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<p>The microbially induced phosphate precipitation (MIPP) method, characterized by use of acid urease, has emerged as an ecofriendly soil improvement technology that successfully mitigates the drawbacks of standard microbially induced carbonate precipitation (MICP) processes. In this study, we developed a MIPP method utilizing a unique bacterium, <i>Pseudomonas</i> sp. which exhibits acid urease activity even at low temperatures. By using bone meal and urea to mineralize calcium phosphate compounds, we achieved effective sand solidification while suppressing ammonia emissions. Experimental results showed that the maximum unconfined compressive strength (UCS) of 0.46&#xa0;MPa was achieved at 25&#xa0;°C. Crucially, although the strength (0.21&#xa0;MPa) at 15&#xa0;°C was lower than that at 25&#xa0;°C, the method demonstrated its applicability even at low temperatures. The results from microstructure analysis indicated that the UCS was attributed to the formation of brushite (CaHPO<sub>4</sub>・2H<sub>2</sub>O), which acted as a cementing material between sand particles. In terms of cost-effectiveness, the proposed MIPP method achieved a significant reduction to 492 JPY per liter of treatment solution, compared to the standard MICP/MIPP method. This reduction is attributed to the use of NBRC 802 medium, which is more economical than the conventional NH₄YE or MRS medium, as well as the utilization of low-cost, waste-derived bone meal. These findings suggest that the proposed MIPP method provides a low-cost, and carbon-neutral solution for ground improvement, particularly suitable for large-scale applications and diverse environments such as cold regions.</p>

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First report of microbially induced phosphate precipitation (MIPP) for sand solidification at low temperatures via acid urease producing bacteria

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Tatsuhiro Kato,
  • Satoru Kawasaki

摘要

The microbially induced phosphate precipitation (MIPP) method, characterized by use of acid urease, has emerged as an ecofriendly soil improvement technology that successfully mitigates the drawbacks of standard microbially induced carbonate precipitation (MICP) processes. In this study, we developed a MIPP method utilizing a unique bacterium, Pseudomonas sp. which exhibits acid urease activity even at low temperatures. By using bone meal and urea to mineralize calcium phosphate compounds, we achieved effective sand solidification while suppressing ammonia emissions. Experimental results showed that the maximum unconfined compressive strength (UCS) of 0.46 MPa was achieved at 25 °C. Crucially, although the strength (0.21 MPa) at 15 °C was lower than that at 25 °C, the method demonstrated its applicability even at low temperatures. The results from microstructure analysis indicated that the UCS was attributed to the formation of brushite (CaHPO4・2H2O), which acted as a cementing material between sand particles. In terms of cost-effectiveness, the proposed MIPP method achieved a significant reduction to 492 JPY per liter of treatment solution, compared to the standard MICP/MIPP method. This reduction is attributed to the use of NBRC 802 medium, which is more economical than the conventional NH₄YE or MRS medium, as well as the utilization of low-cost, waste-derived bone meal. These findings suggest that the proposed MIPP method provides a low-cost, and carbon-neutral solution for ground improvement, particularly suitable for large-scale applications and diverse environments such as cold regions.