The rapid increase in greenhouse gas (GHG) emissions due to the extensive use of fossil resources have necessitated the production of renewable energy sources to sustain current economic activities while reducing net carbon dioxide emission.
Conventional hydrocarbon fuels are produced by distillation of crude oil. This process generates a variety of products including gasoline, diesel, and jet fuel. However, these distillates include sulfur-containing and aromatic compounds that can lead to acid rain, engine corrosion, and particulate formation. This leads to lower performance and increased maintenance costs for the Military.
Then there are synthetic fuels, which are produced by combining specific petrochemical molecules to generate fuel mixtures. Fuels of this type are typically expensive and methods to generate them can be carbon inefficient and energy-intensive.
Hydrazine-based propulsion systems are state-of-the-art for various applications ranging from launchers to large and small satellites. They have a long and successful heritage and a great variety of space-qualified, off-the-shelf components. Hydrazine has dominated the space industry as the choice of propellant for over six decades, due to its high-performance characteristics, despite its environmental and health hazards and the challenges faced in its manufacturing, storage, ground handling, and transportation.
Space agencies are trying to replace the conventional hydrazine rocket fuel, a highly toxic and carcinogenic chemical, with a greener propellant for future missions. These technologies present performance benefits such as reduced launch mass, increased scientific payload mass, and/or extending on-orbit lifetimes. The advantages are further reinforced due to the significant reduction in health risks encountered during launch site and ground handling operations.
Biofuels are fuels, which are chemically similar to gasoline and diesel, but are produced by processing crops, algae or microbial culture. The carbon in biofuels comes from carbon dioxide that plants convert to their biomass through photosynthesis. Traditional biofuels are produced from food crops. This approach is costly and competes with food production in the use of land, water, energy, and other environmental resources. Through the use of synthetic biology it has become possible to engineer microbial cell factories for efficient biofuel production in a more precise and efficient manner.
The use of biosynthetic fuels in jet and diesel engines can decrease costs, increase the range and fuel economy of aircraft, ground vehicles and ships, while reducing the emission of toxic particulates and resulting in lower net greenhouse gas emissions.
Biomanufacturing relies on bacteria and other microorganisms with modified DNA to produce materials that are costly or impossible to obtain otherwise, including high-energy chemical compounds used in explosives. Researchers have used the tools of synthetic biology to manipulate the genes of Escherichia coli, a common gut bacterium, so that it can chew up vegetation to produce diesel and other hydrocarbons.
Synthetic biologists are attempting to get heterotrophic microbes (ones that can’t make their own food with photosynthesis but instead need to be fed with organic compounds) to convert the biomass from plants into usable fuels. Creating biofuels this way would then involve a two-step approach in producing the fuel, where plants are first engineered to grow as quickly as possible and then are ground up and fed to E. coli, yeast, etc., that would convert that biomass into ethanol and other fuels.
The efforts to produce corn ethanol with engineered yeast have become popular recently, and can be considered an extension of what beer and malt brewers have been doing for centuries. Synthetic biology aims to make this process many fold more efficient and better suited for fuels, like octane, that can be used to run existing gasoline engines much more efficiently than ethanol can, which is crucial in making the transition from a fossil fuel to a biofuel-based society as easily as possible.
E. coli is popular in genetic engineering because it is deeply studied and quite hardy, able to tolerate genetic changes well, says chemical engineer Jay Keasling of the University of California, Berkeley. Researchers have already modified E. coli to make medicines and chemicals, and now Keasling and his colleagues have turned the organisms into biodiesel factories.
The scientists first genetically modified E. coli to consume sugar and secrete engine-grade biodiesel, which can float to the top of a fermentation vat—no need for distilling, purifying or breaking cells open to get the oil out, as is the case for making biodiesel from algae.
Biofuels could be made from bacteria that grow in seawater, reported in Oct 2019
Researchers from The University of Manchester are using synthetic biology to explore a more efficient way to produce the next generation of bio-based jet fuels – partly made from a type of bacteria that grows in seawater
The Manchester research group, led by Professor Nigel Scrutton, Director of the Manchester Institute of Biotechnology (MIB) and supported by the prestigious US-based international maritime research agency Office of Naval Research Global (ONR), is using synthetic biology to help identify a more efficient and sustainable method to make biofuel than the one currently used.
Scientists have discovered that the bacteria species called Halomonas, which grows in seawater, provides a viable “microbial chassis” that can be engineered to make high value compounds. This in turn means products like bio-based jet fuel could be made economically using production methods similar to those in the brewery industry and using renewable resources such as seawater and sugar.
The breakthrough behind this approach is the ability to re-engineer the microbe’s genome so to change its metabolism and create different types of high value chemical compounds which could be renewable alternatives to crude oil. Dr Benjamin Harvey and his team of researchers at the world-leading Naval research facilities in China Lake, California, USA, have pioneered this exciting work on converting biological precursors to relevant jet fuels.
Following on from this research, Professor Nigel Scrutton explained: “Effective biofuels strategies require the economic production of fuels derived from a robust microbial host on a very large scale – usually cultivated on renewable waste biomass or industrial waste streams – but also with minimal downstream processing and avoids use of fresh water. With Halomonas these requirements can be met, so minimizing capital and operational costs in the production of these next generation biofuels.”
This research could be groundbreaking news for the wider biofuels industry. “In the case of the jet fuel intermediates we are bio-producing, they are chemically identical to petrochemical-derived molecules, and will be able to ‘drop-in’ to processes developed at China Lake,” added Dr Kirk Malone, Director of Commercialisation at The University of Manchester’s MIB.
BioFuel Alternative for Missile Fuel
Military researchers are helping “scale up” the use of E.coli to produce fuel for Hellfire missiles, part of a larger push to manufacture small batches of specialty chemicals in cheaper and cleaner ways using microbes. The use of gut bacteria to make missile propellant is a “larger proof of concept” for the Army’s expansion of biological manufacturing capabilities.
The hope is that it will wean the U.S. military off chemicals derived from crude oil in “costly petrochemical facilities” and often available through limited suppliers, the Combat Capabilities Development Command Chemical Biological Center said in a statement. “Many crucial chemicals are either manufactured by a single source domestically, or worse yet, inside foreign nations that may not always be willing to supply us,” said Peter Emanuel, the center’s senior research scientist for bioengineering.
Emanuel leads the center’s biomanufacturing initiative, part of what he calls a “manufacturing revolution that can make the United States self-sufficient.” Growth in the bioindustrial sector could see the U.S. face off with China in a superpower manufacturing technology race in the coming years, officials said, but it could also provide an economic boost while reducing the financial and environmental costs of manufacturing.
The Army’s biomanufacturing facility cultivates the microbes that it uses to ferment liquid held in large, shiny steel vats, “just like in a microbrewery,” its statement said. The production of Hellfire missile fuel will be the first major proof-of-concept project for the center’s expanded and upgraded facility at Aberdeen Proving Ground, Md., and will address an immediate defense need, officials said. The facility will produce the fuel’s chemical precursor, called BT, which the Defense Department currently gets from a single U.S. supplier. Other DOD labs will help manufacture the final product, called BTTN.
“Establishing an alternative domestic source for this fuel is important because the Hellfire is the U.S. military’s weapon of choice for precision strikes on high-value targets,” the center says on its website. The fuel is used in virtually all single-stage missiles in the U.S. arsenal because it is more stable than nitroglycerine, the site says.
But traditional manufacturing costs make it “economically infeasible” to use more than 15,000 pounds of BT a year in BTTN production, Navy-funded researchers at Michigan State University found in a 2007 report. To reach desired production levels, the costs would have to be driven down two-thirds to about $15 a pound. The Michigan State researchers used genetically engineered E.coli and fiber from corn hulls to produce half a liter of a 99% pure form of BT through a process that was “relatively environmentally benign” and which they estimated could be improved to yield the chemical for less than $19 a pound.
The Chemical Biological Center, which is slated to receive some $24 million over the next five years for expansion and upgrades, did not provide a price-per-pound estimate for its effort to scale up that process. When construction of the biomanufacturing facility is completed and it is ready to run at full capacity within about two years, the center plans to market it as the “go-to place” for producing high-value chemicals with military applications.
These could include energy-dense propellants and explosives, reactive coatings and textiles, optical and sensor materials that can bend light, and new therapeutics such as antimicrobials and vaccines, said Henry Gibbons, a microbiologist and program manager in charge of the center’s expansion effort.
NAWCWD, Amyris collaborate to develop, test high-energy biosynthetic fuel, reported in May 2020
Biosynthetic research being done in China Lake, California, by Naval Air Warfare Center Weapons Division and Amyris, Inc., a biotechnology company headquartered in Emeryville. Funded by the Defense Advanced Research Projects Agency’s Living Foundries: 1000 Molecules Program, NAWCWD and Amyris’ project starts with specially developed yeast cells and ends with a high-density missile fuel.
“Over the course of the Living Foundries program, DARPA often played ‘matchmaker’ to connect Amyris … with scientists in the Army, Air Force, and Navy,” said Dr. Adam Meadows, principal scientist in Amyris’ Process Development and Manufacturing Department. “Dr. Benjamin Harvey [NAWCWD’s senior research chemist] was able to provide guidance on which classes of biomolecules were most interesting in the fuels and material space.”
“Synthetic missile fuels are expensive and biosynthetic surrogates offer an opportunity to decrease costs,” Harvey said. “The use of biosynthetic fuels in jet and diesel engines can also increase the range and fuel economy of aircraft, ground vehicles and ships, while reducing the emission of toxic particulates and resulting in lower net greenhouse gas emissions.”
More familiar are biofuels like ethanol made through a fermentation process, or biodiesel, which comes from processing vegetable oils. Neither has the energy density, purity, or stability of a biosynthetic fuel.
Through the Living Foundries program, Harvey’s team at NAWCWD developed a process to convert a complex mixture of biosynthetic hydrocarbons (produced by Amyris) to a high-density missile fuel. This fuel was recently ground-tested in a liquid fuel ramjet test stand, representing a first-of-its-kind demonstration.
“No one has ever produced a biosynthetic fuel with comparable energy density to the synthetic missile fuel JP-10, and tested it in both a turbine engine and a system that mimics conditions found in a liquid fuel ramjet engine,” Harvey said.
BioRenewable-1, the fuel Harvey’s team produced, has up to 19% higher volumetric energy density than conventional jet fuel. That’s comparable to JP-10, a synthetic fuel currently used to power cruise missiles around the world.
“BR-1 has an energy density high enough for use in high performance military systems,” said Dr. Anne Cheever, program manager for DARPA’s Living Foundries program. “Biologically produced fuels can have advantages in cost and performance over comparable synthetically produced fuels and could be an additional source of military-grade fuels during times of higher demand.”
Regardless of the fuel source, the cost of logistics must be accounted for. Moving the tons of fuel needed to keep the fleet afloat and the boots on the march is expensive and can be a vulnerable link in the supply chain. Rose noted that moving yeast and sugar as fuel precursors would be more cost-effective and could possibly be less vulnerable due to their lower dollar value and relative ease of acquisition.
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