In this article we will discuss about:- 1. Meaning of Biofuels 2. History of Biofuel 3. Common Plant Sources of Oil 4. European Perspective 5. Advantages 6. Engine Performance 7. Storage Conditions.
- Meaning of Biofuels
- History of Biofuel
- Common Plant Sources of Oil
- European Perspective on Biofuels
- Advantages of Biodiesel
- Engine Performance of Biofuels
- Storage Conditions for Biodiesel
1. Introduction to Biofuels:
Air and water pollution and solid waste management are some of the major problems being faced by the modern society. Biomass has traditionally been the most important source of energy in rural areas and a major fuel even in the urban areas. In spite of rapid increase in the supply of and access to fossil fuels, biomass is likely to continue to play a dominant role in India, as in many other developing countries, in the near future. Thus, developing and promoting techno-economically viable technologies to utilize biomass in an effective manner is of high priority especially in the wake of diminishing fossil fuel resources.
Diesel enjoys a prime position for certain energy needs even amidst the rural populations. Apart from being major transportation fuel, diesel is presently used in engines for generating mechanical energy or electrical energy in decentralized form. Due to depleting nature of this resource and due to its non-uniform distribution, a search for an alternative fuel, which preferably be made available from the local and natural resources, is the need of hour. Rural farmers, anxious for power for irrigation, look forward to this option in the days of increasing power cuts.
Rural people find it difficult to procure diesel as they have to go to the urban outlets to procure it. Biofuels like ethanol and methanol have attracted attention as alternative fuels to diesel due to their similar fuel and combustion properties. However, for country like India, where we find the population pressure, combined with the extent of constraints on the cultivable land, option of growing petro crops yielding ethanol will not be an accepted one for years to come.
The other alternative is to look for biofuels which can be generated from other crops and which, in turn, do not compete with traditional agriculture for food production. This is possible from plants like Jatropha curcas, Pongamia pinnata, Mesua ferrea, etc. which can be grown in the otherwise unutilized waste lands, with marginal inputs of resources like water and fertilizers.
Biofuels can be defined broadly as any fuel derived from biomass. They include biodiesel, bioethanol, a product of bioethanol, i.e., ethyl tertiary butyl ether (ETBE), biogas, biomethanol, biodimethylether and bio-oil. The main candidates for transport are currently bioethanol, a petrol additive/substitute made from starchy materials like cereals, sugar beet or fodder beet and biodiesel, a diesel alternative made from a range of animal and vegetable sources, including recycled vegetable oils and fats from the food chain.
It is intended that the growth of biofuels will:
i. Reduce carbon dioxide (CO2) emissions.
ii. Provide income and employment opportunities.
iii. Contribute to overall energy security.
iv. Improve air quality, especially in congested areas.
v. Be possible within the existing distribution infrastructure.
Biodiesel helps to reduce targeted emissions. Emissions can be hazardous to human health. An independent study has verified that biodiesel used in a 20 : 80 blend with petroleum diesel, along with a catalytic converter, reduces diesel engine air pollution. Biodiesel performs similarly to petroleum diesel in terms of torque, horse power and miles per litre.
Biodiesel reduces emission of smoke, sulphur, particulate matter, carbon monoxide and total hydrocarbons. Biodiesel has higher flash point, and offers low-pressure storage at ambient temperature, handles like diesel and is nontoxic and biodegradable. Biodiesel is also safe to handle and transport.
Biodiesel is non-toxic, biodegradable, low sulphur, aromatics free, renewable and sustainable partial replacement for diesel. It is made through a chemical process called esterification, most being produced using an alkali catalysed reaction whereby a fat or oil is reacted with an alcohol in the presence of a catalyst (usually sodium or potassium hydroxide).
The vegetable/animals oils/fats can be converted into biodiesel by a process called trans-esterification, which proceeds through hydrolysis of triglycerides present in the oils or fats to produce fatty acids glycerine, followed by neutralization of the free fatty acids, removal of glycerine thus formed, and esterification of acids by using an alcohol. This is accomplished by mixing methanol (wood alcohol) with lye (sodium hydroxide) to make sodium methoxide. This strong base is then mixed into vegetable oil. The entire mixture then settles.
Glycerine is left on the bottom and methyl esters, or biodiesel, is left on top. The process mainly produces two valuable by-products – methyl esters (biodiesel) and glycerine which has more than 1,600 commercial applications from toothpaste to cough syrup. Without modification some of today’s diesel engines can be run on 100% biodiesel or biodiesel blended with conventional diesel fuel, and biodiesel can be distributed in the same way as conventional diesel. The resulting biodiesel fuel when used directly in a diesel engine will burn up to 75% cleaner than petroleum fuel.
Trans-esterification was conducted as early as 1853. One of the first uses of biodiesel (trans- esterified vegetable oil) was powering heavy vehicles in South Africa before World War II. The biodiesel, thus, contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel. Biodiesel blends are denoted as ‘BXX’ with ‘XX’ representing the percentage of biodiesel contained in the blend (i.e., B20 is 20% biodiesel, 80% petrodiesel). It can be used in compression ignition (diesel) engines with little or no modification. Biodiesel is simple to use, biodegradable, non-toxic, and essentially free of sulphur and aromatics.
However, there are many issues surrounding its introduction including lack of clarity of emissions, reduction potential, supply/demand balance, product quality, and the cost of the production that may impact the ease with which biofuel is introduced. There are also concerns about vehicle warranty implications. European Union legislation allows up to 5% biodiesel in diesel fuel, provided the biodiesel meets required specifications. Vehicles running on this fuel will be covered by warranty in the normal way. However, in the countries where a higher proportion of biodiesel is permitted, some OEMs have not extended vehicle warranties for use with these fuels while others have adapted their vehicles to allow use of up to 100% biodiesel.
Around the world, different crop-plants are grown to provide the oil for the production of biodiesel. In Europe rapeseed is commonly produced; in the US, soybeans are the largest source, and in Asia it is palm oil and coconut oil that are mostly used. In India, Jatropha (Ratanjot) is being cultivated on gigantic scale in arid areas of Uttar Pradesh and Karnataka.
2. History of Biofuel:
Dr. Rudolf Diesel who invented the first Diesel Engine in 1895 used only bio-diesel in his engine. His visionary statement was – The use of vegetable oils for engine fuel may seem insignificant today. But, such oils may become in course of time, as important as petroleum and coal tar products of the present time. That prediction has become true today as more and more bio-diesel is being used all over the world. Thus, Indian Railways is in the forefront in reintroducing the age-old eco-friendly and renewable source of energy for its locomotives and road vehicles in a more scientific and technologically advanced manner, helping the country and environment.
Dr. Rudolf Diesel used only diesel in his engine, but at that time bio-diesel was not yet known. He himself made tests with cheap derivatives of petroleum. The reference fuel was always the petroleum for lamps in USA. In 1990 at the World Fair in Paris, a small version of a diesel engine run on plant oil (peanut oil) was exhibited. This was organized by the French society for the support of the Otto engine. Biodiesel was invented much later and became technically relevant only after the energy crisis in the year 1973 and afterwards.
Biofuels are likely to meet 10% petrol needs by 2012. Almost 10% of India’s petroleum requirements would be met through biofuels by 2012, according to an estimate of the MNES (Ministry of Non-conventional Energy Sources). Although the amount seems paltry on the face, it implies a total targeted production of about 20 MT of biodiesel, currently produced at negligible levels, by 2012.
However, in order to realize this, the cost of production of biofuels has to be further reduced by expanding the acreage of non-edible oilseeds (e.g., Jatropha seeds)—the basic raw materials for producing biodiesel. Now seeds are available @ Rs.15/kg, which pushes up the production cost of biodiesel to cover Rs.40/litre.
The relevant physical and combustion base properties of Jatropha oil as an engine fuel are compared with similar properties with diesel (Table 8.1).
Lubricity is a major benefit for fuel consumption – Biodiesel contains 10% oxygen. Table 8.2 shows the brake-specific fuel consumption figures.
3. Common Plant Sources of Oil:
India is among the largest petroleum consuming and importing countries. India imports about 70% of its petroleum demand. Wildly fluctuating world prices of oil have been a destabilizing element for the balance of country’s economy. The tune of petroleum imports is currently about 600 billion rupees (about 30% of total import bill) compared to current trade deficit of about Rs.500 billion.
The current yearly consumption of diesel oil in India is approximately 40 million tonnes forming 40% of the total petroleum products consumption. The ongoing economic expansion would increase the demand for transportation fuel in short and medium terms at high rates. To be at par with the developed countries India has to increase the per capita consumption of fuel oils several fold higher than the current Indian consumption levels. In view of this, bio-fuels could be boon for our developing country.
Oil can be extracted from a variety of plants and oilseeds. Under Indian condition only such plant sources can be considered for biodiesel production, which are not edible in appreciable quantity and which can be grown on large-scale on wastelands. Moreover, some plants and seeds in India have tremendous medicinal value, considering these plants for biodiesel production may not be a viable and wise option.
Considering all the above options, probable biodiesel yielding trees in India are:
i. Jatropha curcas or Ratanjot,
ii. Pongamia pinnata or Karanj,
iii. Calophyllum inophyllum or Nagchampa,
iv. Hevea brasiliensis or Rubber seeds,
v. Calotropis gigantia or Ark,
vi. Euphorbia tirucalli or Sher, and
vii. Boswellia ovalifololata.
Of all the above prospective plant candidates as biodiesel yielding sources, Jatropha curcas stands at the top and sufficient information on this plant is already available. These plants can grow on poor degraded soils and do not need much irrigation. Thus, it ensures a reasonable production of seeds with very little inputs. Animals do not like to make it a meal and the plant is highly pest and disease resistant. Within 2 to 5 years of plantation, kernels vary from 0.5 to 12 t/yr basing on soil and rainfall conditions.
The seeds contain 55-60% oil that can be converted into biodiesel by trans-esterification. A yield of 0.3 to 0.8 tonnes of biodiesel could be expected per acre per year from the fifth year onwards. Jatropha plantations yield over long periods of time. The most commonly used oils for biodiesel in USA and European countries are from soybean and rapeseeds.
The important parameters which contribute to the fuel activities of jatropha oil and the corresponding biodiesel are given in Table 6.1.
One acre of Jatropha plantation with 1600 plants under rainfed conditions can yield about 600 litres of oil. It is estimated that about 7 million acres plantation is required to produce oil for 10% replacement of petrodiesel need of India. The residual oil cake obtained after extraction of oil from jatropha can be used as organic fertilizers.
It is also estimated that one acre of Jatropha plantation can produce oil sufficient to meet the energy requirement of the family of 5 members and the oil cake left out, when used as fertilizers can cater to one acre. Jatropha can be grown in any wasteland with less irrigation and, thus, it can be considered as the most important biodiesel source in India. It has been estimated that high protein seed cake (60% crude protein) can be produced at the rate of 0.4 tonnes acre–1 year–1 which can be potentially used as animal and fish feeds and, also as organic fertilizer, particularly in remote areas. The leaf, bark and seed extracts of the plants have various other industrial and pharmaceutical uses. Degraded lands can be restored due to plantation of these plants. Thus, it also generates a huge rural employment.
4. European Perspective on Biofuels:
In May 2003 the European Union (EU) adopted a directive to promote the use of biofuels or other renewable fuels to replace diesel or petrol for transport purposes. Its main objectives are to reduce emissions of CO2 from transport across Europe and to reduce the EU’s future reliance on external energy sources. The Directive requires member states to ensure that biofuels and other renewable fuels account for 2% of all petrol and diesel sold for transport purpose by December 31, 2005, rising to 5.75% by the end of 2010.
The climate change benefits that could result from meeting these proposed targets depend on the extent to which substituting biofuels for conventional fuels saves carbon on a lifecycle basis. The commission suggested the lifecycle CO2 saving around 2 to 2.5 tonnes of CO2 per 1000 litres (about 60-80%) for biodiesel, figures seen by some as optimistic. For example, the UK department of transport, local government and the regions lifecycle analysis suggests that a carbon saving of 20-40% is more realistic.
On the basis of the Commission’s own estimates, the extra production costs for biodiesel could range from around 677 million to 1.25 billion euros per annum. A second optional biofuel directive has been proposed to offset their high cost of manufacture compared to fossil fuels. This involves applying a reduced rate of excise duty to pure or blended biofuels, when used either as heating or motor fuel. If the member states choose this option to meet the additional production cost it could lead to biofuel consumers benefiting at the expense of tax payers.
In USA, of the 200 billion gallons of fuels consumed annually by road transport, only 30% is currently diesel. Therefore, the major focus here is on corn-based bioethanol to supplement gasoline. The Energy Bill demands the doubling of production of renewable fuels to five billion gallons (19 billion litres) by 2012. The bill would also create an excise tax credit for biodiesel made from virgin oils, such as soybeans, of $1.00 for each gallon marketed, bringing biodiesel cost closer to that of conventional diesel but still not at par.
Oil production in Asia Pacific is forecasted to decline in the next few years as key oilfields reach maturity. High oil prices may hold some incentive for exploration, but new oil prospects in the region are likely to be limited. Several Asia Pacific nations have embraced the concept of biofuel production especially the biodiesel and ethanol, in an attempt to replace a significant fossil fuel based energy use, and reduce reliance on oil imports.
It is clear that as global legislators struggle to meet their emissions reduction commitments, measures such as the introduction of biofuels are likely to become even more important. Additive manufacturers are now committed to the development of products to meet the requirements of these new fuels whether as 100% biodiesel or blended with diesel fuel.
To run any engine there is no need of technical modifications for biodiesel engines. It can be used in any conventional, unmodified diesel engine. Biodiesel can be stored anywhere that petroleum diesel fuel is stored.
All diesel fueling infrastructure including pumps, tanks and trucks can use biodiesel without modifications. In France, B5 (Diesel with 5% biodiesel) is in use with the same engines and diesel tanks.
Biodiesel reduces carbon dioxide emissions, the primary cause of the Greenhouse Effect, by up to 100%. Since biodiesel comes from plants and plants breathe carbon dioxide, there is no net gain in carbon dioxide from using biodiesel.
Overall biodiesel emissions are lower than gasoline or diesel fuel emissions. Compared to diesel, biodiesel produces no sulphur, no net carbon dioxide, up to 20 times less carbon monoxide and more free oxygen.
Biodiesel has the following emission characteristics when compared with petro-diesel fuel:
1. Reduction in carbon dioxide emissions (CO2) by 100%.
2. Reduction of sulphur dioxide (So2) by 100%.
3. Reduction of soot emissions by 40-50%.
4. Reduction of carbon monoxide (CO) emissions by 10-50%.
5. Reduction in nitrous oxide (NOx) emissions by 5-10% depending on the age type of engine.
6. Reduction of hydrocarbon (HC) emissions by 10-50%.
7. Reduction of all polycyclic aromatic hydrocarbon (PAHs) and specifically the reduction of the following carcinogenic PAHs:
i. Reduction of phenanthrene by 97%.
ii. Reduction of benzapyrene by 71%.
iii. Reduction of aldehydes and aromatic compounds by 13%.
Biodiesel can reduce emissions in several European Petroleum Act (EPA) targeted air pollution categories.
Tests done at the Colorado Institute for Fuels and High Altitude Engine Research of a 20% biodiesel 80% petroleum diesel blend used in 1991 model Series 60 engines reduced:
i. Particulate matter by 13.72%
ii. Total hydrocarbons by 12.71%
iii. Carbon monoxide by 7.11%
iv. NOx increased by 1.1%
An EPA Transient Cycle Emission test undertaken by Southwest Research Institute compared emissions from an engine burning typical low-sulphur petroleum diesel and an oxidation catalyst, and biodiesel with a one-degree timing change and an oxidation catalyst. The test engine was a 1988 DDC6V-92 DDEC II engine.
Compared with raw sulphur low diesel, a 20/80 blend with an oxidation catalyst reduced:
i. Particulate matter by 45%
ii. Total hydrocarbons by 65%
iii. Carbon monoxide by 41%
iv. NOx increased by 7%
A 20/80 blend with an oxidation catalyst and one-degree timing change reduced:
i. Particulate matter by 40%
ii. Total hydrocarbons by 58%
iii. Carbon monoxide by 34%
iv. NOx by 2%
v. Sulphur by 20%
vi. Biodiesel is more lubricating than petrodiesel fuel, it increases the engine life and it can be used to replace sulphur, a lubricating agent, when burned, produces sulphur dioxide, a noxious gas.
vii. Biodiesel is safe to handle because it is biodegradable and non-toxic. According to the National Biodiesel Board, USA, ‘neat biodiesel is as biodegradable as sugar and less toxic than salt.’
viii. Biodiesel is safe to transport. Biodiesel has a high flash point, or ignition temperature of about 148.88°C compared to petroleum diesel fuel, which has a flash point of 51.66°C.
ix. Engines running on biodiesel run normally and have similar fuel mileage to engines running on diesel fuel. Auto ignition, fuel consumption, power output, and engine torque are relatively unaffected by biodiesel.
x. Biodiesel has a pleasant aroma similar to popcorn popping in comparison to the all-too- familiar stench of petro diesel fuel.
Biodiesel use in the marine market can be practical and safe. In its pure form, biodiesel is less harsh on marine environments, and safer for boaters to handle and store. The marine industry consumes about 10 per cent of the petroleum diesel in the U.S..
i. Biodiesel can Work in Several Marine Factions:
Biodiesel can work in several marine factions because biodiesel can replace or blend with petroleum diesel with little or no engine modifications, it is a viable alternative to several categories of the marine industry, including- recreational boats, inland commercial and ocean-going commercial ships, research vessels and the U.S. Coast Guard Fleet. Today, much of the emphasis is on recreational boats, which consume about 95 million gallons of diesel fuel annually.
ii. Biodiesel is ‘User-Friendly’:
The use of biodiesel and biodiesel blends results in a noticeable change in exhaust odor. The reduction in smell and change of odour are easier on ship workers and pleasure craft boaters. In fact, it has been compared to the smell of French fries. Users also report having no eye irritation. Since biodiesel is oxygenated, diesel engine have more complete combustion than with petroleum.
iii. Biodiesel can Help Boaters Meet Regulations:
The Clean Air Act allows the Environmental Protection Agency (EPA) to access the contribution of non-road emission to air pollution. EPA proposes to include marine diesel compression-ignition engines in the same regulatory framework as land- based, non-road compression-ignition engines. Biodiesel lowers emissions in these engines.
2. Regulatory Liability:
The Oil Pollution Act of 1990 increases the civil and criminal penalties for causing spills and for violating many marine safety and environmental protection laws. The law applies to all vessels, and fines up to $10,000 per day may be levied against serious offenders. Biodiesel, when spilled, does less harm to the environment.
iv. Biodiesel will not Harm Fish:
The 96 hr. LC50 (lethal concentration) for Bluegills for C16-18 methyl esters was greater than 1,000 mg l–1. Concentrations above 1,000 mg l–1 are deemed ‘insignificant’ according to National Institute for Occupation Safety and Health (NIOSH) Guidelines in its Registry of the Toxic Effects of Chemical Substances.
v. Biodiesel is Biodegradable:
C16–18 methyl esters are considered readily biodegradable based on their chemical nature and test data collected for experimentally determined oxygen demand and carbon dioxide production as a per cent of calculated theoretical values. C16-18 methyl esters do not show any microbiological inhibition up to 10,000 mg l–1. In tests performed by the University of Idaho, biodiesel in an aqueous solution after 28 days was 95% degraded. Diesel fuel was only 40% degraded. In a second study done in an aquatic environment (CO2 evolution), various biodiesel products were 85.5-88.5% degraded- in 28 days, which is the same rate as sugar (dextrose). Diesel degradation was 26.24%.
vi. Biodiesel Offers more Environmental Benefits:
For research vessels and consumers using commercial vessels, biodiesel offers a more environmental-friendly alternative to regular diesel. Because it is non-toxic and biodegradable, consumers and researchers may pressure owners for biodiesel use, especially in sensitive or protected waterways areas
vii. Biodiesel is a Renewable Domestic Fuel:
Biodiesel is made from renewable fats and oils, such as vegetable oils, through a simple refining process. The by-product glycerine is used in commercial applications from toothpaste to cough syrup. One of the principle commodities used as a source for biodiesel is soyabeans, a major crop produced by almost 400,000 farmers in 29 states of USA.
viii. Biodiesel Helps Speed Diesel Degradation:
Biodiesel helps speed diesel degradation when used in blends with petroleum diesel fuel. Biodiesel degrades about four times faster than petroleum diesel fuel. Also, when blended with biodiesel, the degradation rate of petroleum diesel tripled when compared to diesel alone, according to a 1995 University of Idaho test.
ix. Biodiesel Costs Rank Well with Other Alternatives:
The cost of biodiesel depends on the market price for vegetables oil. In general, biodiesel blended at a 20% level with petroleum diesel costs 60-80 cents per gallon more than diesel alone. Given the other advantages of biodiesel, through an emission management system with biodiesel is the least-cost alternative. A study by Booz-Allen & Hamilton, Inc., found fleets using a 20% biodiesel blend would experience lower total annual costs than other alternative fuels. Similarly, results reported by the University of Georgia indicate that biodiesel-powered buses are competitive with other alternatively-fuelled buses with neat biodiesel prices as high as $3 per gallon.
Biodiesel emits less toxic compounds due to:
i. Biodiesel has high cetane
ii. In-built oxygen content
iii. Burns fully
iv. No aromatics
v. Complete CO2 cycle
The cetane number of biodiesel compared to petrodiesel indicates potential for higher engine performance. Tests conducted by Haridarshan et al. (1996) have shown that biodiesel has similar or better fuel consumption, horse power, and torque, haulage rate as conventional diesel (Table 8.1). The superior lubricating properties of biodiesel increases functional efficiency of engine. Their higher flash point makes biodiesel safer to store. The biodiesel molecules are simple hydrocarbon chains, containing no sulphur or aromatic substances associated with fossil fuels.
They contain higher amount of oxygen (upto 10%) that ensures more complete combustion of hydrocarbons. Above all biodiesel almost completely eliminates cycle CO2 emission. When compared to petrodiesel, it reduces emission of particulate matters by 40%, unburned hydrocarbons by 68%, CO by 44%, sulphates by 100%, polycyclic aromatic HCs (PAHs) by 80%, carcinogenic nitrates by 90% on an average.
Bio-Fuel and Environmental Benefits:
The use of bio-fuel has immediately positive effects on the environment:
i. Carbon monoxide – Biofuel reduces the amount of carbon monoxide produced by furnaces and boilers in the home.
ii. Sulfur dioxide – Sulphur dioxide is the pollutant that causes acid rain. Bio-fuel contains almost no sulphur and, therefore, reduces the amount of sulphur dioxide in burnt exhaust.
iii. Biodegradable and non-toxic – United States Department of Agriculture tests confirm that bio-fuel is less toxic than table salt and biodegradable as quickly as sugar.
iv. Air quality – While relatively new to heating systems, biodiesel fuel has been used by the automobile industries in some parts of country for a number of years. Carriers can use biodiesel within their fleets to meet the mandates for air quality.
6. Engine Performance of Biofuels:
There are mechanical advantages to using Biodiesel with Reformulated ‘Low Sulphur, Low Aromatics’ Diesel. Biodiesel methyl esters improve the lubrication properties (‘lubricity’) of the diesel fuel blend. Long term engine wear studies conducted in Europe, US and Porsche (Germany) determined that neat (100%) biodiesel reduced long term engine wear in test diesel engines to less than half of what was observed in engines running on current low sulphur diesel fuel.
Lubricity properties of fuel are important for reducing friction wear in engine components normally lubricated by the fuel rather than crankcase oil. When the California Air Resources Board (CARB) mandated stricter laws than the Federal requirements for reformulating ‘low sulphur, low aromatic’ diesel fuel in 1993, the result was a decrease in the lubricity of that fuel. The reduction in aromatics at that time also changed the elastomeric properties of the fuel resulting in the shrinking of gaskets, O-rings and seals in older engines.
The mechanical wear and fuel leaks caused so many problems (e.g., expensive rebuilds of fuel pumps) that California truckers held a one day strike in December, 1993 to protest the new fuel laws. Since then, truckers, boaters and other operators of diesel engines have turned to a variety of petroleum additives (in extreme cases, transmission fluid) in an attempt to protect their engines from excessive wear and gasket leaks associated with the new ‘CARB low sulphur/low aromatics’ diesel fuel.
More than 100 Biodiesel demonstrations, with over 10 million road miles in trucks, have confirmed the performance benefits of this fuel additive for emissions and mechanical lubricity. No adverse durability or engine wear problems were found; in fact, in road tests with heavy duty truck engines, engine wear was significantly decreased after running 1,00,000 miles on blends of Biodiesel (University of Idaho studies).
Biodiesel has been studied extensively in Europe and the U.S. for its effect on long term engine wear, particularly with respect to those components normally lubricated by the fuel itself. Fuel pumps and injector pumps depend on the operating fuel for lubrication of moving parts and shaft bearings. Initial work on the lubricity of Biodiesel, performed by Mark-IV Group and the Southwest Research Institute in 1994, established a clear advantage of blending Biodiesel with petrodiesel to achieve superior lubrication.
Lubricity properties are measured at the Southwest Research Institute (SWRI) by a ‘Ball on Cylinder Lubricity Evaluator’ (BOCLE) machine to measure metal to metal hydrodynamic wear simulating rotating shafts and bearings. A static steel ball is loaded onto the edge of a rotating disc and the diameter of the subsequent scar on the ball is measured (similar reciprocating machines exist in Europe to measure scar on a steel ball, and newer versions have been developed in America to improve lubricity measurements). The BOCLE test does not measure adhesive friction wear.
Tests run by Exxon company in USA showed that, compared to reference diesel fuel in 1993, a 20% blend of Biodiesel had significant, quantifiable improvements in reducing wear (193 micron scar for B-20 vs. 492 micron scar for petrodiesel) and friction (0.13 micron scar for B-20 vs. 0.24 micron for petrodiesel) while improving film coating ability of the blend (93% film with the B-20 vs. 32% film with the petrodiesel). The B-20 blend compared favourably for lubricity results against Exxon’s own lubricity additive.
The SWRI results for the BOCLE tests confirmed the earlier Exxon’s study results. Low sulphur, low aromatic (‘CARB’) diesel was compared to various blends of Biodiesel (soy methyl esters). Data were presented in values of grammes of weight added to the apparatus before failure of the fuel to adequately lubricate the metal. The higher the weight the ball could support, the better the lubricity of the fuel. Neat petrodiesel (low aromatic CARB) had a BOCLE result of 3,500 grammes, whereas the neat Biodiesel had a BOCLE result almost twice as high at 6,100 grammes.
The B-20 blend had a BOCLE result of 4,100 grammes, close to the value for pre-1993 (high sulphur, high aromatic) petrodiesel fuel. In concentrations below 5%, the Biodiesel had no measurable effect on the lubricity of petrodiesel. Follow up BOCLE studies at SWRI in 1996 concluded that Biodiesel methyl esters had even better lubricity properties than previously reported. The Biodiesel (RME) had a BOCLE value of 7,000 grammes vs. 4,250 for low sulphur diesel (not CARB diesel), and the B-20 blend had a BOCLE value of 4,600 grammes. Scar wear diameters were also encouraging, with a 405 micron scar reported for petrodiesel vs. a 190 micron friction scar for the B-20 blend.
Subsequent field studies on light duty truck engines (5.9L Cummins diesel at the University of Idaho) have corroborated these results by finding an ‘absence of wear’ and friction scars on engines broken down for inspection after a 1,00,000 mile road test running on 28% Biodiesel. In a University of Idaho durability test (1,000 hour tests on small diesel engines), it was found that methyl ester Biodiesel was equivalent to No. 2 diesel on the basis of long term engine performance and wear. The primary factors evaluated in that study were engine brake power and torque, injector tip coking (carbon deposition), and engine component wear based on oil analysis.
In house monitoring over the past 5 years of our ‘Biofuel Test Vehicles’ (a Mercedes Benz 300TD diesel station wagon and a 1985 BMW 524-Diesel) at CytoCulture has shown no evidence of unusual wear or polymerization of engine crankcase oil (analysis performed by Herguth Laboratories, Vallejo, CA) after more than 40,000 miles of operation on 30-100% blends with Biodiesel.
Heat of Combustion Properties:
Relative to petroleum diesel No. 2, Biodiesel has a slightly lower heat of combustion on account of its oxygen content (petroleum diesel hydrocarbons are not oxygenated). The heat of combustion for soy methyl esters is 1,28,000 BTU (British Thermal Units) per gallon vs. 130.500 BTU gal–1, for petrodiesel. In the Southwest Research Institute study (1996), the heat of combustion for rapeseed biodiesel in blends were compared with petrodiesel.
Petrodiesel had 18,400 BTU lb–1, neat biodiesel had 16,200 BTU lb–1. (88%) and a 20% blend of rapeseed methyl ester biodiesel had 17,900 BTU lb–1 (97%). However, with the added oxygen, the net combustion efficiency for the blended fuel is increased, which should compensate for the slight drop in BTU content. The differences would be most noticed at low rpm and high engine load when the engine would most benefit from more oxygen.
Studies conducted on blends of Biodiesel and petrodiesel in the U.S. and Europe generally indicated a small decrease in overall power output of engines. Only two studies have been conducted with marine engines, one by a German scientist (Dr. Claus Breuer) at the Technical University in Hannover (Ph.D. thesis in 1994) and the other by Alvin Womac’s group at the Department of Agricultural Engineering at the University of Tennessee. The German study involved a Deutz 4 cylinder marine diesel engine (direct injection) found on fishing boats in Europe and the Tennessee study evaluated a 110 HP Volvo marine diesel engine, also used in work boats and fishing boats. Volvo also makes smaller single and double cylinder diesel engines for recreational sailboats.
The German study confirmed similar results obtained by Mercedes Benz showing that the maximal torque curve for an engine under load remains essentially unchanged for rapeseed methyl esters relative to pure petrodiesel. Despite the lower volumetric heating value and the consequent lower maximum power output of Biodiesel, the practical results are roughly the same. At a 20% blend, there would probably be no noticeable difference in power output. Good performance in fuel combustion with Biodiesel and its blends resulted in a smooth running engine.
In the Volvo marine diesel engine study in Tennessee (110-HP, 2.39 L, 4-cylinder, direct injection engine), a tractor dynamometer was used to measure power outputs under selected loads through an engine-mounted reverse drive gear. Exhaust emissions were also tested along with fuel consumption tests under various loads. The conclusions of these tests were that power produced from 100% soy methyl ester Biodiesel was from 2 to 7 per cent less than that produced from petrodiesel, depending on the load-speed point.
However, at or near maximum throttle (3,800 rpm), the two fuels performed the same. Interestingly, at the lowest engine speed (1855 rpm) at full throttle under heavier load, there was a 13% increase in power with Biodiesel as compared to petrodiesel. The Tennessee study indicated that using 100% Biodiesel in marine direct-injection diesel engines, with design and construction similar to the Volvo test engine, could be recommended without any significant, noticeable differences in operation, power performance and fuel usage.
In the 1998 study at the Southwest Research Institute on Biodiesel, effects on diesel engine performance, engine power in the 1997 Cummings truck engine operating on the B-20 blend was at 98.5% of the power attained with low sulphur No. 2 diesel. At 100% Biodiesel, the engine generated 92% of the power. For a Detroit Diesel truck engine (1997), the power was 98% with the B-20 and 92% with the neat Biodiesel.
Biodiesels are mono-alkyl esters containing approximately 10% oxygen by weight. The oxygen improves the efficiency of combustion, but it takes up space in the blend and therefore slightly increases the apparent fuel consumption rate observed while operating an engine with Biodiesel. In the Southwest Research Institute study (1996), the fuel consumption was found to increase by only 2% for a B-20 blend with methyl esters, and by 14% when methyl ester Biodiesel was used at 100% in the Cummins test engine operated under transient heavy loads. The brake-specific fuel consumption was 0.43 lb/HP-Hr for regular petrodiesel No. 2, 0.44 lb./HP-Hr for the B-20 blend, and was 0.50 lb./ HP-Hr for the neat RME Biodiesel.
In testing Biodiesel in the CytoCulture Mercedes Benz diesel station wagon over the past 4 years, there was about a 15% net decline in the mileage obtained using neat Biodiesel vs. petrodiesel. No change in power, acceleration or engine temperature was observed, but the engine was quieter and smoother at idle when fuelled with Biodiesel. At a 20% blend with petroleum diesel, the fuel consumption differences are practically unnoticeable.
These local observations were confirmed by the 1998 engine performance studies at the Southwest Research Institute. Fuel consumption in a 1995 Cummings B-5.9 truck engine increased by 9% with the B-20 blend, and by 18% with the neat Biodiesel. Better fuel economy was noted for a 1997 Cummings N-14 truck engine with a 3% in fuel consumption using B-20 and a 13% increase with the neat Biodiesel.
The oxygenated methyl esters of vegetable oil cause Biodiesel to have surprisingly strong solvent properties with respect to natural rubber and several soft plastics. As a result, old rubber fuel lines and some seals or gaskets on fuel tanks may slowly deteriorate in the presence of higher concentrations of Biodiesel. Fortunately, few of these solvent effects are noticed at a B-20 blend, and most of the problems associated with the solvent effects occurred with boats using 100% neat Biodiesel.
When fuel lines or gaskets are affected, they usually get sticky over time and soften or swell, causing fuel to drip from connections. In one case, the rubber fuel line between the primary filter and the fuel pump on a Yanmar sailboat engine became tacky, but did not leak, after 4 years of operating on 100% Biodiesel. The best solution is to replace affected lines and gaskets with modern synthetic hoses and seals.
Conventional US Coast Guard approved fuel lines are resistant to Biodiesel (neat) and proven in sailboat testing over the past 3 years. In California, an approved fuel hose readily available in marine stores is –
‘Trident Barrier Fuel Hose, USCG Approved Type A-1, SAE J1527 (2/93)’
In bench top studies conducted at CytoCulture, the Trident hose proved to be resistant to neat Biodiesel over a period of months, although the hose did absorb Biodiesel and swell slightly (tightens under hose clamps). With 20% blends, there have been no reports of any problems with these new fuel hoses. Even at 100% Biodiesel, we have observed only minor swelling on the Trident Barrier fuel hoses used on test engines operating on neat Biodiesel for several years.
Studies conducted for the National Biodiesel Board on the materials compatibility of Biodiesel concluded that the only hose and gasket material that was truly resistant to the solvent effects of methyl esters was Viton. Viton fuel hoses (Goodyear) can be special ordered for boats (usually expensive at over $5.00/ft for 5/16″ line), but we know of only one boat in the San Francisco area that converted to Viton fuel lines as a precaution. In CytoCulture’s 1997 survey of 100 boaters using Biodiesel in the San Francisco Bay area, 2% of the respondents had trouble with drips caused by swelling gaskets and seals, usually at the fuel filter.
Again, replacing these gaskets with modern synthetic materials appeared to solve the problem. Raycor filters, for example, have functioned normally with 100% Biodiesel and have had no gasket problems in engines operated with neat Biodiesel over the past 4 years. (The 1997 boater survey is on the CytoCulture web site). In the survey, 5% of the boaters reported minor problems with the Biodiesel if they spilled it on decks, on their engine or into their bilges.
The solvent properties of the esters in Biodiesel can loosen old paint on engines or on painted surfaces in the bilge. Besides staining raw wood surfaces, the Biodiesel is particularly harmful to teak decks with polysulphide seams (use extra caution when filling tanks via deck ports). The Biodiesel could also harm rubber engine mounts if it were spilled and not cleaned up immediately. Use paper towels or absorbent pads to remove spilled Biodiesel and then clean the surfaces thoroughly with warm soapy water.
Marine diesel engine manufacturers in United States, Europe and Japan have all recognized the growing role of Biodiesel as a viable fuel additive, and in most cases, as a complete alternative fuel (100%). Two of the sponsors of the SUNRIDER expedition of 1992-1994 were the marine diesel engine manufacturers – Mercruiser (inboard/outboard diesel engine) and Yanmar (outboard diesel engines), endorsed Biodiesel as a suitable alternative fuel to power Bryan Peterson’s 28-ft inflatable Zodiac boat around the world. This 35,000 mile adventure remains the most famous and most publicized demonstration of using Biodiesel in marine engines.
Over 18,000 gallons of donated soy methyl ester Biodiesel was provided to SUNRIDER at various destination ports and rendezvous locations (including a mid-ocean fuel transfer from a ship). Bryan started out from Pier 39 in San Francisco in 1992 and returned under the Golden Gate Bridge on September 8, 1994, powered by 100% soybean Biodiesel. Brian’s last 100 gallons of Biodiesel were donated by CytoCulture when he stopped in Santa Cruz on the final leg up the coast of California. At that point, he remarked, “The Biodiesel works….No problems.”
Engine manufacturers in Europe have a long history of supporting the Biodiesel movement, and those that produce marine engines continue to endorse the alternative fuel use in their equipment. Some manufacturers warranty their marine engines for use with 100% Biodiesel for late models or for older engines retrofitted with newer synthetic hoses and gaskets that proved more resistant to the pure methyl esters over extended periods of time. Some prefer to warranty Biodiesel engines on a case by case basis. In the U.S., diesel engine manufacturers generally stand by their warranties as long as the fuel used in their engines meet the ASTM D-975 standards defining fuel for compression ignition engines. All of the B-20 blends of Biodiesel produced in America meet the ASTM D-975 specifications.
Biodiesel can be stored for long periods of time in closed containers with little head space. The containers should be protected from weather, direct sunlight and low temperatures. Avoid long term storage in partially filled containers, particularly in damp locations like dock boxes. Condensation in the container can contribute to the long term deterioration of the petroleum diesel or biodiesel. Low temperatures can cause the Biodiesel to gel, but the Biodiesel will quickly liquefy again as it warms up. In cold weather (near or below freezing), additives can be used to prevent gelation (fuel additives for diesel fuel used in cold weather are available from Exxon, Hammond, and other manufacturers).
Fuel tanks should be kept as filled as possible (regardless of whether they contain Biodiesel), particularly during rainy winter months or periods of inactivity, to minimize the condensation of moisture. Condensed moisture accumulates as water in the bottom of your tank and can contribute to the corrosion of metal fuel tanks, especially with petroleum diesel that also contains sulphur.
The condensed water in the fuel tank can also support the growth of bacteria and mold that use the diesel and Biodiesel hydrocarbons as a food source. These hydrocarbon-degrading bacteria and molds will grow as a film or slime in the tank and accumulate as sediment over long periods of time. These hydrocarbon-degrading microbes are frequently referred to incorrectly as “algae” in advertisements for fuel treatments, perhaps because the colonies often have a reddish orange colour and tend to form mats.
Petroleum diesel and Biodiesel are both susceptible to growing microbes when water is present in the fuel, but the solvent action of the Biodiesel can also cause microbial slime to detach from the inside of the tank. The accumulation of the newly released slime and sediment can be very dangerous if it clogs the fuel filters and causes the engine to suddenly stop. It is very important to monitor the filters on a diesel engine that has been switched over to Biodiesel, particularly if the tank is old and has not been cleaned.
Biocides are available at marine stores to treat diesel fuels suspected of having microbial growth. The biocides are chemicals that kill bacteria and molds growing in fuel tanks without interfering with the combustion of the fuel or the operation of the engine. Used in very dilute concentrations, the biocides can inhibit the growth of microbes over long periods of time. These products are very toxic and should be used only as directed by the manufacturers.
Precautions should be taken to avoid any contact with the products (wear gloves and eye protection) and to prevent any spills or drips. It is important to remember that the biocides may kill the microbes, but they do not remove the accumulated sediment, so expect to replace fuel filters often as the debris is drawn from the tank. In some cases, it may be necessary to have the fuel filtered and the fuel tank cleaned by a professional fuel filtering service.
The microbial slime and sediment problem seems to worsen for boats that are used infrequently since the inactivity allows the microbes to accumulate in stable colonies. When the boat is used again, the slime and sediment can break loose and accumulate in the fuel filters. Accumulated sediment in fuel filters can then interrupt the flow of fuel and shut down the engine, potentially with disastrous consequences. In recent years, several sailboats have washed up on beaches on account of clogged fuel filters with ordinary petroleum diesel caused by the sudden agitation of tank sediments when the boat encountered rough seas off shore.
The addition of Biodiesel to a dirty fuel tank can accelerate the release of accumulated slime. When the boat is then used after sitting idle for a long period of time, the newly suspended sediment can accumulate and potentially clog the fuel filters. All boaters need to check their fuel filters often and be prepared to change them after they introduce Biodiesel to an older fuel tank that may have accumulated slime and sediment.