Standard Active Last Updated: Sep 28, 2022
ASTM E3325-21

Standard Practice for Sampling of Solar Photovoltaic Modules for Toxicity Testing

Significance and Use

6.1 The primary goal of this practice is to extract representative samples from PV modules for TCLP toxicity testing purposes in order to receive unbiased, comparable and repeatable toxicity test results from independent TCLP testing laboratories.

6.2 Solar photovoltaic (PV) modules in the United States and the world reaching end-of-life due to failure, underperformance or breakage due to extreme weather have to be recycled or otherwise safely disposed of following the Resource Conservation and Recovery Act (RCRA) regulation [United States, Resource Conservation and Recovery Act. Pub.L. 94–580, October 1976]. For end-of-life PV modules, the U.S. Environmental Protection Agency (EPA) Method 1311 (TCLP) is used for waste characterization based on leaching potential under simulated landfill conditions.

6.3 Commercial PV modules contain compounds and alloys of various metals (for example, Ag, Al, Cd, Cu, Ga, In, Ni, Pb, Se, Sn, Te, Zn) which are used in semiconductor compounds and electrical contacts.5 Modules that pass the EPA Method 1311 TCLP test, and state protocols (if applicable), can be disposed of in a regular landfill. Otherwise, they are classified as hazardous waste and must go through a more onerous and expensive disposal process. Currently, there is no national or international standard, nor a standardized protocol available for removal of test samples from PV modules for toxicity testing per the EPA Method 1311 standard.

6.4 The validity of the toxicity test results heavily depends on the location of extracted samples in the module, specifically within the laminate area, and the particle size of the extracted samples. Therefore, it is critical that the sample extraction procedure be properly designed to avoid biased or otherwise inaccurate toxicity test results.

6.5 The development and application of a homogeneous and representative sampling standard will help utilities and manufacturers to limit the number of variables and to obtain repeatable test results.

Scope

1.1 The purpose of this practice is to describe a representative and repeatable sample preparation methodology to conduct toxicity testing on solar photovoltaic (PV) modules for use with EPA Test Method 1311: Toxicity Characteristic Leaching Procedure (TCLP).

1.2 This practice refers to the extraction and preparation of PV module samples by EPA Method 1311, the testing for eight (8) distinct metals – mercury (by Method 7470A), arsenic, barium, cadmium, chromium, lead, selenium and silver (by Method 6010C) as well as the analysis and interpretation of the test results on a module level.

1.3 This practice applies to only (1) standard crystalline silicon (c-Si) modules, multi and mono-crystalline silicon with aluminum back surface field (Al-BSF) cell technology and (2) cadmium telluride (CdTe) PV modules.

1.4 Other and newer PV technologies and module architectures, for example, passivated emitter and rear cell (PERC), interdigitated back contact (IBC), hetero-junction technology (HJT), multiwire, half cut, shingled etc., have not been evaluated with this practice, although the concept and practice can be easily extended and applied to other technologies following the conceptual approach presented in this document.

1.5 The sample extraction/removal methodology applied in this practice is the waterjet cutting sampling method. Sample extraction with mechanical cutting has been extensively evaluated but the variability of TCLP test results based on the mechanical cut samples tend to be much higher (30 %) than that of the waterjet cut samples (8 %).2 Therefore, the mechanical cut method is not presented in this practice.

1.6 Only the laminate area of the PV module is considered for TCLP testing, as other possible module parts, such as aluminum frame, junction box and cables contain recyclable materials that are already well-documented and are not specific to the PV modules.

1.7 The material gravimetric density (g/cm3) throughout the laminate area is considered constant.

1.8 This practice was developed to be consistent with three fundamental requirements:

1.8.1 Sample pieces with particle size not to exceed the allowed size limit of EPA 1311 standard which is 9.5 mm,

1.8.2 The particle size used in this practice as sample piece is consistent with the median particle size expected in landfill disposal2, and

1.8.3 An assumption that each laminate sample piece will result in 100 % glass coverage area, due to the presence of bonding encapsulant layers once it is broken in the landfill.

1.9 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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Details
Book of Standards Volume: 12.02
Developed by Subcommittee: E44.09
Pages: 11
DOI: 10.1520/E3325-21
ICS Code: 27.160