The XTL Diet: new paths to feasible, domestic low-carb fuels

August 23, 2011 |

Can synthetic biology capture and utilize atmospheric CO2? And make money?

And mitigate the carbon intensity of no-no feedstocks like coal, gas and oil? Opening up new paths towards low-cost domestic energy security?

Beyond the entire range of conventional and advanced biofuels – or biomass-to-liquid technologies (BTL), lie a range of Coal-to-liquid, and Gas-to-liquid options that have abundant and affordable domestic feedstock supply, and a low-cost, in-place infrastructure for aggregation and distribution.

The high-carb problem

The trouble with CTL, GTL and technologies like them? They produce high amounts of CO2 as a byproduct, and generally run afoul of the principle that alternative fuels should be, at least, no worse on greenhouse gas emissions than conventional fossil fuels.

That principle is, for example, enshrined in Section 526 of the Energy Independence and Security Act, which prevents the US military from buying CTL fuels – something the Air Force is considerably more vexed about than, say, the US Navy.

So what path is the right one? The path with unpopular greenhouse gas problem, but at popular prices – or the biofuels option, which has to this point generally suffered from high costs?

To date, industry has been working on mitigating the CO2 problems of CTL and GTL with carbon capture and storage systems. With a complex technology, they capture and concentrate the CO2, and then inject it into a terrestrial storage unit. It’s a strategy born, to some extent, out of the use of CO2 as a catalyst for enhanced oil recovery. The problem with CC&S? Cost. The skyrocketing costs of the system have bedeviled the projects.

The new low-carb solutions

A new set of bio-based technologies and projects are emerging, that may open up a middle path. Projects that are using algae or other micro-organisms to capture CO2 – and convert the resultant gas stream either to biomass (which can then be converted into fuels, food, feed, or fertilizer), or directly into fuels and high-value chemicals.

In the case of waste CO2 from industrial processes, it’s a value-add, and a talking point for sustainability that, say, an ethanol or cement plant or steel mill is getting a second bite of the cherry with its waste CO2. It’s not reducing the CO2 footprint of the industrial process itself (unless the CO2 is converted to, for example, an algae fertilizer that is stored in the soil). But the combined process is generating a second use of the CO2 – which certainly reduces the overall carbon intensity of both the industrial complex, and the resulting fuel.

In the case of XTL (CTL, GTL) fuels, the possibility is that biomass capture will mitigate the carbon intensity of the XTL fuels, so that they can qualify under Section 526 for military use, or otherwise be used by customers who would otherwise show little interest in high-carb fuels.

Four Making it Happen

Here are four companies aiming at capturing CO2 and either directly converting to fuels, or using it as a means of mitigating the impact of a high-carb fuel.

BioProcess Algae
BioProcess is based in Portsmouth, RI and is currently running a demonstration facility at the Green Plains Renewable Energy ethanol plant in Shenandoah, Iowa. The company’s technology features low-cost autotrophic production of algae biomass using its proprietary Grower Harvester photobioreactors.  Algae is grown out of solution in thin, controlled biofilms to increase productivity and lower dewatering costs, gas transfer costs, pumping costs and mixing costs.

Grower Harvester bioreactors have been tied directly into the plant’s CO2 exhaust gas since October 2009. Initial co-location strategy has focused on bridging First Generation biofuels to Next Generation biofuels and bioproducts.

Has developed out an XTL gasification system (using biomass or coal), and is currently in Tier II testing of its fuels with the US Army and Air Force. Its experimental add-on is bringing in a closed system photobioreactor to capture excess CO2, use it to grow algae, which would in current plans would be sequestered as a soil enhancement to mitigate the CO2 release of XTL fuels and bring  them in to compliance for use as alternative fuels by the US military.

Early-stage company, just coming out of stealth, using an genetically modified organism to ferment CO2 into renewable fuels. Its microbial bioreactor system can capture CO2 from waste industrial gases and convert this carbon source into chemicals used in biodegradable polymers, cosmetics, food additives, industrial lubricants, plastics, other specialty chemicals and fuels.

Where does the hydrogen come from, for the OakBio process? Either commercially shipped hydrogen, or produced on-site via conventional steam reformation of, say, low-cost natural gas.

The LanzaTech process increases industrial energy efficiency by capturing waste gases (CO, CO2) and converting them to valuable fuels and chemicals through its microbial gas fermentation technology. The LanzaTech process is feedstock agnostic and is not dependent on any one resource for gases. The LanzaTech process has already been proven utilizing steel mill off gases as well as synthesis gas derived from biomass.  This means that all synthesis gas is a suitable feedstock including gases derived from coal, petroleum coke, natural gas, municipal solid waste etc.

LanzaTech can use hydrogen-free gases for the production of ethanol. This is because its proprietary microbe can produce hydrogen from carbon and water as required.

The Bottom line

New technologies are getting traction in terms of utilizing the potential of CO2. Reminding us that carbon is not the enemy – our lack of knowledge in how to utilize residues remains our most perplexing environmental challenge.

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