STUDENT ID: F04037100 NAME:

Introduction to Energy Technology (II)

Homework III.

1. Briefly Describe the four Generation of biofuels, and discuss the problem with first

generation which had been overcome through second, third and fourth biofuel.

1st Generation: Agricultural Products

First-generation biofuels rely on food crops as their feedstock. Corn, soy, palm and sugarcane

all have readily accessible sugars, starches and oils. So brewing them into biofuels simply

involves either fermenting the sugars or chopping up the fatty oils through transesterification.

The problems with first-generation biofuels are numerous and well-documented in the media,

ranging from net energy losses to greenhouse gas emissions to increased food prices.

Most biofuel start-ups are not working with first-generation feedstock but biofuel distribution

star tup, such as Propel Biofuels and Conserv Fuel, are working almost exclusively with

food-based biofuels because thats all thats currently available.

2nd Generation: Cellulosic Biomass

Also known as advanced biofuels, Cellulosic biofuels are fuels that can be manufactured from

various types of biomass. Biomass is a wide-ranging term meaning any source of organic

carbon that is renewed rapidly as part of the carbon cycle. Biomass is derived from plant

materials but can also include animal materials.

First generation biofuels are made from the sugars and vegetable oils found in arable crops,

which can be easily extracted using conventional technology. In comparison, second generation

biofuels are made from lignocellulose biomass or woody crops, agricultural residues or waste,

which makes it harder to extract the required fuel.

Second Generation biofuel are developed because first generation biofuels manufacture has

important limitations. First generation biofuel processes are useful but limited in most cases:

there is a threshold above which they cannot produce enough biofuel without threatening food

supplies and biodiversity. Many first generation biofuels depend on subsidies and are not cost

competitive with existing fossil fuels such as oil, and some of them produce only

limited greenhouse gas emissions savings. When taking emissions from production and

transport into account, life-cycle assessment from first generation biofuels frequently

approach those of traditional fossil fuels.

Second generation biofuels are also typically ethanol (and in some cases, related alcohols such

as butanol). The difference is that second generation ethanol is produced from cellulose rather

than sugar made from corn or sugar cane. By not using food crops as the source of sugar, second

generation biofuel production is more sustainable and has a lower impact on food production.

http://www.news.cornell.edu/stories/July05/ethanol.toocostly.ssl.htmlhttp://query.nytimes.com/gst/fullpage.html?res=9B02E3D71F39F93BA35751C0A96E9C8B63&sec=&spon=&partner=permalink&exprod=permalinkhttp://media.cleantech.com/2360/why-ethanol-production-will-drive-world-food-prices-even-higher-in-2008http://propelbiofuels.com/content/http://www.conservfuel.com/http://en.wikipedia.org/wiki/Biomasshttp://en.wikipedia.org/wiki/Carbon_cyclehttp://en.wikipedia.org/wiki/Sugarhttp://en.wikipedia.org/wiki/Vegetable_oilhttp://en.wikipedia.org/wiki/Lignocellulosic_biomasshttp://en.wikipedia.org/wiki/Biofuel#First-generation_biofuelshttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/Life-cycle_assessment

STUDENT ID: F04037100 NAME:

3rd Generation: Oil producing Algae

When it comes to the potential to produce fuel, no feedstock can match algae In terms of

quantity or diversity. The diversity of fuel that algae can produce results from two

characteristics of the microorganism. First, algae produce an oil that can easily be refined into

diesel or even certain components of gasoline. More importantly, however, is a second property

in it can be genetically manipulated to produce everything from ethanol and butanol to even

gasoline and diesel fuel directly.

Third generation biofuels, however, are the real prize. These are fuels much more similar in

composition and fuel value to petroleum. Also termed advanced biofuels, the so-called third

generation biofuels are essentially drop-in replacements for gasoline, diesel, and aviation fuel

produced from sustainable sources such as cellulose, municipal waste, or fast-growing algae.

Combining higher energy yields, lower requirements for fertilizer and land, and the absence of

competition with food, third generation biofuels, when available at prices equivalent to

petroleum derived products, offer a truly sustainable alternative for transportation fuels.

4th Generation: Engineered micro-algae

Four Generation Bio-fuels are aimed at not only producing sustainable energy but also a way

of capturing and storing co2. Biomass materials, which have absorbed co2 while growing, are

converted into fuel using the same processes as second generation biofuels. This process differs

from second and third generation production as at all stages of production the carbon dioxide

is captured using processes such as oxy-fuel combustion. The carbon dioxide can then be

geosequestered by storing it in old oil and gas fields or saline aquifers. This carbon capture

makes fourth generation biofuel production carbon negative rather than simply carbon neutral,

as it is locks away more carbon than it produces. This system not only captures and stores

carbon dioxide from the atmosphere but it also reduces co2 emissions by replacing fossil fuels.

2. What is the best energy crop so far on your opinion?

Forget corn. The heck with soybeans. Dont even mention palm oil. If anyone wants to take a

look at the wonder plant that has the potential to reduce the worlds appetite for oil and save

the planet from global warming, drive through the Great Plains and look out the window. What

you will see is grassswitch grass.

Unlike corn, using the cellulose in switch grass to make ethanol requires less energy from fossil

fuels. Furthermore, cellulose ethanol contains more energy than corn ethanol, so theres a

STUDENT ID: F04037100 NAME:

dramatic reduction in greenhouse gas emissions. Although there are no great switch grass

plantations or farms, scientists are currently working on various methods to make switch grass

the energy of the future. For instance researchers at Auburn University in Alabama grew test

plots of switch grass that produced 15 tons of biomass per acre. The scientists say that each

acre can also produce 1.150 gallon of ethanol each year (source: Oak Ridge National

Laboratory).

3. Pages 153 questions 4.

Q4: A farmer has a small herd of 100 pigs, and wishes to use their wastes to produce methane

to generate part of the electricity used by the farm. Assume that each pig generates 1 kg of

solid waste per day, which yields 0.8 m3 of methane at STP. Methane contains about 38

MJ/m3. Assume that you can convert 25% of this energy into electricity; find how many

kilowatts would the farmer be able to generate in this manner?

Answer to Question 4:

100 pigs

1 pig=1kg of waste=0.83m3of methane and 38MJ=1m3 methane. The formula below shows

how much kg of wastes produced by 100 pigs and how much mills of methane being produced

from that waste and then determining the amount of energy contained by that much methane

and then converting that energy into electricity (in kilowatts).

1 pig=1kg of waste=0.83m3of methane

100pigs=100kg (waste) = x (methane)

80kgm3= 1kgx (methane)

x (methane)=80m3

Now lets find how much energy is there in 80m3of methane

38MJ=1m3 methane

x (energy) =80m3(methane)

1m3(methane) x (energy) = 3040MJm3(methane)

x (energy)= 3040MJ

So 50%of energy from that 3040MJ is

50% multiplied by 3040MJ and so we get 1520MJ

To convert energy into electricity we have:

() =()

()

=

= . kW.

1000watt=1kW and 3600seconds=1hour