

Pine and spruce cones are cheap, renewable and abundant, Guo notes. He figures that enough could be collected from forests to make a significant contribution to CO2 capture on an industrial scale.

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Robert Buntrock (Sun Jan 24 14:30:55 EST 2016)
Is activated carbon from conifer cones any better than activated carbon from other sources? Granted the "green" aspects make this attractive but the efficacy is still important.
Todd Perkins (Sun Jan 24 18:29:20 EST 2016)
KOH naturally absorbs CO2 to begin with, so is the absorption due to the hydroxide or the organic material in the pine cone? If the argument is that pine cone material treated with hydroxide outperforms hydroxide alone, then that data should be shown. Another items that should be shown is the carbon footprint of producing the absorbent versus the amount of carbon bound by its use.

While this research is superficially interesting, many questions relevant to the umbrella topic of removing carbon dioxide from the atmosphere are left un addressed.
JS (Wed Jan 27 15:45:32 EST 2016)
Todd hit the nail on the head. Is it the organic material absorbing CO2, or is residual KOH the culprit? Further, while 'pine and spruce cones are cheap, renewable and abundant', KOH is the other end member of that. In other words, if the carbonized cone is indeed better at absorbing CO2, how much energy (fossil fuel, raw materials, etc.) is necessary to functionalize the cone? Enough for the overall mass-energy balance of the process to be considered carbon sequestering?

What about the product(s) of the CO2 absorption process? Presumably the product is either pure CO2 (from regeneration or using the cones as a biofuel) or some sort of biomass waste. Does this research apply to the gigaton quantities of CO2 emitted globally every year? Or is it more of a niche, small scale technology? Every bit helps...but where does all that pure CO2 go? Underground?
DY (Fri Jan 29 11:19:19 EST 2016)
According to the paper, the authors do wash one sample with HCl near the end of the sample preparation and see no major difference in pore size or CO2 adsorption. Perhaps the properties are not just due to residue KOH.
Lorenz Siggel (Thu Jan 28 03:18:26 EST 2016)
An interesting and green approach. My questions are where does one get enough Spruce cones to make a significant dent in CO2 output and how much CO2 is produced in the manufacturing process (heating the furnace, CO2 from unwanted bits of the cone, etc.) when compared to the storage capacity? This sounds like many ideas, great at the lab scale but not in the real world?
Paul Nelson (Thu Jan 28 18:39:55 EST 2016)
Interesting concept, but...it makes me wonder how much carbon dioxide is generated to carbonize and treat the pinecones (energy to heat the furnace, produce KOH, etc.) relative to the amount of carbon dioxide adsorbed by the pinecones. The same question is relevant to MOFs as well.

For any solution to be sustainable, the net sorption of carbon dioxide must exceed the carbon dioxide generated to produce the sorbent.

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