Recovery of plant nutritional elements and usage as a fertilizer source from fly ash composed of biomass plant

Biomass incineration plants, which have been widely used in recent years to manage crop and forest residue biowaste, produce nutrient-rich biomass ash (BA), but its agricultural use has been limited. Biomass has a high pH (13.04) monitoring feature, the most prominent parameter of its ash. The conductivity values for the biocule are also 27.43 mS cm-1 in diameter. The amount of unburned carbon in the fly ash was found to be low and at a value of approximately 1.98%. This proves that the combustion has taken place completely. The Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) results showed that the basic composition of BA includes high concentrations of potassium, phosphorus and calcium, but the content of earth elements such as silica, aluminum and iron oxides is relatively low. Among the plant nutrients determined in this study, especially P and K were found to be high. The ash used in the study was taken from the samples using 80% chicken litter in the biomass raw material. Phosphorus and other macro/micronutrients from poultry litter in the UK make this waste a valuable raw material source for biofertilizers. In this respect, BA produced by agro-industrial residues can be considered as a useful plant food source. Various technologies have been developed for the solubilization of phosphorus compounds, which can be defined as processes that convert phosphorus into bioavailable forms through a series of chemical reactions and biological interactions. Considering the urgent needs for sustainable waste management, this study aimed to fill the research gap in this field by focusing on vermicomposting method to dissolve potential plant nutrients for crop fertilization. High pH, low solubility of limited plant nutrients, and adverse effects on microbial communities are common disadvantages of BA vermicomposting. BA was collected from the biomass power plant burning poultry litter, forest and crop harvest residues and added to cattle manure to obtain the final nitrogen (N), phosphorus (P) and potassium (K) contents of 0.0% (T0), 3.5% (T1), %. 7.0 (T2) and 10% (T3) are included. Initially, the mixtures were precomposted aerobically for 3 weeks to remove toxic gases and then vermicomposted for 60 days. The sequential phosphorus extraction results showed that vermicomposting improved total phosphorus (TP) and Olsen-P solubility by 69%-79% and 5%-8%, respectively, depending on BA doses. The high pH level of the biocule reached the neutral range level after vermicomposting in all BA vermicompost samples tested. The final nutrient composition of the vermicompost samples was "N 1.31, P 0.53, K 0.90%" (2.74% total) for T0, "N 1.02, P 0.63, K 1.90%" (total 3.55%) for T1, "N 0.8, P 1.78, F 3.86%" (7.16% total) and for T3 "N 0.84, P 2.64, F 6.32%" (9.94% total). In all BA vermicompost samples examined, the maximum P fractions detected were weakly acid-soluble Fe- and Al-bonded P, respectively, followed by the insoluble residual fraction, alkali-soluble and Olsen phosphorus fractions. On the other hand, total phosphorus (TP) content in BA applications varied between 1.41% and 1.77%, while it was 0.63% for control (T0). The results showed that mixtures of BA increased fermentation temperatures and allowed successful earthworm activity in the next vermicomposting phase. In all vermicompost samples, the indicator enzyme activities are urease > β-glucosidase > alkaline phosphatase > acid phosphatase > arylsulfatase, respectively. Phosphate-dissolving microorganisms use phosphatase enzymes and enzyme activators, low molecular weight organic acids and humic acids together to dissolve plant nutrients and convert them into bioavailable form. The phosphatase activity tended to decrease with the increase in the biomass ratio. In addition, the reason for the high urease enzyme activity in all samples compared to other enzyme activities was attributed to the rapid proliferation of the thermophilic phase stage in the microbial population. The reduction in the specific activities of both β-glucosidase and urease in high BA vermicompost treatments was explained by the low organic matter and nitrogen contribution of these treatments as BA was largely devoid of organic carbon and nitrogen. It has been suggested that the decrease in all enzymatic activities due to the increase in the biocul ratio, the decrease in the available substrate ratio and the alkaline effect of the pH value, the most important feature of the bioculum. According to the metagenomic results of vermicompost samples prepared using cattle manure and BA, Proteobacteria (K-23.77%, T0-18.44%, T1-24.34%, T2-23.5%, T3-27.4%) Bacterioids (K-30.5%, T0-15.7%, T1-29%, T2-11.49%, T3-13.94%) and Planctomycetota (K-9.44%, T0-15.32%, T1-12.5%, T2-20.3%, T3-19.85%) were determined as the dominant bacterial phylum in all samples. High correlations were observed in Multiple Linear Regression (MLR) calculations performed between enzyme activities and microbial diversity in vermicompost samples. The coefficients of determination (R2) obtained from multiple regressions between enzyme activities and bacterial population for T0, T1, T2, and T3, were calculated as 0.90, 0.65, 0.73 and 0.90, respectively. The stimulating effect of Flavobacteriales, Burkholderiales, Saccharimonadales and Pseudomonadales on enzyme activities was found to be significant and positive. It has been observed that the bacterial phylum, in which the enzyme activity in worm castings is related to the bacterial population, significantly supports acid phosphatase, alkaline phosphatase, arylsulfatase, β-glucosidase and urease activities. Urease enzyme activity showed the highest activity values in all samples. The urease enzyme plays an important role in converting complex organic nitrogenous matter into simpler forms. Cytophagales population producing hydrolytic enzymes that are effective in the conversion of organic nitrogen forms, which is one of the indispensable organic ingredients in plant development, to urea form, T0, T1, T2 and T3 ratios are 8.44%, 6.14%, 5.97%, 8.09%, respectively. In addition, plant growing trials were conducted to determine the vermicompost effects on common beans (Phaseolus vulgaris L.). Potential fertilization efficiency of nutrient-enriched vermicompost samples with BA, parameters of suitability for growing on bean plant; The chlorophyll content was evaluated using root nodulation and leghemoglobin analyzes and leaf nutrient analyzes. The bean plant was chosen as a model crop since it is sensitive to phosphorus uptake from the soil and especially to phosphorus fertilizers, and phosphorus was reported as the most limiting nutrient in this plant. The results showed that BA-containing vermicompost could promote the growth of plants, increase the chlorophyll content in leaves, and significantly increased leghemoglobin synthesis in the nitrogen fixation of root nodules (p < 0.05). As a conclusion, vermicomposting of BA could improve the solubility of nutrients from BA and that nutrient-enriched vermicompost could be a sustainable bio-based technology for slow release fertilizer production. Moreover, vermicomposted nutrient-rich waste material can improve the nodulation and nitrogen fixing ability of legume crops, thereby increasing the recycling capacity to close the nutrient cycle.