Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor
Pea soup algae ready for processing. Courtesy PNNL.
See: https://www.youtube.com/watch?v=Qs0QZJ0rea0&feature=youtu.be
The algae feedstock (front) and resulting "bio-crude" behind it. Courtesy PNNL.
Green Oil: Scientists Turn Algae Into Petroleum In 30 Minutes
Christopher Helman , FORBES STAFF Big Oil, Big Energy
Pea soup algae ready for processing. Courtesy PNNL.
Scientists at the Pacific Northwest National Laboratory are claiming success in perfecting a method that can transform a pea-soupy solution of algae into crude oil by pressure cooking it for about 30 minutes. The process, called hydrothermal liquefaction, also works on other streams of organic matter, such as municipal sewage. And the crude oil created is lightweight and low in sulfur and can be "dropped in" to refineries that process fossil crudes.
"It's a bit like using a pressure cooker, only the pressures and temperatures we use are much higher," said researcher Douglas Elliott in a statement. "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."
It only makes sense that scientists should be able to figure out how to turn algae into crude oil. After all, most of the oil that we drill out of the ground was formed by algae and other sea-borne flora that piled up at the bottom of the ocean over millenia, then got compacted and heated over eons and transformed into petroleum.
But figuring out how to do it economically is a challenge. A half-century ago researchers were growing algae on the roof of M.I.T. More recently, ExxonMobil raised the hopes of the algae-to-oil crowd in 2009 when it forged a research venture with Craig Venter's Synthetic Genomics. If Venter (who was first to decode the human genome) could find or engineer an algae strain adept at naturally creating oils, Exxon would fund development to the tune of $600 million. Unfortunately Venter called off the quest a few years later. Algaes just weren't oily enough to be commercially viable sources of crude.
A new generation of scientists says that's hogwash. It's not about finding a particularly oily algae, it's about the process of turning any algae into oil, says Jim Oyler, CEO of Genifuel, who has worked closely with Douglas Elliott and other researchers at the PNNL for years and has licensed the technology. "We've proven it can be done.".
A spate of articles in scholarly journals would seem to back him up. In the October issue of Algal Research: Biomass, Biofuels and Bioproducts (a journal published by Elsevier), you can read a couple of pieces by PNNL researchers including one titled "Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor." Similar research has also been done at Ohio State and at Denmark's Aarhus University and the University of Sydney in Australia
Most of these papers are full of geekspeak. Thankfully Oyler was patient enough to walk me through the process. You start with a source of algae mixed up with water. The ideal solution is 20% algae by weight. Then you send it, continuously, down a long tube that holds the algae at 660 degrees Fahrenheit and 3,000 psi for 30 minutes while stirring it. The time in this pressure cooker breaks down the algae (or other feedstock) and reforms it into oil.
Given 100 pounds of algae feedstock, the system will yield 53 pounds of "bio-oil" according to the PNNL studies. The oil is chemically very similar to light, sweet crude, with a complex mixture of light and heavy compounds, aromatics, phenolics, heterocyclics and alkanes in the C15 to C22 range.
The algae feedstock (front) and resulting "bio-crude" behind it. Courtesy PNNL.
Not all the organic matter gets turned into oil. It also yields a stream of carbon dioxide, hydrogen and oxygen, which can readily be turned into a stream of synthetic natural gas and burned to generate heat or electricity.
Also left over is water rich in the plant nutrients (nitrogen, phosphorous and potassium) previously present in the algae. This water can be sold back to the algae ponds as fertilizer.
"Not having to dry the algae is a big win in this process; that cuts the cost a great deal," said Elliott in a statement. "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 researchers figure that at current algae prices of several hundred dollars a ton they could make algae-based fuel for the gasoline equivalent of less than $5 per gallon.
And algae's only the most viable oil source. The same tricks can oil-ify all sorts of other organic wastes such as manure, municipal sewage, vegetable compost, even fish heads. Indeed, if the technology can be successfully scaled up to commercial size, says Oyler our stinky streams of human waste alone could provide the feedstock to meet 10% of our worldwide petroleum demand.
First they'll need to expand their systems beyond the pilot scale -- it will cost about $1 million to build a plant that can handle a ton of algae per day.
Yes, I'm skeptical too. But look at what we've done with corn in recent years. "Corn ethanol was an amazing accomplishment -- to think that we make 15 billion gallons a year using only a small part of the plant," says Oyler. "But we can all accept that corn is not the right path forward. You can grow algae anywhere and in any water. Compared to corn it's not very finicky."
A big criticism of corn ethanol over the years is that the process of growing it requires so much fertilizer, water and other energy inputs that by the time you've got it turned into ethanol you've lost energy not gained it. If an energy system has a negative net energy balance it is necessarily cannibalizing other energy sources.
This appears to be an inconvenient truth for algae as well. Most methods of cultivating it simply eat more energy than is contained in the algae.
The key will be in figuring out how to make massive quantities of algae cheap. Because then, explains Oyler, the rest will support itself: excluding the energy used in growing the algae (a huge caveat), the hydrothermal extraction process developed at PNNL can create about 9 units of energy for every unit used.
No doubt algae cultivation will improve. Until then the big hope for this technology now may be to pair it with a feedstock that cities otherwise have to pay to get rid of -- like sewage. Oyler envisions a distributed system of hydrothermal liquefaction systems set up at regional sewage plants and a fleet of trucks that come to load up on crude oil once a week.
Algae Slurry See: Algae to crude oil: Million-year natural process takes minutes in the lab
Process simplifies transformation of algae to oil, water and usable byproducts
News Release
December 17, 2013
Tom Rickey, PNNL, (509) 375-3732
Algae Slurry
1 of 6
RICHLAND, Wash. — Engineers have created a continuous chemical process that produces useful crude oil minutes after they pour in harvested algae — a verdant green paste with the consistency of pea soup.
The research by engineers at the Department of Energy's Pacific Northwest National Laboratory was reported recently in the journal Algal Research. A biofuels company, Utah-based Genifuel Corp., has licensed the technology and is working with an industrial partner to build a pilot plant using the technology.
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.
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.
While algae has long been considered a potential source of biofuel, and several companies have produced algae-based fuels on a research scale, the fuel is projected to be expensive. The PNNL technology harnesses algae's energy potential efficiently and incorporates a number of methods to reduce the cost of producing algae fuel.
"Cost is the big roadblock for algae-based fuel," said Douglas Elliott, the laboratory fellow who led the PNNL team's research. "We believe that the process we've created will help make algae biofuels much more economical."
PNNL scientists and engineers simplified the production of crude oil from algae by combining several chemical steps into one continuous process. 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.
"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."
While a few other groups have tested similar processes to create biofuel from wet algae, most of that work is done one batch at a time. The PNNL system runs continuously, processing about 1.5 liters of algae slurry in the research reactor per hour. While that doesn't seem like much, it's much closer to the type of continuous system required for large-scale commercial production.
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. Instead, the PNNL team works with the whole algae, subjecting it to very hot water under high pressure to tear apart the substance, converting most of the biomass into liquid and gas fuels.
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. Elliott says such a high-pressure system is not easy or cheap to build, which is one drawback to the technology, though the cost savings on the back end more than makes up for the investment.
"It's a bit like using a pressure cooker, only the pressures and temperatures we use are much higher," said Elliott. "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."
The products of the process are:
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.
Elliott has worked on hydrothermal technology for nearly 40 years, applying it to a variety of substances, including wood chips and other substances. Because of the mix of earthy materials in his laboratory, and the constant chemical processing, he jokes that his laboratory sometimes smells "like a mix of dirty socks, rotten eggs and wood smoke" — an accurate assessment.
Genifuel Corp. has worked closely 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.
"It's a formidable challenge, to make a biofuel that is cost-competitive with established petroleum-based fuels," Oyler added. "This is a huge step in the right direction."
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. Both PNNL and Genifuel have been partners in the NAABB program.
In addition to Elliott, authors of the paper include 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, all at PNNL.
Reference: 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.
Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor
Author links open overlay panelDouglas C.ElliottTodd R.HartAndrew J.SchmidtGary G.NeuenschwanderLeslie J.RotnessMariefel V.OlarteAlan H.ZacherKarl O.AlbrechtRichard T.HallenJohnathan E.Holladay
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Highlights
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Algae-water slurries were processed in a continuous-flow reactor system.
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Whole algal biomass was converted into a gravity separable biocrude.
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Biocrude was hydrotreated into a liquid hydrocarbon mixture, low in O, N, and S.
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Aqueous byproduct from HTL was processed catalytically to produce a fuel gas.
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The resulting water stream could be recycled for nutrients such as ammonia.
Abstract
Wet algae slurries can be converted into an upgradeable biocrude by hydrothermal liquefaction (HTL). High levels of carbon conversion to gravity separable biocrude product were accomplished at relatively low temperature (350 °C) in a continuous-flow, pressurized (sub-critical liquid water) environment (20 MPa). As opposed to earlier work in batch reactors reported by others, direct oil recovery was achieved without the use of a solvent and biomass trace components were removed by processing steps so that they did not cause process difficulties. High conversions were obtained even with high slurry concentrations of up to 35 wt.% of dry solids. Catalytic hydrotreating was effectively applied for hydrodeoxygenation, hydrodenitrogenation, and hydrodesulfurization of the biocrude to form liquid hydrocarbon fuel. Catalytic hydrothermal gasification was effectively applied for HTL byproduct water cleanup and fuel gas production from water soluble organics, allowing the water to be considered for recycle of nutrients to the algae growth ponds. As a result, high conversion of algae to liquid hydrocarbon and gas products was found with low levels of organic contamination in the byproduct water. All three process steps were accomplished in bench-scale, continuous-flow reactor systems such that design data for process scale-up was generated.
