Biodiesel: VOME, BTL or NExBTL?

Kimmo Klemola
29.04.2006
Updated 14.09.2006

Biodiesel is either VOME (vegetable oil methyl ester produced from vegetable or waste food oils and some alcohol, usually methanol, to produce ester)—today you mean VOME when you speak about biodiesel—or BTL (biomass to liquids) diesel, which is possibly tomorrow's biodiesel.

BTL

BTL biodiesel can be produced from any biomass using the conventional syngas and Fischer–Tropsch route just like CTL or GTL to produce more dinodiesel-like biodiesel, but sulfur free. BTL involves the manufacture of H₂ from biomass, and one alternative is to stop there and purify the hydrogen and use it as a fuel.

Synthesis gas from biomass:

C (s) + H₂O (g) → CO (g) + H₂ (g)

Synthesis gas to liquid hydrocarbons that can be processed to high-quality diesel:

CO + H₂ → –(CH₂)– + H₂O
2 CO + H₂ → –(CH₂)– + CO₂CO + H₂O → CO₂ + H₂

The synthesis gas routes:

According to some studies, VOME biodiesel causes 1/2 of the net CO₂ emission compared to dinodiesel, and for BTL biodiesel the same figure is 1/6. The release of 300 million old carbon is thus 50% or 83% lower, respectively. However, it seems that these studies have not taken into account all life-cycle energy inputs. It is also obvious that the energy efficiency of biomass utilization is at its best in heat and power generation and especially in combined heat and power generation.

BTL has the advantage that all biomass including waste biomass can be processed to fuel. Hence it is not so obvious that BTL fuels are competing with food production.

NExBTL

Finland’s Neste Oil has developed its own NExBTL (Next generation biomass to liquids) biodiesel process. In NExBTL, vegetable oils and/or animal fats are hydrotreated to high-quality sulfur-free diesel.

When for example a long-chain vegetable oil fatty acid is hydrogenated, the product is a linear hydrocarbon or a mixture of linear hydrocarbons with high cetane number but poor cold properties.

The linear hydrocarbons are further hydrogenated to yield more branched hydrocarbons with better cold properties, i.e. the linear hydrocarbons are isomerized.

NExBTL biodiesel has second generation biodiesel properties, but it is not a second generation biodiesel, because it is made of food.

NExt generation Biomass To Liquids = NExBTL

"Next or second generation" is not made of food.

Food is not "biomass".

NExBTL is not second generation nor is it biomass to liquids.

Malaysian palm oil (food oil) will be the major raw material for NExBTL. It has been proposed that imports of soya and palm oil from rain forest countries to European Union should be forbidden, because the soya and palm plantations destroy rainforests.

"Speaking at this weekend's informal meeting in the Finnish town of Turku, Environment Commissioner Stavros Dimas said that, "almost all" ministers favour higher environmental taxes and the scrapping of subsidies with negative effects on the environment. The ministers also discussed an import ban on products that are thought harmful to the environment, like soya that is cultivated on cleared soil in the Amazon rain forest." [www.openeurope.org.uk] (palm oil and Malaysia...)

"Even though the spirit is to convert the tropics (as well as the poor parts of the U.S. interior, Eastern Europe, and Russia) into gigantic sources of industrial raw (bio)materials for the more developed countries or regions, the obfuscating language is decidedly 21st century, with terms like “green energy,” “sustainable development,” “renewable development,”, “zero-emissions,” “investment in the developing world,” etc., used most often." [Patzek Tad W., Pimentel David, Thermodynamics of Energy Production from Biomass, Critical Reviews in Plant Sciences, 24(5-6), 327-364, 2005 January 27, 2006.]

“Green fuel is not just a humanitarian disaster; it is also an environmental disaster. Those who worry about the scale and intensity of today’s agriculture should consider what farming will look like when it is run by the oil industry. Moreover, if we try to develop a market for rapeseed biodiesel in Europe, it will immediately develop into a market for palm oil and soya oil. Oilpalm can produce four times as much biodiesel per hectare as rape, and it is grown in places where labour is cheap. Planting it is already one of the world’s major causes of tropical forest destruction. Soya has a lower oil yield than rape, but the oil is a by-product of the manufacture of animal feed. A new market for it will stimulate an industry that has already destroyed most of Brazil’s cerrado (one of the world’s most biodiverse environments) and much of its rainforest.” [Monbiot George, Fuel for nought, The Guardian, November 23, 2004.]

"For example, much has been made of the problems of feedstocks such as palm oil, where growers sometimes chop down virgin rainforest in order to grow palm. Because virgin rainforest is far better at capturing CO2, making this trade is not a net gain in GHG reductions." [Halpern-Lande Anna, Biofuel bonanza, The Chemical Engineer, May, 2006.]

"To fulfill the demand for biofuel, large areas of tropical rainforests are currently already converted into plantations, with the effect, that lowland rainforest, especially in Kalimantan, Indonesian Borneo, are cut down... We simply can not grow enough biomass to meet current and continued energy demands, without destroying more natural habitat and diverting food from the poor... It makes no sense to pursue modest improvements in climate change at the expense of the World's rainforests. Western countries must do better than destroying tropical rainforests to meet their Kyoto goals." [Klute Marianne, Palm oil plantations for biofuel production threaten tropical rainforest in Kalimantan, http://home.snafu.de/watchin/Biofuel.htm, October 13 2005]

VOME

The heart of the vegetable oil methyl ester production is the transesterification reaction between vegetable oil and methanol. The products are biodiesel and glycerol. Glycerol can be used e.g. in cosmetics industry. Increase in biodiesel production has resulted in oversupply of glycerol. In VOME production, also protein-rich animal fodder is produced in large quantities.

VOME biodiesel made of rapeseed oil (in USA soybean oil) and methanol requires huge land areas, if considerable amount of cars are fuelled with it. An average US light-duty vehicle (cars, SUVs, pickup trucks and >8500 lb vehicles that are used like a SUV or pickup truck) is fuelled with the crop of 3.8 hectares of soybean, or 9.4 acres. In USA, there are 240 million light-duty vehicles. To fuel all these vehicles with soybean oil biodiesel, 912 million hectares—equal to the land area of the United States—should be reserved for feeding cars.

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