Amaize-P

International Research Training Group “Adaptation of maize-based food-feed-energy systems to limited phosphate resources” (AMAIZE – P)

Topic

The international research training group (AMAIZE-P) has researchers participating from eleven departments of the University of Hohenheim and the China Agricultural University in Beijing. The goal of the project is to maximize phosphate use efficiency. To achieve this goal research is being carried out in the areas of plant breeding, plant cultivation, animal feeding, human nutrition, nutrient recovery using anaerobic digestion and hydrothermal carbonization systems, and economic analysis. The State Institute of Agricultural Engineering is involved in research subject 3.3. 

Goals

This subject aims to analyze the effect of limited phosphate fertilizer supply in agricultural systems and to optimize phosphate utilization efficiency by providing additional phosphate streams. Since digestate is a rich source of nutrients, in this study digestate was used as a substrate to recover nutrients. The research is now structured to recover phosphorus from anaerobic digestion systems using low and high-technology approaches. The focus was first given to a low-technology approach in which the digestate is treated with additives followed by solid-liquid separation.

Project tasks of the State Institute

Within this framework, the state institute has the task of analyzing the effect of various additives in phosphate recovery from fermentation residues. In this context, research is being conducted into how phosphates can be efficiently recovered to increase transportability.
Currently, the parameters of temperature and treatment time were tested to study their effect on the recovery of phosphorus. The separation efficiency was evaluated based on the amount of total phosphorus bound to the solid phase of digestate after solid-liquid separation. In addition, the distribution of phosphate fractions was analyzed with Hedley fractionation.  The preliminary results shown in the graphic below indicate that treatment with additives had a positive influence on recovering phosphorus from digestate. Especially, the treatment with kieserite had a nearly 40% increase in the recovered phosphorus in the solid phase compared to control. Subsequently, different additive amounts and the effect of pH on the recovery will also be tested.