All about BioDiesel
Biodiesel refers to a diesel-equivalent processed fuel derived from biological sources (such as vegetable oils) which can be used in unmodified diesel-engine vehicles. It is thus distinguished from the straight vegetable oils (SVO) or waste vegetable oils (WVO) used as fuels in some diesel vehicles.
In this article’s context, biodiesel refers to alkyl esters made from the transesterification of vegetable oils or animal fats.
On August 31, 1937, G. Chavanne of the University of Brussels (Belgium) was granted a patent for a ‘Procedure for the transformation of vegetable oils for their uses as fuels’ (fr. ‘Procédé de Transformation d’Huiles Végétales en Vue de Leur Utilisation comme Carburants’) Belgian Patent 422,877. This patent described the alcoholysis (often referred to as transesterification) of vegetable oils using ethanol (and mentions methanol) in order to separate the fatty acids from the glycerol by replacing the glycerol with short linear alcohols. This appears to be the first account of the production of what is known as ‘biodiesel’ today.[1]
Biodiesel is biodegradable and non-toxic, and typically produces about 60% less net lifecycle carbon dioxide emissions than petroleum-based diesel,[2] [3] as it is itself produced from atmospheric carbon dioxide via photosynthesis in plants. Though this figure can actually differ widely between fuels depending upon production and processing methods employed in their creation. Pure biodiesel is available at many gas stations in Germany.[4]
Some vehicle manufacturers are positive about the use of biodiesel, citing lower engine wear as one of the fuel’s benefits. Biodiesel is a better solvent than standard diesel, as it ‘cleans’ the engine, removing deposits in the fuel lines. However, this may cause blockages in the fuel injectors. For this reason, car manufacturers recommend that the fuel filter be changed a few months after switching to biodiesel (the fuel filter, as part of a routine maintenance plan, is generally replaced anyway). Most manufacturers release lists of the cars that will run on 100% biodiesel.[5]
Other vehicle manufacturers remain cautious over use of biodiesel. In the UK many only maintain their engine warranties for use with maximum 5% biodiesel — blended in with 95% conventional diesel — although this position is generally considered to be overly cautious. [6] Scania[7]and Volkswagen[8] are exceptions, allowing most of their engines to operate on 100% biodiesel. Peugeot and Citroën are also exceptions in that they have both recently announced that their PSA HDi engine can run on 30% biodiesel. The Ford Focus has recently been converted to run on Biodiesel.
Branson’s Virgin Voyager, number 220007 Thames Voyager [citation needed] was converted to run on Biodiesel, although an adverse effect occurred when it was proven to reduce reliability and to raise costs of maintenance significantly.
Biodiesel can also be used as a heating fuel in domestic and commercial boilers. Existing oil boilers may require conversion to run on biodiesel, but the conversion process is believed to be relatively simple.
Biodiesel can be distributed using today’s infrastructure, and its use and production are increasing rapidly. Fuel stations are beginning to make biodiesel available to consumers, and a growing number of transport fleets use it as an additive in their fuel. Biodiesel is generally more expensive to purchase than petroleum diesel but this differential may diminish due to economies of scale, the rising cost of petroleum and government tax subsidies. In Germany, biodiesel is generally cheaper than normal diesel at gas stations that sell both products.
Biodiesel Description :
Biodiesel is a liquid which varies in color — between golden and dark brown — depending on the production feedstock. It is practically immiscible with water, has a high boiling point and low vapor pressure. Typical methyl ester biodiesel has a flash point of ~ 150 °C (300 °F), making it rather non-flammable. Biodiesel has a density of ~ 0.88 g/cm³, less than that of water. Biodiesel uncontaminated with starting material can be regarded as non-toxic.
Biodiesel has a viscosity similar to petrodiesel, the current industry term for diesel produced from petroleum. It can be used as an additive in formulations of diesel to increase the lubricity of pure Ultra-Low Sulfur Diesel (ULSD) fuel, which is advantageous because it has virtually no sulfur content. Much of the world uses a system known as the “B” factor to state the amount of biodiesel in any fuel mix, in contrast to the “BA” or “E” system used for ethanol mixes. For example, fuel containing 20% biodiesel is labeled B20. Pure biodiesel is referred to as B100.
Biodiesel is a renewable fuel that can be manufactured from algae, vegetable oils, animal fats or recycled restaurant greases; it can be produced locally in most countries. It is safe, biodegradable and reduces air pollutants, such as particulates, carbon monoxide and hydrocarbons. Blends of 20 percent biodiesel with 80 percent petroleum diesel (B20) can generally be used in unmodified diesel engines. Biodiesel can also be used in its pure form (B100), but may require certain engine modifications to avoid maintenance and performance problems. Biodiesel has about 5–8% less energy density, but better lubricity and more complete combustion can make the energy output of a diesel engine only 2% less per volume when compared to petrodiesel — or about 35 MJ/L.[9]
The common international standard for biodiesel is EN 14214.
There are additional national specifications. ASTM D 6751 is the most common standard referenced in the United States and Canada. In Germany, the requirements for biodiesel are fixed in the DIN EN 14214 standard and in the UK the requirements for biodiesel is fixed in the BS EN 14214 standard, although these last two standards are essentially the same as EN 14214 and are just prefixed with the respective national standards institution codes.
There are standards for three different varieties of biodiesel, which are made of different oils:
- RME (rapeseed methyl ester, according to DIN E 51606)
- PME (vegetable methyl ester, purely vegetable products, according to DIN E 51606)
- FME (fat methyl ester, vegetable and animal products, according to DIN V 51606)
The standards ensure that the following important factors in the fuel production process are satisfied:
- Complete reaction.
- Removal of glycerin.
- Removal of catalyst.
- Removal of alcohol.
- Absence of free fatty acids.
- Low sulfur content.
Basic industrial tests to determine whether the products conform to the standards typically include gas chromatography, a test that verifies only the more important of the variables above. Tests that are more complete are more expensive. Fuel meeting the quality standards is very non-toxic, with a toxicity rating (LD50) of greater than 50 mL/kg.
Production
Chemically, transesterified biodiesel comprises a mix of mono-alkyl esters of long chain fatty acids. The most common form uses methanol to produce methyl esters as it is the cheapest alcohol available, though ethanol can be used to produce an ethyl ester biodiesel and higher alcohols such as isopropanol and butanol have also been used. Using alcohols of higher molecular weights improves the cold flow properties of the resulting ester, at the cost of a less efficient transesterification reaction. A lipid transesterification production process is used to convert the base oil to the desired esters. Any Free fatty acids (FFAs) in the base oil are either converted to soap and removed from the process, or they are esterified (yielding more biodiesel) using an acidic catalyst. After this processing, unlike straight vegetable oil, biodiesel has combustion properties very similar to those of petroleum diesel, and can replace it in most current uses.
A byproduct of the transesterification process is the production of glycerol. For every 1 tonne of biodiesel that is manufactured, 100kg of glycerol are produced. Originally, there was a valuable market for the glycerol, which assisted the economics of the process as a whole. However, with the increase in global biodiesel production, the market price for this crude glycerol (containing 20% water and catalyst residues) has crashed. Research is being conducted globally to use this glycerol as a chemical building block. One initiative in the UK is The Glycerol Challenge.
Usually this crude glycerol has to be purified, typically by performing vacuum distillation. This is rather energy intensive. The refined glycerol (98%+ purity) can then be utilised directly, or converted into other products. The following announcements were made in 2007: A joint venture of Ashland Inc. and Cargill announced plans to make propylene glycol in Europe from glycerol [17] and Dow Chemical announced similar plans for North America [18]. Dow also plans to build a plant in China to make epichlorhydrin from glycerol[19]. Epichlorhydrin is a raw material for epoxy resins.
Biodiesel feedstock
A variety of oils can be used to produce biodiesel. These include:
- Virgin oil feedstock; rapeseed and soybean oils are most commonly used, soybean oil alone accounting for about ninety percent of all fuel stocks; It also can be obtained from field pennycress and Jatropha[20] other crops such as mustard, flax, sunflower, canola, palm oil, hemp, and even algae show promise (see List of vegetable oils for a more complete list);[21]
- Waste vegetable oil (WVO);
- Animal fats including tallow, lard, yellow grease, chicken fat,[20] and the by-products of the production of Omega-3 fatty acids from fish oil.
- Sewage. A company in New Zealand has successfully developed a system for using sewage waste as a substrate for algae and then producing bio-diesel.[22]
- Thermal depolymerization is an important new process that reduces almost any hydrocarbon based feedstock, including non oil based feedstocks, into light crude oil.
Worldwide production of vegetable oil and animal fat is not yet sufficient to replace liquid fossil fuel use. Furthermore, some environmental groups object to the vast amount of farming and the resulting over-fertilization, pesticide use, and land use conversion that they say would be needed to produce the additional vegetable oil.
Many advocates suggest that waste vegetable oil is the best source of oil to produce biodiesel. However, the available supply is drastically less than the amount of petroleum-based fuel that is burned for transportation and home heating in the world. It is important to note that one gallon of waste oil is not equivalent to one gallon of biodiesel.[citation needed]
Although it is economically profitable to use WVO to produce biodiesel, it is even more profitable to convert WVO into other products such as soap. Therefore, most WVO that is not dumped into landfills is used for these other purposes. Animal fats are similarly limited in supply, and it would not be efficient to raise animals simply for their fat. However, producing biodiesel with animal fat that would have otherwise been discarded could replace a small percentage of petroleum diesel usage.
The estimated transportation diesel fuel and home heating oil used in the United States is about 50 billion US gallons (Energy Information Administration, US Department of Energy - http://tonto.eia.doe.gov/dnav/pet/pet_cons_821dst_dcu_nus_a.htm). Waste vegetable oil and animal fats would not be enough to meet this demand. In the United States, estimated production of vegetable oil for all uses is about 24 billion pounds (11 million tons) or 3 billion US gallons (0.011 km³), and estimated production of animal fat is 12 billion pounds (5.3 million tons). (Van Gerpen, 2004)
Biodiesel feedstock plants utilize photosynthesis to convert solar energy into chemical energy. The stored chemical energy is released when it is burned, therefore plants can offer a sustainable oil source for biodiesel production. Most of the carbon dioxide emitted when burning biodiesel is simply recycling that which was absorbed during plant growth[citation needed], so the net production of greenhouse gases is small[citation needed].
Feedstock yield efficiency per acre affects the feasibility of ramping up production to the huge industrial levels required to power a significant percentage of national or world vehicles. The highest yield feedstock for biodiesel is algae, which can produce 250 times the amount of oil per acre as soybeans.[23]
Yields of common crops
| Crop | kg oil/ha | litres oil/ha | lbs oil/acre | US gal/acre | |
|---|---|---|---|---|---|
| corn (maize) | 145 | 172 | 129 | 18 | |
| cashew nut | 148 | 176 | 132 | 19 | |
| oats | 183 | 217 | 163 | 23 | |
| lupine | 195 | 232 | 175 | 25 | |
| kenaf | 230 | 273 | 205 | 29 | |
| calendula | 256 | 305 | 229 | 33 | |
| cotton | 273 | 325 | 244 | 35 | |
| hemp | 305 | 363 | 272 | 39 | |
| soybean | 375 | 446 | 335 | 48 | |
| coffee | 386 | 459 | 345 | 49 | |
| linseed (flax) | 402 | 478 | 359 | 51 | |
| hazelnuts | 405 | 482 | 362 | 51 | |
| euphorbia | 440 | 524 | 393 | 56 | |
| pumpkin seed | 449 | 534 | 401 | 57 | |
| coriander | 450 | 536 | 402 | 57 | |
| mustard seed | 481 | 572 | 430 | 61 | |
| camelina | 490 | 583 | 438 | 62 | |
| sesame | 585 | 696 | 522 | 74 | |
| safflower | 655 | 779 | 585 | 83 | |
| rice | 696 | 828 | 622 | 88 | |
| tung oil tree | 790 | 940 | 705 | 100 | |
| sunflowers | 800 | 952 | 714 | 102 | |
| cocoa (cacao) | 863 | 1,026 | 771 | 110 | |
| peanuts | 890 | 1,059 | 795 | 113 | |
| opium poppy | 978 | 1,163 | 873 | 124 | |
| rapeseed (Canola) | 1,000 | 1,190 | 893 | 127 | |
| olives | 1,019 | 1,212 | 910 | 129 | |
| castor beans | 1,188 | 1,413 | 1,061 | 151 | |
| pecan nuts | 1,505 | 1,791 | 1,344 | 191 | |
| jojoba | 1,528 | 1,818 | 1,365 | 194 | |
| jatropha | 1,590 | 1,892 | 1,420 | 202 | |
| macadamia nuts | 1,887 | 2,246 | 1,685 | 240 | |
| Brazil nuts | 2,010 | 2,392 | 1,795 | 255 | |
| avocado | 2,217 | 2,638 | 1,980 | 282 | |
| coconut | 2,260 | 2,689 | 2,018 | 287 | |
| oil palm | 5,000 | 5,950 | 4,465 | 635 | |
| Chinese tallow | 5,500 | 6,545 | 4,912 | 699 | |
| Algae (actual yield)* | 6,894 | 7,660 | 6,151 | 819 | |
| Algae (theoretical yield)** | 39,916 | 47,500 | 35,613 | 5,000 |
* Actual biomass algae yields from field trials conducted during the NREL’s aquatic species program, converted using the actual oil content of the algae species grown in the specific trials. [24] ** Algae yields are projected based on the sustainable average biomass yields of the NREL’s aquatic species program, and an assumed oil content of 60%. Actual oil content was much less. [25]
- Note: Chinese tallow (Triadica Sebifera, or Sapium sebiferum) is also known as the “Popcorn Tree” or Florida Aspen.
Source: Chinese tallow data, Mississippi State University
Source: Used with permission from the The Global Petroleum Club
Typical oil extraction from 100 kg. of oil seeds
| Crop | Oil/100kg. |
|---|---|
| Castor Seed | 50 kg |
| Copra | 62 kg |
| Cotton Seed | 13 kg |
| Groundnut Kernel | 42 kg |
| Mustard | 35 kg |
| Palm Kernel | 36 kg |
| Palm Fruit | 20 kg |
| Rapeseed | 37 kg |
| Sesame | 50 kg |
| Soybean | 14 kg |
| Sunflower | 32 kg |
Source: Petroleum Club (with permission)
The energy content of biodiesel is about 90 percent that of petroleum diesel.
[edit] Efficiency and economic arguments
According to a study written by Drs. Van Dyne and Raymer for the Tennessee Valley Authority, the average US farm consumes fuel at the rate of 82 liters per hectare (8.75 US gallons per acre) of land to produce one crop. However, average crops of rapeseed produce oil at an average rate of 1,029 L/ha (110 US gal/acre), and high-yield rapeseed fields produce about 1,356 L/ha (145 US gal/acre). The ratio of input to output in these cases is roughly 1:12.5 and 1:16.5. Photosynthesis is known to have an efficiency rate of about 3-6% of total solar radiation [26] and if the entire mass of a crop is utilized for energy production, the overall efficiency of this chain is known to be about 1%. This does not compare favorably to solar cells combined with an electric drive train, however biodiesel out-competes solar cells in cost and ease of deployment. However, these statistics by themselves are not enough to show whether such a change makes economic sense. Additional factors must be taken into account, such as: the fuel equivalent of the energy required for processing, the yield of fuel from raw oil, the return on cultivating food, the effect biodiesel will have of food prices and the relative cost of biodiesel versus petrodiesel. A 1998 joint study by the U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA) traced many of the various costs involved in the production of biodiesel and found that overall, it yields 3.2 units of fuel product energy for every unit of fossil fuel energy consumed. [27] That measure is referred to as the energy yield. A comparison to petroleum diesel, petroleum gasoline and bioethanol using the USDA numbers can be found at the Minnesota Department of Agriculture website[28] In the comparison petroleum diesel fuel is found to have a 0.843 energy yield, along with 0.805 for petroleum gasoline, and 1.34 for bioethanol. The 1998 study used soybean oil primarily as the base oil to calculate the energy yields. Furthermore, due to the higher energy density of biodiesel, combined with the higher efficiency of the diesel engine, a gallon of biodiesel produces the effective energy of 2.25 gallons of ethanol. [29] Also, higher oil yielding crops could increase the energy yield of biodiesel.
The debate over the energy balance of biodiesel is ongoing, however. Transitioning fully to biofuels could require immense tracts of land if traditional crops are used. The problem is especially severe for nations with large economies, since energy consumption scales with economic output. [30] If using only traditional plants, most such nations do not have sufficient arable land to produce biofuel for the nation’s vehicles. Nations with smaller economies (hence less energy consumption) and more arable land may be in better situations, although many regions cannot afford to divert land away from food production. For third world countries, biodiesel sources that use marginal land could make more sense, e.g. honge oil nuts [31] grown along roads or jatropha grown along rail lines. More recent studies using a species of algae with up to 50% oil content have concluded that only 28,000 km² or 0.3% of the land area of the US could be utilized to produce enough biodiesel to replace all transportation fuel the country currently utilizes. Furthermore, otherwise unused desert land (which receives high solar radiation) could be most effective for growing the algae, and the algae could utilize farm waste and excess CO2 from factories to help speed the growth of the algae. [32] In tropical regions, such as Malaysia and Indonesia, oil palm is being planted at a rapid pace to supply growing biodiesel demand in Europe and other markets. It has been estimated in Germany that palm oil biodiesel has less than 1/3 the production costs of rapeseed biodiesel.[33] The direct source of the energy content of biodiesel is solar energy captured by plants during photosynthesis. The website biodiesel.co.uk[34]discusses the positive energy balance of biodiesel:
- When straw was left in the field, biodiesel production was strongly energy positive, yielding 1 GJ biodiesel for every 0.561 GJ of energy input (a yield/cost ratio of 1.78).
- When straw was burned as fuel and oilseed rapemeal was used as a fertilizer, the yield/cost ratio for biodiesel production was even better (3.71). In other words, for every unit of energy input to produce biodiesel, the output was 3.71 units (the difference of 2.71 units would be from solar energy).
Biodiesel is becoming of interest to companies interested in commercial scale production as well as the more usual home brew biodiesel user and the user of straight vegetable oil or waste vegetable oil in diesel engines. Homemade biodiesel processors are many and varied. The success of biodiesel homebrewing, and micro-economy-of-scale operations, continues to shatter the conventional business myth that large economy-of-scale operations are the most efficient and profitable. It is becoming increasingly apparent that small-scale, localized, low-impact energy keeps more resources and revenue within communities, reduces damage to the environment, and requires less waste management.