E-Waste: A Big Challenge to the Environment & Health, and the Solution is Hydroelectric Cell

The energy generation techniques in the form of primary dry cells, secondary Pb acid battery, Li-ion cells and renewable solar cells are being extensively used in our day-to-day life. There is no consideration about the end-of-life disposal practices of discarded batteries and solar panels. Most of these batteries and panels end up in landfills or are improperly recycled for individual monetary gain. It has been found that recycling of discarded batteries is dependent on the monetary value attached with it than the non-renewability, scarcity or environmental effect of the used materials. Improper battery and solar panel disposal are severely contaminating our environment and health affecting all economic classes. Lack of proper recycling norms with no control on informal recycling by the Govt. and poor user awareness on battery disposal further aggravates the situation. The use of bio-degradable, non-toxic and abundant iron oxide, magnesium and lithium oxides in novel hydroelectric cell is the ultimate solution to prevent environment degradation issue by supplying continuous green electricity using few drops of water in an economic manner.

Solar cells E-Waste

Although, three forms of solar cells- crystalline/polycrystalline/thin films are available in market, till date the crystalline solar cells are the most efficient one. Around 2/3^rd of the PV panels installed in world are crystalline silicon based (2015). Solar panel consists of various elements. A typical solar cell composition is described in the Table below.

Composition of a typical solar cell panel.

The average life claimed by the solar cell is in between 20-25 years. While, from the survey it has been found that users observed lower average life of solar cells than claimed by the manufacturing companies. Around 90% of the consumers felt that their shelf life is lower than 10 years.

Harmful effects of Si manufacturing process:

1. Silica Dust – It is produced during processing of quartz. It is associated with silicosis which is a severe lung disease, rheumatoid arthritis, pulmonary heart disease.
2. Silicon Tetrachloride– It is produced by processing of metallurgical grade silicon to poly-silicon. It is an extremely toxic compound which quickly converts itself into acid and poisonous HCl fumes. It can also cause skin burn and acts as an irritant to eyes and respiratory system.
3. Kerf dust– Kerf dust is a by-produce released when silicon ingots are sliced into wafers. It is very harmful if it is inhaled.
4. Chemical burning– The ingots sliced into wafers are chemically etched by exposure to various chemicals like HNO₃, HF and NaOH which require proper medical concern to prevent any chemical burn.
5. Use of silane– Silane gas is used during anti-reflective coating to increase the efficiency of cell by reducing light reflection. However, silane is inflammable and extreme care must be taken care during its handling.
6. Pb soldering– The use of Pb in soldering process is extremely harmful for the environment. Highly toxic Pb can severely pollute land, air and water affecting human life significantly.

Major Disadvantages of Harnessing Solar Energy

1. High energy consumption in manufacturing process.
2. Overall high initial set up cost.
3. Weather dependence on electricity generation.
4. Usage of large space for adequate energy requirements.
5. Expensive storage cost in batteries.
6. Use of hazardous chemical in manufacturing and its association with environmental degradation such as Pb, Sn, In, Ga, Cd.

Direct disposal of solar cells in land is even more harmful as PVs consist of heavy metals which can always be leaked in ground polluting the soil. An average life of solar panel is claimed between 20-30 years implying significant accumulation of PV waste with time. Increase in global PV market worldwide would also increase the number of decommissioned PV panels.

Figure 1. Solar cell disposal in landfills.

The PV waste will thereby grow with time.It has already been estimated by IRENA, June 2016 that approximately 78 million metric tonnes of undisposed solar waste will be deposited till 2050 (Figure 2). Thin film based solar cells contains semi-conductor/hazardous materials In, Ga, Se, CdTe.

Figure 2: Cumulative waste volumes of top 5 countries for end of life solar panels in 2050 estimated by IRENA, 2016.

Around, 90% of the total mass is composed of glass, aluminium and polymer which are non-hazardous. C-Si based other constituents face recycling difficulties. PV recycling is a very cumbersome process requiring material separation and individual element extraction with minimal damage for its re-usability in solar PVs. High capital-intensive recycling process of solar cell lowers the economic benefit of the process triggering its disposal. Poor and developing countries are at a higher risk for bearing the consequences of influx toxic solar waste due to lack of infrastructure of any recycling facilities.

Lithium-ion Batteries (Chargeable):

Secondary batteries accounts for 76.4% of the global market. Its market share will further increase in near future due to a significant increase in the usage of electronic and electrical devices. Electric vehicles based on lithium-ion batteries are getting space worldwide. With the rise in popularity and demand of the electric vehicles (EV), we are moving towards a completely different picture of the world. It is the upcoming tsunami of the e-waste that is going to be generated in a few years. 145 million EVs are to be expected by 2030, with 290 billion batteries, which along with huge solar waste will become a curse for scientists and engineers.

Major disadvantages of Li-ion batteries:

1. Li-ion batteries are extremely sensitive to high temperatures. It requires protection circuit to maintain current and voltage within its safe limit.
2. It shows aging effect- starts degrading and discharging even when not in use. It has to be kept at low temperatures to reduce the aging issue.
3. There are strict transportation laws for shipment of large quantities of these batteries.
4. The manufacturing process is expensive.
5. It is not a fully matured technology as continuous research for development of other suitable electrode/electrolyte material is going on.
6. Over-discharging of Li ion batteries supersaturates the used cathode LiCoO₂ which further converts to Li₂O reducing the charging/discharging efficiency of the cell.

Current Disposal Practices & associated environmental hazards of Li-ion battery

Worldwide, most of the discarded electronic waste in the form of Li-ion batteries ends up in landfills. This method of battery disposal is a sheer waste of numerous precious metals which could have been reused in other applications. Leaching of chemicals in soil due to battery corrosion contaminate both land and ground water.

Risks associated with landfill disposal of Li-ion battery:

1. Resource depletion
2. Wastage of energy
3. Land and ground water pollution.

Issues of improper recycling of Li-ion battery

Even with the potential risks associated with lithium batteries, worldwide there is currently no law prohibiting the disposal of lithium batteries specifically.

Dangers linked with recycling process include electrical danger, burning reaction, chemical danger and intrinsic potential reactions.

Water sensitivity of used electrolyte solution- Lithium hexafluorophosphate is another major issue as it rapidly reacts with water to form HF, which is a highly corrosive acid. Electrolyte is highly toxic and flammable.

Li-ion battery faces exploding issue as well. This occurs during damage or exposure to high temperatures.

Dry Cell E-Waste

Around 85% of the used cells are thrown in dustbins with other household waste ending up in municipal waste (Figure 3). From there, this e-waste is discarded in landfills. 15% of the total consumers were selling the used cells to scrap dealers (Kabadivalas). Mostly, low income groups were involved in selling the cells to unofficial dealers.

Figure 3: Current followed practice for disposal of dry cells in landfills.

Disadvantages of current dry cell disposal methods:

1. Disposal of dry cell in landfills may lead to leaching of toxic materials from used batteries in the soil. The heavy metals could be taken up by plants and get accumulated in fruits/vegetables entering our food chain.
2. Permeation of hazardous chemical waste into ground water, soil, surface water and air.
3. Human consumption of these chemicals via food/water or air.
4. Losing out on non-renewable sources due to landfilling.
5. Missed opportunity of recycling job.
6. Release of toxins into the air with municipal waste combustion.

Toxicity of metals can cause neurological impacts, birth defects, kidney damage and cancer.

Hazardous Effect of Lead exposure from Lead acid Batteries

High toxicity of Lead (Pb) inhibits lead-acid batteries to be directly disposed of in incinerators. Being a poorly regulated industry, recycling process is carried out ignoring major necessary processes and techniques resulting in environmental contamination due to severe exposure with Pb emissions. The process has been associated with high level of occupational human exposure to Pb due to emission of Pb particles or its fumes in air which can be deposited on soils, water bodies and inhaled. Most of the time, used acid having high concentration of Pb ions is dumped onto the land or is released into water severely contaminating it.There are many centres in Delhi for collection of discarded lead acid batteries. These centres include Tis Hazari, Madangiri, Siraspur, Seelampur. Informal recycling units are available at Mandoli, Mangolpuri, Siraspur and Nangloi. Due to government interventions at Delhi centre, the major location has now shifted to the outskirts of Delhi, Ghaziabad.Figure 4 depicts the current scenario of improper recycling in Delhi.

Figure 4: Informal Lead-acid battery recycling in industries. (a) Recycling unit at Mandoli, Delhi (b) Separators and plastic thrown in open in Ghaziabad informal unit (c) Scrap lead dust in open (d) Lead smelting in open furnace (e) Lead ingot formation from recycled lead.

Incorporation of Pb in food chain occurs through the crops grown on contaminated land, or by direct deposition on the crops/food animals grazing on exposed land. The studies conducted on Pb have found that it majorly affects the reproductive, endocrine, neurological and cardio-vascular system of human body. It has been reported that Pb absorption in body reduces the synthesis of hemoglobin responsible for the production of RBCs.

The Solution: Bio-degradable, Environment benign metal oxide based hydroelectric cell

Deriving sustainable, green energy from water molecule splitting at room temperature using metal oxides without any external simulation has resulted in the development of a novel energy generation device “Hydroelectric Cell”. It was invented by Dr. R. K. Kotnala and Dr. Jyoti Shah in CSIR-National Physical Laboratory New Delhi. Hydroelectric cell consists of a metal oxide pellet as water dissociating surface with two electrodes silver (Ag) and zinc (Zn) attached to the opposite surface of metal oxide pellet for collection of dissociated ions. Zn acts as anode having strong affinity towards OH^– ions while inert silver acts as cathode having strong affinity towards H₃O⁺ ions. Spontaneous heterolytic water molecule dissociation occurs on exposed surface defects, under-coordinated cations and anions of metal oxide to form a layer of chemi-dissociated –OH groups. Physisrption of water molecule occur on –OH group by hydrogen bonding. During surface H₃O⁺ ion hopping, these ions get trapped in the pore walls of the oxide to physidissociate water molecules into hydronium and hydroxide ions (equation 1). Ion migration from surface and through interconnected capillaries to individual electrode surface result in electrochemical reactions at Zn and Ag surface (equation 2, 3).

On Metal Oxide Surface:

2H2O →H3O+ + OH-                                                                                                                                                        Eqn 1

At Zn anode:

Zn + 2OH- → Zn(OH)2 + 2e-                                 Eox = 0.76 V                                                                            Eqn 2

At Ag cathode:

H3O+ + 2e- → H2 + H2O                                    Ered = 0.22 V                                                                            Eqn 3

There is a net flow of current from Ag to Zn electrode due to the potential difference between the two electrodes. A 4.84 cm² area lithium magnesium ferrite based hydroelectric cell generates 100 mA cell current and 0.9 V emf.

Advantages of Hydroelectric cell

1. Metal oxides (Fe₂O₃, SnO₂, TiO₂, MgO, Al₂O₃) are highly abundant in earth. They are bio-compatible and non-toxic. Energy generation using iron oxides at room temperature without special processing is an environment friendly and efficient technique.
2. Only water in few millilitres is used as an input source for electricity generation. The cell functions for days with very limited water.
3. No special experimental setups are required for manufacturing hydroelectric cell. The process is facile and very economic.
4. No harmful by-products are produced. Nano ZnO by-product formed during cell reaction finds application in paints, creams and ointments.
5. Another by-product H₂ gas produced is itself a clean source of energy production.

Easy to install in decentralized mode in rural areas as no special conditions are required for cell manufacturing.

Table: Inter-comparison of Disposal of Different energy generation techniques