The utilisation of thermally treated poultry farm waste for energy recovery and soil application

Abstract

The thermal treatment was analysed of poultry farm waste, excrement and litter, and their mixture. Two thermal treatment methods were chosen: Torrefaction at 300 °C and hydrothermal carbonisation (HTC) at 250 °C. The characterisation of raw materials and solid products was performed by proximate and ultimate analysis, and analysis of the high heating value. Thermogravimetric analysis (TGA) was performed of the combustion of raw materials and solid products in an air atmosphere. The kinetic and thermodynamic parameters were determined according to the Flynn–Wall–Ozawa (FWO) kinetic model. The contents of total organic carbon, chemical oxygen demand, total nitrogen and total phosphorus, as well as the content of total phenols, were determined in the process fluids. In addition, a germination test was performed with garden cress.The results show that the torrefied biomass had a higher carbon (C) content and a higher calorific value than raw biomass. The FWO kinetic model proved to be suitable for describing the kinetic of combustion of the tested samples' high fitting coefficients. The Eα for torrefied litter, excrement and their mixture ranged between 129 and 338, 108–550 and 136–489 kJ/mol, while for the HTC-treated samples generally lower Eα values were measured, 187–364, 121–229 and 126–428 kJ/mol, respectively. Germination tests with garden cress and analysis of nutrients showed that the tested products of torrefaction and HTC have a perspective for agricultural use at a sample concentration of up to 10 wt% in the substrate.