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Biofuels and Biotechnology > Lecture 2 - An overview of the major biofuels and routes to their production > Flashcards

Lecture 2 - An overview of the major biofuels and routes to their production Flashcards

1
Q

What is the current price per barrel of oil?

A

~$45 (Brent Crude)

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2
Q

What are the current major types of biofuels? What are the sources of the precursors of these fuels?

A
  • Bioethanol (yeast - Saccharomyces)
  • Biobutanol (bacteria - clostriduim)
  • Biodiesel (plants, algae, bacteria)
  • Biohydrogen (algae, bacteria)
  • Biogas (bacteria and archaea)
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3
Q

What is bioenergy?

A

Any form of energy derived from biological material

  • heat
  • electricity
  • liquid transportation fuels and biogas
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4
Q

What are biofuels?

A

Have a narrower definition than bioenergy.

  • generally liquid transportation fuel and biogas
  • strict definition - requires solid biomass for combustion
    • tree, wood pellets, fast growing grasses
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5
Q

Why are forms of bioenergy not currently economical?

A

Have to be cost competitive with oil. Requres oil to be aroiund ~$70 barrel currently at ~$45

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6
Q

What is the main form of biogas?

A

Methane

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7
Q

Why is bioethanol decribed as a mature biofuel?

A
  • Used on a daily basis in cars in Brazil or the USA (Mid-west/california)
  • over 40 million flex-fuel vehicles worldwide; over 20 million in Brazil, 15 million in the US
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8
Q

How is bioethanol most often used?

A
  • With gasoline to produce blends like E10 (10% ethanol)
  • E85 blend which flex-fuel vehicles can run on (UK: Ford, Volvo, Saab) - Morrisons only network of E85 pumps
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9
Q

What is the current rule for the level of biofuels in the UK?

A

5% of UKs fuel must be biofuel (often in blends)

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10
Q

Why are bioethanol petrol blends cheaper?

A

Don’t go as far, not as energy intense as hydocarbon chains

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11
Q

How is bioethanol a classic 1st generation biofuel?

A
  • Uses maize to produce bioethanol
  • USA: up to 80 million acres of maize, a proportion is used for making bioethanol
  • >14 billion gallons annually US (compared to 400 million gallons gasoline daily)
  • US mid-west ~10% of their fuel is bioethanol
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12
Q

What generation biofuel is bioethanol?

A

1st generation (used maize/corn)

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13
Q

How do 1st generation biofuels impact food security?

A

Multiple pressures on food crops - increase food price

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14
Q

How is bioethanol made? (US)

A
  1. Harvest grains of corn (65-70% starch - mainly the endosperm)
  2. Gound up to a ‘meal’ and ‘cooked’ to break down the starch to glucose
  3. Yeast is added in fermentation
  4. this prodcues CO2 which is compressed and can be used in fizzy drinks or as dry ice
  5. Ethanol is distilled off (yeast dies at a high concentration of ethanol) and further cleaned (molecular sieve).
  6. Can concentrate by distillation - denatured alcohol (no water) - 200% Proof. - combined with petrol at various concentrations.
  7. Spent grains processed to animal feed
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15
Q

What are the features of brazilian bioethanol productin?.

A

Same manner of production as US but sugar cane is the feedstock. Causes problems by soil erosion

Weather means can produce 3 crops yearly.

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16
Q

What are the features of bioethanol on the humber?

A
  • Vivergo - £350m plant at Saltend on the Humber esturary. Opened July 2013 (oil proce per barrel was $100 barrel).
  • 1.1m tonnes of wheat -> 420m litres of ethanol and 500,000 tonnes of high protein animal feed
  • 1st generation biofuel
17
Q

How is the future in cellulosic ethanol?

A
  • 1st generation biofuels don’t exploit the majority of the biomass
  • 2nd gen biofuels convert waste into biofuels (lignocellulose) into cellulistic ethanol
  • Beta renewables opened cellulosic ethanol plant in northern italy in 2013
  • INEOS bio opened a plant in Florida in 2013
  • Other companies hoping to open more
18
Q

Why is n-butanol potentially a better form of bioethanol?

A
  • very versitile transportation fuel
  • can be made biologically by clostridia that use a particular type of fermentation under anaerobic conditions
    • ABE fermentation (for acetone, butanol, ethanol)
    • technology been in use since 1910 in UK - come and gone on the price of oil
19
Q

What are the features of n-butanol?

A
  • 4-carbon straight chain alcohol: small molecule, more C so higher density fuel than bioethanol
  • normally made from oil but can be synthetically made
20
Q

Why is n-butanol considered a highly versitile transportation fuel?

A
  • drop-in biofuel: can be used in normal cars and other vehicles
  • can be pumped around better and is not so corrosive as bioethanol or as volatile
21
Q

How is biobutanol currently made?

A
  • ABe fermentation being re-commercialised in china (until fuel price crash)
  • mainly uses starch as feedstock for clostridia (but when too expensive plants are idle)
  • 2012: first cellulosic n-butanol from residual corn waste (corn shells, corn cobs and stover) produced in china
  • butanol has applications also in the speciality chemistry industry - can be sold as chemical butanol (precursor for plastics, 1-butene) rather than as a cheaper biofuel (price per tonne is higher)
22
Q

What is biodiesel?

A
  • mixture of fatty acid esters (monoalkyl esters of long chain fatty acids)
  • made from neutral lipds (triaglycerols (TAGs) from biological sources
  • most commonly react a TAG with methanol under alkaline conditions to get a fatty acid methyl ester (FAME) in a transesterification reaction in vitro
  • sodium oxide/hydroxide as catalyst
  • produces biodiesel and glycerol - which has value as a commodity chemical
23
Q

What organisms are neccessary for the production of biodiesel?

A
  • organisms that can stockpile TAGs (oleaginous organisms)
  • normally use TAGs as energy stores
  • can be photosynthetic or non-photosynthetic organisms
  • can be used as a straight replacment for petro-diesel
24
Q

What occurs in the engine when biodiesel is used as a straight replacement for petro-diesel?

A

Fuel is cleaner and nicer for diesel engines. Acts as a sovlent, residuals that build up when use fossil fuel (FF) biodiesel precipitates out and bogs up the engine. Need to replace tubes and filters before switch

25
Q

What is the emission state of biodiesel?

A
  • Emissions mostly improved on FF diesel
  • The source of carbon is a biological molecule
  • circular carbon leads to lower emissions - not adding to C in atmosphere
  • lower CO
  • lower particulates
  • high NOx emission - although the literature is unclear, and can twaek the engine to manage the emissions
26
Q

What are the features of plants as TAG producers?

A
  • plants use TAG as major storage lipids in seeds
  • vegetable oil is the most widely used source of TAGs for bioduesel
  • Certain plants v good at this:
    • rapeseed oil
    • sunflower seed oil
    • soybean oil
    • palm oil
    • Trotropha
      • grow in many places
      • big oily nuts
      • but 20 years before fruiting
      • toxic plant
27
Q

How much oilseed rape is grown in the UK annually?

A

`400 000 hectares

28
Q

How is waste vegetable oil being used to make biodiesel?

A
  • Olleco: owned by a company that produces beef - animal fats can also be converted to biofuel
  • Use waste vegetable oil from fryers in commercial outlets as source of raw material
  • cooking oil theft (2013) costs treasury £25m a year in lost duty
29
Q

What are the features of microalga as TAG producers?

A
  • unicellular photosynthetic eukaryotes
  • many accumulate TAGs in reponse to stress and N-limitation (this limits biomass)
  • some spp (Chlorella vulgaris) can have 70% of dry mass as TAGs during N-limitation
  • Engineering: model green algae (Chlamydomonas reinhardtii), removed some compteting pathways to increase TAG yield
  • Algafuels (portugal) have one of the biggest sites in europse - lots of differnt methodologues for growing microalga at scale
30
Q

What are teh features of non-photosynthetic TAG producers for biodeisel?

A
  • Bacteria from order Actinomycetales have uniquely developed a stroage lipid cycle that leads to the accumulation of TAGs
  • Well studies in Rhodococcus species. TAGs are known to:
    • provide a pool of fatty acids for beta-oxidation as a cellular fuel
    • form components of the plasma membrane
    • function as substrates for the enzymatic prodcution of the very-long and highly modified extracellular lipids characteristic of Actinomycetales
  • Rhodococcus opacus strain grown with gluconate as the carbon source can accumulate up to 76% of its cell dry weight in TAGs
31
Q

What are the features fo Hydrogen as a power source?

A
  • can be combusted in an engine
  • 2H2 + O2 -> 2H2O
  • highest energy to mass ratio of any chemical
  • carbon free and main source is water - unlimited resource
  • hard to store - make H on demand?
  • used to send rockets into space, coal gas has a high proportion of H (exploding street lights)
32
Q

How is H2 produced?

A
  • Mainly by steam-reformation of natural gas
    • need high temperature and catalysts
    • CH4 + H2O <—> CO + 3H2
  • some made by water splitting (reverse of the steam reformation reaction) using electrolysis
    • high electricity costs
33
Q

How is hydrogen made biologically?

A
  • water splitting reaction (biophotolysis) occurs in algae during photosynthesis if limited for sulphur
    • levels of production low and variable
    • stressed = lower biomass
  • bacteria can build H2 as part of their normal fermentatice metabolism (dark fermentation)
    • can yeild 4H2 per glucose
    • C6H12O6 + 4H2O —> 2CH3COO- + 2HCO3- + 4H+ + 4H2 (Produces acetate, carbonate, hydrogen)
    • processes uses hydrogenase enzymes for the final step. metalllo-enzymes that are oxygen sensitive and easily damages
    • hydrogenases also work in vitro and can be coupled to an electrode to generate H2
    • New oxygen tolerant hydrogenases may be the future
34
Q

What is Anaerobic digestion (AD)?

A
  • The microbial degradation of organic waste to methane containing biogas and CO2 and a nitrogen rich digestate that can be used as fertiliser
  • anaerobic process
  • involves a complex microbial population (still poorly understood)
  • natural process that occurs in silts, bogs, ruminants and guts
  • flexible in terms of feedstocks
  • governments UK preferred manner to dispose of food waste
  • Also used extensively in the waste water industry as a means of reducing organic content and energy recovery
35
Q

What organism can produce H2?

A

Thermococcus cardenesis

  • uses molecular sulphur as a reducing agent
  • can be grown in lab
  • can be genetically modified - knock out spurrious pathways to produce more H (more energy directed to this pathway)
36
Q

How is biogas produced?

A

Produced biologically by methanogenes by anaerobic digestion

  1. Farm produces manure (household or point in food production)
  2. Put manure conbined with plant material (act as a microbial innoculum - all bacteria from organisms gut) into a digester (monitoring an control) - add in heat
    1. produces solids and liquids (a)
      • (a) dewatered for bedding, compost, fertilised
      • and biogas (b)
    2. (b) put into storage tanks
      • Used by CHP unit to produce heat (low grade heat (<80C) can be used in the digester) and power
37
Q

Once biogas has been made by anaerobic digestion what can happen?

A
  • Can upgrade biogas
  • Typically 45-60% methane
  • Can increase concentration of methan by removing carbon dioxide so that it is 90-95% methane
  • this can be used normall where normally would use natural gas
38
Q

What is the biochemistry of anaerobic digestion?

A
  1. Organistic materials are made up of polysaccharides, long chain molecules used as a source of food and energy
  2. These are degraded - hydolysed to smaller molecules by bacteria
  3. These are then further broken down :
    1. formate, C1 compounds, volatile fatty acids, alcohols, acetate
    2. further broken down to constituent parts H2 and CO2
    3. or reformed by methanogenesis to generate methan and CO2
  4. H can be injected into microoragnisms to upgrade methane,

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