Capturing Carbon: the role of biocatalysts and biofuels (printer-friendly)

August 6, 2013 |

akermin-HQCarbon capture: much talked-about, less seen.

Could biocatalysts and biofuels provide the kicker needed to make this class of technologies feasible?

New news and data from Akermin suggests that bio may be just the ticket.

In Missouri this week, Akermin, a biocatalyst company developing technology to improve the removal of carbon dioxide from industrial gas streams, reached the 1600 hour operational milestone at its pilot plant, which is capturing more than 80% CO2 from a coal-fired power plant gas exhaust stream.

So, why is this significant — and what is the role of biocatalysts and biofuels in the capture and use of carbon dioxide?

By now, Digest readers might well conclude, without extensive discussion, that carbon dioxide capture represents not only a potential value stream for industrial sites that generate it — but that CO2 capture represents a significant “at birth” means of addressing CO2 build-up in the atmosphere — linked by a consensus of researchers (though not unanimously) to climate change and global warming. Thereby, it also represents a “life-saving” technology to power-generation feedstocks, such as coal, that generate significant CO2 streams and are disadvantaged under most, if not all, greenhouse gas regulation schemes.

The problem is cost.

For example, a Congressional Budget Office study of Carbon Capture & Storage technologies concluded that the technology is not (now) economically feasible without a significant increase in the carbon price — as high as $40+ per tonne.

But that is capture and storage — let’s look at capture and re-use, which is where biofuels and biocatalysts may well play a role. For example, with technologies based on algae, or technologies such as Joule that make fuels directly from CO2, water and sunlight. Enhanced oil recovery is another use for industrial CO2 — if the oil wells are close enough to the power plants to minimize transport costs.

The economics of CO2

akermin-capex

Now, the market price of industrial-grade CO2 — that is, pure enough to be used in industrial applications such as algae growth — is generally modeled by producers these days in the $30 per tonne range.

Add to that the cost of a permit to emit CO2 into the atmosphere. Between those two figures, you have the current value of a CO2 stream — in capturing CO2, you not only get the value of the CO2, but you avoid the cost of buying a carbon allowance.

In the EU, carbon allowances are trading these days at around $7 per tonne, after reaching a high of more than $40 per tonne in 2006. Australia currently has a $23 per tonne price for carbon, but it switching to a EU-price emissions trading scheme.

So you have around $37-$53 per tonne to work with.

Now, according to an MIT study from last year, the cost of CO2 capture, modeled across six scenarios and using current technologies and a 90 percent capture rate, comes in at $31 per tonne. Integrated coal Gasification Combined Cycle plants come in much lower, as a breakout, averaging in the $22 per tonne range.

What exactly is flue gas made of?

You might think, from coverage in the popular press, that flue gas is filled with CO2 — alas, no. It’s mostly atmosphere-neutral nitrogen, water and oxygen. Coal fired power plants have about 12 percent CO2 concentration, and natural gas plants have around 7 percent CO2.

The role of the biocatalyst

akermin-system

Carbon capture systems are based on absorbing materials that “scrub” the CO2 out of a flue gas stream. The higher the absorbent column, the higher the capex of the system. That’s where biocatalysts come into play — in the case of Akermin, the enzyme is supplied by Novozymes and the delivery system by Akermin that makes the process more effective and increases enzyme stability, reducing capex.

For example, a study of a specific LNG case with CO2 removal to < 50 ppm using Akermin’s Biocatalyst DeliverySystem concluded that the packing height of the absorber column was reduced more than 65% versus a conventional system. This and other process improvements resulted in a 15-20% reduction in capital cost, a 15-20% reduction in regeneration energy, and lower costs for system maintenance, solvent consumption and by-product disposal.

The impact of biocatalytic systems now and later

akermin-column

What’s the capex requirement for a plant? According to the MIT study – it averages 59 percent of the total cost of a carbon capture project, and 65 percent for the Integrated coal Gasification Combined Cycle plants. An 18 percent reduction in capex cost could reduce the overall break-even point of carbon capture of an IGCC plant — if the figures cited held up in actual practice — down to sub-$20 per tonne ranges. Making carbon capture a viable technology in selected cases. The next-gen technology envisioned by Akermin could broaden the field.

The role of biofuels

Biofuels could well be critical to making these technologies economically viable. The main reasons? They are relatively easy to site next to power plants — compare the problems, in term of costs and logistics, of transporting CO2 over long distances for use in enhanced oil recovery, where the oil field location might be far from the power plant site and pipeline or trucking costs come into play.

Most biofuels technologies that directly require CO2 also require just water, a nutrient package including phosphorus and nitrogen, and in most cases also require sunlight. The sunlight intensity can pose some restrictions, but generally these technologies are designed to use water already consumed in power plant cooling operations, or brackish water not otherwise suitable for human or agricultural use.

Prominent among the technology options? Sapphire Energy, BioProcess Algae, Aurora Algae and Cellana just to name four among the algae contenders. There is Joule, which uses CO2, water, sunlight and nutrients to directly generate ethanol, diesel and jet fuel. Proterro uses the same combination of inputs as Joule, with an aim of making low-cost renewable sugars. The class of technologies known as the electrofuels also generally use these inputs to generate alcohol fuels as well as drop-ins such as diesel and jet fuel.

Scale of operations

Coal-fired power plants are big, in the US – generating an average of 667 megawatts each, according to the EPA — and generating, based on 98% uptime, 3.39 million tonnes of CO2 each per year. With a capture rate at 85 percent and using 2.1 pounds of CO2 to make a pound of algae (with a 25 percent oil content), that supports the production of around 120 million gallons of biodiesel per year. With 457 coal-fired plants figuring into this equation — there’s 54 billion gallons of fuel in potential production. That’s without food inputs. But you’d have a lot of land used up in the equation — something on the order of 18 million acres of algae, if production rates reached 3,000 gallons per acre per year.

Next steps

In the case of catalysts, Akermin is currently developing and testing a next generation approach that uses an environmentally-friendly solvent and proprietary process scheme with on-line biocatalyst replenishment.  This approach has the potential to reduce the avoided cost of capture by as much as 40% versus the solutions that have recently been evaluated for commercial-scale demonstration on coal-fired power plants throughout North America and Europe.

akermin-co2

Meanwhile, the current Akermin technology may well proceed to commercialization – though we do not have firm date ranges or decision-points at this time.

Feasible or not feasible?

The jury’s out on algae technologies (and other CO2-munchers) for fuels at the moment — some companies say it’s a matter of time, some are more cautious on the endgame and in particular on the timing. Certainly, the business case is getting better and more companies are moving past pilot-stage and towards commercial operations. Certainly, the potential of CO2 supply far outstrips the capital available for algae commercial-scale ventures, right at this moment, and the capacity for absorbing new fuels supply, particularly biodiesel which is still winning acceptance at B20 and higher blend rates.

More on the story

A presentation containing Akermin’s pilot plant results is available here.

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Category: Research

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