The Venus Technology: Algae joins wood at the Liquefaction and supercritical frontier for biofuels

December 23, 2013 |

venus-1PNNL develops a project that, using conditions usually found on the planet Venus, produces a continuous stream of drop-in advanced biofuels, from algae, with the potential for dramatically lowered costs.

It’s another step forward in the subcritical temperature region — and may solve the algae dewatering and extraction problems forever.

If Venus has not been in your travel itineraries this year, let us be the first to forgive you — the planet, ironically named for the Roman goddess of beauty, has turned out to be a hostile environment with temperatures in the 800 degree range, atmospheric pressures 100 times that of Earth, and a CO2-laden atmosphere. Some beauty. Some weather.

But it turns out that Venusian conditions might be just what the doctor ordered for the continuous, low-cost production of drop-in fuels from algae.

That’s the electrifying news from a team of researchers in Douglas Elliott’s lab at Pacific Northwest National Laboratory, who have created a continuous chemical process that produces useful crude oil minutes using a near-to-supercritical thermal liquefaction process.

The system runs at around 350 degrees Celsius (662 degrees Fahrenheit) at a pressure of around 3,000 PSI, combining processes known as hydrothermal liquefaction and catalytic hydrothermal gasification.

In the PNNL process, a slurry of wet algae is pumped into the front end of a chemical reactor. Once the system is up and running, out comes crude oil in less than an hour, along with water and a byproduct stream of material containing phosphorus that can be recycled to grow more algae.

The recent work is part of DOE’s National Alliance for Advanced Biofuels & Bioproducts, or NAABB. This project was funded with American Recovery and Reinvestment Act funds by DOE’s Office of Energy Efficiency and Renewable Energy.

The commercial pathway

Interesting … just to learn that the technology has advanced to the stage when it has been licensed to Genifuel, which is working towards developing a pilot-scale plant. Important…because the research team reports that they have combined several chemical steps into one continuous process and eliminated the need for separate dewatering and extraction steps.


The most important cost-saving step is that the process works with wet algae. Most current processes require the algae to be dried — a process that takes a lot of energy and is expensive. The new process works with an algae slurry that contains as much as 80 to 90 percent water.

The PNNL system also eliminates another step required in today’s most common algae-processing method: the need for complex processing with solvents like hexane to extract the energy-rich oils from the rest of the algae.

“Not having to dry the algae is a big win in this process; that cuts the cost a great deal,” said Elliott. “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.”

The research by engineers at the Department of Energy’s Pacific Northwest National Laboratory was reported recently in the journal Algal Research.

More about hydrothermal processing

Hydrothermal Processing uses hot, pressurized water just below the supercritical point. Under these conditions, organic materials can be converted to either liquid or gas fuels, specifically oil or methane. The type of fuel produced depends on whether there is a catalyst present or not. The process of Hydrothermal Liquefaction (HTL) operates without a catalyst and produces oil, while Catalytic Hydrothermal Gasification (CHG) operates with a catalyst and produces methane (natural gas).

The two processes can be used together to convert essentially all of the organic feedstock to fuels. The process is clean and environmentally benign, leaving primarily clean sterile water from the original feedstock. This water will contain plant nutrients present in the feedstock, and can be used as liquid fertilizer.

Typical feedstocks include food and biofuel processing wastes, beverage brewing waste, wastewater solids, wet municipal solid waste, animal wastes, and many others. Aquatic plants such as algae and water hyacinths are excellent feedstocks.

The product set

In all, there are four outputs from the process.

• Crude oil, which can be converted to aviation fuel, gasoline or diesel fuel. In the team’s experiments, generally more than 50 percent of the algae’s carbon is converted to energy in crude oil — sometimes as much as 70 percent.

• Clean water, which can be re-used to grow more algae.

• Fuel gas, which can be burned to make electricity or cleaned to make natural gas for vehicle fuel in the form of compressed natural gas.

• Nutrients such as nitrogen, phosphorus, and potassium — the key nutrients for growing algae.

The Genifuel connection

Genifuel Corp. has worked with Elliott’s team since 2008, licensing the technology and working initially with PNNL through DOE’s Technology Assistance Program to assess the technology.

“This has really been a fruitful collaboration for both Genifuel and PNNL,” said James Oyler, president of Genifuel. “The hydrothermal liquefaction process that PNNL developed for biomass makes the conversion of algae to biofuel much more economical. Genifuel has been a partner to improve the technology and make it feasible for use in a commercial system.

More about Genifuel

According to its Genifuel supplies equipment to produce renewable fuel from wet organic materials. The process, called Hydrothermal Processing, is the most efficient process known today to achieve this conversion.
With additional conventional refining, the crude algae oil is converted into aviation fuel, gasoline or diesel fuel. And the waste water is processed further, yielding burnable gas and substances like potassium and nitrogen, which, along with the cleansed water, can also be recycled to grow more algae.

The cautionary notes

The PNNL system runs continuously, processing about 1.5 liters of algae slurry in the research reactor per hour. So, it’s pre-pilot,. as noted above.

And it is not going to be cheap to build out, at scale, a system that requires 350 degrees and 3000 PSI.

On the liquefaction front

For some time, the Digest has been reporting on breakthroughs in areas related to solvent and thermal liquefaction of biomass into targeted biofuels.

Perhaps the most fascinating report on liquefaction came out last year, when it was revealed that a pathway to $2.18 per gallon gasoline was developed at Chevron-Weyerhaeuser owned Catchlight Energy, using a solvent liquefaction technology, yet the project was sidelined — allegedly because Chevron determined it was cheaper to buy advanced biofuels waivers than it was to produce advanced biofuels.

We noted some qualifiers when the news was revealed in Bloomberg last year. The technology was at at pilot stage. The Bloomberg report points to “a $504 million solvent liquefaction plant producing 92 million gallons a year at a cost of $2.18 a gallon.” Originally the venture was intended to build 17 plants by 2029, making 2 billion gallons of renewable fuel, starting with a $370 million commitment by 2013 and a first commercial plant in 2014.

According to Bloomberg, When it was projected that the projects would make a return on investment of between 5 and 10 percent per year, compared to Chevron-wide average return of 17 percent, the Catchlight board said in April 2010 that there was “no urgency” in advancing the technology, set the minimum annual return at 20 percent to greenlight a project, and reduced Catchlight’s 2013 budget from $370 million to $8.9 million.

According to Bloomberg, R&D on solvent liquefaction is now reduced primarily to a $3.5 million program at Iowa State, $2.8 million funded by a federal grant and $700,000 by Catchlight.

But we also highlighted NextFuels this past year. They took an underlying technology that was originally explored at Shell as far back as the 1980s, when oil prices rose to scandalous heights — and like algae, research came to a crashing halt when oil prices fell into the sub-$20 range in the 1990s. But a team of researchers , with support from the Shell Foundation, later took its development through a 1000-hour pilot test.

Their focus: finding a modular design — that can create, from the various types of palm waste, a liquid flow of a bitumen biocrude, concentrating the energy by a factor of 10-20 times, suitable for transportation and shipping to markets for use in powergen, or upgraded into transportation fuel.

The company is collaborating on its commercial strategy with Enagra, a biofuel trading company with extensive contacts and partnerships throughout the industry, on the development of its technology. The two companies are owned by the same investors and managed by executives with extensive experience in biofuels. Over the past ten years, Enagra has conducted over $1 billion in biofuel transactions and will achieve revenues of approximately $150 million in 2013.

Supercritical water and biofuels

As we reported in “Extreme energy, supercritical water, nanostuff and biofuels“:

“At the frontier of exotic temperature and pressures, even everyday materials like water begin to act strangely in ways that can drive energy transformation.

“At a well-known “supercritical” point – at 374 degrees Celsius and 221 atmospheric pressures – the boundary between liquid water and steam becomes ill-defined and “supercritical water” begins to act as excellent solvent for cellulose — separating C6 sugars from lignin in seconds, compared to the hours or days associated with enzymatic systems.”

The exploration of supercritical water as a biofuels technology is at the heart, as it happens, of the Renmatix Plantrose system — producing a stream of C5 and C6 sugars, plus a lignin fraction — at what it believes, at scale, will be industry-transforming low costs. Renmatix is building towards that scale right now.

Now, there’s much more to the Plantrose system than simply bathing biomass in supercritical water. For one, the relatively easy-to-extract C5 sugars (xylose) are extracted from hemicellulose in a separate pre-process — and there’s are entire biomass-handling and lignin recovering processes that are a part of the overall system. But supercritical is at the heart of it.

Another group, ECR Renewable Fuels and Georgia Alternative Fuels, has been pursuing nanocatalysts and their effect on supercritical boundaries for several years. The goal? To reduce the temperature and pressure barrier at which liquids begin to demonstrate supercritical properties — using catalysis to reduce the energy levels.

“We can now compete with mid-west ethanol on the East Coast,” said Alan Lawson, who heads the group. “Our per pound sugar cost using biomass is about $0.04 per pound verses $0.125 per pound for corn ethanol. Our model is small cellulosic ethanol plants highly distributed over the East, at less than 10 million gallons per year.”

The Bottom Line on Genifuel and hydrothermal liquefaction

It’s an exciting breakthrough at lab-scale. But let’s emphasize “lab-scale” as much as “exciting breakthrough”.

There’s a long way to go, and at this stage we’ll have to invoke the Biofuels Development Maxim #1: “In the lab, all glass is rose-colored.”

But a breakthrough on dewatering and extraction — a new path towards affordable algae biofuels at scale. Even if you have to travel to Venus to see it done in ambient conditions, it’s be worth the trip. Just bring along a pressure suit.

More on the PNNL story

Douglas C. Elliott, Todd R. Hart, Andrew J. Schmidt, Gary G. Neuenschwander, Leslie J. Rotness, Mariefel V. Olarte, Alan H. Zacher, Karl O. Albrecht, Richard T. Hallen and Johnathan E. Holladay, Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor, Algal Research, Sept. 29, 2013, DOI: 10.1016/j.algal.2013.08.005.

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