Lecture 14: Biofuels Flashcards
What is fracking?
Released vast amounts of hydrocarbons for human use
Established industrial process which getting cheaper
Who is the biggest oil producer?
USA
What did brazil do after the 1976 oil crisis?
Brazilian government institutionalised the National Alcohol Program to institute a switch from gasoline to ethanol from sugar cane
Mandatory blending of 10-22% ethanol fuel with gasoline
Why is the production of ethanol from sugar cane effective?
1) sugar is cheap (10cents per pound of refined sugar)
2) yeast naturally produces ethanol under anaerobic conditinos
3) yeast can be continually reused (reduces cost)
What is the yields of ethanol production from sugar cane?
V. high yields
1. ~74 T/ha/year -> 58 T raw cane
2. 1 T raw cane -> 740kg juice (135kg sucrose, 605kg water) +
260kg bargasse
3. 135kg sucrose -> 70L ethanol (76% sugar to ethanol efficiency)
4. Thus 1 ha -> 4000L ethanol per year
What is the environmental costs of ethanol production from sugar cane
- Inputs (all req some form of energy input)
a. land (may once have been rainforest) - tillage, planting
b. Water
c. Fertiliser (energy intensive to produce)
d. Labour (planting and cutting)
e. Transport - Outputs (pollution and fertiliser run off)
What are the main feedstocks for ethanol production in differet countries?
US - maize
Brazil - sugar cane
EU - cereals, sugar beet
China - maize, wheat, sugar beet
India - sugar cane, cassava
How is ethanol produced from startch?
Starch (corn) > enzymatic transformation to sugar > fermentation (30C, 36-48hrs) > distillation > ethanol
How is statch turned into sugar?
- pretreatment & milling
- Liquefaction + alpha-amylase enzyme (100C, 2hrs)
- Saccharification + glucoamylase (60C, 15-24hrs)
- SUAGR!
How is biodisel produced?
Oil bearing seeds (rape, soy, jatropha, palm) -> crushing -> (fats >) esterification -> separation -> glycerol biodiesel
How is biodiesel synthesised?
Neutralization of FFAs:
the levels of FFAs are assayed and quantity of base req to neutralize the acid is determined
Transesterification:
an amount of base (usually NaOH or KOH) slightly in excess of that req for neutralization is dissolved in the alcohol (methanol or ethanol). The alcohol or base is reacted with the oil at elevated temp (typically 50C) for several hours (4 to 8 typically)
Processing:
Lower layer = glycerol and other waste products. Upper layer = biodiesel and alcohol is separated. Often several water washes to remove alcohol, hydroxide, and soap.
What is the impact of cutting down rainforests for palm oil?
174 tons of carbon emissions are generated per hectare of rainforest converted to palm oil plantation
How did the EU drive deforestation?
Bad policies
1. EU mandated that 10% of transport fuel in every eu contry should be biofuels
- Biodiesel from argentinian soy beans and asian palm oil is cheaper than that from eu rape seed
- lots of import
- in terms of emissions, biodiesel is 80% worse than oil, palm oil is three times worse
- Eu has stated it wil cut out palm oil in biodiesel by 2030
what are 2nd generation bioguels?
Use of ‘non-food’ parts of plants
e.g., wheat straw, sugar cane bagasse, agave and other cacti, corn stover
Why is second generation biofuels challenging?
lignocellulose: hemicellulose, cellulose, ether, lignin
