BIODIESEL data and engine design

Commenced 4-14-05 by Ken Wear

Biodiesel, ethanol and hydrogen can replace petroleum as portable energy sources in the U.S. While hydrogen will enjoy niche markets, temperatures and pressures necessary to its storage present safety concerns and its production requires significant expenditure of energy. Biodiesel and ethanol are produced from agricultural crops while gasoline requires petroleum; agriculture must become the major energy source. Ethanol from corn (a heavily-subsidized crop) requires significant acreage and its energy return is questionable; ethanol from sugar cane (as in Brazil) -- also heavily subsidized in the U.S. -- has apparently not been pursued in the U.S. Biodiesel becomes the most likely candidate.

In choosing between gasoline and diesel, diesel engines are, with today's designs, more expensive because of higher pressures in the engine. But diesel is more efficient and gives a significant improvement in miles per gallon. Performance-wise, diesel can enjoy the same quickness of response, as evidenced by Mercedez-Benz automobiles, but I suspect that, with some sacrifice in pick-up, engine designs may be devised that are comparable in cost to gasoline engines. However that may be, the power plant is only one of several costs in the manufacture of vehicles. Purchase decisions are based on the total cost including expected maintenance, insurance and cost of operation.

Comparing biodiesel and petro diesel, biodiesel performs as well as petro diesel while reducing emissions of particulate matter, CO, hydrocarbons and SOx. Emissions of NOx are higher in many engines. It is biodegradable and appears to reduce emissions of carcinogens.

There are disadvantages, which have been catalogued by the government, to biodiesel. Currently it is more expensive than petrodiesel; extensive use would require crop lands already in use for other purposes; emissions of NO2 would be increased; it is more viscous and presents low temperature problems; it requires more gallons to yield the same power; it may dissolve engine deposits produced by petrodiesel and require filter change when switching over; seals and gaskets may need to be replaced because of the greater chemical activity of biodiesel.

I said 'biodiesel;' that is not quite correct. There are two basically different directions you may take: SVO (Straight Vegetable Oil) or Biodiesel, which may be made from SVO by a straightforward process that is being carried out by many hobbyists and experimenters. Formulae and process descriptions are available on the World Wide Web but what descriptions I have read include some pretty nasty chemicals even though the final product is no more dangerous than petro diesel.

Of interest to climatologists is that biodiesel offers reduced emission of CO2 , SOx, carbohydrates and particulates, although some designs produce more NOx.

Low temperature start-up has been a problem with diesel since its invention. #2 diesel fuel will develop low temperature problems sooner than #1 diesel fuel, which is known as kerosene. Gelling of diesel fuel in cold climates has been countered by blending with kerosene, use of a fuel additive to improve viscosity, fuel tank or fuel line heaters, and storage in or near a heated building. A B20 blend has been used in cold climates with performance virtually identical to diesel. Half and half #1 and #2 diesel plugs its filter (apparently the most meaningful test of suitability of a fuel in cold weather) at -22oF.

Biodiesel may be substituted(?)1 (To view footnote, click here gallon by gallon for petroleum diesel. However, most vehicle manufacturers are hesitant to recommend biodiesel in their products, so the user must accept responsibility for any untoward results. The only American-made vehicle at a recent (4-14-05) auto show for which biodiesel was suggested was a Jeep SUV, and that was only B5 (5% bio in petro); there were no other American-made cars even hinting of diesel. However, Volksvagon and Mercedes both offer their diesel-operated cars in the U.S.A., and there are a number of diesel-operated cars available to the French, German and British publics. Import must consider domestic requirements for air pollution control, import duties and other taxes, availability of fuel, etc.

Of concern in engine design is lubricity of the fuel. Biodiesel reportedly offers better engine lubrication than even petro diesel. Some years ago I was forcibly reminded that each piston stroke consumes some oil from the crankcase in that a microscopic layer of oil is carried by the piston rings up the cylinder wall, to be burned during the next combustion stroke. However, some water is absorbed into the crankcase lubricant, so over time the lubricating ability of crankcase oil is reduced even though the dip stick may show no loss.

With the price of gasoline in Europe exceeding $5 per gallon in many places, considerable attention has been given to vegetable oils; in fact, waste oils as from cooking have been successfully used with only minor processing to remove solids and control acidity. (Imagine auto exhaust smelling of popcorn and French fries.) And, not only are noxious emissions greatly reduced when using vegetable oils, but engines run cleaner. I have found a great deal of information on efforts in other countries, notably Germany, at www.journeytoforever (June 2004) and resulting for searching "veg-oil-car." Different sources of oil have their peculiarities but filtering and controlling acidity apparently allow freely mixing oils to make "biodiesel." And progress has been made, by engine modifications, toward using biodeisel in engines designed for gasoline. 7-24-07 Since composing the original article, has been greatly expanded and improved.

Conversion kits: Elsbett (Germany) uses heaters:
Goat Industries (N. Wales) two tank design: try

To locate a biodiesel station, go to and use the link there. In the Atlanta area ('06) there are only two stations listed, one for B20 and one for B100.

Hydrogen gas may be used (in appropriately designed engines) as either diesel or spark-ignited or fuel cell input to generate electricity. I will insert here some factual information about hydrogen.
Autoignition temp aprx 565.5C or 1050F
Density .00521 lb/cuft or .08342 kg/m3
Dynetek offers cylinders for hydrogen rated at 5000 psi. At about 2 cuft per cylinder, that expands to 680 cuft at STP with an energy content of 216920 BTU, the equivalent of about 1.69 gallons of gasoline. With efficiencies significantly better than that of a gasoline engine, one cylinder of hydrogen may possibly be equated to somewhat more than 2.0 gallons of gasoline.

Agricultural considerations:
CORN: At 90-95% of theoretical, one ton of corn would yield about 370 kg of ethanol; there should be (after drying) 1300 kg/ha of stover (cured stalks without the ears -- used as fodder for animals) residue. (145 kg/ha of oil per Wikipedia) In 1982 the U.S. recorded 114.8 bushels per acre, which is estimated to be 1/4 of theoretical maximum with all inputs optimum. There are 6 types of cultivar of corn and some 200 cultivars grown in the U.S.

CANNABIS (Hemp): Many varieties are cultivated, some for fiber, some for oil, some for narcotics. Selection of seed and method of cultivation depend on the purpose; psychoactive THC forms at the time of flowering and fiber degrades after flowering while seeds require the plant mature, and closer spacing encourages height while bushiness encourages seeds. Varieties grown for seed oil are short (up to 5.3 m) in height, mature early and produce large quantities of seed. Grown for seeds, an average crop yield is 1300 to 1600 kg of seeds per hectare; oil content is around 40%. (305 kg/ha of oil per Wikipedia) Fiber can be treated to be rough to fine (burlap to linen) and has aprx 250% the water capacity of cotton. Hurds, the portion left after the stalk is stripped of its fiber, has many uses such as charcoal, methanol, paper and newsprint. Economic considerations apparently dictate that early processing (retting, breaking, etc.) be on the farm or within some 50 miles.

In large part because of the "war on drugs" and the resultant regulation and harassment, hemp cultivation in this country has dwindled so the infrastructure has largely fallen into disuse. Internationally, other crops such as sisal, jute, abaca, . . ., have been developed for fiber and become more competitive than hemp.

SOY: Not known in the wild state. Average yields per hectare (ha) are 5000 kg of hay and 1700 kg (60 bu (bushels)) of seeds, which, at 18.5% oil, yield some 300 kg/ha of oil. Soybean oil is some ten times more viscous than #2 diesel fuel. (375 kg/ha of oil per Wikipedia; oil 14% of seed)

RAPE: Seed yields vary from 900-3000 kg/ha, with an average of 40% oil on a dry matter basis. At 1500 kg/ha, oil would be 500 kg with 1000 kg of high protein meal. As a diesel extender, 75% rapeseed oil may be used, compared with 20% alcohol. Rape is the most important oil seed crop in Europe and Canada. Grain/straw ratio varies greatly (0.2-0.8, I suppose depending on the cultivar planted) so cultivation for oil leaves a great deal of residue to be used or discarded. (1000 kg/ha of oil per Wikipedia; oil 37% of seed)

JOJOBA: Per Wikipedia, 1528 kg/ha of oil; native to Sonoran and Mojave Deserts of Arizona, California and Mexico. (Included here because of yield)

PALM OIL: Per Wikipedia, 5000 kg/ha of oil; native to West Africa. (Included here because of yield); oil 36% of seed, 20% of fruit.

Crop kg oil/ha -- Crop kg oil/ha -- Crop kg oil/ha
Corn 145 Hemp 305 Soy 375
Rape 1500 Jojoba 1528 Palm Oil 5000
Conversion to biodiesel is not 100% efficient but should be similar for all oils.

Energetic return is placed at 2:1 for soybeans, 5:1 for sunflower, 3:1 for peanuts, 1:1 for cottonseed. (I have no precise definition for energetic return.)

Atmospheric impact: It is estimated that burning biodiesel in vehicles would introduce 15% more nitrogen oxides into the atmosphere than petrodiesel; other emissions would be reduced.

I was frustrated in finding relative prices for various seed oils, but did find this:
June 15, 1981: Compared with gasoline at 0.25/lb, corn oil was $0.232/lb, peanut oil 0.38, poppyseed oil 1.39/lb, tung oil 0.65, linseed oil 0.33, coconut oil 0.275, cottonseed oil 0.265, soybean oil 0.21. These prices were, of course, determined by bidding at the commodity exchange for delivery on futures contracts.

I have sought, with limited success, information on oil yield per acre cultivated since this seems crucial to selection of crop for cultivation for biofuel and must be heavily dependent on local conditions of terrain, soil and weather. My early life was on a non-operational farm so I have little understanding of the economics that dictates choices; my motivation here is to encourage biodiesel as a means of reducing dependence on petroleum. Infrastructure considers the whole plant and motivations of entrepreneurs in uses for the rest of the plant, a much more complex picture than I feel adequate to address. Our Governors, agronomists, engineers and investors must all become involved. (Finally found yield data in Wikipedia.)

In the short run, possibly 15-20 years, it seems likely that agricultural prodsucts will be the most likely source of biodiesel. In the longer run algae, with its much igher yield per acre, will undoubtedly be t he source of choice. What information I have accumulated on algae is called up by clicking here.

If you linked to Biodiesel from Energy, you may use your BACK button to return there, or click here.
Or you can go to the Table of Contents of this web site by clicking here.

1Footnote One
I have no specific information on BTU/gal; vegetable oils generally have 85% the energy content of petroleum derivatives. Neither have I information on peculiarities of various biodiesels prepared from various seed oils, although viscosity differs oil by oil. Hopefully my research will produce specifics.

Viscosities in centipoise (cp)
Oil- 0oC -- +10oC - - +20oC -- 30oC -- 40oC -- 50oC -- Other: cp @ ToC
Olive1388436.312.4 @ 70oC
Linseed* @ 90oC
Cottonseed 70.4
Sperm42 @ 15.6oC; 4.6 @ 100oC
Cylinder oil (filtered)18.7 @ 100oC
Compared with #2 petrodiesel and biodiesel from soy bean oil**
#2 diesel8.
*Linseed oil has high iodine value
**Taken from a chart provided by the National Biodiesel Board

Based on reduction in viscosity of soy bean oil when converted to biodiesel, biodiesel enjoys considerable advantage over SVO and you must choose which you will pursue or design for interchange.
I hazard the guess that other oils will produce comparable proportionate reduction in viscosity as temperature is increased.
In general vegetable oils must be heated to 70-80oC for indirect injection engines (IDI)

Conversions: In reading various reports, I have found the following conversions are helpful:
1 kg = 2.2 lb; 1 metric ton = 1000 kg = 2200 lb.
1 acre = 0.4047 hectare (ha) or 1 hectare is aprx 2.5 acre

In considering SVO, melting point and iodine value may be important. Some values are:
Oil Melts Iodine -- Oil Melts Iodine -- Oil Melts Iodine
ToC Value ToC Value ToC Value
Coconut +25 10 Palm kernel +24 37 Palm +35 54
Peanut+3 93 Rapeseed -10 98 Cottonseed -1 105
Sunflower -17 125 Soybean -16 130 Linseed -24 178
Since oils must pass through a filter, oil must be liquid at operating temperature.
Iodine Values above some 25 suggest need for more frequent servicing.

Your BACK button will return you to the text.
My printer requires 4 pages or 2 sheets of paper to print this document.