By Richard E. Engler, Ph.D., special to The Digest
In the first installment of this series, I wrote about how the Toxic Substances Control Act (TSCA) regulates products. In this article, we will look across a manufacturing process.
TSCA applies to chemical substances that are used for purposes other than food, food additives, animal feed, cosmetics, drugs, tobacco and tobacco products, pesticides, munitions, and nuclear source materials. Biobased chemicals, that is, chemicals made from lignocellulose or other biomass, are finding markets in food and cosmetic markets, but much of the recent innovation focuses on biobased fuels and commodity chemicals. For these final products, TSCA applies. Chemical products must be listed on the TSCA Inventory of Chemical Substances (the Inventory) or be eligible for an exemption. If the product is not listed on the Inventory, the manufacturer must file a premanufacture notification 90 days before manufacturing (or importing) that substance or qualify for an appropriate exemption.
Importantly, in addition to final chemical products, TSCA also applies to the other chemicals used in the manufacturing process. Looking at the various stages of a typical manufacturing process (Figure 1) allows us to examine how TSCA applies at each stage.
“Feedstock” means something different at different points along the supply chain. At the very beginning of the supply chain for biobased chemicals and biofuels are plants (that is crops, not facilities). Plants, of course, are naturally occurring. “Naturally occurring” substances are defined under TSCA as:
[A]ny chemical substance which is naturally occurring and:
(1) Which is (i) unprocessed or (ii) processed only by manual, mechanical, or gravitational means; by dissolution in water; by flotation; or by heating solely to remove water; or
(2) Which is extracted from air by any means. . . .
Harvesting, chopping, grinding, washing with water, and drying crops or agricultural residues does not change the status as naturally occurring substances. It is important to note that naturally occurring substances are automatically included on the Inventory and need not be reported as “new” chemicals nor be reported under the Chemical Data Reporting (CDR) program.
Some bioeconomy companies do not start with agricultural residues — some start with sugars, some start with waste. Companies may use municipal solid waste, including paper or food scraps, paper mill waste such as low-value lignocellulose waste, or waste fats and grease from commercial kitchens. TSCA specifically exempts waste from reporting, provided the waste is being disposed of as waste or incinerated. If you are using it as a feedstock, it is not waste. Your use of the waste in a commercial process means that the waste must be listed on the Inventory and the producer of that waste must report under CDR. Some wastes are already listed on the Inventory, including:
Fats and Glyceridic oils, vegetable, yellow grease.
Definition: A refined product produced from waste restaurant vegetable oils and fats that were used in processing and cooking foods.
Many other waste streams are not listed on the Inventory. Bioeconomy companies that use waste as a feedstock must engage with their suppliers to ensure that those wastes are properly characterized and listed on the Inventory to prevent supply disruptions.
As with companies that rely on waste as a feedstock, companies that purchase fermentable sugars should be sure to determine the TSCA status of their feedstock. Starch, acid-hydrolyzed starch, base-hydrolyzed starch, and D-glucose are all separate identities. Your supplier should provide you with the correct TSCA identity for the product you purchase.
The next stage of manufacturing is intermediates. Intermediates are arguably the most confusing part of how TSCA regulates chemical manufacturing process.
If an intermediate is isolated, it, like the final product, must be listed on the Inventory, and we will take a look at what qualifies as “isolated” below. The most common intermediate in the bioeconomy is pre-treated biomass. Any pre-treatment, such as acidic, basic, solvent or other treatment that alters the chemical bonding of the feedstock changes the chemical identity of the feedstock. Your feedstock may be naturally occurring, but the acid-pretreated feedstock is not — it is an intermediate.
Non-biologic manufacturing processes may have a number of intermediates as the feedstock is chemically converted stepwise into a final product. At each step, consider whether chemical bonds are being made or broken; if so, you have made an intermediate. Once you have identified the intermediates, the question then becomes, are they isolated? Nonisolated intermediates are defined as:
[A]ny intermediate that is not intentionally removed from the equipment in which it is manufactured, including the reaction vessel in which it is manufactured, equipment which is ancillary to the reaction vessel, and any equipment through which the chemical substance passes during a continuous flow process, but not including tanks or other vessels in which the substance is stored after its manufacture.
Nonisolated intermediates are exempt from TSCA reporting, but isolation may even occur if the reaction vessel is closed off from the rest of the process by valves. These distinctions are often very subtle and even counterintuitive from an engineering perspective. For example, agricultural residues are shredded and added to a reaction vessel with aqueous acid where it is stirred and heated to begin the breakdown of the lignocellulose. The resulting slurry is pumped into a fermentation vessel where it is converted to ethanol. Because the acid pre-treated biomass is pumped from one vessel to another, it is isolated and is reportable under TSCA, even if the pre-treated biomass is never exposed to air.
In the final step, an intermediate substance reacts, often with a catalyst, enzyme, or microorganism, in some solvent, to convert that intermediate into the product. Everything intentionally added to that pot must be listed on the Inventory. In many bioeconomy reactions, the solvent for this step is water. Water is listed on the Inventory, and is also a naturally occurring substance.
Another typical input in this last step is a catalyst. The catalyst must also be listed on the Inventory, whether it is a traditional metal catalyst, an enzyme, or a microorganism. Traditional metal catalysts and enzymes are relatively straightforward to identify and determine if they are on the Inventory. Microorganisms, which are considered chemical substances regulated by TSCA, require a more complex determination. A naturally occurring organism, such as brewer’s yeast (Saccharomyces cerevisiae), is automatically included on the Inventory and would not require notification. On the other hand, if the organism has been modified, it may no longer be naturally occurring.
Under its TSCA Biotechnology Program, EPA considers an organism “new” if it is a “microorganism created to contain genetic material from organisms in more than one taxonomic genera.” These intergeneric microorganisms require premanufacture notification via a submission that is called a Microbial Commercial Activity Notice (MCAN). A yeast that has been genetically modified to simply up- or down-regulate expression of a gene is probably still considered naturally occurring, but one that has had a gene from an extremophile inserted into its genetic material is no longer naturally occurring and would require a MCAN.
I have tried to provide illustrative examples, but bioeconomy processes lead to TSCA questions that are not cut-and-dried. Companies are well advised to seek advice from experts in TSCA notifications and identities. A company may consult directly with EPA through pre-notice communication or inventory correspondence to get EPA’s input and judgment on issues such as the reportability of various substances. A company may also wish to seek technical or legal advice from a firm that is expert in the field.
Rich Engler is a Senior Policy Advisor with Bergeson & Campbell, P.C. and The Acta Group. Previously, he worked at EPA for 17 years, where he was a staff scientist in the Office of Pollution Prevention and Toxics. At EPA, he reviewed numerous chemicals under TSCA, led the Green Chemistry Program, including the Presidential Green Chemistry Challenge, and worked on many other projects, including the Risk-Screening Environmental Indicators and Trash-Free Waters.
Prior to joining EPA, Rich taught organic chemistry at the University of San Diego. He holds a Ph.D. in physical organic chemistry from the University of California, San Diego.