In India, especially in metro cities, air pollution is rapidly increasing because of an increased rate of urbanization, some anthropogenic actions, and rising industrialization that diminishes the air quality. As per the report of Health Effects Institute (HEI), the emission of Particulate Matter (PM) was found to be the third prime cause of death and it was recorded highest in India. According to the HEI (2019) report, 1.1 million deaths were found in India in 2017 because of increased air pollution. As 5th most polluted country, 21 of 30 polluted cities are in India (according to WHO data 2019). The outdoor air quality is mainly affected by different pollutants such as PM2.5, Volatile Organic Compounds (VOCs), CO, NO2, ozone, toluene, benzene, aromatic hydrocarbons, etc., which are released into the environment as a result of different activities. There are different air filtration technologies available such as Fibrous filter, Trombe wall, Bio-filter, Electro-static air filter, and Cold plasma air filters, but these filtration technologies are still facing some intrinsic limitations i.e., higher operational cost and requirement of more auxiliary energy.
Need of industrial invention
Therefore, there is a need to develop industry oriented, low-cost solar assisted and effective air filtration technology using some cheaper, and renewable adsorbent material. The annual production of biomass in India is estimated to be around 500 million tons with agricultural waste and forest waste considered as primary resources of biomass. This solid organic waste has become one of the reliable alternative precursor materials for activated carbon production rather than fossil resource like coal. Presently, coal is widely used for the preparation of activated carbon with a large surface area due to its higher carbon content. As the coal mines are very limited and non-renewable in nature, agricultural waste constitutes a high percentage of carbon that can make them an efficient raw material for activated carbon. The features like larger surface area, well-built internal porous morphology, well appeared micro, meso and macro porous structure, and availability of surface functional groups make activated carbon a versatile adsorbent material for air pollution control.
Activated carbon for air filtration
Biomass can be activated for the preparation of activated carbon in two ways; physical activation where CO2 and steam are used as activating agents during the biomass pyrolysis process. While, in the case of chemical activation the chemical dehydrating agents like H3PO4, KOH, and ZnCl2 are applied for biomass activation. Biochar production from biomass through thermochemical conversion route, i.e., pyrolysis or carbonization and followed by activation for obtaining activated carbon has been paid significant attention. Here, thermo-solar assisted pyrolysis technology will be designed and developed, which reduces the need of auxiliary energy requirement. Due to excellent physicochemical composition, the granular activated carbon-based air filter has a good potential for the adsorption of gas-phase contaminants.
Expected deliverables
- Activated carbon-based air filtration towers
- Standardized procedure for air filtration tower development
- Installation of towers in metro cities
- Activated carbon-based respiratory masks for human application
There are some advantages and disadvantages of solar assisted activated carbon based air filtration technology summarized hereafter:
Advantages
- Self-sustainable technology for air filtration
- Cost effective adsorbent
- Environmentally friendly
- Easy for operation
- No need of external energy
- No need of skilled trainer for operation
- Biomass waste management
- Effectively improves the air quality
Disadvantages
- Higher capital investment
- Non-uniform availability of solar energy
- Time consuming
- Biomass handling
- Storage
Conclusion
Keeping the above points in mind the research problem is formulated to develop a thermo-solar-pyrolysis reactor for biomass activation to produce activated carbon. After quantity and quality assessment, the produced activated carbon can be further used in air filtration towers and in respiratory masks for the adsorption of contaminants present in the air.
References
- World Health Organization (WHO). 2019. World Air Quality Report 2019
- Health Effects Institute (HEI). 2019. State of Global Air Report 2019 India-Specific Findings
Dr. Ashish Pawar (CSIR Fellow) is a Research Associate at Sardar Swaran Singh National Institute of Bio-energy, Kapurthala (Punjab), which is an Autonomous Institute of Ministry of New and Renewable Energy, Govt. of India.
