Besides favorable economics and environmental and health benefits, the development of reliable standards, which will instill confidence in biodiesel users, engine manufacturers, and other parties, is a milestone in facilitating commercialization (6). Austria (ONORM С 1190) and Germany (DIN V 51606) have established similar standards for neat biodiesel. In the United States, an ASTM standard was suggested (9). Table V gives the German standard and Table VI lists the proposed ASTM standard. The standards contain specifications particular to biodiesel (for example, glycerol quantitation) which are not given for conventional DF.

a) This specification is the process of being evaluated by ASTM. A considerable amount of experience exists in the U. S. with a 20 percent blend of biodiesel with 80 percent petroleum-based diesel. Although biodiesel can be used in the pure form, use of blends of over 20 percent biodiesel should be evaluated on a case-by-case basis until further experience is available.

b) Or equivalent ASTM testing method.

c) Austrian (Christina Plank) update of USDA test method (author’s note: refers to Refs. 97 and 104).

this is not without problems (55). Biodiesel from vegetable oils with high amounts of saturates (low I Vs) will have a higher CN while the low-temperature properties are poor. Biodiesel from vegetable oils with high amounts of unsaturates (high I Vs) will have low CN while the low-temperature properties are better. Thus, CN and low-temperature properties run counter to each other and this must affect I Vs for biodiesel standards. Another argument against inclusion of the IV in biodiesel standards is the observation that different fatty acid compositions give identical IVs (e. g., neat methyl oleate has the same IV as a 1:1 mixture of methyl stearate and methyl linoleate). The IV also does not take into consideration structural factors of fatty compounds as discussed above where the CNs depend on double bond position, etc. Furthermore, once in place, the IV will hinder further research and development. It is possible that plants with desirable high- cetane fatty acid profile can be genetically engineered and bred (for example, substituting A6 unsaturated Cl8:1 acids for A9 unsaturated ones) or that combustion­improving additives are developed which are highly effective even for high degrees of unsaturation. It was suggested that it appears better to limit the amount of higher unsaturated fatty acids (e. g. linolenic acid) than to limit the degree of unsaturation by means of the IV {34). Note that soybean oil, rapeseed oil, and canola oil (low-erucic rapeseed oil) have very similar 18:3 fatty acid content (Table II), which is the most problematic in the formation of engine deposits through polymerization. However, linseed oil methyl ester (high 18:3 content and IV) satisfactorily completed 1000 hours of testing in a DI engine while neat linseed oil caused the engine to fail {35 and references therein). These observations make the IV even more debatable.

Since most esters have higher CNs than neat vegetable oils and conventional DF, the esters could accommodate higher CNs than the minimum of 40 given in the ASTM standard for conventional DF. For example, the lowest reported CN for methyl soyate is 46.2 (see Table IV).

The German biodiesel standard includes the so-called Cold-Filter Plugging Point (CFPP) that pertains to the low-temperature flow properties of biodiesel. This low — temperature property test is used in Europe, South America, and the Pacific rim. In North America, a more stringent test, the Low-Temperature Flow Test (LTFT), is used and specified by ASTM D4539. Although the LTFT is more useful in evaluating low — temperature flow properties, ASTM requires only specification of cloud point for certification.