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<p>The sustainable management of sewage sludge (SS) and municipal solid waste (MSW) poses increasing challenges due to their high volumes and associated environmental risks. Pyrolysis offers a promising valorization pathway by converting these wastes into biochar with agronomic potential. This study assessed the dose-dependent effects of biochars derived from SS (BSS) and MSW (BMSW) on soil organic matter mineralization, leachate chemistry, and the growth response of a leguminous crop, <i>Medicago sativa</i>. These interactions remain poorly understood for high-ash biochars <i>such as</i> BSS and BMSW. Over a 12-week incubation, carbon and nitrogen dynamics were strongly influenced by biochar dose and feedstock type. During the first week, BMSW induced a negative priming effect (PE), while BSS induced a positive PE, an effect that reversed by the end of incubation <i>period</i>. BMSW enhanced microbial activity and nitrate levels at intermediate rates, while BSS increased microbial biomass carbon at low doses but suppressed respiration and nitrification at higher rates due to its high ash content. Both biochars <i>increased</i> total organic carbon and available phosphorus, with BSS showing a stronger effect at 40 t ha⁻¹. In pot trials, <i>an application rate of</i> 10 t ha⁻¹ significantly improved alfalfa biomass and nodulation, but higher doses inhibited nodulation and triggered oxidative stress. Leaching tests showed minimal heavy metal mobility, confirming environmental safety at <i>the</i> tested rates. Overall, low-dose applications of BSS and BMSW can enhance soil fertility and legume productivity, while excessive rates may disrupt plant–microbe symbiosis. These results underscore the importance of optimizing biochar type and <i>application rate</i> in sustainable soil management.</p>

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Impact of sewage sludge and municipal solid waste derived biochars on soil carbon priming, leachate quality, and legume growth and nodulation

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Amani Haddouk,
  • Saif-Allah Chihaoui,
  • Zeineb Louati,
  • Ismail Trabelsi,
  • Mohamed Ali Wahab

摘要

The sustainable management of sewage sludge (SS) and municipal solid waste (MSW) poses increasing challenges due to their high volumes and associated environmental risks. Pyrolysis offers a promising valorization pathway by converting these wastes into biochar with agronomic potential. This study assessed the dose-dependent effects of biochars derived from SS (BSS) and MSW (BMSW) on soil organic matter mineralization, leachate chemistry, and the growth response of a leguminous crop, Medicago sativa. These interactions remain poorly understood for high-ash biochars such as BSS and BMSW. Over a 12-week incubation, carbon and nitrogen dynamics were strongly influenced by biochar dose and feedstock type. During the first week, BMSW induced a negative priming effect (PE), while BSS induced a positive PE, an effect that reversed by the end of incubation period. BMSW enhanced microbial activity and nitrate levels at intermediate rates, while BSS increased microbial biomass carbon at low doses but suppressed respiration and nitrification at higher rates due to its high ash content. Both biochars increased total organic carbon and available phosphorus, with BSS showing a stronger effect at 40 t ha⁻¹. In pot trials, an application rate of 10 t ha⁻¹ significantly improved alfalfa biomass and nodulation, but higher doses inhibited nodulation and triggered oxidative stress. Leaching tests showed minimal heavy metal mobility, confirming environmental safety at the tested rates. Overall, low-dose applications of BSS and BMSW can enhance soil fertility and legume productivity, while excessive rates may disrupt plant–microbe symbiosis. These results underscore the importance of optimizing biochar type and application rate in sustainable soil management.