Possible utilization of ash from meat and bone meal and dried distillers grains gasification as a phosphorus fertilizer: crop growth response and changes in soil chemical properties

Purpose

Gasification process is regarded as a viable option for disposal of various types of organic waste. Its application to meat and bone meal (MBM) and dried distillers grains (DDG) is a new concept that is recently receiving more attention as possible strategy for safe recycling of these materials to benefit from their energy and nutrient value. Besides, this process produces ash that is rich in phosphorus (P) and may be suitable for utilization as a P fertilizer. Therefore, the objective of this study was to evaluate the effectiveness of these specific types of ashes as P fertilizer via evaluating their direct effect on canola growth, P uptake, apparent P recovery and changes in some selected soil chemical properties after their addition to a P-deficient soil.

Materials and methods

A growth chamber experiment was set up to meet the study objective. The experimental treatments included meat and bone meal ash (MBMA) and dried distillers grains ash (DDGA) applied at three rates (25, 50, or 100 kg P ha^?1) in comparison to a mineral (mono-calcium phosphate) fertilizer (MP) applied at the same rates in addition to non-P-treated soil (control).

Results and discussion

After a growth period of 5 weeks, the DDGA was the most effective ash type and provided biomass yield, P uptake, and apparent P recovery better or similar to that of MP, indicating high availability of its P. The MBMA had a limited effect on measured crop variables, suggesting that a significant portion of this ash P is present in insoluble form and is not as readily available for plant uptake. This was also indicated by its lesser effect on enhancing extractable available P remaining in soil after harvest in comparison to MP or DDGA. Application of all ash material caused a slight but significant change in soil content of inorganic N as well as soil pH and EC; however, this change was more evident with DDGA treatments.

Conclusions

Ash derived from gasified DDG was the most effective P fertilizer and was comparable to mineral fertilizer. The results of this study demonstrated that the effectiveness of organic material ash as a P fertilizer is controlled by the type of gasified feedstock. The positive results obtained from this study should stimulate further research on utilization of these ashes as a source of P for different crops in different soil types, especially repeated application under field conditions.