6 Flashcards
Why do we need alternative fuels?
To meet growing energy needs, ensure national energy security, reduce dependency on fossil fuels, and address environmental concerns.
What are biofuels?
Any liquid, solid, or gaseous fuel made from organic matter.
What are first generation biofuels and why are they controversial?
Derived from crops, can impact food markets if competing for land with agriculture.
What are second generation biofuels?
Produced from non-food crops or waste plant material.
What are third generation biofuels?
Oil generation using algae.
How is biodiesel produced?
From oils like rapeseed oil using transesterification methods.
What is the process for producing bioethanol from sugar cane?
sugar cane, which has 15% sucrose and essential nutrients for yeast fermentation to produce ethanol.
What are the main issues with first generation biofuels?
They may divert resources from the food chain, impact biodiversity, are not always renewable, require complex processes, and are often dependent on subsidies.
What are the advantages of biobutanol over bioethanol?
Higher energy density, non-corrosive, can be used directly or mixed with existing fuels.
What are the disadvantages of biobutanol production?
Production of inhibitors during fermentation, low productivity, high distillation costs, toxic.
What is second generation bioethanol used for?
As a liquid fuel in engines, domestic cooking, power generation, and fuel cells.
What are the properties of bioethanol?
Colourless liquid, flash point 12.8°C, ignition point 425°C.
What processes are involved in preparing plant waste for bioethanol production?
Acid hydrolysis, alkali treatment, steam explosion, solvent extraction followed by enzyme treatment.
What are the main challenges in using yeast for bioethanol production from plant waste?
Yeast strains are not effective at utilizing complex sugars, requiring breakdown of plant material before fermentation.
How does the production of bioethanol contribute to sustainability?
Bioethanol combusts as a clean fuel with CO2 release equal to the CO2 fixed in photosynthesis, not a net contributor to greenhouse gas emissions.
What potential feedstocks have future potential for ethanol production?
Macroalgae, chitin, and other waste materials like those from alcoholic beverages and glycerol.
Why can ethanol not be directly used in unmodified engines?
Can erode plastics and rubber, low ignition temperature means engines cannot fire at low temperatures.
What are the energy efficiency comparisons between bioethanol and petroleum fuels?
Less efficient than petroleum, resulting in less mileage per gallon or kilometer per liter.
Describe the production steps for 2nd generation bioethanol.
Pre-treatment of biomass, conversion to sugar, fermentation with yeasts, and distillation.
What is the SHF method in lignocellulosic ethanol production?
Separate Hydrolysis and Fermentation, good process control, time-consuming due to separate processes.
What is the SSF method in lignocellulosic ethanol production?
Simultaneous Saccharification and Fermentation, faster fermentation, more efficient enzyme activity, harder to control.
What is the CBP method in lignocellulosic ethanol production?
Consolidated BioProcessing, simplified process, no enzyme addition needed, requires GMO and significant research.
How do ethanol plant production capacities compare to oil refineries?
Ethanol plants produce 50 million gallons per year, while oil refineries can produce 6-7 billion gallons per year.
What are the main challenges in ethanol production from plant materials?
Plant cell walls contain lignin which is hard to digest; solutions include increasing sugars or reducing lignin in plants, and discovering or breeding new yeast strains.
