Alternative Fuel

Alternative fuel
Abstract
Alternative fuels, known as non-
conventional or advanced fuels, are any
materials or substances that can be used as
fuels, other than conventional fuels.
Conventional fuels include: fossil fuels
(petroleum (oil), coal, and natural gas), as
well as nuclear materials such as uranium
and thorium, as well as artificial
radioisotope fuels that are made in nuclear
reactors.
Some well-known alternative fuels include
biodiesel, bioalcohol (methanol, ethanol,
butanol), chemically stored electricity
(batteries and fuel cells), hydrogen, non-
fossil methane, non-fossil natural gas,
vegetable oil, propane, and other biomass
sources.
Background
The main purpose of fuel is to store energy,
which should be in a stable form and can be
easily transported to the place of
production. Almost all fuels are chemical
fuels. The user employs this fuel to
generate heat or perform mechanical work,
such as powering an engine. It may also be
used to generate electricity, which is then
used for heating, lighting, or other
purposes.
Biofuel
Biofuels are also considered a renewable
source. Although renewable energy is used
mostly to generate electricity, it is often
assumed that some form of renewable
energy or a percentage is used to create
alternative fuels.
Biomass
Biomass in the energy production industry
is living and recently dead biological
material which can be used as fuel or for
industrial production.
Algae-based fuels
Algae-based biofuels have been promoted
in the media as a potential panacea to
crude oil-based transportation problems.
Algae could yield more than 2000 gallons of
fuel per acre per year of production. Algae
based fuels are being successfully tested by
the U.S. Navy Algae-based plastics show
potential to reduce waste and the cost per
pound of algae plastic is expected to be
cheaper than traditional plastic prices.
Biodiesel
Biodiesel is made from animal fats or
vegetable oils, renewable resources that
come from plants such as, soybean,
sunflowers, corn, olive, peanut, palm,
coconut, safflower, canola, sesame,
cottonseed, etc. Once these fats or oils are
filtered from their hydrocarbons and then
combined with alcohol like methanol,
biodiesel is brought to life from this
chemical reaction. These raw materials can
either be mixed with pure diesel to make
various proportions, or used alone. Despite
o e’s i ture prefere e, iodiesel ill
release smaller number of pollutants
(carbon monoxide particulates and
hydrocarbons) than conventional diesel,
because biodiesel burns both cleanly and
ore effi ie tl . E e ith regular diesel’s
reduced quantity of sulfur from the ULSD
(ultra-low sulfur diesel) invention, biodiesel
exceeds those levels because it is sulfur-
free.
Alcohol fuels
Methanol and ethanol fuel are primary
sources of energy; they are convenient fuels

for storing and transporting energy. These
alcohols can be used in internal combustion
engines as alternative fuels. Butanol has
another advantage: it is the only alcohol-
based motor fuel that can be transported
readily by existing petroleum-product
pipeline networks, instead of only by tanker
trucks and railroad cars.
Ammonia
Ammonia (chemical formula NH3) can be
used as fuel. A small machine can be set up
to create the fuel and it is used where it is
made. Benefits of ammonia include no need
for oil, zero emissions, low cost, and
distributed production reducing transport
and related pollution.
Carbon-neutral and negative fuels
Carbon neutral fuel is synthetic fuel—such
as methane, gasoline, diesel fuel or jet
fuel—produced from renewable or nuclear
energy used to hydrogenate waste carbon
dioxide recycled from power plant flue
exhaust gas or derived from carbonic acid in
seawater. Such fuels are potentially carbon
neutral because they do not result in a net
increase in atmospheric greenhouse gases.
To the extent that carbon neutral fuels
displace fossil fuels, or if they are produced
from waste carbon or seawater carbonic
acid, and their combustion is subject to
carbon capture at the flue or exhaust pipe,
they result in negative carbon dioxide
emission and net carbon dioxide removal
from the atmosphere, and thus constitute a
form of greenhouse gas remediation. Such
carbon neutral and negative fuels can be
produced by the electrolysis of water to
make hydrogen used in the Sabatier
reaction to produce methane which may
then be stored to be burned later in power
plants as synthetic natural gas, transported
by pipeline, truck, or tanker ship, or be used
in gas to liquids processes such as the
Fischer–Tropsch process to make traditional
transportation or heating fuels.
Carbon-neutral fuels have been proposed
for distributed storage for renewable
energy, minimizing problems of wind and
solar intermittency, and enabling
transmission of wind, water, and solar
power through existing natural gas
pipelines. Such renewable fuels could
alleviate the costs and dependency issues of
imported fossil fuels without requiring
either electrification of the vehicle fleet or
conversion to hydrogen or other fuels,
enabling continued compatible and
affordable vehicles. Germany has built a
250-kilowatt synthetic methane plant which
they are scaling up to 10 megawatts. Audi
has constructed a carbon neutral liquefied
natural gas (LNG) plant in Werlte, Germany.
The plant is intended to produce
transportation fuel to offset LNG used in
their A3 Sport back g-ton automobiles, and
can keep 2,800 metric tons of CO2 out of
the environment per year at its initial
capacity.
The least expensive source of carbon for
recycling into fuel is flue-gas emissions from
fossil-fuel combustion, where it can be
extracted for about US $7.50 per ton.
Automobile exhaust gas capture has also
been proposed to be economical but would
require extensive design changes or
retrofitting. Since carbonic acid in seawater
is in chemical equilibrium with atmospheric
carbon dioxide, extraction of carbon from
seawater has been studied. Researchers
have estimated that carbon extraction from
seawater would cost about $50 per ton.
Carbon capture from ambient air is more
costly, at between $600 and $1000 per ton
and is considered impractical for fuel
synthesis or carbon sequestration.

HCNG
HCNG (or H2CNG) is a mixture of
compressed natural gas and 4-9 percent
hydrogen by energy.
Liquid nitrogen
Liquid nitrogen is another type of
emissionless fuel.
Compressed air
The air engine is an emission-free piston
engine using compressed air as fuel. Unlike
hydrogen, compressed air is about one-
tenth as expensive as fossil oil, making it an
economically attractive alternative fuel.
Natural Gas Vehicles
Compressed natural gas (CNG) and Liquified
Natural Gas (LNG) are two a cleaner
combusting alternatives to conventional
liquid automobile fuels.
CNG Fuel Types
CNG vehicles can use both renewable CNG
and non-renewable CNG.
Conventional CNG is produced from the
many underground natural gas reserves are
in widespread production worldwide today.
New technologies such as horizontal drilling
and hydraulic fracturing to economically
access unconventional gas resources,
appear to have increased the supply of
natural gas in a fundamental way.
Renewable natural gas or biogas is a
etha e‐ ased gas ith si ilar properties
to natural gas that can be used as
transportation fuel. Present sources of
biogas are mainly landfills, sewage, and
a i al/agri‐ aste. Based o the pro ess
type, biogas can be divided into the
following: Biogas produced by anaerobic
digestion, Landfill gas collected from
landfills, treated to remove trace
contaminants, and Synthetic Natural Gas
(SNG).
Practicality
Around the world, this gas powers more
than 5 million vehicles, and just over
150,000 of these are in the U.S. American
usage is growing at a dramatic rate.
Environmental Analysis
Because natural gas emits little pollutant
when combusted, cleaner air quality has
been measured in urban localities switching
to natural gas vehicles Tailpipe CO2 can be
redu ed 5‐ 5% ompared to gasoline,
diesel. The greatest reductions occur in
medium and heavy duty, light duty and
refuse truck segments.
CO2 reductions of up to 88% are possible by
using biogas.
Similarities to Hydrogen Natural gas, like
hydrogen, is another fuel that burns cleanly;
cleaner than both gasoline and diesel
engines. Also, none of the smog-forming
contaminates are emitted. Hydrogen and
Natural Gas are both lighter than air and
can be mixed together.
Hydrogen
Hydrogen fuel is a zero-emission fuel which
uses electrochemical cells, or combustion in
internal engines, to power vehicles and
electric devices. It is also used in the
propulsion of spacecraft and can potentially
be mass-produced and commercialized for
passenger vehicles and aircraft.
Hydrogen lies in the first group and first
period in the periodic table, i.e. it is the first
element on the periodic table, making it the
lightest element in the universe. Hydrogen
is neither a metal nor a non metal but still is
considered as non metal. It acts as a metal
when compressed to high densities.

Since hydrogen gas is so light, it rises in the
atmosphere and is therefore rarely found in
its pure form, H2. In a flame of pure
hydrogen gas, burning in air, the hydrogen
(H2) reacts with oxygen (O2) to form water
(H2O) and releases heat. Other than water,
hydrogen combustion may yield small
amounts of nitrogen oxides.
Combustion heat enables hydrogen to act
as a fuel. Nevertheless, hydrogen is an
energy carrier, like electricity, not an energy
resource. Energy firms must first produce
the hydrogen gas, and that production
induces environmental impacts. Hydrogen
production always requires more energy
than can be retrieved from the gas as a fuel
later on. This is a limitation of the physical
law of the conservation of energy.
H2 Production
SMR Process
Steam reforming, sometimes called Fossil
fuel reforming is a method for producing
hydrogen or other useful products from
hydrocarbon fuels such as natural gas. This
is achieved in a processing device called a
reformer which reacts steam at high
temperature with the fossil fuel. The steam
methane reformer is widely used in industry
to make hydrogen. There is also interest in
the development of much smaller units
based on similar technology to produce
hydrogen as a feedstock for fuel cells.
Small-scale steam reforming units to supply
fuel cells are currently the subject of
research and development, typically
involving the reforming of methanol or
natural gas but other fuels are also being
considered such as propane, gasoline,
autogas, diesel fuel, and ethanol.
Electrolysis of water
Electrolysis of water is the decomposition of
water (H2O) into oxygen (O2) and hydrogen
gas (H2) due to an electric current being
passed through the water.
Equations
In pure water at the negatively charged
cathode, a reduction reaction takes place,
with electrons (e−
) from the cathode being
given to hydrogen cations to form hydrogen
gas (the half reaction balanced with acid):
Reduction at cathode: 2 H+
(aq) + 2e−
→
H2(g)
At the positively charged anode,
an oxidation reaction occurs, generating
oxygen gas and giving electrons to the
anode to complete the circuit:
Oxidation at anode: 2 H2O(l) → O2(g) + 4
H+
(aq) + 4e−
The same half reactions can also be
balanced with base as listed below. Not all
half reactions must be balanced with acid or
base. Many do, like the oxidation or
reduction of water listed here. To add half
reactions they must both be balanced with
either acid or base.
Cathode (reduction): 2 H2O(l) + 2e−
→ H2(g)
+ 2 OH-
(aq)
Anode (oxidation): 4 OH-
(aq) → O2(g) + 2
H2O(l) + 4 e−
Combining either half reaction pair yields
the same overall decomposition of water
into oxygen and hydrogen:
Overall reaction: 2 H2O(l) → H2(g) + O2(g)
The number of hydrogen molecules
produced is thus twice the number of
oxygen molecules. Assuming equal
temperature and pressure for both gases,
the produced hydrogen gas has therefore
twice the volume of the produced oxygen
gas. The number of electrons pushed
through the water is twice the number of

generated hydrogen molecules and four
times the number of generated oxygen
molecules.
Techniques
Fundamental demonstration
Two leads, running from the terminals of a
battery, are placed in a cup of water with a
quantity of electrolyte to establish
conductivity in the solution. Using NaCl
(table salt) in an electrolyte solution results
in chlorine gas rather than oxygen due to
a competing half-reaction.With the correct
electrodes and correct electrolyte, such as
baking soda, hydrogen and oxygen gases
will stream from the oppositely
chargedelectrodes. Oxygen will collect at
the positively-charged electrode (anode)
and hydrogen will collect at the negatively-
charged electrode (cathode). Note that
hydrogen is positively charged in the H2O
molecule, so it is "pulled out" at the
negative electrode. (And vice versa for
oxygen.)
Note that an aqueous solution of water
with chloride ions will, when electrolysed,
either result in either OH−
if the
concentration of Cl−
is low, OR in chlorine
gas being preferentially discharged if the
concentration of Cl−
is greater than 25% by
mass in the solution.
Hofmann voltameter
The Hofmann voltameter is often used as a
small-scale electrolytic cell. It consists of
three joined upright cylinders. The inner
cylinder is open at the top to allow the
addition of water and the electrolyte.
A platinum electrode is placed at the
bottom of each of the two side cylinders,
connected to the positive and negative
terminals of a source of electricity. When
current is run through the Hofmann
voltameter, gaseous oxygen forms at
the anode (positive) and gaseous hydrogen
at the cathode(negative). Each gas displaces
water and collects at the top of the two
outer tubes, where it can be drawn off with
a stopcock.
Industrial electrolysis
Many industrial electrolysis cells are very
similar to Hofmann voltameters, with
complex platinum plates or honeycombs as
electrodes. Generally the only time
hydrogen is intentionally produced from
electrolysis is for specific point of use
application such as is the case
with oxyhydrogentorches or when
extremely high hydrogen purity or oxygen is
desired. The vast majority of hydrogen is
produced from hydrocarbons and as a
result contains trace amounts of carbon
monoxide among other impurities. The
carbon monoxide impurity can be
detrimental to various systems including
many fuel cells.
High pressure electrolysis
High pressure electrolysis is the electrolysis
of water with a compressed
hydrogen output around 120-
200 Bar (1740-2900 psi). By pressurising the
hydrogen in the electrolyser the need for an
external hydrogen compressor is
eliminated, the average energy
consumption for internal compression is
around 3%.
High-temperature electrolysis
High-temperature electrolysis (also HTE or
steam electrolysis) is a method currently
being investigated for water electrolysis
with a heat engine. High temperature
electrolysis may be preferable to traditional
room-temperature electrolysis because
some of the energy is supplied as heat,
which is cheaper than electricity, and
because the electrolysis reaction is more
efficient at higher temperatures.

Combustive Properties of Hydrogen
• Wide range of flammability
• Low ignition energy
• Small quenching distance
• High auto ignition temperature
• High flame speed at stoichiometric
ratios
• High diffusivity
• Very low density
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