Blood is an important by-product in the meat industry that is generated during the slaughter of livestock and poultry. Due to high volumes of blood produced in slaughterhouses and its great polluting capacity, blood is one of the biggest problems for environment and food health worldwide. The aim of this research work was to apply the sub-critical water hydrolysis for recycling method and convert blood from slaughterhouses into amino acids and synthesis of zinc (Zn)-amino chelate for plant nutrition. In the first part of the experiment, the effect of hydrolysis time and substrate to water ratio on the amino acid yield was investigated. For this purpose, under constant pressure (5 bar) and temperature (150 °C), the effects of different reaction times (0, 10, 15, 20, 30, 40, 50, 60, 90, and 120 min) and the ratio of substrate to water (2:1, 1:1, and 1:2 v:v) were investigated in a batch reactor. Results showed that the reaction time had a substantial effect on the hydrolysis yield and by increasing the reaction time, significant increase in the amino acids extracted from blood was observed. Based on the results, under the tested pressure (5 bar) and temperature (150 °C), the highest amino acid yield by hydrolysis of blood was obtained at the reaction times of 90 and 120 min with the substrate to water ratios of 1:2 and 2:1. In the second part of the experiment, Zn-amino chelate was synthesized using amino acids produced by sub-critical water hydrolysis of blood and then, the efficiency of the synthesized chelate on growth and Zn uptake of corn ( Zea mays L.) was compared with Zn-sulphate. A nutrition solution culture experiment was set up as completely randomized design in triplicates. Zinc was used as foliar spray in the form of complexed with blood-extracted amino acids and Zn-sulphate. A control free of Zn was also considered. After harvesting, plant height, root and shoot dry masses and Zn, nitrogen (N) and iron (Fe) concentrations were measured. In addition, concentration of chlorophyll a and b and carotenoids in the plant leaves were measured. Application of Zn, regardless of the source used, significantly increased root and shoot dry mass of corn in comparison with the control. The largest plant height and root and shoot dry mass was observed at the synthesized Zn-amino chelate treatment. Leaf Fe concentration at all treatments was within the sufficiency range of this nutrient element for corn; although the plant receiving Zn-amino chelate had higher concentration of Fe as compared with those receiving Zn-sulphate and control plants. A significant increase in the leaf chlorophyll concentration of plants supplied with Zn-amino chelate and Zn-sulphate was observed in comparison with the control. Overall, our results showed that Zn complexed with blood-extracted amino acids can be considered as a proper source of Zn for plants, although further research particularly under field conditions is needed. Keywords: Sub-critical water hydrolysis, blood, amino chelate, protein, ferrous ion chelating ability.