Cotton gin trash, the by-product of the cotton ginning industry which is produced in large quantities every year, can be utilized as feedstock for deriving high quality organic materials such as biochar, compost and co-composted derivates for improvement of soils’ key physical, chemical and biological properties. This is the first report in which cotton gin trash was both thermally and biologically converted at the same time into biochar (BC), compost (C) and co-compost (Coc), and their effects on soil properties and on plant performance were examined. In order to find the optimum rate, the products were used as soil amendments in a greenhouse experiment at 2.5 t ha⁻¹, 5 t ha⁻¹and 10 t ha⁻¹ rates. All of the amendments contributed in improving the soil properties and provided agronomic benefits to plants, however plants (radish var. Cherry belle) showed significantly (p < 0.05) better growth attributes and almost a 315% increase in biomass yield observed when co-composted biochar (10 t ha⁻¹) was applied to the soil, thus suggesting its role in compensating fertilizer application. Amendments (2.5 and 5.0 t ha⁻¹) considerably increased plant growth parameters; however, differences between 5 and 10 t ha⁻¹ amendments were not so significant. As a result, replenishing soil with Coc (5 t ha⁻¹) on a regular basis can promote plant growth and improve soil qualities over time.

Nickel (Ni) leftovers arise from both catalyst application interventions and Ni alloy piping of the cooking oil industry (COI) being wasted as pollutants of freshwater bodies via discharged effluent. The current study assessed one of the indigenously feasible Ni removal systems comprising autochthonous Arthrospira platensis Gomont (AP)-driven Ni phycoremediation cells (NPCs). After screening AP for hyperaccumulation in the Ni spiked solution, AP was transferred to the NPCs. Propagation of the AP inoculum was proportionate to the pollution load drop of COI with 22.97 and 55.07% drops in the biochemical (BOD) and chemical oxygen demand (COD), respectively. With the 0.11 bioconcentration factor, there was an uptake of 14.24 g mineral with 16.22% Ni removal and a 36.35 desorption ratio. The experimental data closely fitted with the Langmuir and Freundlich isotherms, respectively. The study concluded that A. platensis could be taken for treatment of Ni-loaded industrial effluents at the microcosmic level.