_applied_  
_sciences_  
_Review_  
**The Processing of Calcium Rich Agricultural and Industrial Waste for Recovery of Calcium Carbonate and Calcium Oxide and Their Application for Environmental Cleanup: A Review**  
**[PERSON] 1,*, [PERSON] 2,3,*(r), [PERSON] 4,*(r), [PERSON] 5, [PERSON] 6, [PERSON] 7,*(r), [PERSON] 9, [PERSON] 10, [PERSON] 11 and [PERSON] 12,**  
**[PERSON] 12,**  
1 School of Life Sciences, Jajpur National University, Jajpur 302017, Rajasthan, India  
2 Institute of Environment and Development Studies, Bundekhand University, Kanpur Road,  
Jhans 284128, UP, India  
3 Faculty of Science and Technology, Madhyanchal Professional University Rathabad, Bhopal 462044, M.P, India  
4 Geobitec Research Centre, Department of Geoscience, University of Aveiro, 3810-193 Aveiro, Portugal  
5 School of Nano Sciences, Central University of Gujarat, Gandhinagar 382030, Gujarat, India; [EMAIL_ADDRESS]  
6 Department of Chemistry, Guidy Campus, University of Madras, Chennai 600025, Tamil Nadu, India; [EMAIL_ADDRESS]  
7 Mechanical Engineering Department, College of Engineering, King Khalid University,  
Abha 61411, Saudi Arabia; [EMAIL_ADDRESS] or [EMAIL_ADDRESS]  
8 Research Center for Advanced Materials Science (RCAMS), King Khalid University, Guarajer,  
Abha 61413, Asir, Saudi Arabia  
9 Centre for Environment Science and Climate Resilient Agriculture, Indian Agricultural Research Institute, New Delhi 110012, India; [PERSON]S]  
10 Civil Engineering Department, College of Engineering, Jazan University, Jazan 114, Saudi Arabia; [EMAIL_ADDRESS]  
11 Civil Engineering Department, College of Engineering, King Khalid University,  
Abha 61411, Asir, Saudi Arabia; [EMAIL_ADDRESS]  
12 Department of Civil Engineering, Jamia Millia Islamia, New Delhi 110025, India; [EMAIL_ADDRESS]  
13 Correspondence: [EMAIL_ADDRESS] (V.K.Y.); [EMAIL_ADDRESS] (K.K.Y.); [EMAIL_ADDRESS] (M.M.S.C.-P)  
**Abstract:** Every year a million tonnes of calcium rich agro and industrial waste are generated around the whole globe. These calcium rich waste like finger citron, shells of cockle, mussel, oysters etc., and egg shell are biological sources which have various organic compounds. The inorganic calcium rich waste includes gypsum, dolomite, sludge etc., which are produced in surplus amount globally. Most of these by-products are mainly dumped, while few are used for land-filling purposes which leads to the pollution. These agro and industrial by-products could be processed for the recovery of calcium carbonate and calcium oxide particles by physical and chemical method. The recovery of calcium carbonate and calcium oxide particles from such by products make them biocompatible. Moreover, the products are economical due to their synthesis from waste materials. Here, in this current review work we have emphasized on the all the calcium rich agro industries and industrial by products, especially their processing by various approaches. Further, we have also focused on the properties and application of such calcium carbonate and oxide particles for the remediation of organic and inorganic pollutants from the environments. The recovery of such particles from these byproducts is considered not only economical and eco-friendly but it also minimizes the pollution present in the form of solid waste.  
**Keywords:** calcium carbonate nanoparticles; calcium oxide nanoparticles; incense sticks ash; fly ash; sludge; eggshell