Vegetable oil can be used as an alternative fuel in diesel engines and in heating oil burners. When vegetable oil is used directly as a fuel, in either modified or unmodified equipment, it is referred to as straight vegetable oil (SVO) or pure plant oil (PPO). Conventional diesel engines can be modified to help ensure that the viscosity of the vegetable oil is low enough to allow proper atomization of the fuel. This prevents incomplete combustion, which would damage the engine by causing a build-up of carbon. Straight vegetable oil can also be blended with conventional diesel or processed into biodiesel or bioliquids for use under a wider range of conditions.
Usable vegetable oils
Most rapeseed oil is used as vegetable oil fuel in Germany. However, there are many thousands of oil plants worldwide that could be used as fuel. Basically, all vegetable oil types and also animal oils are suitable for operation in converted vehicles. Occasionally, motorists also use filtered waste oils and liquid edible fats. However, they must be thoroughly cleaned, dehydrated and, if necessary, neutralized before use. When using vegetable oil as fuel, high quality standards must always be observed.
Although camelina oil has better properties, the proportion of rapeseed oil in the market outweighs because farmers can neither derive any financial benefit from mixed crops nor use the press residues as feed as this was prohibited until 2009 by Annex 5 point 31 of the Animal Feed Regulation.
Vegetable oil is one of the densest forms of energy produced by photosynthesis. The calorific value is significantly lower with 37 MJ / kg than with petrol (43 MJ / kg) and diesel fuel with EN 590 (42.5 MJ / kg), but higher than with hard coal (30 MJ / kg). The volume-related energy density is around 9.2 kWh per liter, between gasoline with 8.6 kWh / L and mineral diesel oil with 9.6 kWh / L.
Pure vegetable oil consists mainly of triacylglycerides, d. H. Glycerin – esters of long chain fatty acids (ie not from alkanes) and is less flammable (see flash point) than diesel. The ignitability (cetane number) is generally limited because unheated vegetable oil from the injector is insufficiently atomized in the combustion chamber (therefore vortex and vortex chamber motors are better). Due to its higher viscosity, which increases even more when the temperature drops, the flow resistance in the fuel lines, the injection pump and the injection nozzles increasesover that of diesel fuel. Some injection systems, such as the common rail or the pump nozzle, therefore use vegetable oil outside their specifications, which can lead to abnormal wear and even total failure.
Application and usability
Modified fuel systems
Most diesel car engines are suitable for the use of straight vegetable oil (SVO), also commonly called pure plant oil (PPO), with certain modifications. Principally, the viscosity and surface tension of the SVO/PPO must be reduced by preheating it, typically by using waste heat from the engine or electricity, otherwise poor atomization, incomplete combustion and carbonization may result. One common solution is to add a heat exchanger and an additional fuel tank for the petrodiesel or biodiesel blend and to switch between this additional tank and the main tank of SVO/PPO. The engine is started on diesel, switched over to vegetable oil as soon as it is warmed up and switched back to diesel shortly before being switched off to ensure that no vegetable oil remains in the engine or fuel lines when it is started from cold again. In colder climates it is often necessary to heat the vegetable oil fuel lines and tank as it can become very viscous and even solidify.
Single tank conversions have been developed, largely in Germany, which have been used throughout Europe. These conversions are designed to provide reliable operation with rapeseed oil that meets the German rapeseed oil fuel standard DIN 51605. Modifications to the engines cold start regime assist combustion on start up and during the engine warm up phase. Suitably modified indirect injection (IDI) engines have proven to be operable with 100% PPO down to temperatures of −10 °C (14 °F). Direct injection (DI) engines generally have to be preheated with a block heater or diesel fired heater. The exception is the VW Tdi (Turbocharged Direct Injection) engine for which a number of German companies offer single tank conversions. For long term durability it has been found necessary to increase the oil change frequency and to pay increased attention to engine maintenance.
Unmodified indirect injection engines
Many cars powered by indirect injection engines supplied by in-line injection pumps, or mechanical Bosch injection pumps are capable of running on pure SVO/PPO in all but winter temperatures. Indirect injection Mercedes-Benz vehicles with in-line injection pumps and cars featuring the PSA XUD engine tend to perform reasonably, especially as the latter is normally equipped with a coolant heated fuel filter. Engine reliability would depend on the condition of the engine. Attention to maintenance of the engine, particularly of the fuel injectors, cooling system and glow plugs will help to provide longevity. Ideally the engine would be converted.
Vegetable oil blending
The relatively high kinematic viscosity of vegetable oils must be reduced to make them compatible with conventional compression-ignition engines and fuel systems. Cosolvent blending is a low-cost and easy-to-adapt technology that reduces viscosity by diluting the vegetable oil with a low-molecular-weight solvent. This blending, or “cutting”, has been done with diesel fuel, kerosene, and gasoline, amongst others; however, opinions vary as to the efficacy of this. Noted problems include higher rates of wear and failure in fuel pumps and piston rings when using blends.
When liquid fuels made from biomass are used for energy purposes other than transport, they are called bioliquids.
With often minimal modification, most residential furnaces and boilers that are designed to burn No. 2 heating oil can be made to burn either biodiesel or filtered, preheated waste vegetable oil (WVO). If cleaned at home by the consumer, WVO can result in considerable savings. Many restaurants will receive a minimal amount for their used cooking oil, and processing to biodiesel is fairly simple and inexpensive. Burning filtered WVO directly is somewhat more problematic, since it is much more viscous; nonetheless, its burning can be accomplished with suitable preheating. WVO can thus be an economical heating option for those with the necessary mechanical and experimental aptitude.
Combined heat and power
A number of companies offer compressed ignition engine generators optimized to run on plant oils where the waste engine heat is recovered for heating.
The main form of SVO/PPO used in the UK is rapeseed oil (also known as canola oil, primarily in the United States and Canada) which has a freezing point of −10 °C (14 °F). However the use of sunflower oil, which gels at around −12 °C (10 °F), is currently being investigated as a means of improving cold weather starting. However, oils with lower gelling points tend to be less saturated (leading to a higher iodine number) and polymerize more easily in the presence of atmospheric oxygen.
Polymerization also has been consequentially linked to catastrophic component failures such as injection pump shaft seizure and breakage, injector tip failure leading to various and/or combustion chamber components damaged. Most metallurgical problems such as corrosion and electrolysis are related to water based contamination or poor choices of plumbing (such as copper or Zinc) which can cause gelling- even with petroleum based fuels.
Some Pacific island nations are using coconut oil as fuel to reduce their expenses and their dependence on imported fuels while helping stabilize the coconut oil market. Coconut oil is only usable where temperatures do not drop below 17 degrees Celsius (63 degrees Fahrenheit), unless two-tank SVO/PPO kits or other tank-heating accessories, etc. are used. The same techniques developed to use, for example, canola and other oils in cold climates can be implemented to make coconut oil usable in temperatures lower than 17 degrees Celsius (63 degrees Fahrenheit)
Recycled vegetable oil
Recycled vegetable oil, also termed used vegetable oil (UVO), waste vegetable oil (WVO), used cooking oil (UCO), or yellow grease (in commodities exchange), is recovered from businesses and industry that use the oil for cooking.
As of 2000, the United States was producing in excess of 11 billion liters (2.9 billion U.S. gallons) of recycled vegetable oil annually, mainly from industrial deep fryers in potato processing plants, snack food factories and fast food restaurants. If all those 11 billion liters could be recycled and used to replace the energy equivalent amount of petroleum (an ideal case), almost 1% of US oil consumption could be offset. Utilizing recycled vegetable oil as a replacement for standard petroleum-derived fuels like gasoline would reduce the price of gasoline by preserving the supply of petroleum.
Virgin vegetable oil
Virgin vegetable oil, also termed pure plant oil or straight vegetable oil, is extracted from plants solely for use as fuel. In contrast to used vegetable oil, is not a byproduct of other industries, and thus its prospects for use as fuel are not limited by the capacities of other industries. Production of vegetable oils for use as fuels is theoretically limited only by the agricultural capacity of a given economy. However, doing so detracts from the supply of other uses of pure vegetable oil.
Problems with use
Change of engine oil
Unburned fuel – especially during cold starts and at high engine speeds – gets into the engine oil and worsens its lubricating properties or polymer chains form in the engine oil, which can agglomerate into lumps and clog pipes and filters. This problem occurs especially when using modern fully synthetic lubricating oils, obviously fully synthetic oils bind foreign substances (free radicals) very well, what they should – if there are not too many.
Pure diesel fuel begins to evaporate at about 55 ° C. Thus, when the engine oil reaches this temperature while driving, the diesel fuel evaporates from the engine oil. Since vegetable oil, unlike diesel, does not start to evaporate until about 220 ° C and the engine oil never reaches this temperature, vegetable oil inevitably accumulates in the engine oil. A conversion of the vehicle to the operation with vegetable oil can only slow down this process, but not prevent it. Therefore, it is always advisable to check the oil level regularly and to halve the oil change intervals.
Vegetable oil is much thicker than diesel fuel, but the injection system of the engine is designed for less viscous diesel fuel. The flash point of vegetable oil is about 165 K above that of diesel fuel. Both properties have a decisive influence on the combustion.
A conversion must therefore either adapt the engine to use with vegetable oil and / or change the vegetable oil so that it comes as close as possible to the properties of diesel. In order to ensure as complete a combustion as possible, it is necessary to spray the vegetable oil just as finely as diesel fuel during injection. For this purpose, either the viscosity of the vegetable oil has to be adapted to that of diesel fuel or the injection pressure has to be increased. In practice, both options are usually used.
The viscosity of vegetable oil is strongly temperature dependent, d. that is, the farther the vegetable oil is heated, the thinner it becomes. At room temperature, the viscosity of vegetable oil is about 100 times greater than that of diesel, which would lead to enormous forces in unmodified injection pumps. Only at approx. 150 ° C does vegetable oil reach the viscosity of diesel. Most Pöl is heated with a cooling water heat exchanger but only to 65-85 ° C.
Theoretically, it would also be possible to increase only the injection pressure accordingly, but the cost is very high, which is why the injection pressure is only slightly raised. In older injection systems, this can be easily achieved by changing the opening pressure of the injectors. Since the injection pump then takes a little longer to build up the higher pressure, the fuel is injected later; the injection time must then be reset.
Admixture of diesel / gasoline
In addition to heating, the admixture of diesel or gasoline is a way to change the viscosity and the flash point of the vegetable oil. This technique is used by some converters such. B. “Klümper-Pflanzenöltechnik” and “Danhag” used.
Vegetable oil is thicker than diesel. Therefore, a mixture of diesel and vegetable oil, regardless of the mixing ratio, never reach the viscosity of diesel fuel. A combination of admixture and heating has been proven in practice. On the one hand, the vegetable oil at the same temperature is much less viscous than without the addition of diesel, on the other hand, the flash point of the mixture drops to a value between 55 ° C (diesel) and 220 ° C (vegetable oil), which has a better combustion result,
Gasoline is less viscous than diesel, so a vegetable oil-gasoline mixture can reach the viscosity of diesel. This is the case with a mixing ratio of about 60% oil to 40% gasoline. However, the anti-knock agents added to the gasoline in the diesel engine inhibit spontaneous combustion of the mixture, i. H. the cetane number drops sharply, causing the engine to start poorly and not perform well. Therefore, in this case, ignition-enhancing additives which increase the cetane number must be mixed. In addition, the gasoline addition deteriorates the lubricating properties of the vegetable oil, which can lead to damage to the injection pump. This is where the addition of two-stroke oil helps. A mixture of 59% oil, 39.5% gasoline, 1% two-stroke oil and 0,
Vegetable oil should be stored as cool and dark as possible. The storage can be done easily in above-ground and underground tank facilities, where due to their relatively constant low temperature underground facilities have advantages.
The advantage of the good biodegradability of the vegetable oil is associated with a poor aging resistance and deteriorates the shelf life. Bacterial attack, oxidation and water accumulation are the main problems. Therefore, when storing vegetable oil, care must be taken to prevent chemical reactions that deteriorate the quality of the vegetable oil, such as
the polymerization and
the enzymatic degradation.
The storage must therefore be dark, cool (between 5 and 10 ° C), dry and with a small contact surface to the atmospheric oxygen. The tanks, pipelines and fittings must be made of stainless steel (without catalytic alloying constituents such as copper) or opaque plastic (eg HDPE) and contain a water-separating filter for ventilation. Earth tanks are cheap because of the usually low storage temperature. The tanks should be cleaned on a regular basis, as the sediment from impurities accelerates the progress of quality deterioration due to chemical reactions (see above).
In the production of vegetable oil in the oil mill, the following combination of bearings is common:
The first tank stores the vegetable oil from the current production
The second storage tank stores the vegetable oil whose samples are examined for quality
The third tank contains the vegetable oil, which can be delivered to the final customer for quality after the quality approval.
Denatured vegetable oil may smell or taste unpleasant. A study funded by Shell, Daimler-Chrysler, Volkswagen and the Association of the German Biofuels Industry study by the Federal Agricultural Research Center came to the conclusion that the emissions of a pure rapeseed oil powered diesel truck engine in comparison with a conventional diesel-powered engine are about 30 times more carcinogenic. Experts of the Federal Environment Agencywith reference to this study, claim that trucks are no longer fueled by pure rapeseed oil. In particular, the employees in the truck repair shops are at risk. These statements have since been refuted in a recent study by the Technology and Promotion Center (TFZ), Straubing and the bifa environmental institute in Augsburg.
This study has shown:
Compared to diesel emissions, vegetable oil emissions showed a roughly halved mutagenic effect when using bioltec technology. The mutagenic effect is a measure of the carcinogenic potential of the exhaust gases.
The fine dust emissions are about halved when using load-dependent defined vegetable oil / diesel mixtures compared to pure diesel operation.
The result was confirmed several times in the investigation with different measurements and control measurements.
The properties of the vegetable oil differ, depending on which plant they were obtained from. For example, camelina oil is longer liquid than rapeseed oil. While uniform quality standards can be guaranteed for diesel fuels, vegetable oil is not that easy. It does not exist as a standardized liquid and there is still no large-scale market, which relies on a central processing and would allow a controlled mixing of oils of different origin and thus constant quality.
To create uniform quality standards for the very commonly used rapeseed oil, on 23 May 2000 the “LTV Working Group Decentralized Vegetable Oil Production, Weihenstephan ” formulated a “Quality standard for rapeseed oil as fuel (RK quality standard)”. This was replaced by DIN 51605: 2010-09 Fuels for vegetable oil suitable engines – rapeseed oil fuel – requirements and test methods:
|Properties / Ingredients||unit||limits||test methods|
|Density at 15 ° C||kg / m³||900||930||EN ISO 3675, EN ISO 12185|
|Flash point according to P.-M.||° C||220||–||EN 2719|
|calorific value||kJ / kg||36,000||–||DIN 51900-1, -2, -3|
|Kinematic viscosity at 40 ° C||mm² / s||–||36.0||EN ISO 3104|
viscometry (test conditions are developed)
|Ignitability ( cetane number )||–||39||–||(Test method is developed)|
|Carbon Residue||Dimensions-%||–||0.40||EN ISO 10370|
|Iodine number||g / 100 g||95||125||EN 14111|
|sulfur content||mg / kg||–||10||ISO 20884/20864|
|total contamination||mg / kg||–||24||EN 12662|
|acid number||mg KOH / g||–||2.0||EN 14104|
|Oxidation stability at 110 ° C||H||6.0||–||EN 14112|
|phosphorus content||mg / kg||–||3||EN 14107|
|magnesium||mg / kg||–||1||EN 14538|
|calcium||mg / kg||–||1||EN 14538|
|ash content||Dimensions-%||–||0.01||EN ISO 6245|
|water content||Dimensions-%||–||0,075||EN ISO 12937|
|These values represent a draft standard so far .|
Volume consumption and performance characteristics are approximately the same for both diesel and rapeseed oil fuels. However, vegetable oil burns a little “softer”, as the combustion proceeds more slowly. As a problem, the coke residue is seen by the engine manufacturer, whereby there are no or hardly releases for vegetable oil. In addition, vegetable oil in combination with the additives of the motor oil tends to polymerize, ie formation of solid compounds and lumps. This is caused by the unavoidable entry of unburned vegetable oil via the cylinder wall into the engine oil, especially during short-distance driving.
Market and costs
In Germany alone, according to a recent estimate of the VCD, there are around 20,000 vehicles powered by vegetable oil. At vegetable oil filling stations or at oil mills, the price for pure vegetable oil incl. Tax component is usually at a similar price level as diesel fuel at regular filling stations.
Unlike conventional fuels, rapeseed oil is only available at a few hundred filling stations in Germany. In addition, there are many suppliers and oil mills that offer vegetable oil in common for refueling quantities.
The refueling of vegetable oil from 1-liter bottles of the retail is everywhere possible (food refining oil complies with DIN 51605), but uncomfortable. Furthermore, one would be obliged to pay the resulting tax later to the tax office. Many vegetable oil operators therefore operate a reservoir with a pump on a private property (farm filling station). A usual size is about 1 m³. Small storage tanks are already available for around 50 euros.
For agricultural producers rapeseed oil is cheaper than agricultural diesel. In 2001, a DM 5.6 million “100 Tractor Program” was launched by the Ministry of Consumer Protection. A total of 111 farm tractors from various manufacturers whose engines comply with the technological standards of the EURO I and EURO II emissions standards were Operation retrofitted to gain experience. The project ran from April 2001 to October 2005 and was supervised by the Institute of Energy and Environmental Engineering of the University of Rostock.
Depending on the method, the costs (including VAT) for a conversion amount from 360 € (1-tank) or 1,500 € (2-tank) to 4,000 € per engine or vehicle or stationary aggregate. For self-installers, sets from € 260 (1-tank) or € 600 (2-tank) are available. In some regions public subsidies are also offered up to half of the net conversion costs.
The use of vegetable oils as fuel has ecological advantages and disadvantages that can not always be offset against each other. The German Federal Environmental Agency (UBA) said in 1999: “From the point of view of environmental protection and for economic reasons promotion of the use of rapeseed oil and RME in the fuel sector is still NOT to be advocated.” (Lit. Kraus et al., P. 21). In March 2007, UBA’s website on the subject of “Biodiesel”, on the other hand, states: “Biodiesel or the cultivation of rapeseed can make a small contribution to the conservation of fossil energy resources and to climate protection.”
The use of vegetable oils as fuel is not CO 2 -neutral in the broader sense. It is true that during combustion only the amount of CO 2 released by the plants through photosynthesis from the atmosphere is releasedhave taken. However, in the production (pressing) itself, a mostly small percentage of electricity or mineral fuel is consumed, and thus, in fact, a small amount of carbon dioxide is released. In addition, the ordering of the acreage including the energy costs for the extraction and logistics of the fertilizer or sprays (pesticides and agents for disease, pest and weed control) and the harvest requires energy, which also leads to carbon dioxide release.
The use of naturally produced energy sources leads to a lower CO 2 pollution in the long term and in the long term compared to crude oil. The carbon dioxide produced during combustion is taken up again by renewable producer plants and converted into new energy.
In view of exhausting fossil resources, raw materials for energy production as well as for the chemical industry, which are increasingly produced by agriculture, will become more important in the future. The oil companies also take this development into account and invest in appropriate research.
The risk of contamination of waters (including groundwater) is not as great with vegetable oil as with conventional petroleum-based fuels. Whether vegetable oil that is not used as food or feed is considered to be hazardous to water depends on the composition. The main stock of vegetable oils is with the identification no. 760 of Annex 1 to the Administrative Regulation on Substances Hazardous to Water (VwVwS) and thus “non-hazardous to water”: triglycerides (technically untreated or hydrogenated, fatty acid radical saturated and unsaturated, with even, unbranched C chain and C number ≥ 8). Since vegetable oil is not a pure substance, but a mixture of substancesrepresents, the mixing rule of the VwVwS applies. After that z. For example, components of water hazard class 1 may only contain less than 3% to classify the substance as “non-hazardous to water”. Therefore, depending on the plant species and oil recovery method, the oil may be hazardous to water if it contains too much triglyceride with short-chain fatty acids, too much free fatty acids (if these do not meet the Code No. 661 in Appendix 1 of the VwVwS) or other contaminants. The Federal Environment Agency held a technical discussion in June 2007 on the subject of “Water hazard through biogenic oils”. As a result, the commission for the evaluation of substances hazardous to water, which advises the Federal Government, has determined that biogenic oils are classified as slightly hazardous to water in WGK 1, provided that no further hazardous properties occur.
Natural substances can also damage rivers, lakes and groundwater. Thus, § 5 Water Act requires “to apply the necessary care according to the circumstances in order to avoid an adverse change in the water quality”. A classification as “non-hazardous to water” merely means that the special requirements of §§ 62 and 63 of the Water Resources Act and the regulations issued thereafter do not apply.
The risk of fire compared to diesel oil or fuel oil EL, since it is flammable at normal temperature because of the flash point of 220 ° C (see chapter quality standard below) and can not form explosive gas / air mixtures.
Agricultural and regional effects
Vegetable oil fuel can also be produced by small oil mills near the agricultural producer with relatively simple means. With increased demand, the recultivation of abandoned agricultural land offers. The transport route from the producer to the consumer is comparatively short. Even the by-product of production, the oil or press cake, can be used as a high-quality protein and energy carrier as animal feed. The sales market has been falling sharply in recent years. If it was up to 800,000 tons in 2007, it literally plummeted to 100,000 tons by the year 2009. In the biofuels report 2009/2010 If this is explained by the competitive situation with the biodiesel, associations see the reason in the biofuel policy of the government Merkel II, which does not further promote existing pure fuels.
Differentiated effect of cultivation methods
A central importance for the ecological balance as well as for the profitability of the use of vegetable oil is the cultivation form. You can distinguish between two types here:
Cultivation in monoculture with mineral fertilizers
Cultivation in mixed culture with biological fertilizers
Most scientific arguments (such as the opinion of the UBA) are based on the assumption that the necessary quantities of vegetable oil can only be produced in intensive agriculture through rape cultivation in monocultures with high fertilizer and pesticide use.
Less known to the public since 1997 are experiments in Bavaria with mixed crop cultivation in organic agriculture. It is understood by the cultivation of a mixture of different crops in the same field at the same time. When leafy plants with stalks, deep roots with flatroots or plants with different nutrient needs grow together in one field, they complement each other. Thus, a favorable effect has been demonstrated for camelina or rape with peas, wheat or barley. The mixed cultivation requires less fertilizer (the peas provide the nitrogen) and makes the use of herbicides against weeds unnecessary. In cereals, the same area yield was due to the lower weed pressure obtained with a higher quality grain with an additional yield of about 80 to 150 liters of vegetable oil per hectare.
The core of the biological approach is the extensive use of all resources. Due to the reciprocal favoring of the plants can be dispensed with fertilizers in addition to pesticides largely. The sorting of the crops takes place directly in the harvester. Remaining plant material can serve as a basis for fiber materials or be processed as biomass into energy. The obtained from the oil press cake can be used as animal feed and then finally as liquid manure for biogas productionbe used. The digested residues can then be applied as fertilizer again. The advocates point out here that the cultivation of oil plants their materially and energetically valuable by-products may not simply exclude. Under this holistic approach, the superiority of modern biotechnology compared to mineral oil products becomes clear.
Another possibility, according to the proponents, would be the extensive cultivation of erucic acid-rich natural rape, which would be better suited as a fuel than currently grown erucic acid-free rape (so-called OO varieties, which have a good edible oil production potential).
It is further argued by proponents that in the discussion other oil plant varieties which are in extensively Germany would tillable as sunflower, garden rocket, radish, mustard, turnip rape, false flax, linseed or hemp, not enough to be considered.
Taxation of fuel
Taxation on SVO/PPO as a road fuel varies from country to country. It is possible that the revenue departments in many countries are even unaware of its use or consider it too insignificant to legislate. Germany used to have 0% taxation, resulting in it being a leader in most developments of the fuel use.
Source from Wikipedia