The current research encompasses utilization of peanut shells (PS) as feedstock for pyrolysis carried out at various temperatures (250, 400, and 550 °C) for deriving biochar, namely PS-BC250, PS-BC400, and PS-BC550. After analyzing the biochar types physicochemically, it was applied as a soil ameliorant for the growth of cucumber. The results showed that in prepared biochar type, bulk density, volatile contents, hydrogen, oxygen, and nitrogen content decreased, whereas pH, electrical conductivity, ash content, fixed carbon content, and surface area increased with the increasing temperature. Scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) presented high porosity, re-orientation of vessels, and a greater number of aromatic compounds, respectively, for PS-BC prepared at 550 °C. On applying PS-BC250, PS-BC400, and PS-BC550 as amendments in potted soil at 2, 4, and 6% (w/w), it improved soil quality (viz pH, EC_e, BD, and soil water holding capacity) and increased the yield of cucumber. Because of improved soil properties and crop yield, PS-BC550 at the rate of 4% (w/w) demonstrated a great potential for agricultural application while provisioning dual circular economic indicators in the form of diverting PS waste to an effective alternative of chemical fertilizer having intensive carbon footprints in cucumber production.

The current study is aimed at deriving biochar (BC) from rice straw (RS-BC) and waste bones (WB-BC), being wasted without adequate return at the expense of environmental degradation. The RS and WB feedstocks were pyrolyzed at 550 °C, and the potential of derived biochar as a slow nutrient releasing soil amendment was examined during the growth of ridge gourd. Proximate analysis of the prepared biochars showed significant improvement in ash content and fixed carbon as compared to their raw biomasses. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analysis of RS-BC and WB-BC displayed a diverse range of functional groups viz. derivatives of cellulose and hydroxylapatite (HA); macro and microporosity; multiple nutrients. Application of RS-BC and WB-BC in potted soil alone and as biochar composite (RS-BC+WB-BC) at 5, 10 and 15% (w/w) and chemical fertilizer (CF) resulted in a significant increase in soil pH, electrical conductivity (ECe), cation exchange capacity (CEC) and water holding capacity (WHC) in exchange for growth and yield of ridge gourd. However, there were insignificant differences in the growth of plants in response to RS-BC, WB-BC alone and CF with biochar composite at 15% amendment. For giving insignificantly different growth results than CF, the prepared biochar composite showed outstanding potential as an organic fertilizer applicable in agrarian soils to elevate soil properties and yield of agricultural commodities.

Constructed wetland systems (CWSs) can offer cost-effective wastewater treatment in developing countries like Pakistan. This study focused on optimizing design and operational parameters of CWSs in horizontal surface flow (HSF), vertical surface flow (VSF), and hybrid mesocosms for treating sewage and textile effluents using local hydrophytes: Lemna minor, Typha latifolia, and Eichhornia crassipes. Pollutants and heavy metals (Cd, Cr, Cu, Pb, Ni, and Zn) were removed under different flow configurations, bedding materials, hydrophyte species, and hydraulic retention times (HRT) to optimize the overall contaminant removal efficiency (RE). Key findings indicated that the hybrid CWS achieved a maximum RE of 63.62% for total suspended solids (TSS) and 57.9% for biochemical oxygen demand (BOD) at an HRT of 3 days, with efficiencies declining at longer retention times. Additionally, the hybrid system showed maximum metal removal, with Cd and Cr RE reaching 75.2% and 70.5%, respectively. The study also highlighted the critical role of hydrophyte species and HRT in optimizing RE. Furthermore, the choice of hydrophyte species significantly influenced pollutant removal, with treatment cells containing mixed hydrophytes achieving the highest removal efficiencies (63.62%), followed by Eichhornia crassipes with high Cd (643.33 mgkg⁻¹) and Cr (1103.72 mgkg⁻¹) uptake. A lower HRT of 3 days resulted in the highest overall removal efficiency of 57.5%, which decreased with longer HRTs (from 6 to 9 days). Optimizing design and operational parameters is crucial for maximizing CWS treatment potential.

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.

The present study aimed at converting meat industry waste, particularly waste bones and chicken feathers, into biochar to recycle valuable nutrients present in it, which ultimately become part of the municipal waste. The bone biochar (BB) and feathers biochar (FB) were prepared at 550 °C, and their potential was evaluated as an organic amendment for the growth of sunflower. The ash content (AC) and fixed carbon (FC) improved significantly in prepared biochars as compared to raw feedstock. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses signaled the occurrence of various functional groups viz. amide group and hydroxyapatite, porosity, and multiple nutrients. Application of BB and FB in potted soil alone as well as in composites (1:1, 1:2, 2:1) at 1%, 3%, and 5% (w/w) and synthetic fertilizer significantly increased soil pH, electrical conductivity (EC_e), organic matter (OM) and water holding capacity (WHC), while reducing the bulk density (BD). The growth of plants grown in soil treated with a 2:1 composite of feathers and bone biochar at 5% application rate showed significantly greater differences in plant height, total chlorophyll content, and plant dry weight than the control but was comparable to growth with chemical fertilizer, rendering it a potential alternative to chemical-based synthetic fertilizer.

Untreated tannery wastewater (UTW) poses unprecedented threats to the aquatic and irrigation systems due to severely limited pollution removal efficiency (RE %) by the limited capacity and design of wastewater treatment plants in developing countries. An exploitation of treatment wetlands (TWs) like floating treatment wetlands (FTWs) face hydraulic performance and survivability and establishment challenges of transplanted hydrophytes in the severely toxic UTW. Such challenges were overcome by designing a horizontal flow floating treatment wetland (HFFTW) and diluting UTW at 0, 25, 50, and 75 with harvested rainwater (HRW), viz. UTW:HRW (% v:v) for lowering phytotoxicity to the phytotolerance range of the tested hydrophytes, viz. Eichhornia crassipes (EC) and Pistia stratiotes (PS) in the HFFTW, i.e., EC-HFFTW and PS-HFFTW. Both hydrophytes showed heavy metals’ translocation factor being ≥1, i.e., and acted as excellent hyperaccumulators of heavy metals. The average metal RE (%) was 64 (Cr), 61 (Cd), 45 (Pb), 44 (Cu), and 50.1 (BOD) for E. crassipes, and 44 (Cr), 54 (Cd), 42.2 (Pb), 42 (Cu), and 40 (BOD) for P. stratiotes. Significant reductions in the organic pollution load witnessed by significant drops in BOD and COD made UTW a safer irrigation medium for Petunia hybrida while inducing an increase in the bioconcentration factor (BCF) of PS and EC. The study concluded that the designed HFFTW showed significantly greater RE (%) and yield of reclaimed water than conventional FTWs based on its hydraulic performance. The design HFFTW carries a field scale application capacity for improvising treatment efficiency of the combined effluent plant of KTWMA (Kasur Tannery Waste Management Agency), Kasur, Pakistan.