Date: Mar 23, 2009
Biodiesel is a biomass-based, renewable, diesel fuel derived from vegetable oils and animal fats. Unlike renewable fuels such as straight vegetable oil or waste vegetable oil that are produced by mechanical processing of oils and fats, we understand that manufacture of biodiesel involves chemical transformation of the starting oils and fats. The chemistry is straight-forward: base-catalyzed transesterification of the triglyceride components of vegetable oils and animal fats with short chain alcohols, such as methanol or ethanol, followed by removal of glycerol, which is liberated as a byproduct, yields biodiesel as a mixture of the monoalkyl esters of the component fatty acids. As a result, the fuel production process raises a regulatory consideration, namely, how to correctly identify the output under the jurisdictional statute for industrial chemical substances use known as the Toxic Substances Control Act (TSCA).
Before manufacturing or importing a chemical substance for a commercial purpose subject to TSCA, prospective manufacturer or importer must determine whether that substance is listed on the TSCA Chemical Substance Inventory (Inventory), or if it is covered by an applicable exclusion or exemption. Substances which are listed on the Inventory are existing chemical substances and are not subject to premanufacture notification under TSCA. Any substance not explicitly or implicitly included on the Inventory is a new chemical substance, potentially subject to TSCA premanufacture notification if not otherwise exempt.
Biodiesel may be manufactured from a broad range of vegetable oils and animal fats. Plant-based feedstocks include waste vegetable oil as well as virgin oil feedstocks such as soybean oil, palm oil, rapeseed oil, and sunflower oil. Animal-based feedstocks include tallow, lard, poultry fat, yellow grease, and fish oil. Manufacture may be based on single or multiple feedstocks. When determining whether a substance manufactured from these feedstocks is listed on the Inventory, a prospective manufacturer or importer may need to consult the appropriate formal and informal Inventory chemical nomenclature policies and guidance developed by EPA and its contractor, the Chemical Abstracts Service (CAS). Failure to understand and properly apply these policies and guidance could result in mischaracterization of a new chemical substance as an existing chemical substance. The resulting failure to file a timely premanufacture notice (PMN) could subject a company to civil penalties of up to $37,500 per day. Knowing or willful violation of TSCA could subject a manufacturer or importer to criminal penalties.
Of particular relevance to manufacturers and importers of biodiesel are Inventory policies and guidance with respect to naming commonly-occurring alkyl groups. In addition to conventional, specific chemical names, the EPA and CAS employ three additional major approaches to characterizing alkyl groups for purposes of Inventory reporting and premanufacture notification. These are natural source descriptions, Soap and Detergent Association (SDA) alkyl-range descriptors, and non-SDA alkyl range descriptions.
Conventional nomenclature rules, such as those developed by CAS, are used for naming specific, well-defined alkyl group derivatives. For example, stearic acid and methyl stearate are listed on the Inventory as Octadecanoic acid with CAS Registry Number (CASRN) 57-11-4 and Octadecanoic acid, methyl ester with CASRN 112-61-8, respectively. In both cases, the representation of the substance, as captured in its unique Chemical Abstracts (CA) Index Name, is defined by its molecular composition, which is based on molecular formula and structure.
At least two issues are associated with naming substances using specific substance names. First, different CA Index names with unique CASRNs describe a substance with varying degrees of specificity. Second, the identification of a commercially available substance by a single chemical name does not guarantee or imply that the substance is comprised solely of that chemical.
Concerning the first issue, one should use the description that is consistent with conveying the chemical identity as completely as possible. With regard to the second issue, EPA has stated that "entries on the Inventory should be considered as precisely descriptive as possible of the commercial chemical substance, consistent with industry practice." EPA also has recognized that there are complex or impure substances present in commerce that are described by a single, well-defined chemical name, and provides for use of the well-defined name in certain cases. Regardless of how extensively a name is used in commerce, this nomenclature convention is not appropriate unless the named component is actually a principal component of the commercial product.
Natural Source Descriptors
EPA uses natural source descriptors to describe alkyl species that are derived from a particular animal or vegetable source. We understand that both EPA and CAS currently regard source-based names as the most specific, very narrowly-based description of fatty acid products. Such substances must be derived solely from the named source. For example, soybean oil is listed on the Inventory as Soybean oil with CASRN 8001-22-7, while the esters produced by methanolysis of soybean oil are listed as Soybean oil, Me ester with CASRN 67784-80-9. Similarly, tallow is listed on the Inventory as Tallow with CASRN 61789-97-7, while the esters produced by methanolysis of tallow are listed as Tallow, Me esters with CASRN 68910-48-5.
Unless the operation is captured in the chemical description (e.g., Soybean oil, hydrogenated with CASRN 8016-70-4), neither removal nor concentration of the individual components in the original alkyl group mixture is permitted. Further, unless the combination is denoted in the chemical description (e.g., Glycerides, mixed soya and tung-oil mono-, di- and tri- with CASRN 68440-36-8), no additional alkyl derivatives from a different source may be combined with the product.
The broadest definition of a source-based alkyl-descriptor and its derivatives that appears on the Inventory is vegetable oil. EPA holds that use of this term should be restricted only to materials for which the identity is not known or cannot be reasonably ascertained to any greater degree of specificity. EPA further cautions that the term vegetable oil should not be used as a "catch-all" description for a product that can be prepared by interchangeably using any number of different specific vegetable sources of oils. Hence, biodiesel producers must exercise extreme caution when employing what at first glance appears to be an attractively-broad, essentially generic Inventory listing for the methyl esters of vegetable oils, namely Fatty acids, vegetable-oil, Me esters with CASRN 68990-52-3. While this description may be appropriate for biodiesel produced by methanolysis of poorly-specified, highly-variable, used vegetable frying oil collected from food service establishments, vegetable oil-based descriptions are not appropriate to describe biodiesel produced from one or more specific oil sources, such as a virgin corn oil feedstock.
SDA Alkyl-Range Descriptors
In connection with reporting to the initial Inventory, EPA and SDA jointly developed a system for naming chemical substances derived from natural fats and oils and their synthetic substitutes. This is referred to as the SDA system and is described in Section I of Addendum III to the Candidate List of Chemical Substances, published by EPA in March 1978, and in Appendix A, Volume I, of the 1985 printed edition of the Inventory. Substances named using SDA nomenclature are identified in electronic versions of the current Inventory by an SDA substance definition. EPA further identified these substances in printed versions of the Inventory by appending a dagger (†) to the CASRN.
The SDA system describes long-chain alkyl derivatives based on an alkyl descriptor; a functionality descriptor to identify the functional group(s) associated with an alkyl group; and a salt descriptor to identify cations associated with the functional groups. The Agency provides specific guidance on the most appropriate alkyl descriptor for a limited number of source-derived alkyl groups. For example, the alkyl descriptor "C16-18 and C18-unsaturated" is the appropriate SDA description for a substance derived from soybean oil which has not been fractionated or combined with materials described by other alkyl descriptors. The same alkyl descriptor is used to describe chemical derivatives of a number of other important virgin oil feedstocks, such as palm oil, rapeseed oil, and sunflower oil. The SDA alkyl descriptor for derivatives of tallow is "C14-18 and C16-18 unsaturated." The same alkyl descriptor is used to describe chemical derivatives of lard and poultry fat.
EPA also provides detailed procedures on how to determine the best SDA alkyl-range description for a given product. Application of the SDA system is based on selecting the narrowest alkyl range distribution value (alkyl descriptor) which describes the predominant long-chain alkyl groups of a substance while optionally disregarding certain minor components. Uniquely, the SDA system permits limited branching of "linear or essentially linear" alkyl groups if chain branching is limited to no more than one secondary methyl or ethyl group per chain. Critically, SDA nomenclature cannot be used to describe any single component substances. Nor can SDA nomenclature be applied to any combination of such substance prepared by mixing chemicals without reaction. However, if single component substances, SDA-named alkyl range substances, or both are caused to react, or are further caused to react with other feedstocks, the resulting reaction product may be named using SDA nomenclature.
Based on the appropriate SDA alkyl descriptor for derivatives of the parent animal fats, the methyl esters produced by treatment of tallow, lard, or poultry fat, or combinations of those fats would conform to the following Inventory listing:
Fatty acids, C14-18 and C16-18-unsatd., Me esters with CASRN 67762-26-9, Chemical Substance Definition: This substance is identified by SDA Substance Name: C14-C18 and C16-C18 unsaturated alkyl carboxylic acid methyl ester and SDA Reporting Number: 04-010-00. Consult SDA Substance Identification Procedure.
Note that when appended to a CA Index Name, a Chemical Substance Definition forms part of the full Inventory listing. Such a scope note often provides detailed additional information regarding the composition or identity of the listed substance. Accordingly, persons always should consult an applicable scope note to determine the breadth of an Inventory listing.
Non-SDA Alkyl-Range Descriptors
In addition to the limited number of alkyl-range descriptions provided by the SDA system, many substances are listed on the Inventory using alkyl ranges that are not described within the SDA system or do not comply with the detailed requirements of the SDA system. Such substances may be identified in current, electronic versions of the Inventory by their lack of an accompanying SDA definition.
EPA has offered little guidance concerning non-SDA alkyl-range descriptors. In light of the Agency's policy that chemical substances should be described as accurately as possible, it is generally advisable to include all alkyl groups that reasonably could be anticipated to contribute commercial value to the product, and to make sure that no alkyl groups that contribute commercial value to the product are excluded from such a listing. Further, the limited methyl and ethyl branching permitted under the SDA system should not be assumed for non-SDA names. Rather, non-SDA alkyl group descriptors are assumed to describe linear alkyl chains substituted at the one position.
Based on the limited guidance provided by EPA, non-SDA alkyl range descriptors should not be used to describe a combination of chemical substances that does not span the entire range of the alkyl descriptor. Nor should such descriptors be used to decribe a combination of chemical substances that contains alkyl groups outside the carbon range of the descriptor when those alkyl groups are present in significant quantities and contribute commercial value to the product. Lastly, non-SDA alkyl range descriptors should not be used to describe a combination of chemical substances that contain only odd carbon numbers when the available alkyl-range listings are even-even, odd-even, or even-odd numbered (this holds if even replaces odd and vice-versa).
There are many subtleties in TSCA nomenclature that can trap the unwary. Getting the identity right for the Inventory assures that not only will penalties be avoided for violations of Section 5 premanufacture notification and other requirements, it will also prevent disruption of business in the future. When Inventory issues arise, manufacturers are also left with the Hobson's choice of disclosing the violation to EPA and taking steps to remedy the situation. Manufacturers are often left with no choice but to discontinue production, and work to remedy the issues. Careful assessment of the product to be made and its starting materials, in addition to the Inventory searches and reviews, are inexpensive insurance against major business problems.
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