Agro Environmental Benefit and Risk of Manure and Bone Meal Derived Pyrogenic Carbonaceous Materials as Soil Amendments: Availability of PAHs, PTEs, and P
The worldwide boom of biochar and pyrogenic carbonaceous material application as a potential soil additive has brought about not only agricultural benefits such as enhanced crop yield, nutrients supply (P) and soil organic carbon increase, but also, on the other hand, environmental risk of organic (polycyclic aromatic hydrocarbons (PAHs) and potentially toxic element (PTE) penetration into arable soils. Therefore, our study assessed pyrogenic carbonaceous materials (PCM) produced from the P rich feedstocks chicken manure (CM) and bone meal (BM) as promising and safe alternatives for inorganic P fertilizers. Pyrogenic materials produced in the process of slow pyrolysis at residence time 2 h, 400 and 500 degC, were characterized by determination of pH, electrical conductivity (EC) elemental analysis of total C, H, N, S scanning electron microscopy (SEM) total content of P, selected potentially toxic elements (PTEs) and available forms of PTEs and P by diethylenetriaminepentaacetic acid (DTPA) and calcium acetate lactate (CAL) extractions. CMPCM4, CMPCM5, BMPCM4, and BMPCM5 were characterized by determination of total 16 US EPA (U.S. Environmental Protection Agency) PAHs by toluene extraction protocol and available concentrations by Tenax resin approach. Additionally, CMPCM4, CMPCM4, BMPCM4, and BMPCM5 were tested in earthworm avoidance test with Eisenia foetita and short term rye seedling germination test. Obtained results showed decreasing of total carbon in the order of BM BMPCM4 BMPCM5 and increasing in the order of CM CMPCM4 CMPCM5. Total phosphorus content increased from 56.8 1.7 g kg 1 (BM) to 85.2 4.2 g kg 1 (BMPCM4) to 110.5 7.0 g kg 1 (BMPCM5) In the case of chicken manure derived pyrogenic materials, total phosphorus content increased in the order of CM (22.9 2.0 g kg 1) CMPCM4 (37.0 4.5 g kg 1) CMPCM5 (40.0 3.4 g kg 1) Availability of selected PTEs and P decreased in pyrogenic materials compared to feedstock. Total concentration of 16 US EPA PAHs in BMPCM4 and BMPCM5 was 3.92 mg kg 1; CMPCM4, 7.33 mg kg 1; and CMPCM, 6.69 mg kg 1. The Tenax available 16 PAHs showed concentrations of 0.53 mg kg 1 for BMPCM4, 0.26 mg kg 1 for BMPCM5, 1.13 mg kg 1 for CMPCM4, and 0.35 mg kg 1 for CMPCM5. Total P concentrations determined in rye aboveground tissues showed the highest accumulation ability in the case of CMPCM5 compared to other samples. Pyrogenic carbonaceous materials produced from chicken manure and bone meal at 400 and 500 degC have the potential to be P slow release fertilizers and may be ecologically safe.