A new approach for biogas slurry disposal by adopting CO₂-rich biogas slurry as the flower fertilizer of Spathiphyllum: Feasibility, cost and environmental pollution potential

A new approach for biogas slurry disposal was put forward in this study through converting biogas slurry to the organic fertilizer of Spathiphyllum. The biogas slurry was firstly concentrated by vacuum distillation to reduce its volume by 80% who is called 5CBS, and then CO₂ saturated to reduce its pH to about 6.50 ± 0.20. With or without adding the exogenetic Ca, Mg and P nutrients, CO₂-rich 5CBS (i.e., CR-5CBS) was adopted as the root or foliar fertilizer to cultivate Spathiphyllum. Additionally, the commercial Spathiphyllum fertilizer was also experimented as a control. Results showed that the cases adopting CR-5CBS as the root or foliar fertilizer can obtain the agronomic traits and ornamental values of Spathiphyllum better those irrigated by the commercial fertilizer. Exogenetic nutrients added into CR-5CBS can lead to a decreased dead leaf number of Spathiphyllum, an enhanced N assimilation performance, however only a slightly improved assimilation performance of Ca, Mg and P. In terms of the fertilizer economy, CR-5CBS without exogenetic nutrient addition may be a promising for replacing the commercial Spathiphyllum fertilizer in the future. Economic and environmental pollution potential (EPP) analyses indicated that treating biogas slurry as the organic flower fertilizer can achieve a high net profit with about $ 28.89/m³-biogas slurry and a negative EPP value (-3.9), showing its profitability and environmental friendliness.