Biodiesel can
also be used as a heating fuel in domestic and commercial boilers, a mix of
heating oil and biofuel which is standardized and taxed slightly differently
than diesel fuel used for transportation. It is sometimes known as
"bioheat" (which is a registered trademark of the National Biodiesel
Board [NBB] and the National Oilheat Research Alliance [NORA] in the U.S., and
Columbia Fuels in Canada). Heating biodiesel is available in various blends.
ASTM 396 recognizes blends of up to 5 percent biodiesel as equivalent to pure
petroleum heating oil. Blends of higher levels of up to 20% biofuel are used by
many consumers. Research is underway to determine whether such blends affect
performance.
Older furnaces
may contain rubber parts that would be affected by biodiesel's solvent
properties, but can otherwise burn biodiesel without any conversion required.
Care must be taken, however, given that varnishes left behind by petrodiesel
will be released and can clog pipes- fuel filtering and prompt filter
replacement is required. Another approach is to start using biodiesel as a
blend, and decreasing the petroleum proportion over time can allow the
varnishes to come off more gradually and be less likely to clog. Thanks to its
strong solvent properties, however, the furnace is cleaned out and generally
becomes more efficient.[citation needed] A technical research paper[19]
describes laboratory research and field trials project using pure biodiesel and
biodiesel blends as a heating fuel in oil-fired boilers. During the Biodiesel
Expo 2006 in the UK, Andrew J. Robertson presented his biodiesel heating oil
research from his technical paper and suggested B20 biodiesel could reduce UK
household CO2 emissions by 1.5 million tons per year.
A law passed
under Massachusetts Governor Deval Patrick requires all home heating diesel in
that state to be 2% biofuel by July 1, 2010, and 5% biofuel by 2013.[20] New
York City has passed a similar law.
Historical background
Transesterification
of a vegetable oil was conducted as early as 1853 by scientists E. Duffy and J.
Patrick, many years before the first diesel engine became functional. Rudolf
Diesel's prime model, a single 10 ft (3 m) iron cylinder with a flywheel at its
base, ran on its own power for the first time in Augsburg, Germany, on 10
August 1893 running on nothing but peanut oil. In remembrance of this event, 10
August has been declared "International Biodiesel Day".[citation
needed]
It is often
reported that Diesel designed his engine to run on peanut oil, but this is not
the case. Diesel stated in his published papers, "at the Paris Exhibition
in 1900 (Exposition Universelle) there was shown by the Otto Company a small
Diesel engine, which, at the request of the French government ran on arachide
(earth-nut or pea-nut) oil (see biodiesel), and worked so smoothly that only a
few people were aware of it. The engine was constructed for using mineral oil,
and was then worked on vegetable oil without any alterations being made. The
French Government at the time thought of testing the applicability to power
production of the Arachide, or earth-nut, which grows in considerable
quantities in their African colonies, and can easily be cultivated there."
Diesel himself later conducted related tests and appeared supportive of the
idea.[21] In a 1912 speech Diesel said, "the use of vegetable oils for
engine fuels may seem insignificant today but such oils may become, in the
course of time, as important as petroleum and the coal-tar products of the
present time."
Despite the
widespread use of fossil petroleum-derived diesel fuels, interest in vegetable
oils as fuels for internal combustion engines was reported in several countries
during the 1920s and 1930s and later during World War II. Belgium, France,
Italy, the United Kingdom, Portugal, Germany, Brazil, Argentina, Japan and
China were reported to have tested and used vegetable oils as diesel fuels
during this time. Some operational problems were reported due to the high
viscosity of vegetable oils compared to petroleum diesel fuel, which results in
poor atomization of the fuel in the fuel spray and often leads to deposits and
coking of the injectors, combustion chamber and valves. Attempts to overcome
these problems included heating of the vegetable oil, blending it with
petroleum-derived diesel fuel or ethanol, pyrolysis and cracking of the oils.
On 31 August
1937, G. Chavanne of the University of Brussels (Belgium) was granted a patent
for a "Procedure for the transformation of vegetable oils for their uses
as fuels" (fr. "Procédé de Transformation d’Huiles Végétales en Vue
de Leur Utilisation comme Carburants") Belgian Patent 422,877. This patent
described the alcoholysis (often referred to as transesterification) of
vegetable oils using ethanol (and mentions methanol) in order to separate the
fatty acids from the glycerol by replacing the glycerol with short linear
alcohols. This appears to be the first account of the production of what is
known as "biodiesel" today.[22]
More recently,
in 1977, Brazilian scientist Expedito Parente invented and submitted for
patent, the first industrial process for the production of biodiesel.[23] This
process is classified as biodiesel by international norms, conferring a
"standardized identity and quality. No other proposed biofuel has been
validated by the motor industry."[24] Currently, Parente's company Tecbio
is working with Boeing and NASA to certify bioquerosene (bio-kerosene), another
product produced and patented by the Brazilian scientist.[25]
Research into
the use of transesterified sunflower oil, and refining it to diesel fuel
standards, was initiated in South Africa in 1979. By 1983, the process for
producing fuel-quality, engine-tested biodiesel was completed and published
internationally.[26] An Austrian company, Gaskoks, obtained the technology from
the South African Agricultural Engineers; the company erected the first
biodiesel pilot plant in November 1987, and the first industrial-scale plant in
April 1989 (with a capacity of 30,000 tons of rapeseed per annum).
Throughout the
1990s, plants were opened in many European countries, including the Czech
Republic, Germany and Sweden. France launched local production of biodiesel
fuel (referred to as diester) from rapeseed oil, which is mixed into regular
diesel fuel at a level of 5%, and into the diesel fuel used by some captive
fleets (e.g. public transportation) at a level of 30%. Renault, Peugeot and
other manufacturers have certified truck engines for use with up to that level
of partial biodiesel; experiments with 50% biodiesel are underway. During the
same period, nations in other parts of the world also saw local production of
biodiesel starting up: by 1998, the Austrian Biofuels Institute had identified
21 countries with commercial biodiesel projects. 100% Biodiesel is now
available at many normal service stations across Europe.
In September
2005 Minnesota became the first U.S. state to mandate that all diesel fuel sold
in the state contain part biodiesel, requiring a content of at least 2%
biodiesel.[27]
In 2008, ASTM
published new Biodiesel Blend Specifications Standards.[28]
Properties
Biodiesel has
better lubricating properties and much higher cetane ratings than today's lower
sulfur diesel fuels. Biodiesel addition reduces fuel system wear,[29] and in
low levels in high pressure systems increases the life of the fuel injection
equipment that relies on the fuel for its lubrication. Depending on the engine,
this might include high pressure injection pumps, pump injectors (also called
unit injectors) and fuel injectors.
The calorific
value of biodiesel is about 37.27 MJ/kg.[30] This is 9% lower than regular
Number 2 petrodiesel. Variations in biodiesel energy density is more dependent
on the feedstock used than the production process. Still these variations are
less than for petrodiesel.[31] It has been claimed biodiesel gives better
lubricity and more complete combustion thus increasing the engine energy output
and partially compensating for the higher energy density of petrodiesel.[32]
Biodiesel is a
liquid which varies in color —between golden and dark brown —depending on the
production feedstock. It is immiscible with water, has a high boiling point and
low vapor pressure. *The flash point of biodiesel (>130 °C, >266 °F)[33]
is significantly higher than that of petroleum diesel (64 °C, 147 °F) or
gasoline (−45 °C, -52 °F). Biodiesel has a density of ~ 0.88 g/cm³, higher than
petrodiesel ( ~ 0.85 g/cm³).
Biodiesel has
virtually no sulfur content, and it is often used as an additive to Ultra-Low
Sulphur Diesel (ULSD) fuel to aid with lubrication, as the sulfur compounds in
petrodiesel provide much of the lubricity.
Material compatibility
• Plastics: High density polyethylene
(HDPE) is compatible but polyvinyl chloride (PVC) is slowly degraded.[citation
needed] Polystyrenes are dissolved on contact with biodiesel.
• Metals: Biodiesel has an effect on
copper-based materials (e.g. brass), and it also affects zinc, tin, lead, and
cast iron.[citation needed] Stainless steels (316 and 304) and aluminum are
unaffected.
• Rubber: Biodiesel also affects
types of natural rubbers found in some older engine components. Studies have
also found that fluorinated elastomers (FKM) cured with peroxide and base-metal
oxides can be degraded when biodiesel loses its stability caused by oxidation.
Commonly used synthetic rubbers FKM- GBL-S and FKM- GF-S found in modern
vehicles were found to handle biodiesel in all conditions.[34]
Technical standards
Main article:
Biodiesel standard
Biodiesel has a
number of standards for its quality including European standard EN 14214, ASTM
International D6751, and others.
Low temperature gelling
When biodiesel
is cooled below a certain point, some of the molecules aggregate and form
crystals. The fuel starts to appear cloudy once the crystals become larger than
one quarter of the wavelengths of visible light - this is the cloud point (CP).
As the fuel is cooled further these crystals become larger. The lowest
temperature at which fuel can pass through a 45 micrometre filter is the cold
filter plugging point (CFPP). As biodiesel is cooled further it will gel and
then solidify. Within Europe, there are differences in the CFPP requirements
between countries. This is reflected in the different national standards of
those countries. The temperature at which pure (B100) biodiesel starts to gel,
varies significantly and depends upon the mix of esters and therefore the
feedstock oil used to produce the biodiesel. For example, biodiesel produced
from low erucic acid varieties of canola seed (RME) starts to gel at
approximately −10 °C (14 °F). Biodiesel produced from tallow tends to gel at
around +16 °C (61 °F). There are a number of commercially available additives
that will significantly lower the pour point and cold filter plugging point of
pure biodiesel. Winter operation is also possible by blending biodiesel with
other fuel oils including #2 low sulfur diesel fuel and #1 diesel / kerosene.
Another approach
to facilitate the use of biodiesel in cold conditions is by employing a second
fuel tank for biodiesel in addition to the standard diesel fuel tank. The
second fuel tank can be insulated and a heating coil using engine coolant is
run through the tank. The fuel tanks can be switched over when the fuel is
sufficiently warm. A similar method can be used to operate diesel vehicles
using straight vegetable oil.
Contamination by water
Biodiesel may
contain small but problematic quantities of water. Although it is not miscible
with water, it is, like ethanol, hygroscopic (absorbs water from atmospheric
moisture).[35] One of the reasons biodiesel can absorb water is the persistence
of mono and diglycerides left over from an incomplete reaction. These molecules
can act as an emulsifier, allowing water to mix with the biodiesel.[citation
needed] In addition, there may be water that is residual to processing or
resulting from storage tank condensation. The presence of water is a problem
because:
• Water
reduces the heat of combustion of the bulk fuel. This means more smoke, harder
starting, less power.
• Water
causes corrosion of vital fuel system components: fuel pumps, injector pumps,
fuel lines, etc.
• Water
& microbes cause the paper element filters in the system to fail (rot),
which in turn results in premature failure of the fuel pump due to ingestion of
large particles.
• Water
freezes to form ice crystals near 0 °C (32 °F). These crystals provide sites for
nucleation and accelerate the gelling of the residual fuel.
• Water
accelerates the growth of microbe colonies, which can plug up a fuel system.
Biodiesel users who have heated fuel tanks therefore face a year-round microbe
problem.
• Additionally,
water can cause pitting in the pistons on a diesel engine.
Previously, the amount of water contaminating
biodiesel has been difficult to measure by taking samples, since water and oil
separate. However, it is now possible to measure the water content using water-in-oil
sensors.[citation needed]
Water
contamination is also a potential problem when using certain chemical catalysts
involved in the production process, substantially reducing catalytic efficiency
of base (high pH) catalysts such as potassium hydroxide. However, the
super-critical methanol production methodology, whereby the transesterification
process of oil feedstock and methanol is effectuated under high temperature and
pressure, has been shown to be largely unaffected by the presence of water contamination
during the production phase.
Availability and prices
Global biodiesel
production reached 3.8 million tons in 2005. Approximately 85% of biodiesel
production came from the European Union.[citation needed]
In 2007, in the
United States, average retail (at the pump) prices, including federal and state
fuel taxes, of B2/B5 were lower than petroleum diesel by about 12 cents, and
B20 blends were the same as petrodiesel.[36] However, as part as a dramatic
shift in diesel pricing over the last year, by July 2009, the US DOE was
reporting average costs of B20 15 cents per gallon higher than petroleum diesel
($2.69/gal vs. $2.54/gal).[37] B99 and B100 generally cost more than
petrodiesel except where local governments provide a tax incentive or subsidy.
Production
For more details
on this topic, see Biodiesel production.
Biodiesel is
commonly produced by the transesterification of the vegetable oil or animal fat
feedstock. There are several methods for carrying out this transesterification
reaction including the common batch process, supercritical processes,
ultrasonic methods, and even microwave methods.
Chemically,
transesterified biodiesel comprises a mix of mono-alkyl esters of long chain
fatty acids. The most common form uses methanol (converted to sodium methoxide)
to produce methyl esters (commonly referred to as Fatty Acid Methyl Ester -
FAME) as it is the cheapest alcohol available, though ethanol can be used to
produce an ethyl ester (commonly referred to as Fatty Acid Ethyl Ester - FAEE) biodiesel
and higher alcohols such as isopropanol and butanol have also been used. Using
alcohols of higher molecular weights improves the cold flow properties of the
resulting ester, at the cost of a less efficient transesterification reaction.
A lipid transesterification production process is used to convert the base oil
to the desired esters. Any free fatty acids (FFAs) in the base oil are either
converted to soap and removed from the process, or they are esterified
(yielding more biodiesel) using an acidic catalyst. After this processing,
unlike straight vegetable oil, biodiesel has combustion properties very similar
to those of petroleum diesel, and can replace it in most current uses.
A by-product of
the transesterification process is the production of glycerol. For every 1
tonne of biodiesel that is manufactured, 100 kg of glycerol are produced.
Originally, there was a valuable market for the glycerol, which assisted the
economics of the process as a whole. However, with the increase in global
biodiesel production, the market price for this crude glycerol (containing 20%
water and catalyst residues) has crashed. Research is being conducted globally
to use this glycerol as a chemical building block. One initiative in the UK is
The Glycerol Challenge.[38]
Usually this
crude glycerol has to be purified, typically by performing vacuum distillation.
This is rather energy intensive. The refined glycerol (98%+ purity) can then be
utilised directly, or converted into other products. The following
announcements were made in 2007: A joint venture of Ashland Inc. and Cargill
announced plans to make propylene glycol in Europe from glycerol[39] and Dow
Chemical announced similar plans for North America.[40] Dow also plans to build
a plant in China to make epichlorhydrin from glycerol.[41] Epichlorhydrin is a
raw material for epoxy resins.
Production levels
For more details
on this topic, see Biodiesel around the world.
In 2007,
biodiesel production capacity was growing rapidly, with an average annual
growth rate from 2002-06 of over 40%.[42] For the year 2006, the latest for
which actual production figures could be obtained, total world biodiesel
production was about 5-6 million tonnes, with 4.9 million tonnes processed in
Europe (of which 2.7 million tonnes was from Germany) and most of the rest from
the USA. In 2008 production in Europe alone had risen to 7.8 million
tonnes.[43] In July 2009, a duty was added to American imported biodiesel in
the European Union in order to balance the competition from European, especially
German producers.[44] [45] The capacity for 2008 in Europe totalled 16 million
tonnes. This compares with a total demand for diesel in the US and Europe of
approximately 490 million tonnes (147 billion gallons).[46] Total world
production of vegetable oil for all purposes in 2005/06 was about 110 million
tonnes, with about 34 million tonnes each of palm oil and soybean oil.[47]