Biodiesel
Biodiesel is a renewable energy fuel produced from animal fats and vegetable oils by lipid transesterification. Chemically, it is a fatty acid mono alkyl ester.
Biodiesel is nonflammable and nonexplosive (flash point 150ºC for biodiesel and 64ºC for petrodiesel) . It is biodegradable and nontoxic.
History
Transesterification of a vegetable oil was conducted as early as 1853, by scientists E. Duffy and J. Patrick , making it before the first diesel engine became functional.
At Augsburg, Germany on August 10, 1893, Rudolf Diesel's prime model, a single 10-foot iron cylinder with a flywheel at its base, ran on its own power for the first time. Because of this, the International Biodiesel Day is on August 10 every year.
Rudolf Diesel demonstrated his engine at the Exhibition Fair in Paris, France in 1898. This engine stood as an example of Diesel's vision because it was fueled by peanut oil - the "original" biofuel. He thought that the utilization of a biomass fuel was the real future of his engine.
In a 1912 speech, Rudolf Diesel said “the use of vegetable oils for engine fuels may seem insignificant today, but such oils may become, in the course of time, as important as petroleum and the coal tar products of the present time.”
During the 1920's diesel engine manufacturers created a major challenge for the biofuel industry. Diesel engines were altered to utilize the lower viscosity of the fossil fuel residue (chiefly, petrodiesel) rather than a biomass fuel. The petroleum industries were growing and establishing themselves during this period. Their business tactics and the wealth that many of these "oil tycoons" already possessed greatly influenced the development of all engines and machinery. The alteration was first step in the elimination of the production structure for biomass fuels and its competition as well as the first step in forcing the concept the of biomass as a potential fuel base into obscurity, erasing the possibilities from the public awareness.
Production
Biodiesel can be produced from biolipids. This is:
- From virgin oil feedstock from such crops as mustard, rapeseed, and soybeans, as well as other crops;
- From waste vegetable oil (WVO);
- And from animal fats.
According to a study written by Drs. Van Dyne and Raymer for the Tennessee Valley Authority, although the average US farm requires 33 litres (8.75 gallons) of fuel to cultivate 40 acres (one acre) of land, rapeseed produces an average of 420 l (110 gallons) of oil per acre. The average yield of high-yield rapeseed fields is 550 l (145 gallons) per acre. Unfortunately by themselves these statistics are not enough to show whether such a change makes economic sense.
The issue is economic: one of the exceptions Nassau Senior noted to the idea that machines aren't harmful to wages is, where the machines themselves make demands on resources that would have gone into food production. So the important question isn't whether biodiesel can be produced as whether that it is the most efficient use of resources, and the expense of biodiesel in comparison to traditional forms of diesel suggests that the answer is no.
For third world countries biodiesel sources that use marginal land could make more sense, e.g. Honge nuts grown along roads, and biodiesel is often economically profitable when it is used to process oils which otherwise would be discarded.
The direct source of the energy content of biodiesel is solar energy captured by plants during photosynthesis. The website biodiesel.co.uk 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).
The production of biodiesel processors is measured in metric tonnes/year with a specific gravity of 0.89
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. Home brew biodiesel processors are many and varied.
Oil preparation
Biodiesel processor machines, need the vegoil have some properties:
- Suspension particles lower than 1% (mass/mass) and than 5 micrometers. Because of this, it´s neccessary:
- Filtration to 5 micrometers.
- Washing with hot water.
- Decantation.
- Heating of the oil.
- Second decantation.
- Anhydrous (waterless). Because of this, the final step of preparation, after the second decantation, it is the drying.
- Easy solubility in the alcohol to use.
Biodiesel recipe
Like a recipe for making a cake, a biodiesel recipe specifies quantity ofe every ingredient required, and the steps for combining and processing them to make biodiesel fuel.
The most common recipe uses waste vegetable oil (WVO), alcohol (methanol or ethanol) and sodium hydroxide (caustic soda), to produce biodiesel and glycerol. To produce 1 t of biodiesel, one need:
- One need 1 t of biolipids (oil from animal or vegetables) and 0,1 t of methanol.
- One recieves 0,1 t of glycerol.
The most common steps are:
- Preparation: cleaning/heating biolipid (i.e. WVO). Seen before. With wet oil, you will obtain soap with the biodiesel, the conversion index from vegoil to biodiesel will be smaller and you will obtain an excess of triglycerides.
- Titration of WVO sample. Optimal pH for Biodiesel is 7 (neutral), the same as distilled water (and most tap water). When some fat has a high level of free fatty acids is recommended an acid esterification ( to obtain an acid number lower than 3) before the alkaline transesterification.
- Mixing the bioalcohol (methanol or ethanol) and catalyst (sodium hydroxide) in exact amounts,
- Combining at 50ºC the anterior mixing (3) with the biolipids.
- Separation:
- Of biodiesel and glycerine (by decantation, centrifugation...).
- Removing of alcohol (by destillation).
- Biodiesel purification: posterior separation from the biodiesel of the wastes (catalyst and soap): washing and drying the biodiesel.
- Disposing of the wastes.
Fuel properties and quality
Biodiesel is a clear amber-yellow liquid with a viscosity similar to petrodiesel (the industry term for diesel produced from petroleum).
Pure Biodiesel (BD100) can be used in any petroleum diesel engine.Biodiesel has the disadvantage of degrading rubber gaskets and hoses in older vehicles (prior to 1992), but not in newer vehicles.
When mixed with petrodiesel , biodiesel can be used at any concentration and is commonly referred to according to its "B factor": 20% biodiesel is called B20, and 100% biodiesel is called B100.
Quality of biodiesel to ensure trouble free operation in diesel engines is:
- Complete reaction.
- Removal of glycerin.
- Removal of catalyst.
- Removal of alcohol.
- Absence of Free fatty acids.
Properties
- Because biodiesel is an effective solvent, it also cleans the fuel system. Fuel filters catch petrodiesel particulates when biodiesel is used, so clogging is not an issue once the precipitates have been removed.
- Biodiesel reduces emissions carbon monoxide (CO) by approximately 50%. The CO2 is reabsorved by vegetables.
- Biodiesel contain less aromatic hydrocarbons: benzoflúoranthene - 56%; Benzopyrenes - 71%.
- It also eliminates sulfur emissions ( SO2), because biodiesel doesn´t include sulfur.
- Reduces in a 65 % the emission of particulates (small particles).
- Diesel vehicles burning BD100 can utilize nowadays usual catalytic converters to eliminate NOx emissions, which are similar to petrodiesel.
- It has a higher cetane rating (less knocking) than petrodiesel
See also: batch, bioalcohol, bubble wash, energy balance, hydrogen car, renewable energy, WVO.