Management of Antimony Containing Solar PV Glass

May 5, 2019

antimony solar PV glass

    For many years, solar PV panels are enjoying the status of being environment-friendly. Lot has been written about their all-around clean-and-green characteristics. However, with the research and development, substances which are not so environment-friendly are being used in panel manufacturing over the last few years. Hence, their secure and scientific disposal has became the the need of time.

    I have been following a story related to the management of antimony-containing solar PV glasses for the last couple of years. It is now on its interesting point where a lot of information related to the effects of antimony present in the solar glass is available. This why I decided to write an article on it.

    A PV module is essentially made up of glass, metal, silicon and polymer fractions. Glass and frame (Aluminium), together make most of the part of the module when measured in terms of weight. Around 70-80% of the total weight is constituted by these two materials. The polymeric materials (back sheet and encapsulants i.e. EVA) cannot be recovered and is typically incinerated.

    Antimony is used in solar glass to improve light refraction and visible transmission property. It also increases the resistance of glass to the ultraviolet light for the long term. However, Antimony being a heavy metal might affect the ecology wherein the modules will be kept after their end of life. It is necessary to study the phenomenon in detail.

    Most of the SECI-organized auction documents rest the responsibility of handling and disposing PV waste on the developers as per E-waste (Management and Handling) Rules, 2011. However, the E-waste rules make no mention of solar PV waste as of today.

antimony solar PV glass

Development in India

August 2017:

    Mrs./Ms Niharika filed an application against Union of India before Hon’ble National Green Tribunal (NGT) regarding use of Antimony containing solar PV glasses in panels and the possible environmental risks or consequences at the end-of-life of such solar panels.

February 2018:

    NGT constituted Expert Members committee to present a report based on this matter. The committee was comprised of;

  • Professor V. A. Juvekar, IIT Bombay
  • Rajesh Kumar, Senior Director, MNRE
  • Shri B. Vinod Babu, Scientist-E, CPCB

    The report focused on issues like;

  • Whether antimony was toxic?
  • Its effects on the environment
  • If there is any possibility of leaching the heavy metal and if so, to what extent?
  • Remedial measures, if any

January 4, 2019:

    NGT acknowledged the fact that there is no policy or rules on the management of Antimony containing glass used in solar panels.

    NGT directed that Ministry of Environment Forest and Climate Change (MoEF&CC), Ministry of New and Renewable Energy (MNRE) and Central Pollution and Control Board (CPCB) to specify minimum time period required for preparation of the policy.

February 2019:

    NGT directed MNRE to complete the exercise of preparation of blueprint within a period of three weeks.

    NGT directed MOEF&CC to complete the exercise of preparing and declaring a policy within three weeks after receipt of the blueprint from MNRE

March 2019:

    MNRE published ‘Concept Note/ Blue Print on Management of Antimony Containing Glass from End-of-Life of the Solar PV Panels’

Inputs from MNRE concept note

    Antimony is found either as Antimony trioxide (ATO) or Potassium Antimony Tartrate (APT) in most of the commercial applications. Out of these two, APT is more toxic in nature and require secure treatment. In the case of Solar glass, ATO type of Antimony is found in the expert committee report. Here is what they actually did;

  • Two samples of Antimony containing glass from used solar panels were studied by CPCB for Antimony concentration.
  • The analysis of which indicates that the concentration of Antimony in textured glass in the range of 0.13 and 0.29 %, respectively.

    antimony solar glass test 1
    Source: Ref1
  • CPCB also conducted Soluble Threshold Limit Concentration (STLC) test on Antimony containing glass.
  • The leached liquor was tested for concentration of Antimony so as to compare with standards stipulated under Hazardous and Other Waste Materials (HOWM) Rules, 2016 to categorize the waste as hazardous.
antimony solar glass test 2
Source: Ref1

     Results indicate that samples of waste solar panel glass containing Antimony does not fall in the category of hazardous waste as per the concentration limits stipulated for Antimony in Schedule II of Hazardous and Other Waste Management Rules, 2016.

    Even after long contact with water, the toxicity produced by its products after its hydrolysis is much less compared to APT. Antimony can be treated as ‘low effect’ waste. Its disposal should be regulated with proper policies.

Management of PV modules

    Management of PV modules need to follow the cradle-to-grave life cycle assessment in four stages:

  1. Component production
  2. Module manufacturing
  3. Module use
  4. End-of-life-use stage.

    Recycling facilities are required to be created by industry once the adequate quantity of PV waste is available for recycling.

Regulatory interventions

    The following regulatory interventions are proposed in the concept note;

  • Recycling of end of life solar panel glass containing Antimony may be made mandatory on the generators as part of environmental liability.
  • Producers may be made responsible for ensuring recycling of end-of-life glass panels as part of their extended producer’s responsibility (EPR) as in case of E-Waste, used lead acid batteries, packaging material, etc.
  • Generators shall ensure environmentally sound handling of used solar panel waste

Recommendations

    The recommended options are given below;

(a) Reuse/ Recycling

  • The generator or the manufacturers may be given the responsibility of recycling of used solar glass panel for reproducing new glass for solar panels.
  • Every generator may set up facilities for the safe dismantling of used solar panels or tie-up with an authorized dismantling facility.
  • It shall be ensured that Antimony containing glass should never get mixed with normal glasses for recycling, as it may contaminate entire glass being produced.
  • The possibility of utilizing used solar panels by co-processing in cement kilns should also be explored.

(b) Handling & Storage

  • The end-of-life solar panels are required to be collected and stored safely under a covered shed till the time the material is sent for recycling
  • Transportation of waste solar panels should be done in covered trucks, preferably in trucks authorized for transportation of hazardous wastes as per the Motor Vehicles Act.

(c) Ultimate Disposal in Secured Landfill

  • End-of-life solar panels shall never be disposed or dumped in open landfills
  • Only the non-recyclable material in solar panel after removal of glass, Aluminium and junction box, may be allowed for disposal through secured landfills.
  • Considering the leaching potential of Antimony, the end-of-life solar panels may be treated as ‘low effect waste’ and handled as per the provisions under Hazardous and Other Wastes Management Rules, 2016 with a valid authorization from concerned State Pollution Control Boards.

    The estimated waste production factor is about 75 MT of waste for every 1 MW of solar PV installed capacity. (If a plant has 4000 modules of 250Wp each, each should have a weight of 18.75 Kg). The recycling of 1 ton of PV panel produces 686 Kg. of clean glass and 14 Kg of contaminated glass. The recycled glass can be used to produce new SPACG. This shows the potential and scale of recycling plants required in the coming future.

    Right now, rigid PV-waste related policies are only available in Europe. In America, few states have regulated the disposal of PV modules but it will be only effective if the federal policy is introduced. Talking about India, we need to wait for the Ministry of Environment, Forest and Climate Change for further action on this story. It will be interesting to see if they come up with a rigid policy or just another ministerial-level document.

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Ref1: https://mnre.gov.in/sites/default/files/webform/notices/DraftBluePrintAntimony.pdf

Note: Some part of the article is shared on a as-is basis from concept note while the rest of the article is written in simplistic way so that most of the audience can understand the content. You can find the concept note here: https://mnre.gov.in/sites/default/files/webform/notices/DraftBluePrintAntimony.pdf