Environmental Engineering Reference
In-Depth Information
Table 2.1
Detailed classification and characteristics of biofuels on generation basis
Biofuels
Basic technology
Feedstock
First generation
1. Bio-diesel
Transesterification of fats and oils
Rapeseed, sunflower oil soya
2. Plant oils
Transesterification, pyrolysis, micro
emulsification
Coconut oil, jojoba oil, sunflower
oil, rapeseed oil
3. Bio-gas
Microbial metabolism via
fermentation
Energy crops, waste material, pro-
teins, carbohydrates, cellulose,
fats
Second generation
1. Bio-alcohols
Breakdown of cellulosic biomass in
several steps including fermenta-
tion and hydrolysis
Wheat, wood, sugar cane and
bagasse
2. Wood diesel
Fischer tropsch process, gasification
Woody biomass
3. DMF
Conversion of carbohydrates to
DMF via acid catalyzed dehydra-
tion process reaction
Lignocellulosic biomass, waste
biomass carbohydrates
Third generation
1. Algal fuel
Use of bioreactors, pyrolysis,
transesterification
Marine or fresh water micro algae
can be in the form of solid, liquid or gases. Wood, charcoal and bagasse (sugar cane
after juice extraction) are some useful examples of solid biofuels which are exten-
sively consumed for domestic purposes such as cooking in rural areas of most third
world countries. Waste bagasse; the fibrous material obtained from the processing
of sugar cane is widely used for power generation in raw sugar mills. Liquid bio-
fuels like ethanol, methanol, plant oils and methyl esters produced from these oils
are biodiesel, whereas methane and producer gas are forms of gaseous biofuels. Ac-
cording to the research analysts, energy demand will increase with alarming celerity
up to more than 50 % between 2020 and 2030. Because of the emerging economies
of the developing countries in recent years, energy consumption will directly en-
hance the demand for renewable, cost effective energy generation sources.
The depleting life expectancy of natural fossil fuels in the world market has
led research institutes, policy makers and enterprises to discover alternative means
of generating transportation fuel. One such prominent and promising alternative
is “Biofuels” which not only contribute to diminishing the increasing bubble of
“Global Warming” but also generates substantial amount of energy in a less cum-
bersome manner. Biofuels are categorized according to their current and future
availability as first, second or third generation biofuels as shown in Table
2.1
. First
generation biofuels are manufactured using conventional technology. Starch, sugar
and vegetable oils are the main substrates used to provide the synthesis of first gen-
eration bio-fuels. Some common examples of first generation biofuels include bio-
diesel, biogas and vegetable oils. Second generation biofuels are considered more
preferable over the first generation biofuels, since they are obtained from biomasses
produced by non-food crops, cellulosic materials like wood and waste materials of
animals. Wood diesel, dimethyl ether and bio-alcohol are a few examples of second
generation biofuels.
