Vali Naeimeh, Zabihi Samyar, Mohsenzadeh Abas, Pettersson Anita
Swedish Centre for Resource Recovery, Faculty of Textiles, Engineering and Business, University of Borås, 501 90 Borås, Sweden.
ACS Omega. 2025 May 19;10(21):21308-21323. doi: 10.1021/acsomega.4c11089. eCollection 2025 Jun 3.
Municipal sewage sludge (MSS) has been identified as a promising feedstock for producing biochar with potential applications as a soil conditioner and animal feed. However, the high heavy metal content and limited availability of nutrients, such as phosphorus (P), pose significant challenges. This study aimed to improve the quality of MSS-derived biochar through copyrolysis with wheat straw (rich in K and Si) and bakery waste husks (rich in K) at temperatures of 500, 650, and 900 °C. Thermodynamic equilibrium calculations (TEC) were performed using FactSage and HSC Chemistry to predict the stability of P-bearing compounds and the fate of heavy metals in the biochars. The morphology and physicochemical properties of the biochars were examined by using SEM and Brunauer-Emmett-Teller (BET) analyses. The results indicate that increasing the proportions of wheat straw and bakery waste husks, along with higher pyrolysis temperatures, reduced the biochar yield. TEC demonstrated that these blends enhanced the formation of plant-available phosphates compared with pure MSS biochar. This improvement was primarily because of the formation of K/Mg-bearing phosphates in different amorphous and crystalline phases, such as KPO, CaKPO, KPMgO, and KZnPO, instead of Fe/Al-based phosphates. Additionally, copyrolysis reduced the concentrations of heavy metals such as cadmium (Cd), lead (Pb), and zinc (Zn) in the biochars compared to MSS pyrolysis alone. However, it had no significant effect on the copper (Cu), chromium (Cr), and nickel (Ni) levels. In conclusion, copyrolysis with wheat straw and bakery waste husks not only improved the nutrient profile and physicochemical properties of MSS-derived biochar but also mitigated heavy metal contamination. Additionally, this method reduced the presence of heavy metals, making it a more suitable alternative to biochar produced through monopyrolysis for use in agricultural applications.
城市污水污泥（MSS）已被视为一种有前景的原料，可用于生产生物炭，生物炭在土壤改良剂和动物饲料等方面具有潜在应用价值。然而，其高重金属含量以及诸如磷（P）等养分的有限有效性构成了重大挑战。本研究旨在通过在500、650和900℃的温度下与富含钾（K）和硅（Si）的小麦秸秆以及富含钾的面包房废料壳进行共热解，来提高源自MSS的生物炭的质量。使用FactSage和HSC Chemistry进行了热力学平衡计算（TEC），以预测含磷化合物的稳定性以及生物炭中重金属的归宿。通过扫描电子显微镜（SEM）和布鲁诺尔-埃米特-泰勒（BET）分析来检测生物炭的形态和物理化学性质。结果表明，增加小麦秸秆和面包房废料壳的比例以及提高热解温度会降低生物炭产量。TEC表明，与纯MSS生物炭相比，这些混合物增强了植物可利用磷酸盐的形成。这种改善主要是由于形成了不同非晶态和晶态的含钾/镁磷酸盐，如KPO、CaKPO、KPMgO和KZnPO，而非铁/铝基磷酸盐。此外，与单独的MSS热解相比，共热解降低了生物炭中镉（Cd）、铅（Pb）和锌（Zn）等重金属的浓度。然而，对铜（Cu）、铬（Cr）和镍（Ni）含量没有显著影响。总之，与小麦秸秆和面包房废料壳进行共热解不仅改善了源自MSS的生物炭的养分状况和物理化学性质，还减轻了重金属污染。此外，这种方法减少了重金属的存在，使其成为农业应用中比单热解生产的生物炭更合适的替代品。
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