The Recovery of Phosphate and Ammonium from Biogas Slurry as Value-Added Fertilizer by Biochar and Struvite Co-Precipitation

Abstract

Biowaste materials could be considered a renewable source of fertilizer if methods for recovering P from waste can be developed. Over the last few decades, there has been a high level of interest in using biochar to remove contaminants from aqueous solutions. This study was conducted using a range of salts that are commonly found in biogas slurry (ZnCl2, FeCl3, FeCl2, CuCl2, Na2CO3, and NaHCO3). Experiments with a biogas digester and aqueous solution were conducted at pH nine integration with NH4+, Mg2+, and PO43− molar ratios of 1.0, 1.2, and 1.8, respectively. The chemical analysis was measured to find out the composition of the precipitate, and struvite was employed to remove the aqueous solutions. The study found that the most efficient removal of phosphate and ammonium occurred at pH nine in Tongan sludge urban biochar and rice biochar, respectively. Increasing the concentration of phosphate and ammonium increased the phosphate and ammonium content. Moreover, increasing the biochar temperature and increasing the concentration of phosphate and ammonium increased the efficiency of the removal of ammonium and phosphate. The removal efficiency of ammonium and phosphate increased from 15.0% to 71.0% and 18.0% to 99.0%, respectively, by increasing the dose of respective ions K+, Zn2+, Fe3+, Fe2+, Cu2+, and CO32.The elements were increased from 58.0 to 71.0 for HCO3− with the increasing concentration from 30 mg L−1 to 240 mg L−1.This study concluded that phosphate and ammonium can be recovered from mushroom soil biochar and rice biochar, and phosphate can be effectively recovered via the struvite precipitation method.

Biochar integrated reactive filtration of wastewater for P removal and recovery, micropollutant catalytic oxidation, and negative CO2e: Process operation and mechanism

“…With the biochar modification (i.e., Fe‐BC P in this study), the Fe treatment on the biochar creates nanoparticulate iron oxide (e.g., hydrous ferric oxide) that increases the adsorption affinity of the biochar for P (Bakshi et al, 2021; Zhang et al, 2020). This is supported by studies that show metal modifications on biochar facilitate the formation of metal‐biochar bridges between phosphate anions and negatively charged weak‐acid functional groups on the biochar (Garcia‐Perez et al, 2022; Kubar et al, 2021; Nageshwari et al, 2022).…”

Nutrient Recovery from Poultry Wastewater by Modified Biochar: An Optimization Study

“…Furthermore, in our study, the sample after adsorption had N and P at 1.04 and 21.13 % (w/w), respectively, showing that the biochar was effectively recovering N and P. Other compounds in biochar such as CaCO3 and KCl did not change into other forms or affect the modified biochar except for increasing the amount of carbon content in the biochar [14]. In Table 1, the decline of Mg percentage in EDX results was evidence of precipitation between Mg-N-P [27,28,[56][57][58][59]. Furthermore, the presence of N and P after adsorption verified the adsorption ability of this material.…”

“…From this Table, the actual values (60.64 mgNH4 + -N/g and 66.24 mgPO4 3--P/g) and predicted values (62.59 mgNH4 + -N/g and 64.93 mgPO4 3--P/g) were well in agreement with each other. For comparison, ammonium removal with modified biochar reports in the literature were: oak sawdust/LaCl3 (3.12 mg N/g with initial concentration 25.7 mgNH4 + /L [57,66]), mixed hardwood (2.8 mgNH4 + /g with influent 980 mgNH4 + -N/g [67] and 0.48 mgPO4 3--P/g with phosphate concentration of 24 mgPO4 3--P/L), corn cob (1.09 mgNH4 + -N/g with 100 mgNH4 + -N/L) [40], unmodified sawdust (5.38 mg NH4 + -N/g) [65], unmodified sesame straw (26.84 mg NH4 + -N/g) [65,68], corn stalk (37.72 mg NH4 + -N/g, 73.29 mg PO4 3-/g) [32], and coal gangue modified oilseed rape straw (7.9 mg/ PO4 3--P g) [48]. MgO impregnation increases the adsorption effectiveness of the biochar, as observed for sugarcane [14], poplar chips [22], unmodified sawdust [65], unmodified sesame straw [65,68], corn stalk [32], coal gangue modified oilseed rape straw [48], and brown marine macroalgae [69].…”

Overview on agricultural potentials of biogas slurry (BGS): applications, challenges, and solutions

“…Maximum adsorption values recorded using iron-modified biochars were 11.68 and 26.14 mg g −1 for nitrogen and phosphorous respectively [ 213 ]. Kubar et al [ 215 ] in a biochar and struvite co-precipitation method recorded maximum recovery of P (45.36% with ZnCl 2 ) and NH 4 + (33% with NaHCO 3 − ) using rice biochar and Tongan sludge urban biochar respectively (adsorbent dose=0.2 g).…”