Biological Conversion of Methane Gas to Liquid Garrett Mcleod Nalin Samarasinghe Lydia Spahr Alex Payne Jennifer Rhodes Shrikaran Mahavandi Jordan Frank
Introduction
Introduction • Methane is a colorless and odorless gas, with a wide abundance in nature. • Methane is a tetrahedral molecule with four equivalent C-H Bonds. Its electronic structure is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H. • Methane, is the primary component of natural gas, it is plentiful and more efficient than oil, while producing less pollution. • Methane actually produces about 25% less CO2 emissions compared to gasoline or diesel fuel. -Since Methane is so abundant, and produces less CO2, it seems enticing as an alternative fuel source.
Methane Feedstocks •
Feedstocks for Methane can include natural gas fields, biodegradab biodegradable le waste materials, such as waste paper paper,, grass clippings, leftover food, sewage, and animal waste.
•
The process of collecting and burning methane from landfills actually act ually generates a significant amount of electricity.
•
In 2009, Germany produced enough electricity from biogas to power 3.5 million homes.
Methane Feedstocks Continued •
The major source of methane is extraction from geological deposits known as natural gas fields, with coal seam gas extraction becoming a m ajor source.
• Another source is “stranded natural gas,” which is currently c urrently flared or vented at remote oil fields, and which represents an enormous unused energy resource. •
Methane hydrate may also be seen as a future source of methane. This is a combination of methane trapped in a crystalized structure of water. This was thought to only occur in the outer regions of our solar system. It has now been found under sediments on the ocean floor.
Anaerobic Diges Digestion tion • Anaerobic digestion is a process that microorganism microorganisms s break down biodegrable material. During anaerobic digestion, bacteria bact eria break down manure in an oxygen-free environment. One of the natural products of anaerobic digestion is biogas, which typically contains between 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and trace amounts of other gases. • The process produces a biogas, consisting of methane, carbon dioxide and traces of other „contaminant‟ „contaminant‟ gases. This process may also occur naturally in wetlands, lakes, and ocean basin sediments. -Anaerobic digestion (AD) of animal manures shows great promise in the United States and has environmental and economic advantages over land application of untreated manure. • Currently, Currently, treatment processes such as anaerobic digestion and composting offer the only biological route for recycling matter and nutrients from the organic fraction of municipal solid waste.
Anaerobic Digestion
Chemical Conversion of Methane Gas to Liquid
Chemical Conversion of Methane to Liquid • Methane is a very un-reactive gas [1] C-H bond strength
438.8 kJ/mol
High ionization potential
12.5 eV
Low proton affinity
4.4 eV
Low acidity
pKa=48
• To activate: – Very reactive species – Catalysts – Higher temperatures
• Energy intensive • Environmentally unfriendly
Chemical Processes • Indirect conversion – Fischer –Tropsch process – Methanol to Gasoline process (MTG) – Syngas to gasoline plus process (STG+)
• Direct Conversion – Homogeneous Oxidation – Non thermal dielectric barrier discharge
Fischer –Tropsch Process Fischer –Tropsch : collection of chemical reactions. Involves Involves conversion conv ersion of CO and H2 to liquid hydr hydrocarbon. ocarbon. [1]
• Step 1 : Steam Reforming CH4 + H20
Ni catalyst H =49.3 kcal 800 to 1000 oC
CO + 3H2
Synthesis sis • Step 2: Synthe CO + 2H2
50-100 atm H =-21.7 kcal
CH3OH
Methanol to Gasoline Process (MTG) • Step 1: Synthesis of Methanol as above • Step 2: Methanol to gasoline – Mobil process 1.
DME production CH3OH
2.
CH3OCH3 + H2O
Gasoline Pr Production ZSM-5 CH3OCH3
Mixture of aromatics
Syngas to Gasoline Plus Process (STG+)
Streamlined process
Homogeneous Oxidation • Gas phase reaction [1] Catalyst: alyst: Ni, Zn, Ag, Fe, modified Pt [2] • Cat
• Temperatures around 200 oC Pressure 40 bar [3] • Same conditions as Methanol oxidation conditions • Methanol yield is around 2%
Non Thermal Dielectric Barrier Discharge • More recent • High voltage to create discharge • Creates Creates a plasma of high energy en ergy electrons electrons and particles • Non thermal
Hybrid Methods Methane Steam Reforming
Synthesis Gas CO CO2 H2
Syngas Fermentation
Products Acetate Ethanol Butyrate Butanol
•
Adantages – Utilization of the whole biomass, including lignin, irrespective of biomass quality – Elimination of complex pre-treatment steps and costly enzymes – Independence of the H 2:CO ratio for bioconversion – Bioreactor operation at ambient conditions – No issue of noble metal poisoning
•
Disadvantages – Poor mass transfer properties of the gaseous substrates (mainly CO and H2) – Low ethanol yield of biocatalysts
Syngas Syng as Fermentation Microorganisms – A lot of microorganisms that can give a lot of products [1] Species
Products
References References
Acetate
Genthner and Bryant (1987)
Butyribacterium methylotropphicum
Acetate, ethanol, butyrate, butanol butanol
Grethlein et al., 1991 , Lynd et al., 1982 and Shen et al., 1999
Butyribbacterium methylotrophicum
Acetate, Butyrate, Lactate, Pyruvate
Shen et al. (1999)
Clostridium aceticum
Acetate
Sim et al. (2007)
Clostridium autoethanogenum
Acetate, ethanol
Clostridium carboxidivorans
Acetate, ethanol, butyrate, butanol butanol
Liou et al. (2005)
Clostridium leatocellum SG6
Acetate, lactate, ethanol
Ravinder et al. (2001)
Clostridium ljungdahlii
Acetate, ethanol
Tanner et al. (1993)
Eubacterium limosum
Acetate
Genthner and Bryant, 1987 and Genthner and Bryant, 1982
Mesophilic bacterium P7
Acetate, ethanol, butyrate, butanol butanol
Rajagopalan et al. (2002)
Oxabactor pfennigii
Acetate, n-butyrate
Krumholz and Bryant (1985)
Peptostreptococcus productus
Acetate
Lorowitz and Bryant (1984)
Acetobacterium woodii
Carboxydocella sporoproducens
H2
Abrini et al. (1994) (1994)
Slepova et al. (2006)
Clostridium thermocellum
Acetate
Florenzano and Poulain (1984)
Desulfotomaculum thermobenzoicum subsp. Thermosyntrophicum
Acetate, H2S
Parshina et al. (2005)
Moorella thermoacetica (Clostridium thermoaceticum)
Acetate
Daniel et al. (1990)
Moorella thermoautotrophica
Acetate
Savage et al., 1987
Syngas fermentation Reactors
Continuous stirred-tank
Bubble column reactors
Monolithic biofilm reactors
Trickle-bed reactor
Syngas Fermentation Fermentation Limitations Limitations • Inhibitory compounds • Mass transfer • Reactor type • Temperature • pH • Growth media • Types of microbes
Product Yields of Syngas Fermentation Microorganism
Ethanol/(g/L)
Acetate/(g/L)
Cell yield/(g cell/g)
References
C. ljungdahlii
48.0
3.0
0.45
Klasson et al. (1993)
C. ljungdahlii
3.0
2.0 – 3.0 3.0
–
C. ljungdahlii
0.062
0.094
1.378
Bacterium P7
0.15
0.025
0.25
Rajagopalan et al. (2002)
C. ljungdahlii
0.55
1.3
0.3
Younesi et al. (2005)
C. ljungdahlii
11.0 – 12.0 12.0
28.0
1.15
Najafpour and Younesi (2006)
Note: Units:
∗
∗
∗ ∗
Klasson et al. (1990) ∗∗
∗∗
- mol C in products per mol CO consumed;
Phillips et al. (1994)
- g/mol of CO. [1]
Chemical Conversion of Methane to Liquid • Advantages – Established – High Efficiency
• Disadvantages – Not good for small sources of methane – High energy cost
Biochemical Conv Conver ersion: sion: Methanotrophs
The Use of Methanotrophic Bacteria • One method of Biological conversion of Methane to Methanol • Methanotrophs - Studied for ~100 years -Isolated in 1970 by Whittenbury • Can be grown aerobical aerobically ly or anaerobically
What Are Methanotrophs? • “MethaneMethane-Utilizing Utilizing Bacteria” - Use methane as main source of carbon and energy • Found in many habitats • Contain special enzyme: Methane Monooxygenase
Diverse Habitats
Some Live in Extreme Environments • Acidic Peat Wetlands Wetlands (Siberia) • Alkaline Lakes (Central Asia and Kenya) • Hot Springs (Hungary) • Saltine Lakes (Antarctica)
How Do They Metabolize Methane? 1.
2.
3.
Use enzyme Methane Monooxygenase (MMO) to oxidize methane to Methanol -Must have aerobic conditions Methanol is then converted to Formaldehyde through methanol dehydrogenase Formaldehyde either synthesizes multi-carbon compounds or is oxidized to formate
How Do They Metabolize Methane? 3. Metabo Metaboliz lize e Formald Formaldehy ehyde de to affec affectt carbon carbon assimilation using one of two pathways: 1. RuMP pathway -Uses ribulose monophospate 2. Serine pathway -Uses ribulose bisphosphate carboxylase
Which Pathway? ●
Which pathway is used depends on the type of methanotroph? There are three types: -Type I: Uses RuMP pathway -Type II: Uses Serine pathway -Type X: Uses both pathways and thrives at higher temperatures
Is It Worth It? ●
Advantages: -Utilizes methane which is abundant -More mild operating conditions as compared to conventional metal catalysts - Useful in development of better biocatalysts
●
Disadvantage: - Not very high energy yield
Biochemical Conversion: Ammonia Oxidizing Bacteria
What Are AOBs? • Are also referred to as Nitrifying Bacteria due to their role in nature • They catalyze the first step of aerobic nitrification, the oxidation of ammonia (NH3) to nitrite (NO2-). • They are highly important for the turnover of inorganic nitrogen in many ecosystems and for biological wastewater wastewat er treatment
Nitrification • Nitrification Nitrification is the biological oxidation of ammonia with oxygen, then converted into ammonium, then into nitrite followed by the oxidation of nitrite into nitrates. • It is a two step oxidation process of ammonium (NH 4+) or ammonia (NH3) to nitrate (NO 3-) catalyzed by two ubiquitous bacterial groups. The first reaction is oxidation of ammonium to nitrite by ammonium oxidizing bacteria (AOB) • Nitrosomonas species. • Chemolitho-autotrophic ammonia-oxidizing bacteria
Nitrifying bacteria that oxidize ammonia Genus
Phylogenetic group
DNA (mol% GC)
Habitats
Characteristics
Nitrosomonas
Beta
45-53
Soil, Sewage, freshwater, Marine
Gram-negative short to long rods, motile (polar flagella)or nonmotile; peripheral membrane systems
Nitrosococcus
Gamma
49-50
Freshwater, Marine
Large cocci, motile, vesicular or peripheral membranes
Nitrosospira
Beta
54
Soil
Spirals, motile (peritrichous flagella); no obvious membrane system
Soil
Pleomorphic, lobular, compartmented cells; motile (peritrichous flagella)
Nitrosolobus
Beta
54
Molecular Process • Ammonia oxidation in autotr autotrophic ophic nitrification is a complex process that requires several several enzymes, proteins and presence of oxygen. • Key enzymes: 1. Ammonia Monooxy Monooxygenase genase (AMO) 2. Hydr Hydroxylamine oxylamine Oxidoreductase (HAO). NH3 + O2 → NO−2 + 3H+ + 2e− NH3 + O2 + 2H+ + 2e− → NH2OH + H2O NH2OH + H2O → NO−2 + 5H+ + 4e−
Molecular mechanism of ammonium oxidation by AOB
AMO • Ammonia Monooxygenase (AMO) is responsib responsible le for the oxidation of ammonia. • Besides ribosomal RNA, the gene of the alpha subunit of ammonia monooxy monooxygenase genase (amoA) is suitable as phylogenetic phylogenetic and also as functional marker for the specific detection and identification of AOB in the environment. • This gene is restricted to AOBs
Study by Taher Taher and Chandran • In this study, Taher and Chandran used ammonia-oxidizing bacteria (AOB) to selectively and partially oxidize methane (CH4) to methanol (CH3OH). • Procedure of their experiment • Resulting hypothesis
Methane to Methanol • Metabolic versatility versatility of ammonia oxidizing bacteria • Biologically engineered to convert "dirty" digester off-gas, off-gas, which contains a mixture of methane and CO2 (both co-substr co-substrates ates for methanol producing ammonia oxidizing bacteria) to methanol.
The Pros vs. Cons • Pros: – Could be responsible for turning wastewater treatmentt plants into biorefineries producing treatmen methanol – Neutral biological nitrogen removal • Cons: -There is not an existing commerical way to grow and utilize AOBs
References •
http://www.ncbi.nlm.nih.gov/pubmed/23473425
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http://en.wikioffuture.org/Biological_conversion_of_methane_to_metha nol_using_monooxygenic_pathways_in_autotrophic_ammonia_oxidizing _bacteria
•
http://www.microbial-ecology.net/ammoniaoxidizers.asp
Methane Oxidation Enzymes
Methane to Butanol: Biological Conversion
Methanotrophs • Methanotr Methanotroph oph function. • Creating Creating another another microbial host able to generate butanol. • Useful due to reengineering of natural organism organism for low-cost low- cost bio fuel.
Steps for Generating Butanol • Methane is released from biomass. • Used to efficiently create butanol from butyric acid. • Large amount of heat is needed for this. • Methane is used as a sort of “blocker “blocker”” to block a pathway for acetone to be formed.
Recent Technology • REMOTE(Reducing REMOTE(Reducing Emissions Using Methanotrophic Organisms for Transportation Energy) • Biocataly Biocatalyst st Engineering Engin eering • Bioprocess Intensifica Intensification tion
Areas for Breakthroughs • High Efficiency Biological Methane Activa Activation. tion. • High Efficiency Biological Synthesis of Liquid Fuel. • Process Intensification Intensification Approaches for Biological Methane Conv Conversion. ersion.
Works Cited • https://shar https://share.sandia.gov/news/resour e.sandia.gov/news/resources/new ces/new s_releases/remote_fuels/#.U0la5fldXXq • http://www.xylenepower.com/Biofuel.htm • http://www.greencarcongress.com/2013/03/r emote-20130317.html
Comparison Betwee Between n the Diff Different erent Methods
Pros: Chemical Conversion • Fischer-Tropsch: Established, good for large scale projects • MTG: Economically competitive fuel, product flexibility • ST STG+: G+: Energy efficient, highest yield
Cons: Chemical Conversion Conversion • Fischer-Tropsch: Expensive, not energy efficient • MTG: Environmental footprint • STG+: STG+: Not as established as other two processes
Pros: Biological Conversion • Methanthropic: Worldwide distribution, can be grown anaerobically or aerobically • Ammonia Oxidizing Bacteria: Continuous fuel cycle possibilities, more efficient product • Conversion to Butanol: Use of carbon dioxide in process • Will be more cost effective than chemical conversions once they are developed. • Do not require a clean source of methane.
Cons: Biological Conversion Conversion • Methantrophic and Ammonia Oxidizing Bacteria: – Slow production • Conversion to Butanol: Not readily available • All currently produce small yields in comparison to chemical conversions.
Best Method Overall • Currently: – Chemical Conversion to Liquid - STG+
• Future: – Biological Conver Conversion sion
Conclusion
Conclusion • Fisher-Tropsh Reactions • Gasoline Conver Conversion sion • Methanotrophs • Ammonia Oxidizing Bacteria • Oxidation by Enzymes • Methane to Butanol
Chemical or Biological Conversion? • Chemical conversion conversion methods are more suitable in comparison to biological methods. • Currently, there are no commercially viable biological approaches. • Synthetic approaches: expensive & inefficient
Environment • Improved Research and Technology – Reduction of harmful green house gas emissions • Conventional fuel technologies • Small-scale remote natural gas resources r ich gas residues • Methane and Carbon rich
Economy • Bioconv Bioconversion ersion to Liquid Fuels – Expansion of U.S. natural gas resources resources • Contribute tens of billions of dollars to the nation's economy • Reduce and stabilize transportation fuel prices
• Improved Bioconversion Process – Create cost-competitive liquid fuels foreign eign oil • Reduces demand for for
U.S. Research & Technologies Lawrence Berkeley National Laboratory
University of Washington & University of North Carolina
• •
–
•
Method of converting Methane gas into a liquid fuel UNC Chemistry Professor Maurice Brookhart states: “The next step is to use knowledge gained from this discovery to formulate other complexes and conditions that will allow us to catalytically replace one hydrogen atom on methane with other atoms and produce liquid chemicals such as methanol.”
Innovation could lead to: – –
•
– Genetically engineering a bacterium called Methylococcus
Important step forward –
Many uses for Methane Facilities capable of taking on production processes
Methane-to-Methanol transform transformation ation technologies are highly researched –
Most convenient form of transformed t ransformed Methane
Focusing on the conver conversion sion of Methane
• Produce an enzyme that binds Methane with a common fuel precursor to create a liquid fuel • Process relies on Methylat Methylation ion • Construct enzyme enzyme called a PEP Methylase • Bioengineer new metabolic pathways
•
Process will – Enable low-cost, energy-efficient fuel production from Methane – Create a new industry for the liquid fuel conversion of natural gas, Methane waste streams, and biogas
Methane • Methane Pros: – – – –
A potent fuel Generates Generat es smaller amount of pollution vs. oil, coal or natural gas More efficient than oil Abundant resource
• Methane Cons: – Difficult and costly to transport and obtain temperatures and pressures on the Earth's surface – Remains a gas at temperatures
• Natural gas is primarily Methane – Natural gas can be found in abundance throughout the United States – Often used for heating, cooking, cooking , and electrical power generation
The Future of Methane • To benefit from our country’s natural gas resources the demand for innovative biological processes is high • Biocatalysts are needed • Extensive research and improved technologies can overcome obstacles • The future… Methane Conversion to Liquid Fuels
References •
http://arpa-e.energy http:// arpa-e.energy.gov/?q=arpa-e-projects/ .gov/?q=arpa-e-projects/enzymes-methane-c enzymes-methane-conversion onversion
•
http://news.softpedia.com/new http://ne ws.softpedia.com/news/How-to-T s/How-to-Turn-Methane-Gas-int urn-Methane-Gas-into-Liquid-Fuel-125096.sh o-Liquid-Fuel-125096.shtml tml
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http://www.sciencedaily http://www .sciencedaily.com/releases/2 .com/releases/2009/10/091022141110.h 009/10/091022141110.htm tm
