Week 10 Flashcards
How much will temperature increase?
Between 1850 to 2025
0 to ~1.1°C
Worst case are >900 ppm = 4.9°C rise
What is the greenhouse effect?
Solar radiation
Absorbed radiation warms the earth
Absorbed radiation emitted as infra-red radiation
CO2 absorbs intra-red and re-emits in all directions
Why is climate change human caused?
CO2 levels fluctuated throughout time however post industrial levels CO2 levels increased beyond recent peaks
What is the change in greenhouse gases overtime?
CO2 - 345 ppm to 400 ppm from 1985 to 2015
CH4 - 1650 ppb to 1850 ppb from 1985 to 2015
N2O - 303 ppm to 327 ppm from 1985 to 2015
What is a biofuel?
A fuel composed of or produced from biological raw materials (Merriam-Webster 3rd Unabridged Dictionary)
or
Fuel derived immediately from living matter (Oxford English Dictionary)
What is an overview of Biofuels: ancient and old?
Wood (oldest)
Early diesel engines ran on plant oils
What is an overview of biogas production?
Organic matter (manure, sewage sludge, municipal solid waste, etc) – (acetogenesis)–> Fatty acids, H2 and CH3COOH –(methanogenesis)–> Biogas (~60% CH4)
What is an overview of biodiseal production?
Vegetable oil (rapeseed, soybean, jatropha) –(neutralisation)–> esterification (base + ethanol) –> Biodiesel (ethyl esters of fatty acids) + glycerol
What is an overview of bioalcohols production?
Carbohydrate (sucrose, starch and plant cell walls) –depolymerisation–> Mono- and disaccharides –fermentation–> Alcohols
What is an overview of the light dependant reaction?
Water donates electrons to chlorophyll (H2O split / O2 produced)
Light energy excites chlorophyll molecule (high energy electron)
Electron transport along a chain of carriers generates a proton gradient
Proton gradient dissipated by ATP synthase, producing ATP (photophosphorylation)
Electron passed on to NADP+ producing NADPH
What is an overview of the three stages of the Calvin-Bensen cycle?
Carboxylation of the CO2 acceptor ribulose 1,5-bisphosphate producing two molecules of 3-phosphoglycerate
Reduction of 3-phosphoglycerate to triose phosphates
Regeneration of 1,5-bisphosphate
What are the two outcomes of rubisco?
In presence of CO2 formation of 2 molecules of 3-phosphoglycerate, which can be used in photosynthesis
In presence of O2 formation of 1 molecule of 3-phosphoglycerate and 2-phosphoglycerate
What is the process of C2 Oxidative Photosynthetic Carbon Cycle?
Involves 3 organelles
2 glycolate and 1 glutamate diffuse to peroxisome
Glycolate + O2 –> glyoxylate
Gloxylate + glutamate –> glycine + oxoglutarate
2 glycine –> 1 serine + CO2 + NH4 in mitochondrion
Serine –> hydroxypyruvate –> glycerate in peroxisome
Glycerate –> 3-phosphoglycerate in chloroplast
Why is the C2 Oxidative Photosynthetic Carbon Cycle bad?
Requires a long process of energeticly expensive reactions
Releases CO2 into atmosphere rather than locking it into processable molecule
What is an overview of C4 photosynthesis?
The reactions are spatially separated.
At peripheral sites (closer to atmosphere) PEP carboxylase catalyses the fixation of carbon into oxaloacetate and this is converted to malate or aspartate.
The 4-C acid moves across a diffusion barrier into less peripheral tissue.
The C4 acid is decarboxylated, producing CO2
The CO2 is fixed by the Calvin-Benson cycle.
What is an overview of FACE?
FACE – Free Air CO2 Enrichment
Net photosynthetic rate in C3 plants increased by ~20%
Net photosynthetic rate in C4 plants unchanged
What is a definition of first generation biofuels?
‘First generation biofuels’ are defined as those derived from the food parts of food crops
What are the top producing ethanol countries in 2020?
Total - 99,000
USA - 52,700 (53%)
Brazil - 30,500 (30%)
EU - 4,700 (6%)
What are the main crops used as First generation biofuels sources?
Currently feedstocks are either starch-rich (maize, wheat, cassava) or sugar-rich (sugar cane, sugar beet)
USA - Maize
Brazil - Sugar Cane
EU - Cereals and sugar beet
What is an overview of sucrose and starch synthesis?
Sucrose is the main form in which carbohydrate is translocated in the phloem.
Starch is an insoluble, stable carbohydrate reserve (two main forms, amylose an amylopectin (has branches).
Both sucrose and starch are synthesised from triose phosphate generated by the Calvin cycle
What is an overview of ethanol production from sucrose crops?
Sugar cane –(grind feedstock)–> Cane juice –(yeast fermentation)–> Ethanol (5-12%) –(distillation)–> Ethanol (95-99.8%)
What are the co-products of ethanol production from sucrose crops?
Co-products: bagasse (fibrous stalks, used as boiler fuel) and CO2 (some used in beverages)
What is the yield of ethanol production from sucrose crops?
Yield of sugar cane (Brazil) ~ 74 T/ha/year –> 58 T raw cane
1 T raw cane –> 740 kg juice (135 kg sucrose, 605 kg water) + 260 kg bargasse
135 kg sucrose –> 70 L ethanol (therefore sugar to ethanol efficiency = 76%)
Thus 1 ha –> 4000 L ethanol per year
What is the mechanism of the produciton of ethanol from starch crops (wet milling)?
Grain –(Soak grain with sulphuric acid and mill)–> Starch-rich endosperm + protein-rich germ and fibrous husks, –(Amylase + other enzymes (used on former)–> Glucose –> Yeast –(fermentation)–> Ethanol (5-12%) –(Distillation)–>Ethanol (95-99.8%)
What is the mechanism of the produciton of ethanol from starch crops (dry milling)?
Grain –(Mill dry grain directly)–> Seed granules + protein-rich, fibrous dried distillers grains (DDG) –(Amylase + other enzymes (used on former)–> Glucose –> Yeast –(fermentation)–> Ethanol (5-12%) –(Distillation)–>Ethanol (95-99.8%)
What is the reaction for ethanol as a fuel?
C2H5OH + 3O2 –> 2CO2 + 3H2O
What is an overview of ethanol as a fuel?
Gasoline is a range of hydrocarbons (C5H12 to C12H26)
Per litre, ethanol contains about two-thirds as much energy as gasoline
Ethanol though has a higher octane rating than gasoline and adding it to gasoline increases the octane rating – reducing the likelihood of ‘knocking’ (premature fuel combustion) and thus increasing efficiency.
What is an overview of ethanol and oxygen?
Ethanol contains oxygen (unlike gasoline) and this can aid the combustion process, reducing the emission of carbon monoxide, unburned hydrocarbons and carcinogenic particulates.
This also leads however to more reaction with atmospheric nitrogen and (marginally) increased nitrogen oxide (NOx) emissions.
How does ethanol improve environment?
Ethanol is low in sulphur (almost none), thus SOx emissions are reduced.
Carbon in ethanol was only recently fixed from the atmosphere thus net CO2 emissions may be greatly reduced
What is an overview of biodiseal production?
European Biodiesel production accounts for 41% of the world total
Main European crops are rapeseed and sunflower
Main US crop is soybean
What is an overview of lipid storage structure?
Most storage lipids are triacyl glycerols that accumulate in sub-cellular organelles called oil bodies
What is biodiseal chemistry?
Biodiesel is methyl or ethyl esters of fatty acids
Ester: carboxylic acid in which -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group
Transesterification reactions with methanol or ethanol
What is the reaction that produced biodiseal?
Triglyceride + Alcohol –> Fatty acid methyl esters (FAME) (Biodiesel) + Glycerin or Glycerol
Why is neutralisation required?
The levels of free fatty acids are assayed and quantity of base required to neutralize the acid is determined.
What is an overview of the neutralisation of free fatty acids?
An amount of base (usually NaOH or KOH) slightly in excess of that required for neutralisation is dissolved in the alcohol (methanol or ethanol).
Alcohol/base is reacted with the oil at elevated temperature (typically 50oC) for several hours (4 to 8 typically).
What is an overview of the processing stage in biodiesal formation?
The lower layer of the process is composed primarily of glycerol and other waste products.
The upper layer composed of biodiesel and alcohol is separated away and the alcohol removed (by distillation or extraction with water - the latter requires that the product is dried).
Often there are several washes with water to remove alcohol, hydroxide and soap.
What is the catalyst for biodiseal production?
Methanol is usually used as the catalyst in the commercial production of biodiesel as it is cheaper than ethanol and glycerol extraction is less problematic
What is the use of co-products of biodiesal production?
Glycerol is the primary co-product – used as a lubricant and in cosmetics and ink and as a preservative. Off-sets only about 5% of the cost of biodiesel production though.
What is an overview of biodiesal as a fuel?
Biodiesel contains 88 – 95% of the energy of petroleum diesel
Mixed with petroleum diesel it improves lubricity and raises cetane value (cetane number is a measure of ignition quality)
What are the problems with biodiesel?
Biodiesel is sensitive to cold. At lower temperatures it may gel.
Biodiesel has detergent-like properties, loosening and dissolving residues in engines and storage tanks. It can corrode rubber and rubber parts of conventional diesel engine need to be replaced.
Microbial degradation can be a problem but 1% petroleum diesel is sufficiently toxic to prevent this
What are the problems with first generation biofuels?
Food vs fuel: insufficient arable land to sustain both
‘Field-to-wheel’ analysis: CO2 emissions are still high
What is a breakdown of UK arable land?
Wheat - 32%
Sugar Beat - 3%
Rape seed - 9%
Total used - 44%
How much land is required to replace petrol with bioethanol?
UK petrol market ~ 14 million T/year
10% target requires 2.1 million T of bioethanol
3.5 T bioethanol /ha
Thus require approximately 0.6 million ha. This is ~10% of total arable land – just for 10% requirement and just for petrol.
How much is required to replace diesel with biodisesel?
UK diesel market ~21.3 million T/year
10% target requires 2.33 million T of biodiesel
1.3 T biodiesel/ha
Require approximately 1.8 million ha. This is ~31 % of total UK arable land – just for 10% requirement and just for diesel!
What is the ‘field to wheel’ CO2 savings of bioethanol?
Maize: 3,900 L/ha - GHG emissions 35-52% lower than gasoline
Sugarcane: 7,200 L/ha - GHG emissions 80% lower than gasoline
What is the ‘field to wheel’ CO2 savings of biodiesel?
Rapeseed, Soybean and Oil Palm - 5,700 L/ha - GHG emissions 29 - 65% lower than diesel
What is the ‘field to wheel’ CO2 savings of HVO (hydrotreated vegetable oil) diesel?
Oil Palm, Waste cooking oil, waste animal fats, rapeseed, soy and camelina - GHG emissions 45 - 70% lower than diesel
What is the amount of straw gained from corn and the amount of ethanol you can get from it?
Corn - 1:1 (LKg^-1)(staw to crop), 0.29LKg^-1 ethanol, 0.29 alchohol: crop ratio
What is the amount of straw gained from rice and the amount of ethanol you can get from it?
Rice - 1.4:1 (LKg^-1)(staw to crop), 0.28 LKg^-1 ethanol 0.39 alchohol: crop ratio
What is the amount of straw gained from wheat and the amount of ethanol you can get from it?
Wheat - 1.3:1 (LKg^-1)(staw to crop), 0.29 LKg^-1 ethanol, 0.38 alchohol: crop ratio
How much biofuel ethanol is produced and how much does it replace?
Total potential alcohol production from crop residue: 491 GL year-1
491 GL of alcohol could replace 353 GL of gasoline (32% of the global gasoline consumption)
What seperates plant cells?
Primary cell walls of adjacent cells are separated by the middle lamella
Some plants synthesise a multi-layered secondary cell wall (S1, S2, S3 opposite)
What is an overview of pectic polysaccharides?
Pectic polysaccharides (pectins) are a group of highly hydrated polysaccharides rich in galacturonic acid (GalA). They are major components of the middle lamella.
What is included in pectic polysaccharides?
They include homogalacturan (HGA) – highly methylated chains of α(1–>4)-GalA, xylogalacturanan, a class of substituted HGAs and rhamnogalacurans.
What is an overview of cellulose?
Cellulose is the main polysaccharide: 15-30% of primary cell walls and more of secondary cell walls.
What is the structure of cellulose?
Several dozen β(1–>4) glucan chains are tightly linked by hydrogen bonds and form a paracrystalline array called a microfibril.
The β(1–>4) glucan chains in a microfibril are parallel.
What is an overview of cross-linking glycans?
Cross-linking glycans (sometimes called hemicelluloses) hydrogen bond to the cellulose microfibrils.
What are the main cross-linking glycans?
The major cross-linking glycans are xyloglucans (XyGs) and glucuranoarabinoxylans (GAXs). XyGs cross-link the cell walls of all dicots and about half of monocots but the “commelinoid” monocots (includes the grasses) have GAXs.
What are type 1 cell walls?
Found in dicots and noncomelinoid moncots The have about equal quantities XyGs and cellulose.
The XyGs span gaps between microfibrils and lock them inton position. The XyG-cellulose matrix is embedded in pectin.
What are type 2 cell walls?
Type II walls have GAXs instead of XyG and are pectin poor
What is an overview of lignification?
The secondary cell walls of many plants are modified by the incorporation of lignins, irregular, insoluble polymers of phenylpropanoid derivatives
For example, Norway spruce lignin is almost entirely coniferyl alcohol while paracoumaryl alcohol is found almost exclusively in grasses
What is an overview of the production of lignins?
Synthesised from monolignols, either coniferyl alcohol, sinapyl alcohol or paracoumaryl alcohol. Different plants use different monolignols.
What are breakdowns of plant cell wall structure?
Species - Cellulose % : Hemicelulose % : Lignin %
Hardwood stems - 40 -55 : 24 - 40 : 18 - 25
Softwood stems - 45 - 50 : 25 - 35 : 25 - 35
Wheat straw - 30 : 50 : 15
Rice straw - 36 - 47 : 19 - 25 : 10 - 24
What is an overview of industrial cellulose?
Commercially, fungal enzymes are used to degrade lignocellulose. Trichoderma reesei cellulases are the current industry standard.
What is an overview of cellulose enzyme complexes?
Endoglucanase - randomly cleaves intermolecular (chain) bonds
Exoglucanase (exocellobiohydrolase) - removes 2 - 4 glc moieties from the chain ends
Cellobiase (β-glucosidase) - hydrolyses glucose dimers
What is an overview of pectinases?
Pectin degradation involves pectinases (endopolygalacturonases), pectate lyases, pectate methylesterases and other enzymes specific for the non GalA sugars
What is an overview of degradation of cross-linking glycans?
These are extremely diverse molecules with a very wide array of different sugars and linkages. Although in nature there are enzymes that are able to break all of the linkages, commercially these linkages pose a significant problem.
What are examples of fungi that can degrade cross-linking glycans?
Anaerobic fungi (Piromyces spp., Neocallimastix spp. and Orpinomyces spp.), which form part of the rumen microflora are source xylanases
Thermophilic fungi (such as Theromascus aurantiacus, Acremonium thermophilium) are being actively investigated as sources of these enzymes.
How are coss-linking glycans degraded?
Glucuranoaribnoxylans (GAXs) can be depolymerised by endo-β(1–>4) xylanases following removal of side chains with α-arabinofuransidases, α-glucuronidases, ferulic acid esterase and acetyl esterases.
Depolymerisation results in xylooligosaccharides (incl. xylotriose and xylobiose) that can be degraded to xylose by β-xylosidases.
What is the method for the production of ethanol from lignocellulose?
Lignocellulosic material –(Pretreatment:
Milling and/or treatment with acid or alkali and/or treatment with steam)–> either Enzymic hydrolysis or Acid hydrolysis —>Complex mixture of monosaccharides and non-degraded polymers (especially lignin) –Fermentation–> Ethanol (5-12%) –Distillation–> Ethanol (95-99.8%)
What are disadvantages of ethanol production from lignocellulose?
Difficult to release the sugars
Many of the sugars are not fermented by yeast
What is the overview of pre-treatments of ethanol production from lignocellulose?
Pre-treatments are designed to increase accessibility of the substrate to enzymes. Steam pre-treatment disrupts the lignin barrier – impregnation with SO2 reduces time and temperature required. Acids and alkalis hydrolyse a variety of chemical bonds.
How effecitve is duckweed for ethanol?
Enzyme cellulase concentrations of 4000 U g-1 got 80% glucose release
Steam explosion pretreatment solubilised starch and 230°C temperature steam explsuion gets 90+% of sugars
When sugars feed to 4x yeat get 90% conversion to ethanol
What is an overview of Lignocellulosic ethanol yields?
Cane bagasses - 424 L/tones biomass
Corn strover - 428 L/tones biomass
Rice straw - 416 L/tones biomass
Saw dust - 383 L/tones biomass
What is an overview of ethanol production from lignocellulose in real life?
Commercial ligocellulose bioethanol facility. The plant, owned and operated by the Mossi & Ghisolfi Group, will produce bioethanol from agricultural residues and Arundo donax (‘Giant cane’, a grass). The capacity is 50 million L per annum
What traits are selected for in lignocellulosic crops?
Yield - Photosynthetic efficiency and stomatal patterning
Feedstock quality - Cellulose quantity and structure and Lignin quantity and quality
Resource Use Efficiency - Water use efficiency and Nitrogen use efficiency (NUE)
What is an overview of fermentation?
Glucose to Pyruvate through glycolysis consuming 2NAD+
(Done twice) Pyruvate –(pyruvate decarboxylase)–> Acetaldehyde –(alchohol dehydrogenase)–> Ethanol (releasing NAD+)
NAD+ main product Ethanol is waste product
What is an overview of yeast?
Eukaryotic microorganisms
Classified in the kingdom Fungi (both Ascomycota and Basidiomycota) ~1,500 species
Unicellular (=‘yeast’ form; may also exhibit filamentous forms)
Reproduce by budding or binary fission’
What is an overview of bakers yeast?
Saccharomyces cerevisiae
Reproduces through budding
What are examples of High-oil algae and their oil content?
Botryococcus braunii - 25-75% of dry weight
Schizochytrium - 50-77% of dry weight
Nannochloropsis sp - 31-38%
What are the growth rates and yield of High-oil algae?
Doubling times during exponential growth can be as short as 3.5 h
Annual oil production from high-oil microalgae can be in the range of 58,700 to 136,900 L per hectare
What was the cheng and Timilsina quote about high oil algae?
“If this microalgal oil is used for biodiesel production, it would take approximately 1.0-2.5% of the current cropland in the US to meet 50% of the US transportation fuel needs” - Cheng & Timilsina (2011)
How much oil and biodiesel do different high oil algae produce?
High oil content - 136,900 L oil/ha year 121,104 kg biodiesel/ha year
Medium oil content - 97,900 L oil/ha year 86,515 kg biodiesel/ha year
Low oil content - 58,700 L oil/ha year 51,927 kg biodiesel/ha year
Only upper estimate fullfuls the quote
What is an overview of Open pond production systems?
Used since 1950s.
Natural waters (lakes, lagoons, and ponds) and artificial ponds or containers. Raceway ponds are the most commonly used artificial system
Direct flow of water with areas of CO2 infusion until harvested at the end
What is an overview of Photobioreactors (PBRs)?
Closed systems usually of glass or plastic tubes (generally <10 cm diameter)
Input of culture medium and CO2
Pumped around in across layers of 3d tubes but extremely expensive in part due to stacking layers
What is the production process for high-oil algae?
Algae photobioreactors or algal ponds –> Biomass harvested –> filtrated –> centrifuged –> Products
Oil extraction –> Anaerobic digester to make biogas or animal feed
Biodiesal process to make biodiesel
What is an overview of heterotrophic production of high-oil algae?
Heterotrophic production in which microalgae are grown on organic carbon substrates such as glucose in tank bioreactors can be employed. In one study using Chlorella protothecoides lipid concentration increased from 14.5% to 55.2% - autotrophic vs phototrophic growth
What is mixtrophical algae?
Some species can grow mixotrophically: photosynthesis utilises light for growth while aerobic respiration uses an organic carbon source.
What impacts lipid productivity in algae?
Lipid% of dry mass can be increased by nitrogen limitation.
Lipid levels increase and composition changes – triacyl glycerols increase and free fatty acids decrease.
Cell proliferation is prevented but carbon is still assimilated by the cell and converted to TAG lipids that are stored within existing cells thereby increasing the concentration
What are the downsides of limiting nitrogen?
BUT it can be argued that lipid yield is a more important consideration than % lipid. E.g. in Dunaliella salina:
N-sufficient conditions lipid yield: 0.46 g l-1 day-1
N-limiting conditions light 0.12 g l-1 day-1
What are ways to improve the algael biofuel production for yield?
Development or selection of fast-growing, high-lipid strains
Development or selection of thermo-tolerant strains
Development or selection of oxygen-tolerant strains
Improved competitiveness of oil-rich strains against wild strains;
What are ways to make algael biofuels more economcially viable?
‘Biorefining’ algae and developing co-products such as animal feed from the protein-stream or human food including ‘functional’ foods or using waste streams as ‘bio-fertiliser’.Reduced capital costs including the use of cheaper equipment;
Reduced operating costs including improved, lower-cost harvesting;
What is an overview of engineering salt tolerance in freshwater alga Chlamydomonas reinhardtii?
‘Genome shuffling’ - random mutagenesis, multiple rounds of sexual reproduction – combined with growth in increasingly saline conditions
After 4th genome shuffling the best lived in 700 nM NaCl concentrations
The progenitor strain – ‘initial’ – doesn’t grow at >300 mM NaCl
