# Biodiesel

Biodiesel

Biodiesel sample
other names

Fatty acid methyl esters (FAME), "fatty acids, C16-18 and C18 unsaturated, methyl esters"

Brief description Fuel for self-igniting piston engines (diesel fuels), solvents
origin

biosynthetic

CAS number

67762-38-3

properties
Physical state liquid
viscosity

7.5 mm² / s (at 20 ° C)

density

(0.875… 0.885) kg / L (at 20 ° C)

calorific value

37 MJ / kg

Calorific value

40 MJ / kg

Cetane number

54-56 CZ

Melting range −10 ° C
Boiling range

about (176 ... undetermined) ° C

Flash point

180 ° C

Ignition temperature approx. 250 ° C
safety instructions
GHS labeling of hazardous substances
 no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Biodiesel (less often agro- diesel ), chemically fatty acid methyl ester , is a fuel that has the same use as mineral diesel fuel . The chemical industry produces biodiesel by transesterifying vegetable or animal fats and oils with monohydric alcohols such as methanol or ethanol .

Biodiesel mixes with petrodiesel in every ratio. Many countries therefore use biodiesel as a blend component for conventional diesel fuel. Since 2009, conventional diesel has been mixed with up to 7% biodiesel in Germany, marked as "B7" at filling stations. As a result of the decline in tax incentives since January 2013, sales of biodiesel as a pure fuel in Germany fell significantly.

Compared to diesel based on mineral oil, biodiesel produces fewer emissions , although the raw emissions of nitrogen oxides are higher. It is obtained from renewable raw materials , is biodegradable and has good lubricating properties , which is an advantage when using low-sulfur diesel.

Biodiesel is the biofuel that has so far made the largest contribution to supplying the transport sector in the European Union . Towards the end of the 20th century, there was broad social consensus on the introduction and expansion of biodiesel supply, as it was considered sustainable and climate-friendly. The growing consumption over the years led to an international biodiesel trade, which was partly connected with the expansion of agricultural land, for example through slash and burn . The social acceptance of widespread use depends on whether the raw materials used are sustainably provided and do not compete with food and feed production or lead to the extinction of species.

## nomenclature

Biodiesel consists of the term diesel , a deonym after Rudolf Diesel , and the prefix bio . This does not indicate an origin from organic agriculture, but to the vegetable or animal origin, in contrast to mineral oil. This is why the term agro- diesel is sometimes used, although there is a risk of confusion with the term agro-diesel . This refers to diesel, which is used in agricultural vehicles and work machines and is partially refunded for tax purposes.

The EN 14214 standard describes the minimum requirements for fatty acid methyl esters for the use of this class of substances as biodiesel fuel. The standard does not specify any raw material for the production of fatty acid methyl esters directly, but in contrast to the US standard ASTM D 6751 , the limit values ​​for parameters such as oxidation stability, the iodine number and the proportion of polyunsaturated fatty acids indirectly limit the raw material composition. According to EN 14214, FAME is the general abbreviation for all methyl esters based on vegetable and animal oils after the English name Fatty Acid Methyl Ester . Depending on the type of vegetable oil used, a distinction is made between palm oil methyl ester (PME), with vehicle manuals from the 1990s also using the abbreviation PME for vegetable oil methyl ester , sunflower methyl ester, rapeseed oil methyl ester (RME), also called rapeseed methyl ester or rapeseed diesel, and soybean oil methyl ester (SME). In addition, methyl esters based on used fats and animal fats are available, such as used fats methyl esters (AME) and animal fats methyl esters (FME).

Biodiesel is considered an alternative fuel of the first generation , for which only the oil, sugar or starch of the fruit is used. Second generation fuels use the whole plant.

Blends, i.e. mixtures of biodiesel with mineral diesel, are designated with a B and a number from 1 to 99, the number indicating the percentage of biodiesel in the blend. According to this nomenclature, B100 is the name for pure biodiesel.

## history

Rudolf Diesel (1883)

Patrick Duffy described the production of biodiesel by transesterifying vegetable oils with alcoholic potassium hydroxide as early as 1853 - years before Rudolf Diesel developed the diesel engine . The target product was the glycerine released during transesterification , which served as the raw material for the manufacture of glycerine soap.

Rudolf Diesel reported on the use of pure vegetable oil fuel for diesel engines at the World Exhibition in 1900 in a lecture to the Institution of Mechanical Engineers of Great Britain :

“At the 1900 Paris Exposition, a small Otto diesel engine was shown running on arachid oil (an oil made from peanuts) at the request of the French government , and it worked so smoothly that very few people noticed. The engine was designed to use mineral oil and then worked with vegetable oil without any changes. "

- Rudolf Diesel

During World War II , many nations studied the use of pure vegetable oils as motor fuel. Belgium , France , Italy , the United Kingdom , Portugal , Germany , Brazil , Argentina , Japan and the Republic of China tested and used vegetable oils as a diesel substitute. Brazil, for example, limited the export of rapeseed oil , while China used tung oil as a fuel substitute. The Japanese Navy operated one of their largest battleships , the Yamato , partly with refined soybean oil due to a fuel shortage .

The use of pure vegetable oils led to engine problems due to the higher viscosity compared to diesel , since the reduced fuel atomization caused increased soot deposits. Scientists and engineers investigated various technical approaches to reducing the viscosity, such as heating the fuel beforehand, mixing the vegetable oil with other fuels, pyrolysis , emulsification and transesterification , which ultimately led to biodiesel.

The work of the Belgian George Chavanne from the University of Brussels led to the first use of biodiesel as a fuel in road traffic. On August 31, 1937, he was granted the Belgian patent 422,877 for the transesterification of vegetable oils with ethanol and methanol to improve their properties for use as motor fuel. In 1938, Belgian transport companies successfully tested a palm oil-based biodiesel produced using this method while operating a bus route between Brussels and Leuven .

In the post-war period, however, the use of biodiesel was forgotten because of the easily accessible crude oil deposits and the associated high and inexpensive availability of mineral fuels. It was not until the oil crisis of the 1970s that the use of vegetable oils as fuel came back into focus. Research into the production and use of biodiesel took place in Brazil and South Africa in the 1970s . In 1983, the process for the production of fuel grade biodiesel was published internationally. The company Gaskoks in Austria built the first commercial biodiesel plant in Europe in 1989 with an annual capacity of 30,000 tons based on a South African patent. In 1993, Joosten Connemann from the Connemann oil mill received a patent for a process with which biodiesel can be obtained from rapeseed oil and other vegetable oils in a continuous process. In 2007 the twelve largest plants in the world used this method. Investors have been building many biodiesel plants in Europe since the 1990s, and as early as 1998, 21 European countries were carrying out commercial biodiesel projects. In September 2005 , the US state of Minnesota was the first state in the United States to introduce an obligation to mix 2% biodiesel with regular diesel. Since May 2012, a ten percent admixture has been mandatory; an increase to 20% is planned by 2015.

Germany regulates the use of biodiesel through the obligation to use according to the Biofuel Quota Act and through fuel standards . From 2007, 4.4% biodiesel was used in Germany with conventional diesel; since 2009, up to 7% biodiesel has been added to conventional diesel in accordance with the EN 590 fuel standard . In 2010 the consumption in Germany was 3.255 million tons of biodiesel. Furthermore, pure biodiesel (B100) can also be counted towards the biofuel quota.

In the course of political efforts to reduce carbon dioxide emissions , numerous other countries have introduced or are planning to introduce quota obligations. The European Union consumed a total of 11.255 million tons of biodiesel in 2010. Besides Germany, the largest consumers were France with 2.536 million tons and Spain with 1.716 million tons.

## Manufacturing

Vegetable and animal fats and oils are esters of glycerine with unbranched, saturated and unsaturated monocarboxylic acids , the fatty acids . The transesterification of these triglycerides with methanol , i.e. the replacement of the trihydric alcohol glycerine with the monohydric alcohol methanol, is the most common process for the production of biodiesel.

${\ displaystyle {\ text {Oils / Fats}} + {\ text {Methanol}} {\ xrightarrow [{}] {[{\ text {Cat.}}]}} {\ text {Biodiesel}} + {\ text {glycerine}}}$

Methanol is mainly used for cost reasons; other monohydric alcohols such as ethanol , propanols and butanols are also technically suitable for the production of biodiesel. In Brazil , for example, transesterification is carried out with bioethanol , which is available in large quantities . The fatty acid butyl esters have a lower pour point , which is particularly advantageous when using animal fats.

The transesterification is catalyzed by acids and bases , whereby higher reaction rates can be achieved by base catalysis . After the transesterification, the further process steps are the separation of glycerine and excess methanol and the processing of the by-products , such as the purification of the glycerine. The raw materials are recovered by distilling the excess methanol and recycling residual amounts of non-esterified fatty acids.

Schematic representation of the manufacturing process

### raw materials

Different types of soybeans

All vegetable and animal fats and oils are suitable as raw materials for the production of biodiesel. The vegetable oils are obtained from oil seeds or other oil-containing parts of plants. Different oils are preferred as raw materials depending on the climate, amount of precipitation and solar radiation.

In Europe, rapeseed oil is mainly used, which is obtained from the seeds of rapeseed (Brassica napus oleifera) . This seed has an oil content of 40 to 45%. The fatty acids present in rapeseed oil have a narrow carbon chain distribution and a constant degree of saturation . The oil is obtained in oil mills by pressing the rapeseed; rapeseed meal or rapeseed cake for the animal feed industry is produced as by-products. In Germany, the amount of protein-containing animal feed obtained in this way was around 3.2 million tons in 2012, which covered around 37.6% of German demand.

In North America, soybean oil is the main raw material, only a small part of the biodiesel is produced there from rapeseed oil. Palm oil is the main raw material for biodiesel in Southeast Asia, coconut oil is also used there. In addition, there are small amounts of processed vegetable oil residues and, in Central Europe, animal fats. Many other vegetable oils have been studied and used for biodiesel production, such as castor oil , sunflower oil and jatropha oil .

The biodiesel produced in Germany in 2012 consisted of 84.7% rapeseed oil, 10.7% used cooking and animal fats and 3% soybean oil. Only 1.6% of palm oil was processed in Germany. The raw materials or their mixtures must be selected so that the specifications according to the European standard EN 14214 or the American ASTM D 6751 standard are met.

In 2016, the share of palm oil, mainly from Indonesia and Malaysia, was around 19%. This can contribute to the clearing of rainforest.

The methanol required for the transesterification is a basic organic chemical and an alcohol produced on an industrial scale. The technical production of methanol takes place exclusively in catalytic processes from synthesis gas . The synthesis gas required for the production of methanol can be obtained through coal gasification from fossil raw materials such as coal , lignite and petroleum fractions or through steam reforming or partial oxidation of natural gas .

### Transesterification

In 2012, around 20 million tons of biodiesel were produced worldwide, corresponding to around 1% of annual fuel consumption. The production of biodiesel takes place in batch or continuous reactors with acid or basic catalysis.

Reaction equation for the production of biodiesel: in a triglyceride (left) with three different fatty acid residues (the fatty acid residue marked in
blue is saturated, the one marked green is single, the one marked red is triple unsaturated ). In the equilibrium reaction, glycerine is split off and biodiesel is produced, a mixture of several fatty acid methyl esters - three in the example.

The first step of the production is the transesterification with mixing of the methanol, catalyst and oil phase. The solution is kept at temperatures between 50 and 70 ° C. for several hours in order to complete the reaction. After the reaction has ended, the mixture is in two phases . The lighter phase contains biodiesel with additions of methanol, the heavier phase mainly glycerine, excess methanol and by-products such as free and neutralized fatty acids and water.

The biodiesel phase is separated off and washed in further steps to remove traces of alkali and the methanol, and finally dried by distillation. The glycerine phase must also be cleaned before further use, the excess methanol is recovered. The neutralized fatty acid forms a soap . This makes phase separation more difficult by forming an emulsion and must be made acidic with the formation of free fatty acids.

${\ displaystyle \ mathrm {\ CH_ {3} (CH_ {m}) _ {n} CO_ {2} Na \ + \ H ^ {+} \ longrightarrow \ CH_ {3} (CH_ {m}) _ {n } COOH \ + \ Na ^ {+}}}$

The transesterification can be catalyzed under acidic or basic conditions, the reaction rate being higher with basic catalysis than with acid catalysis. When using raw materials with a low content of free fatty acids, basic catalysts are preferred in technical practice. Sodium methoxide (NaOCH 3 ) and other methoxide , which are used dissolved in methanol, are particularly suitable as the basic catalyst .

The methanolate CH 3 -O - attacks one of the carbonyl carbon atoms of the triglyceride nucleophilically with the formation of a tetrahedral transition state . The methyl ester is formed with the release of the glycerol R 1 -O - . The glycerinate reacts with the excess methanol to form glycerin and methanolate. Although the reaction steps are in principle reversible , the insolubility of glycerol in the methyl ester phase shifts the reaction to the methyl ester side due to phase separation .

Potassium hydroxide or sodium hydroxide are less suitable as a catalyst because water is released when reacting with free fatty acids or methanol. The water reacts with the target product fatty acid methyl ester to form free acid and methanol, so the raw material should only contain small amounts of free water.

${\ displaystyle \ mathrm {\ CH_ {3} (CH_ {m}) _ {n} CO_ {2} CH_ {3} \ + \ H_ {2} O \ longrightarrow \ CH_ {3} (CH_ {m}) _ {n} COOH \ + \ CH_ {3} OH}}$

Raw materials with a high content of free fatty acids, which react with a basic catalyst to form soap , are esterified with acidic catalysts such as sulfuric acid or toluenesulfonic acid.

The methanol is added beyond the stoichiometric ratio of vegetable oil to alcohol in order to shift the reaction to the side of the methyl ester. In practice, an approximately two-fold stoichiometric excess of methanol has proven to be suitable. Partly transesterified mono- and diglycerides are formed as intermediate products, some of which remain in the biodiesel.

Modern biodiesel plants have a production capacity of around 100,000 to 200,000 tons per year.

### Alternative technologies and raw materials

Jatropha curcas seeds

Research focuses on raw materials, catalysis and process engineering. Since all fats and oils can be used as raw materials for the production of biodiesel, numerous new sources of fat and oil were investigated. Every year around 10,000 tons of alligator fat are produced , which are often disposed of as waste. A biodiesel made from it meets the American biodiesel standard. Waste fats from chicken processing can also be processed into biodiesel.

Great expectations are attached to plants such as jatropha , which can be grown with high oil contents in areas that are otherwise difficult to use for agriculture and therefore do not compete with food production. Also algae are of interest because of the high yields surface, wherein the recovery of the lipids , for example by extraction , is energy intensive.

Another research focus is the change in the chemical structure of biodiesel by alkene metathesis in order to adapt the boiling curve of biodiesel to that of diesel. The biodiesel contained in the engine oil does not evaporate due to its higher boiling temperature and can form polymers that are deposited as oil sludge . Metathesis can change the boiling behavior of biodiesel so that it can evaporate more easily from the engine oil.

A disadvantage of the current biodiesel production by transesterification is the use of homogeneous catalysts , the separation of which from the end product is complex and requires further production steps. Therefore, the use of heterogeneous catalysts that can be easily separated from the end product has been carefully investigated. The use of ionic liquids as a catalyst system was also investigated.

Transesterification with supercritical methanol in a continuous process offers a catalyst-free alternative without the use of potassium hydroxide . In this process, oil and methanol form a homogeneous phase and react spontaneously and quickly. The process is insensitive to traces of water in the raw material and free fatty acids are esterified into biodiesel . Furthermore, the step of washing out the catalyst is omitted. The process requires systems for high pressures and temperatures, the total energy consumption is comparable to the conventional process, since several process steps are omitted. One advantage is the lower water consumption.

The intensification of the mixing process of the poorly miscible oil and methanol phases through the use of ultrasound has been studied many times. This shortened the reaction time and lowered the reaction temperature. In order to increase the miscibility of the oil, methanol and catalyst phase, solvents such as tetrahydrofuran were used in large excesses of methanol. This made it possible to significantly shorten the reaction time with a conversion rate of more than 98%. This process requires the separation of the highly flammable solvent as an additional step.

Another branch of research focuses on the microbial production of biodiesel, using microorganisms such as microalgae , bacteria , fungi and yeast . Hemicellulose , a main component of plant biomass, is used as raw material . Genetically modified and metabolically optimized Escherichia coli strains can produce biodiesel de novo on an industrial scale from sustainable raw materials. In addition to biodiesel, the resulting product also contains fatty acids and alcohols .

Enzymes also catalyze the transesterification of oils with methanol. This process allows the esterification of free fatty acids in addition to the transesterification of the oil.

## properties

Biodiesel sample based on soybean oil

Depending on the raw material used, biodiesel is a yellow to dark brown liquid that is hardly miscible with water and has a high boiling point and low vapor pressure . Compared to mineral diesel, it is lower in sulfur and contains neither benzene nor other aromatics . In contrast to diesel fuel, biodiesel is not a hazardous good because of its higher flash point and therefore does not have a UN number . The lubricating properties of rapeseed methyl ester are better than that of mineral diesel, which reduces the wear and tear on the injection mechanism.

The European Committee for Standardization has in 2003 for biodiesel (fatty acid methyl ester - FAME), the standard EN 14214 specified. This was presented in a new version in 2010. This defines limit values ​​for the chemical composition, the content of inorganic components such as water , phosphorus or alkali metals , the total pollution and physical parameters such as the density or viscosity of the biodiesel. Furthermore, the standard defines important engine parameters such as oxidation stability, the cold filter plugging point , the cetane number and the cloud point . Biodiesel made from pure soy or palm oil has so far not been able to meet the EN 14214 standard, in contrast to ASTM D 6751, which is valid for biodiesel in the United States of America .

### Chemical composition

EN 14214 specifies the content of fatty acid methyl esters, a measure of the degree of transesterification, the purity and quality of the biodiesel to be at least 96.5% ( mol / mol ). The content of fatty acid methyl esters is determined according to EN 14103 by means of gas chromatography . The same method is used to determine the content of linolenic acid , a polyunsaturated fatty acid. The proportion of unsaturated fatty acids is also determined using the iodine number . According to EN 14214, the proportion of unsaturated fatty acids is limited to an iodine number of 120, which corresponds to the addition of 120 grams of iodine per 100 grams of biodiesel. The proportion of unsaturated fatty acid methyl esters and structural features, such as the chain length distribution of the fatty acid methyl esters, are linked to fuel properties such as the cetane number and oxidation stability.

Free fatty acids in biodiesel cause corrosion and form soaps with basic components such as alkali or alkaline earth salts . These can lead to filters sticking and clogging. The proportion of free fatty acids is determined by the acid number according to EN 14104, the upper limit being 0.5 milligrams of potassium hydroxide per gram of biodiesel. The proportion of partial and triglycerides is a measure of the degree of transesterification, the concentration of which is influenced by the conduct of the reaction. Triglycerides are usually the lowest, followed by di- and monoglycerides. According to EN 14214, biodiesel may contain a maximum of 0.80% (mol / mol) monoglycerides, the concentration of di- and triglycerides should be below 0.2% (mol / mol). The content of free glycerine should be less than 0.02% (mol / mol).

### Inorganic components

The sulfur content of biodiesel must not exceed 10  ppm . Fuels with a sulfur content of less than 10 ppm are considered sulfur-free by definition.

The water content of biodiesel is determined using Karl Fischer titration in accordance with EN ISO 12937. Since biodiesel is hygroscopic , the water content increases with transport and storage duration. Biodiesel should not contain more than 300 ppm water, because the water reacts with the methyl ester, releasing methanol and fatty acids.

The content of the alkali metals sodium and potassium is determined according to EN 14538 by optical emission spectrometry with inductively coupled plasma (ICP-OES) and should not exceed a total of 5 ppm. The metals come from the basic catalyst used in the manufacturing process. The alkaline earth metals calcium and magnesium come from the water used for the washing process of manufacture. The total limit is also 5 ppm.

The phosphorus content determined according to EN 14107 must not exceed a value of 4 ppm in biodiesel according to EN 12214 . The phosphorus comes mainly from phospholipids naturally occurring in vegetable oil .

The total contamination , a measure of the proportion of particles that cannot pass through the filter, is determined in accordance with EN 12662 and must be below 24 ppm. To determine this, the biodiesel is filtered and the filter cake is weighed.

### Physical and application-specific properties

The flash point is over 130 ° C and is therefore significantly higher than that of regular diesel. The lower limit is set at 101 ° C. The density , the quotient of the mass and the volume of a substance, is 0.88 g / cm³ for biodiesel, with the lower and upper limits of the specification being 0.86 and 0.9 g / cm³. The viscosity is comparable to that of diesel. It is determined in accordance with EN 3104 and must be between 3.5 and 5 mm² / s at 40 ° C.

The oxidation stability is a parameter for the chemical stability of biodiesel during storage. Oxidative degradation products can lead to deposits on the injection pumps or to filter misalignment. The oxidation of biodiesel takes place through atmospheric oxygen , which reacts with unsaturated fatty acids in radical reactions and leads to secondary and degradation products such as aldehydes , ketones , peroxides and low molecular weight carboxylic acids . The oxidation stability is defined by the induction time. A biodiesel sample is kept at a temperature of 110 ° C for several hours in a stream of air. The organic components of the air stream are absorbed in water, the conductivity of the absorbate being measured. A break point in the conductivity curve is known as the induction time. According to the standard, it must be less than 6 hours.

With Cloud Point a cold property of diesel fuel and heating oil is called. It is the temperature in degrees Celsius at which the first temperature-related cloudiness forms in a bare, liquid product when it cools under defined test conditions. The limit values ​​of the specification depend on the season and are between –0.6 and 7.4 ° C. The cloud point of biodiesel depends on the raw material used and, without the addition of additives, can be between around –10 ° C for rapeseed methyl ester and +16 ° C for animal fat methyl esters.

The temperature limit for filterability ( Cold Filter Plugging Point , CFPP) is the temperature at which a test filter becomes clogged with crystallized substances under defined conditions and is therefore a measure of its usability in the cold. It is determined according to the EN 116 method. The parameter can be influenced by adding suitable additives. The limit values ​​depend on the season and are –20 ° C in winter and 7.9 ° C in summer.

An important technical engine parameter is the cetane number of biodiesel. It is a dimensionless number to describe the ignitability . The ignitability is tested by comparing it with a mixture of cetane, an older name for n - hexadecane , and 1-methylnaphthalene , whereby the volume fraction of cetane in the comparison mixture corresponds to the cetane number. Both ASTM D 6751 and EN 14214 require a special engine or a single-cylinder CFR test method to determine the cetane number . The lower limit of the cetane number of biodiesel is 51 according to EN 14241.

## Drive and vehicle technology

Biodiesel for Mercedes 300D

Conventional diesel engines use small amounts of biodiesel as an admixture in mineral diesel without any problems. From January 1, 2007, a biofuel quota of 5% applied in Germany , from 2009 a quota of 7% biodiesel is required by law and is implemented by the mineral oil companies . A technical approval from the vehicle manufacturer is not required for this.

For higher admixtures and pure biodiesel operation, the engine must be biodiesel-proof, as evidenced by technical approvals from the vehicle manufacturer. The plastic parts that come into contact with the fuel , such as hoses and seals, must be resistant to biodiesel. Diesel tends to form sediments . The sediments are deposited in the fuel tank and the fuel lines and collect there. Biodiesel has good solvent properties and can therefore loosen deposits from the tank and lines that have arisen during diesel operation and which can clog the fuel filter. Coarse contamination can impair the injection system . In a vehicle that is not compatible with biodiesel, it can quickly break down the fuel-carrying hoses and seals , which can affect seals in the injection system and cylinder head gaskets . If the exposure time is long enough, biodiesel can attack car paint .

Biodiesel shows a tendency towards microbiological contamination, especially with a high water content. Among other things , this creates proteins that form slimy emulsions and influence the quality of the fuel.

One problem is the entry of biodiesel into the engine oil . As with normal diesel operation, unburned biodiesel reaches the cylinder wall and thus into the lubrication circuit. Pure diesel fuel begins to evaporate at around 55 ° C. If the engine oil reaches this temperature while driving, the conventional diesel evaporates from the engine oil and is added to the intake air via the crankcase ventilation and burned. Since rapeseed methyl ester does not begin to evaporate until around 130 ° C and the engine oil does not reach this temperature, biodiesel accumulates in the engine oil. As a result of higher local temperatures in the lubrication circuit, the biodiesel content gradually decomposes with coking and polymerization , which leads to solid or slimy residues. This and the deterioration in the lubricating properties with high biodiesel concentrations in the engine oil can lead to increased engine wear, which is why the oil change is necessary at shorter intervals when using biodiesel. Operation with biodiesel can be problematic for modern exhaust gas aftertreatment systems , as the traces of inorganics present in biodiesel can lead to deposits and damage these systems.

The energy content of diesel is around 36 MJ / l, while biodiesel has an energy content of 33 MJ / l. Because of the lower energy density , the use of biodiesel can result in a performance loss of around 5 to 10% or an equally increased fuel consumption.

Engines with common rail technology approved for biodiesel can optimize the injection time and quantity via a sensor, which provides the engine management with information about which fuel or which fuel mixture is being used. This makes it possible to comply with emission standards regardless of the fuel used and its mixing ratio. Various sensor systems based on spectroscopy or as conductivity detectors for the detection of the biodiesel content in fuel were tested.

A study by the Darmstadt Materials Testing Institute has shown that corrosion protection layers such as galvanizing can be attacked by biodiesel. The critical factor here was that biodiesel has a slightly hygroscopic effect and, if there is a water content, ester hydrolysis produces free fatty acids, which can lower the pH value and have a corrosive effect. This effect is completely prevented by adding conventional diesel.

## use

In 2005, the transport sector in Germany consumed around 20% of total energy, 80% of which was accounted for by road traffic. With 70% in 2011, biodiesel had the largest share of renewable energies in the transport sector. Road traffic is the area in which the use of biodiesel is most widespread; blends such as B5 and B7 are standard worldwide. In Germany, the consumption of biodiesel in the road traffic sector reached a preliminary peak in 2007 with a share of around 7%.

Between 1992 and 2013, transport performance rose by 24% in passenger transport and by 60% in freight transport , with energy efficiency increasing significantly over the same period. For goods traffic with heavy commercial vehicles and passenger cars with high mileage, which are largely powered by diesel engines, continued strong growth is expected, accompanied by a further increase in the share of diesel fuel of 66 to 76% of the demand for liquid fuels for internal combustion engines . The total demand for biodiesel will continue to rise accordingly through fixed admixture quotas.

### Rail transport

Distribution of biodiesel by rail

The rail transport sector relies heavily on petroleum-based fuels. Therefore, the use of biodiesel and its mixtures with the aim of reducing greenhouse gases and lowering petroleum consumption was investigated in many countries.

A locomotive of the Virgin Voyager Gesellschaft (train no. 220007 Thames Voyager ) owned by Richard Branson was converted to use a 20 percent biodiesel mixture . Another train, which will run on a 25% rapeseed oil-based mixture of 25% biodiesel during the summer months, was deployed in the eastern part of Washington State .

The entire fleet of Prignitzer Eisenbahn GmbH has been running on biodiesel since 2004. The vegetable oil previously used could no longer be used for the new railcars.

In India , the use of jatropha- based biodiesel has been studied extensively as this plant appeared best suited to growing in a variety of climatic conditions. The use of biodiesel blends was also investigated in Lithuania . It was shown that diesel locomotives work efficiently with a B40 blend based on rapeseed oil methyl ester.

### shipping

The Earthrace in Hamburg

The use of biodiesel instead of conventional diesel for commercial shipping or water sports activities on inland waters, which serve as drinking water reservoirs, reduces the risk of drinking water pollution due to its rapid biodegradability. For example, the Sir Walter Scott excursion boat on Loch Katrine in Scotland runs on biodiesel so that, in the event of an accident, the drinking water supply of Glasgow fed from this lake is not endangered by contamination with hydrocarbons, as would be the case with diesel. For Lake Constance, it is to be investigated whether biodiesel can be used as an alternative fuel. This would make a significant contribution to the protection of the waters of Lake Constance. The Federal Environment Agency also recommends the use of biodiesel as a fuel in sport boats under aspects of water protection.

The Earthrace trimaran was developed to demonstrate the general applicability of biodiesel in shipping . It was powered exclusively by biodiesel and in 2008 orbited the earth in 60 days, 23 hours and 49 minutes.

### air traffic

The use of biodiesel in aviation is still under development; the operation of commercial aircraft with low concentrations of biodiesel in mixtures with kerosene appears to be technically feasible without any significant changes to the aircraft, airport infrastructure or flight operations. The aviation industry used around 216 million tons of kerosene in 2011 . This means that the amount of biodiesel produced worldwide could replace around 7% of consumption. The company Green Flight International carried out the first flights using pure biodiesel for the majority of the route: in 2007 with the short-haul Aero L-29 Delfin in Nevada , the following year about 4,000 kilometers across the United States.

Previous attempts with Boeing 747 traffic machines have used biodiesel mixed with fossil kerosene . A test flight of the airline Virgin Atlantic from London Heathrow Airport to Amsterdam took place in February 2008 with a biofuel admixture of 20% , in December 2008 Air New Zealand carried out a test flight from Auckland in which an engine was powered by a mixture of kerosene and 50% biofuel was powered from jatropha oil . The use of biodiesel in ground vehicles and aircraft would also reduce particle emissions at airports.

### Heating oil

In principle, biodiesel can be used as bio- heating oil , with high requirements being placed on the chemical resistance of the heating system components used due to the good solvent properties. Unlike previous fuels, biodiesel as a substitute for heating oil is not subsidized by a comparable tax reduction, since heating oil is taxed less anyway. Heating oil with an admixture of 5 to 20% biodiesel has been on the market in Germany since 2008 and can be used in the heating market thanks to suitable additives.

## Political guidelines

The European Union, especially in the transport sector, is dependent on fuels based on mineral oil . Ever since the oil crisis in the 1970s, the general Anxiety took over dependence on crude oil imports to. The reporting on global warming , especially since the climate conference in Kyoto , also stimulated varied discussions about the influence of carbon dioxide emissions on the climate .

### European Union

The use of biodiesel in the EU is controlled through political measures with the fundamental aim of increasing the use of renewable energy sources . The EU pursues this policy for ecological reasons such as the reduction of greenhouse gases and the reduction of local environmental pollution through exhaust emissions , the creation of jobs and income and to contribute to a secure energy supply . For these reasons, the European Commission formulated a white paper in 1997 with the aim of doubling the share of renewable energies in total primary energy consumption to 12% by 2010. In a Green Paper issued in 2000 , the Commission continued to set out a strategy for Europe's energy security. With its biofuels directive , the European Union set a step-by-step schedule for the targets set for covering fuel consumption with biofuels. All Member States should cover 2% of their fuel consumption in the transport sector with biofuels by 2005. From 2010 it should be 5.75%, by 2020 it should be 10%. This could be done by using biofuels in their pure form, as an admixture or by using other renewable energies. This guideline contained the authorization of the member states to adjust the taxation of biofuels with regard to their ecological balance . Thereupon an intensive discussion began about the life cycle assessment of biodiesel in Germany and at the European level. The International Organization for Standardization published the associated methodology in the ISO 14044 standard , which is the standard for an ISO-compliant life cycle assessment.

Furthermore, on October 27, 2003, the Energy Tax Directive came into force. It is the legal basis for the national regulations and laws relating to tax breaks for biofuels. The guideline was only valid for six years, but could be extended if necessary. The member states were assured of free taxation as long as the environmental objectives were achieved. Member States reported the progress to the European Commission, which in turn reported to the European Parliament.

As part of a policy to promote renewable energy sources, the European Commission presented an action plan for biomass in 2005 with the aim of ensuring competitiveness , sustainable development and security of supply and reducing Europe's dependence on energy imports. The action plan was supplemented in 2006 by a European Union strategy for biofuels. The strategy served to promote biofuels in the EU and in developing countries, including research into second generation biofuels .

The Renewable Energy Sources Directive of April 23, 2009 replaced and repealed the Biofuels Directive . With this directive, the member states of the European Union stipulated the share of renewable energies in total energy consumption to be achieved by 2020. The goal by this year is for the share of renewable energies to be at least 20%.

A controversial issue is the impact of indirect land use change (English: indirect land use change (impacts of biofuels) , iLUC). It describes the effect that the planting of biomass, for example for palm oil production for biodiesel, displaces land use for food or feed production. In 2011, a study by the International Food Policy Research Institute (IFPRI) called for a tightening of the calculation of the climate footprint , taking into account indirect land use change. The IFPRI's model approach is based on complex econometric equilibria; other model approaches lead to different results. For biodiesel, the range of calculated additional emissions is between 1 and 1434 gCO 2 / MJ. Most models, however, lead to the conclusion that when the indirect land use change is included in the life cycle assessment, emissions are higher than in previous calculations.

### Germany

Tax relief led to low biodiesel prices (prices as of 2006)

As early as 1997, under the Kyoto Protocol, Germany committed itself to reducing its emissions in the first commitment period from 2008 to 2012 by an average of 5.2% compared to 1990, for example by promoting renewable raw materials for energy purposes. Before 2003, pure biofuels such as vegetable oil or biodiesel were not at all or only slightly affected by the mineral oil tax. An amendment to the Mineral Oil Tax Act on January 1, 2004 formally put biodiesel on an equal footing with petrodiesel; the tax portion on biodiesel was initially 0 cents per liter. As of 2003, the legislator introduced the compulsory admixture, the admixture share of 5% was also tax-privileged. Many, especially commercial road users, took advantage of this regulation, and the market share for biodiesel rose sharply as a result. The resulting tax shortfalls subsequently led to a reduction in tax advantages and the formulation of extended statutory admixture quotas in order to comply with the targets for reducing greenhouse gases.

The Biofuel Quota Act passed by the Bundestag in 2006 stipulated that the proportion of biofuels should increase to 6.75% by 2010 and to 8% by 2015. The law set requirements for the sustainable management of agricultural land and to protect natural habitats and demanded specific Kohlenstoffdioxidverminderungspotenzial. ( § 1 ) By the law amending the promotion of biofuels 15 July 2009 it was decided that this rate in 2009 at 5.25% to and freeze at 6.25% from 2010. Conventional mineral oil diesel has been allowed to be mixed with up to 5% biodiesel since 2004, and since February 2009 a new diesel standard has allowed the admixture of up to 7%. Since January 1, 2011, the proportion of biodiesel made from used cooking fats and animal fats has been added to the biofuel quota compared to the proportion of rapeseed, soy or palm oil methyl esters, weighted twice.

On June 29, 2006, the Bundestag passed the Energy Tax Act , which provided for the gradual taxation of biodiesel and vegetable oil fuel. From 2012, the full mineral oil tax rate applied to both substances. Pure biodiesel was taxed at nine cents per liter from August 2006, an annual increase of six cents was anchored in the Energy Tax Act. This led to a significant decrease in the proportion of biodiesel in the total diesel demand. That is why the Energy Tax Act was changed in June 2009. An annual increase was still planned, but the full tax rate did not apply until 2013. In December 2009, the taxation of biodiesel was changed again as part of the Growth Acceleration Act. The annual increase for 2011 and 2012 was suspended, so that the tax on biodiesel rose in a leap from 18.6 ct to 45.03 ct per liter at the beginning of 2013. Since the calorific value of biodiesel is lower than that of mineral oil, the volume-based tax rate will remain two cents below the rate for fossil fuels. The tax reduction for pure biofuels is granted in accordance with Section 50, Paragraph 1, Clause 5 of the Energy Tax Act only for the quantities of biofuels that exceed the minimum proportions specified in Section 37a, Paragraph 3 of the Federal Immission Control Act , the so-called "fictitious quota".

The Biofuel Sustainability Ordinance , issued on September 30, 2009, serves to implement the requirements of the Renewable Energy Sources Directive. According to this, producers are only allowed to use raw materials for the production of biodiesel that come from sustainable cultivation. The energy obtained is only taken into account within the framework of the Renewable Energy Sources Directive if it contributes to a reduction in greenhouse gas emissions of at least 35%. The percentage will rise to 50% from 2017. Accredited bodies issue sustainability certificates ( § 15 ) that confirm that the requirements have been met throughout the manufacturing process. According to the Federal Agency for Agriculture and Food , Germany saved around 7 million tonnes of carbon dioxide equivalent in 2011 through biofuels , corresponding to a saving of around 50% compared to fossil fuels. In 2012, however , the EU Commission announced that there was a European certificate and that the German proof of sustainability would therefore no longer be recognized.

### Austria

The biofuel directive was implemented in Austria in November 2004 by an amendment to the fuel ordinance in national law and adapted in June 2009. Accordingly, since October 2005 there has been an obligation to add 2.5% biofuels to all petrol and diesel fuels. The energy content of the fuels is used as the basis for assessing the blending rate. The proportion increased to 4.3% in October 2007 and in January 2009 the blending rate was increased to a maximum of 7%.

The implementation of the biofuel guideline in Austria was mainly achieved by adding biodiesel. In 2011 Austria had 14 biodiesel plants with a production capacity of almost 700,000 tons per year. Biodiesel and other heating and fuels that have been produced entirely or almost entirely from biogenic materials are exempt from the mineral oil tax.

### Switzerland

Switzerland has committed itself to reducing carbon dioxide emissions under the Kyoto Protocol . In Switzerland, up to seven percent is added to biodiesel, but there is no legal obligation to add biodiesel. Since July 1, 2008, biodiesel has been exempt from mineral oil tax in Switzerland , provided that it meets statutory ecological and social criteria. The associated greening of the mineral oil tax promotes environmentally friendly fuels from a fiscal point of view. These measures are not profitable for the federal budget, since a higher taxation of gasoline compensates for shortfalls in income. In Switzerland, only renewable fuels are permitted that do not compete with the food or feed industry (plate-trough-tank principle).

## Market and capacity development

A former biodiesel filling station

The development of the market and capacity for biodiesel goes hand in hand with the political requirements, in particular the tax incentives and the prescribed proportion of blending in petrodiesel. The share of biodiesel rose steadily for several years and reached a peak of around 12% on the German diesel fuel market in 2007, with the pure fuel being used in particular by commercial consumers such as freight forwarders . In 2007, trucking companies bought around half of the pure biodiesel, around 7% was sold through petrol stations and 3% to farmers. However, the price advantage of biodiesel has already decreased since 2006, partly as a result of the annually increasing tax burden, partly due to the price development on the vegetable oil and crude oil markets. After several years of increasing sales, sales of pure biodiesel fuel in Germany declined from 2008 onwards. The fuel-related additional consumption, technical residual risks and, if necessary, retrofitting costs could only be offset by a price advantage for biodiesel. In the peak year 2007, around 2.15 million tons of B100 were sold in Germany, in 2012 only 100,000 tons. The energy tax on pure biodiesel rose from originally 9 cents in 2006 to 18.6 cents from 2010 to 45 cents per liter on January 1, 2013. As a result, the sale of biodiesel as a pure fuel in Germany practically came to a standstill since January 2013.

The obligatory addition of biodiesel to fossil diesel increases sales in this segment, but this did not compensate for the losses in the case of pure fuel. The Biofuels Directive of May 2003 required that from December 31, 2005, EU member states must use at least 2% and by December 31, 2010 at least 5.75% of the fuels intended for transport from renewable sources. A quota of 5.8% was achieved. Austria implemented the EU directive early and from November 1, 2005, filling stations only offered diesel with 5% biodiesel additive and since February 2009 only diesel with 7% biodiesel.

Biodiesel sales in Germany
year Pure fuel
(in million liters)
Total
(in kilotons)
2000 not specified 340
2001 163 450
2002 190 550
2003 360 810
2004 477 1,180
2005 589 1,970
2006 539 2,870
2007 2,150 3,320
2008 1,230 2,700
2009 270 2,430
2010 330 2,530
2011 110 2,420
2012 100 2,230

The cultivation of rapeseed as a raw material for biodiesel production led to an expansion of the cultivation areas, which in Germany are largely in the eastern German states of Mecklenburg-Western Pomerania , Saxony-Anhalt , Brandenburg and Saxony . At the same time, the production capacity for biodiesel also increased; between 2004 and 2007 alone, the capacity quadrupled from 1.2 to 4.8 million tons. In 2011, 22.12 million tons of capacity were already available.

In 2012, a total of 51 manufacturers produced biodiesel in Germany, 31 of which were based in the new federal states . In 2012, a total of 17,900 people were employed in the biodiesel industry. However, due to the political framework and the market situation, capacities are often not fully utilized. The plant utilization in 2006 was around 81%, but by 2010 it had fallen to around 43%.

In 2012, the European Union dominated the global biodiesel market as the largest manufacturer and consumer. This is explained by the market share of registered passenger cars with diesel engines . It is around 55% in Western Europe, compared to 2.6% in the United States. In 2010, Germany and France produced the largest quantities of biodiesel, followed by Spain and Italy. With the abolition of the tax concessions and the introduction of the quantity-defined blending quotas, the refineries had an incentive to add inexpensive imported biodiesel based on soy and palm oil.

By 2009, much of the imported biodiesel came from the United States . The reason was the 2004 United States Congress passed tax break on biodiesel. It made it possible to import biodiesel into the United States, mix less than 1% petrodiesel with B99 and, after taking advantage of the tax break of around USD 1 per gallon , export it to the EU. The customs duties levied on B99 by the EU from March 2009 put an end to this so-called splash and dash practice ('Splash and Dash' refers to a term for a short stopover taken from motorsport ). Since March 2009, the import share of biodiesel from countries such as Canada and Singapore has increased . This was US biodiesel that was exported through these third countries. In 2010 Argentina exported 64 to 73% of the biodiesel produced there from soybean oil to the European Union. Argentina has a high export tariff on agricultural products , while the tariff is lower on processed products such as biodiesel. The price advantage is around 140 to 150 euros per ton of soybean oil methyl ester compared to soybean oil. In 2010 Indonesia exported around 80% of domestic palm oil-based production to the EU, mainly to the Netherlands , Italy and Spain .

## Ecological aspects

Since biodiesel is made from renewable raw materials, its use replaces petroleum-based fuels, the future availability of which is considered to be limited in the medium term. In addition, as a renewable energy source, biodiesel reduces the German energy supply's dependency on imports in the motor vehicle sector, as there is currently no alternative drive in sufficient quantity and efficiency. In 2011, biofuels contributed 120  PJ to primary energy consumption in Germany. Lowering carbon dioxide emissions was the original goal of using biodiesel. In addition to the use of external energy associated with greenhouse gas emissions in the production of biodiesel, the life cycle assessment must also consider the effects caused by changes in land use.

The investigation of the biological degradability of biodiesel and its blends by measuring the carbon dioxide development showed that biodiesel of various origins is easily biodegradable and is therefore less polluting than conventional diesel if it leaks. The latter is classified as hazardous to water in water hazard class 2, while biodiesel has been classified as slightly hazardous to water in water hazard class 1. Pure vegetable oil is not considered to be hazardous to water. For biodiesel of various origins, degradation rates between 84 and 89% were found within 24 hours. The values ​​are comparable to the breakdown of dextrose . Pure vegetable oil was degraded more slowly, with rates found between 76 and 78%. Pure diesel was degraded to 18%.

Gas chromatographic examinations of the breakdown of B50 showed that the rate of breakdown of the diesel fraction doubled compared to that of pure diesel. Therefore, biodiesel was considered for cleaning oil polluted beaches. Studies have shown that the degradation of biodiesel and its blends on the contaminated soil changed the microbiological communities.

The rapid biological degradability of biodiesel can have a disadvantage in practical use in motor vehicles, since it is associated with poor aging resistance. After improper and long storage of biodiesel or its blends, microbiological contamination, oxidation and water enrichment can worsen the properties of the biodiesel and lead to partial biological degradation. This can be counteracted by adding small amounts of petrodiesel - even 1% petrodiesel is sufficient.

### Exhaust emissions

The low aromatic and sulfur content of biodiesel reduces the emission of sulfur dioxide and particles. Compared to diesel fuel, a reduction in emissions of hydrocarbons , carbon monoxide and fine dust is found. This is mainly attributed to the oxygen content of biodiesel. It was found that the emission rate for hydrocarbons such as 2,2,4-trimethylpentane , toluene , xylenes and for polycyclic aromatic hydrocarbons is reduced by up to 90% when using biodiesel and blends. The reduction in oxygen-containing components such as formaldehyde or acetaldehyde was 23 to 67%, although the results are inconclusive. A significant dependence of the proportion of unsaturated fatty acids in biodiesel on the emission characteristics was found. The emission of volatile organic compounds from blends such as B20 was 61% lower than from diesel.

In contrast, most studies report increased emissions of nitrogen oxides . In addition to biodiesel-specific factors such as the source of raw material used, the level of nitrogen oxide emissions depends on engine-related factors such as injection timing , ignition delay or the adiabatic flame temperature. Modern engines with optimized injection technology or exhaust gas recirculation as well as advanced catalytic converter systems reduce nitrogen oxide emissions considerably. When operated with biodiesel blends such as B7, modern vehicles meet the emission standards for diesel engines. The raw emissions can be reduced by using NO x storage catalysts or selective catalytic reduction systems.

### Co-products

In the production of biodiesel from oil plants, there is hardly any waste, since all by- products are recycled. Rapeseed straw is chopped up and worked into the soil as an organic fertilizer . It contributes to the preservation of the humus body and thus to soil fertility . The production of oil plants in mixed crop cultivation or within the framework of crop rotation can prevent soil leaching and increase the yield of food in the long term, which can reduce the use of herbicides. Corresponding tests have already been carried out in practice and have resulted in positive results. The main source of biodiesel used in Germany, rapeseed , is grown in the same field about every 3 to 4 years.

Rape-cake and soybean cake , produced during the pressing with a residual oil content of about 10%, are used as high-quality feed.

The glycerine produced during transesterification can be reused in the chemical industry, for example in cosmetics . Monomers such as 1,3-propanediol , epichlorohydrin , acrylic acid and propene can be made from glycerine. The functionalization of glycerine leads to ethers , acetals , ketals and esters , which can be used as fuel additives for gasoline or diesel. With genetically modified Escherichia coli strains, 1,2-propanediol can be produced from the crude glycerine obtained during biodiesel production.

### Climate impact

The climate neutrality of biodiesel is controversial. The carbon dioxide binding during the growth of the plant must not only be compared with the carbon dioxide release during combustion, but also the emissions of climate-relevant substances during cultivation, production and use must be taken into account. In addition to carbon dioxide, nitrous oxide emissions, which are controversial in terms of their amount, play a role here and are considered to be an important source of ozone-damaging emissions. For the cultivation of rapeseed, an emission factor for nitrous oxide from the use of nitrogen fertilizers is assumed to be 0.0125 kg N 2 O / kg per kilogram of nitrogen equivalents applied. Depending on the study, the climate balance of biodiesel is estimated to be around 20 to 86% more favorable than that of mineral oil diesel. In 2010, the US Environmental Protection Agency (EPA) published an extensive study on the life cycle assessment of biodiesel based on soybean oil and waste fat, which also looked at changes in land use caused by oil crop cultivation . Among other things, the energy required for biodiesel production, the international land use change, the required operating resources, the use of fertilizers , the consumption of mineral fuels for distribution, the direct land use change and methane emissions were considered . A 57% reduction in greenhouse gases compared to mineral diesel was found, with values ​​of 22 to 86% being determined in a confidence interval of 95%. An 86% reduction was determined for biodiesel made from used fats.

### External energy demand

The production of the amount of biodiesel corresponding to 1 kg diesel equivalent requires considerable amounts of energy for the production of methanol, fertilizers , transport and the processing process.

The following applies to the amounts of energy (total energy), (energy requirement of biodiesel production itself) and (actually available amount of energy of biodiesel): ${\ displaystyle E _ {\ mathrm {ges}}}$${\ displaystyle E _ {\ mathrm {prod}}}$${\ displaystyle E _ {\ mathrm {net}}}$

${\ displaystyle E _ {\ mathrm {ges}} = E _ {\ mathrm {prod}} + E _ {\ mathrm {net}} = E _ {\ mathrm {net}} \ cdot {\ frac {k} {k-1 }}}$,

where the ratio k is comparable to the Carnot efficiency of a heat pump .

An amount of energy of 25 MJ / kg must be used for extraction, including further processing into biodiesel (plowing, sowing, treating with plant protection, fertilizing, harvesting, esterifying). In contrast, biodiesel has a calorific value of 37 MJ / kg.

The ratio k (cf. petroleum: k about 10) is accordingly

${\ displaystyle k _ {\ text {PME}} = {\ frac {37 \, \ mathrm {\ frac {MJ} {kg}}} {25 \, \ mathrm {\ frac {MJ} {kg}}}} = 1 {,} 48}$

in contrast to

${\ displaystyle k _ {\ text {Diesel fuel}} = {\ frac {43 \, \ mathrm {\ frac {MJ} {kg}}} {5 \, \ mathrm {\ frac {MJ} {kg}}}} = 8 {,} 6}$.

This representation does not take into account that with conventional diesel, chemically bound energy (crude oil) has to be added, which is taken from a finite reservoir. With biodiesel, on the other hand, the radiant energy of the sun is neglected, which is already available and practically inexhaustible. Assuming k = 1.48, the required cultivation area roughly triples; around 29.8 m² of cultivation area are required for 1 kg of diesel equivalent provided. One reason why the energy yield is relatively low is that only the oil fruits are used and the remaining biomass residue (rapeseed straw and rapeseed meal) is not used for energy. In an alternative form of fuel production from biomass to Sundiesel , the entire plant is used, which roughly doubles the gross fuel yield .

In studies of rapeseed cultivation for biodiesel production in Poland and the Netherlands , values ​​between 1.73 to 2.36 in Poland and from 2.18 to 2.60 in the Netherlands were found for the harvest factor ( Energy Return On Energy Invested, EROEI ) found.

### Space requirement

Rapeseed fields

The Federal Environment Agency stated in a report dated September 1, 2006:

“Because of the limited arable land, rapeseed grown in Germany can replace a maximum of around five percent of the diesel fuel required in the transport sector and one to four percent of greenhouse gas emissions in this area can be avoided. For this, half of the entire German arable land would have to be used for biodiesel rape cultivation in a four-year crop rotation, which is rather unrealistic. The actual potential is therefore more in the order of 1 to 2% of the amount of diesel. "

In the US, processing the entire soybean crop into biodiesel would only meet 6% of demand. In relation to the global demand for diesel-like fuels, palm oil methyl ester could become an important fuel both because of the oil yield of the plant and the size of the potential cultivation area. The area required for the production of, for example, 1 kg of biodiesel results from the following calculation:

The biodiesel yield per square meter is around 0.12 to 0.16 liters of biodiesel per year. With a density of 0.88 kg / l, this is around 0.14 kg biodiesel / m². In 2015 around 37 million tons of diesel fuel were used in Germany . Diesel has a calorific value that is around 9% higher than that of biodiesel. In order to provide 1 kg of diesel equivalent, the yield of around 7.8 m² of cultivation area is required. In order to replace 37 million tons of diesel fuel with biodiesel, since rape cannot be cultivated in the two to three following years due to self- intolerance, approx. 4 × 7.8 m² / kg × 37,000,000 t = 1,154,400 km² of arable land would be required.

In 2006 about 50% of the area of ​​the Federal Republic of Germany of 357,121 km² was used for agricultural production, so more than 6 times the total agricultural area of ​​Germany would be required to obtain sufficient biodiesel from rapeseed.

As early as 2006, the demand for vegetable oils as biodiesel and vegetable oil fuel exceeded the domestic cultivation of rapeseed of 1.5 million tons with 3.4 million tons, so that the rest had to be imported.

### biodiversity

The transformation of natural habitats through population development and the associated expansion of settlement areas and the supply infrastructure is one of the main factors for the reduction of biodiversity . In order not to intensify this effect by growing plants for the production of biodiesel, areas with a high level of biodiversity must be protected. A key demand for the sustainable production of biodiesel is the preservation of biodiversity (English: biological diversity or biodiversity ) in the cultivation of energy crops.

Vegetable oils for the production of biodiesel, which according to the Renewable Energy Sources Directive should be regarded as sustainably produced, must not be extracted on areas with great biodiversity. This includes all areas not converted for agricultural purposes after 2008 such as primary forests, nature reserves and areas with threatened or endangered ecosystems . The application of the rules for biodiversity is a criterion for protecting endangered areas from a change in land use. Biodiversity is regarded as a protected good with a global depth of effect and can be demanded as a binding property of trade goods in accordance with the rules of the World Trade Organization .

Differences in terms of the development of biodiversity can be identified both in terms of the plant cultivated and the geographical location. It was found that between 1990 and 2005 more than 50% of the new oil palm plantations in Malaysia and Indonesia took place in rainforest areas at the expense of biodiversity. When planting fallow land with oil-producing, xerophytic plants such as Jatropha curcas , it is expected that this will lead to an improvement in biodiversity.

### Land use change

Fruits of the oil palm

The quantities of oil crops from domestic agriculture are too small for self-sufficiency, which is why imports would be necessary to replace larger quantities of fuel. Against biodiesel it is often argued that its production has an impact on natural landscapes and especially on rainforests.

The term land use change refers to the use of an area prior to the cultivation of energy crops . An example of a direct land use change is the conversion of grassland into arable land for the cultivation of rapeseed or soybeans, an indirect land use change is the conversion of arable land for the cultivation of food crops into arable land for the cultivation of energy crops. The change in the plant world through changes in land use influences the carbon dioxide binding capacity, whereby more carbon dioxide can both be bound and released depending on the type of management.

The impact of direct and indirect land use changes on the ecological balance is assessed inconsistently. Due to the effects on the greenhouse balance as well as on social aspects, however, this concept is used in many legal works on biofuels. The approaches to calculating the impact are complex, subject to uncertainty and therefore controversial.

In most of the scenarios examined, however, there is an agreement that it is advantageous to promote energy crops that have low land use change rates and to promote the cultivation of land that has already been cleared and fallow. Biodiesel could create a stable source of income through cultivation and sustainable management of degraded areas. The size of the areas in question is estimated at 500 to 3500 million hectares.

One potential impact of land use change is food shortages. The cultivation of oilseeds on existing arable land or the use of vegetable oils to produce biodiesel can lead to a shortage or increase in the price of food, although the precise effects are controversial. In a study in 2011, no quantitative supply problems in the area of ​​food and feed supply through energy crop production could be detected at European or national level, although this is described as conceivable.

In rapeseed cultivation, only 40% is produced as oil, in soybean cultivation only 20%, the remaining 60 to 80% of the plants are used as rapeseed and soy cake for animal feed production. Rapeseed meal and rapeseed cake are increasingly used for dairy cattle feeding, but can also be used in pig and poultry fattening.

The rise in the price of food is a key problem in biodiesel production, sometimes referred to as agflation. The Renewable Energy Sources Directive made the EU Commission obliged to assess the effects of the production of biofuels both in the member states of the EU and in third countries.

## toxicology

In studies of the toxicology of biodiesel, no deaths and only minor toxic effects were found after administration of up to 5000 mg per kilogram of body weight to rats and rabbits .

Fears that the absorption of biodiesel in the body could release methanol through hydrolysis and damage nerve cells through the physiological breakdown product formic acid were not confirmed. When doses of 5 to 500 mg biodiesel per kg body weight were administered in animal experiments , no or only a minimally increased plasma level for methanol or formic acid could be found in all test groups even after weeks .

## literature

• Sven Geitmann: Renewable energies and alternative fuels. Hydrogeit Verlag, 2nd edition, Jan. 2005, ISBN 3-937863-05-2 .
• Sven Geitmann: Alternative fuels. Hydrogeit Verlag, 2008, ISBN 978-3-937863-12-2 .
• Philipp Dera: “Biodiesel” - a growth market with a sustainability guarantee? Socio-economic dimensions of palm oil production in Indonesia. regiospectra, Berlin 2009, ISBN 978-3-940132-10-9 .
• Gerhard Knothe, Jon Harlan Van Gerpen, Jürgen Krahl: The Biodiesel Handbook. AOCS Press, 2005, ISBN 1-893997-79-0 .

Wiktionary: Biodiesel  - explanations of meanings, word origins, synonyms, translations
Commons : Biodiesel  - Collection of pictures, videos and audio files

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