Background for this classification summary
- Visit the Classification Index to see other groups.
- The summary on this page follows the classification scheme of Elsner and Hoelzer, 2016. Quantitative Survey and Structural Classification of Hydraulic Fracturing Chemicals Reported in Unconventional Gas Production. Environmental Science and Technology. 3290-3314. DOI: 10.1021/acs.est.5b02818.
- Elsner and Hoelzer’s thorough and influential article provides a wealth of chemical context about fracking materials including health and environmental implications and suggestions for deeper analysis. However, the work was based partially on a early set of FracFocus (through 2013). Subsequent years have added new materials and millions more records. To extend their analysis to the rest of the FracFocus materials, we used Google’s Gemini to assist us in assigning classifications in line with EH’s methodology.
- Analysis from a FracFocus download, Jan 2025.
- Masses are not available for all records, so reported masses below are sums of only the available masses. See documentation.
- To provide useful technical information about these chemical groups, we use generative AI tools to assist with summaries (Google’s Gemini). These tools are prompted with details of the classification scheme (by Elsner and Hoelzer, 2016) and information about reported chemicals in the group. To limit inaccuracies, we feed the resulting output to competing models (OpenAI’s ChatGPT) to check for accuracy and ambiguity. In addition, we consulted Fink, Johannes, “Petroleum Engineer’s Guide to Oil Field Chemicals and Fluids” Third Edition. (2021) Gulf Professional Publishing. 1028pp.
- Functions reported here are summarized from the FracFocus field “Purpose.” There are limitations to this data: not all chemical records have a reported purpose (the “systems approach” explicitly excludes “Purpose” values from chemical records). Furthermore, “Purpose” typically describes the product, not individual chemicals within the product. The individual ingredient may serve a chemical role in the product that is different from the reported “purpose” (for example, synthetic polymers might be labeled “proppant”, but they are not primary proppants, but rather coatings for sand grains to enhance their performance.) In general, consider these “functions” as the larger purpose played by the product that contains the ingredient.
Biopolymers constitute a substantial class of naturally derived polymers used in hydraulic fracturing, with 68,200 records totaling 2.49 billion pounds reported to FracFocus between 2014 and 2024. These polymers, sourced from renewable biological materials, play key roles in modifying the rheological properties of fracking fluids and facilitating efficient fluid transport. While their environmental impact varies depending on processing and use, their biodegradability and natural origins offer advantages in specific applications. Over the course of those years, the most common biopolymer, guar gum, declined in use from half of disclosures in 2014 to about 10% in 2024.1
Common examples include polysaccharides such as guar gum (alpha-D-Galactopyrano-beta-D-mannopyranan, CASRN 9000-30-0), xanthan gum (CASRN 9004-32-4), and gellan gum (CASRN 11138-66-2), as well as microbial polysaccharides like diutan gum (CASRN 125005-87-0). These biopolymers contribute to a range of fracking functions, including:
- Gelling agents: Increasing the viscosity of fracking fluids to enhance proppant transport.
- Viscosity modifiers: Controlling shear-thinning behavior and fluid rheology.
- Diagnostics: Aiding in formation evaluation.
- Crosslinking systems: Serving as a base for crosslinked polymeric gels.
- Proppant transport agents: Improving the suspension and placement of proppants in fractures.
- Carriers: Acting as delivery systems for other additives.
The specific role of a given biopolymer depends on its structure and origin.
Number of reported materials: 22¶
Most common :
| Material | Name | Records and mass |
|---|---|---|
| 9000-30-0 | alpha-D-Galactopyrano-beta-D-mannopyranan (guar gum) | 56,100 records — 2,460,000,000 pounds |
| 9004-32-4 | Edifas B (xanthan gum) | 3,690 records — 3,790,000 pounds |
| 11138-66-2 | Corn sugar gum (gellan gum) | 3,130 records — 5,450,000 pounds |
| 125005-87-0 | Diutan gum | 2,150 records — 93,200 pounds |
| 8013-01-2 | Yeast extract | 1,050 records — 78,700 pounds |
- All molecular structure images courtesy of the US EPA, except where noted. ↩︎