(Source: FrontPage Mag)
High-pressure burning/liquification process is fast, efficient, and most importantly cheap

Professor Douglas C. Elliott is convinced that in the future our cars will burn algal biofuels.  His team at the U.S. Department of Energy's (DOE) Pacific Northwest National Laboratory (PNNL) in Richland, Wash. believed they've worked out a fast, efficient method of converting algal "sludge" into oily algal "crude".

I. Algal Fuel -- Perhaps the Most Promising Biofuel, But Hard to Produce

The future of biofuels appears in flux.  The food for fuel debate looks on the verge of boiling over, with Congress preparing to cut artificially created demand for corn ethanol. Meanwhile cellulosic ethanol has failed to live up to years of bold promises, and appears commercially stalled, if not dead.

Algal biofuel is still much more in the research stage, but it does have some big backers, most notably the U.S. Navy, which is paying a premium to startups to test the future fuel.  And while it's hard not to hear some similarities between the big promises that cellulosic ethanol made a half decade ago and some in the algal fuel industry are today making, algal fuel does enjoy some distinct advantages in the future fuels race.

Algae Biofuels
Algal biofuel is arguably the most promising synthetic hydrocarbon fuel, but also the most frustrating in terms of production problems. [Image Source: Solix Biofuels]

First, you can grow algae anywhere it's sunny with a proper tank system.  Growing systems can be pricey, but they have the ability to be installed in locations that traditional seed oil or fermented sugar-crop-derived fuels can't exploit, such as rooftops or deserts.  Second, algae are an easy organism to genetically modify, to make them as oil-rich as possible.

The fundamental problem with cellulosic ethanol always seemed to be where to find the large quantity of waste feedstock (biomass) required.  After all, some startups had very clever bacterial or fungal conversion schemes, but struggled to establish a delivery network that could sustain a commercial scale plant.

An algae plant
A farmer at a pilot algae farm shows off growing equipment. [Image Source: Green Living]

Algal fuel avoids this issue, as the microorganisms handing the basic oil stock are the source of oil themselves.  The difficulty with algal biofuels is to take the oily sludge that comes from filtered, ground up algae and chemically transform it into fuels that resemble crude oil.  The result is that algal fuel is available but remains very expensive.

Due to the cost algae has been targeted by with serious criticism, despite its promise.  Even its advocates acknowledge this fundamental problem -- cost reduction is vitally needed.

II. (Almost) No Catalysts Needed

Professor Elliott's team has long approached this challenge from the industry standard approach -- using catalyst driven reactions to convert dried extracts of algal "sludge" to crude.  The team has tested a wide range of catalytic metals, including palladium, platinum, nickel, ruthenium, and rhodium, on carbon support.

One such catalyst method is so-called hydrotreating (HT).  While common, this method is slow, requiring as much as 4-6 hours to reach high yields.  It's also relatively expensive.  Professor Elliott is no stranger to HT production -- he's spent much of his career trying to perfect it.  But now he thinks he may have found a remarkably cheaper and simpler alterantive.

The latest work by Professor Elliot uses hydrothermal liquification (HTL), a combustion process that first turns the algal oil to a solid, then liquifies that solid to produce the final fuel.  The method is fast and affordable.

Algal slurry
Starting 35% by weight algal fuel-stock is poured into a test beaker.
[Image Source: Algal Biofuels/PNNL]

In layman's terms HT methods involve metallic catlyst structures "grabbing" fuel molecules, stripping them of their oxygen atoms and replacing them with hydrogen from a surrounding gas.  This approach intuitively has restrictions -- catalysts are 2D surfaces.  And if you pattern them to be closer to 3D, you raise the risk of "fouling" (the products getting "stuck" to the catalyst, blocking future reactions).  And then there's that gas that was mentioned in passing.

The HTL process, by contrast, essentially filters out unwanted organics like phosphorous, to get a pure hydrocarbon sludge, which is then burned.  At standard pressures this burn would destroy the carbon chains, producing CO2).  But under high pressures and moderately high temperatures it essentially does the same thing as the HT catalysts -- it strips off the oxygen replacing it with hydrogen.  Except, instead of feed gas hydrogen is grabbed from neighboring molecules.
The product is a solid that is then liquefied (broken down and blended) to produce oil comparable to HT.
The process does have its downsides.  As mentioned, it requires rather high pressures -- up to 50 percent higher in the reactor (operating at 3,000 psi (~206.8 bar), versus 1950 psi (135 bar) for an average HT process).  And as one might realize from the previous description, as it grabs hydrogen from neighboring molecules, as small amount of feedstock carbon is released as gas waste.  A small amount is also lost as a solid during the liquefaction process.

oil production
An HTL reactor system burns, then liquefies algal hydrocarbons. [Image Source: Algal Research/PNNL]

But compared to HT and other approaches, HTL does have one big advantage -- it doesn't use any catalysts during the initial oil production.  This dramatically lowers the cost of production, as catalysts are typically expensive due to their use of rare metals and complex construction.
III. After Forty Years, Nearly Forgotten Method Reaches Maturity
The HTL method also offers other benefits.  It operates at a somewhat lower reactor temperature (around 660 ºF (~350 ºC) versus 770 ºF (~410 ºC) for HT) and requires no feed gas (versus the H2 required for HT).  It also makes liquid fuel product faster than HT or other methods, producing liters of fuel in under an hour.
Yet another benefit is that the HTL method doesn't require drying of the algae and extraction of its lipid content, as a HT and similar methods do.  The HTL method "uses the whole buffalo" as the old saying goes, turning all of the algae biomass into carbon fuel.

Algal fuel
The liquified crude is pictured in the center, with the refined "oil" on the left.
[Image Source: Algal Biofuels/PNNL]

Professor Elliott summarizes in a press release:

Cost is the big roadblock for algae-based fuel.  We believe that the process we've created will help make algae biofuels much more economical.

Not having to dry the algae is a big win in this process; that cuts the cost a great dea/  Then there are bonuses, like being able to extract usable gas from the water and then recycle the remaining water and nutrients to help grow more algae, which further reduces costs.

It's a bit like using a pressure cooker, only the pressures and temperatures we use are much higher.  In a sense, we are duplicating the process in the Earth that converted algae into oil over the course of millions of years. We're just doing it much, much faster

PRNL Doug Elliott
Professor Elliott spent much of his career studying HT and CHG production of algal biofuel.  Now he thinks he's found a far better alternative. [Image Source: PNNL]

HTL sounds like a biofuel dream scenario -- faster, simpler, relatively efficient, and -- most importantly -- very cheap conversion.  So why did it take so long to devise?  Well, it turns out that it's been toyed with since the 1970s, but has been largely overlooked due to difficulties with impurities.  It was largely assumed you needed to remove water from the feedstock slurry before feeding it into the reactor.  But Professor Elliott's team threw out that restriction. 

As for why his HTL succeeded where early implementations in the 1970s stuttered, he tells CNBC:

[We have] some technology tricks that other people don't have.

Specifically, it appears these advances involve syringe injection of the slurry (which reduces water content by an inexpensive pressure-based approach, rather than a chemical approach) and jacketed plug-flow beds to assure efficient heat exchange during the preheating and final stages of the reaction.

An important note/clarification is that after the "crude" oil is produced, catalysts are required to convert the algal fuel to final products, resembling gasoline or diesel.  However, this is typically the case with alternative processes (HT, etc.) as well.

Algal fuel

The new method only requires catalysts in the post-processing process (yellow/orange), eliminating catalysts from crude production. [Image Source: PNNL/Algal Biofuels]

The key difference when it comes to HTL is that process of producing the "crude" oil stock does not require additional catalysts.
Another note is that the wastewater -- containing dissolved CO2 and other byproducts from the dehydrogenation pressure cooking process -- can be fed back to the algae, nurturing them, and cutting back on the carbon losses.
IV. Pilot Plant Will Move Patent-Pending Technology Towards the Market
The success has not gone unnoticed.  After a journal paper which was published in a September 2013 edition of the peer-reviewed Elsevier journal Algal Research, Professor Elliott took his patent pending technology to the private sector, licensing it to Genifuel Corp. -- an algae biofuel producer.
Genifuel is looking to supplement expensive, difficult to maintain Catalytic Hydrothermal Gasification (CHG) converters with the new process (CHG is a catalyst-based method similar to HT).  That brings up a final unmentioned beauty of the HTL method.  While its liquefied distillates can be blended directly with diesel and other fuels for automotive, industrial, or aerospace use, the "waste" hyrdocarbons -- aromatics and other undesirable byproducts -- can be treated by existing HT/CHG catalyst reactor systems to produce methane gas.

algal fuel
Genifuel is setting up a pilot plant to use the new reactor system. [Image Source: iStock via Genifuel]

So a company like Genifuel can switch to the more efficient HTL method for its primary production.  But rather than having to throw out its existing HTL system for its pilot plant, it can simply repurpose it as a byproducts recycler, producing methane fuel.
While there's still lots of work to be done in terms of algae farming and genetic engineering, this new HTL technology has the potential to revolutionize the algal fuel industry, cutting costs from hundreds of dollars per gallon to a few dollars per gallon thanks to its inexpensive, ridiculously intuitive design.
Again, given the cellulosic ethanol hype and flop, it's easy to be skeptical of big boil claims in the biofuels industry.  But this new PNNL refinement of a long overlooked alternative method certainly sounds like far more of a simple and less cumbersome approach that many so-called "breakthroughs".

Sources: PNNL, Algal Biofuels, CNBC

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