Improving the value of CO2 and biogas slurry in agricultural applications: A rice cultivation case

To cope with the global warming caused by CO2 concentration rising, it should be considered to supply CO2 into plants through other suitable forms for encouraging more CO2 uptake by plants. In this study, the physiological toxicity of CO2-stored biogas slurry to crops and its application prospects were investigated using biogas slurry as a carrier to convert CO2 into HCO3- for plant planting. The results showed that the physiological toxicity of biogas slurry after CO2 absorption (i.e., CO2-rich biogas slurry, CRBS) to rice diminishes. Compared with the biogas slurry without storing CO2, the pH values of CRBS and the CO2-rich 5-times concentrated biogas slurry (CR5BS) decrease significantly by 14.5% and 18.5% respectively, and the EC values increase significantly by 49.1% and 19.0%, respectively. The rice cultivated with CRBS and CR5BS have the higher root activities by 86.9% and 29.0% than the rice cultivated with biogas slurry without CO2-storage, respectively. When using CRBS and CR5BS, the physiological toxicity of HCO3- to rice decreases, offering a favorable rhizosphere environment for rice growth. Adopting CRBS and CR5BS can promote the tillering of rice and shorten the tillering stage of rice, when compared to irrigate the biogas slurry without CO2-storage. Similarly, compared with the rice cultivated with biogas slurry without CO2-storage, the accumulation of nitrogen and ferrum by rice cultivated in CRBS increases by 78.2% and 26.1%, respectively. The corresponding values increase by 72.3% and 29.8% for the case adopting CR5BS.

Automated summary

To mitigate global warming caused by increased CO2 concentration, it is suggested to supply CO2 to plants through other forms to enhance their CO2 uptake. This study investigated the potential of using CO2-stored biogas slurry as a carrier for plant growth by converting CO2 into HCO3-. Results showed that the physiological toxicity of CO2-rich biogas slurry to rice diminished, as indicated by decreased pH and increased EC values. Rice cultivated with CO2-rich biogas slurry exhibited higher root activities and reduced toxicity from HCO3-. Furthermore, adopting this method promoted rice tillering and nutrient accumulation compared to traditional biogas slurry irrigation.