Fast pyrolysis of poultry litter in a bubbling fluidised bed reactor: Energy and nutrient recovery

Abstract

Livestock production is among the most rapidly growing sectors of the agricultural economy driven primarily by growing demand for animal protein, but also posing significant waste disposal issues and environmental impacts. Moreover, opportunities exist for utilising animal waste at the farm level for heat and power generation (thermal conversion) which can contribute to economic sustainability and also provide a bio-fertiliser for soil amendment. The present study is focused on energy and nutrient recovery from poultry litter using a thermochemical conversion technology (fast pyrolysis). The formation of products (gases, biochar and bio-oil) during the fast pyrolysis of poultry litter was experimentally investigated in a laboratory-scale bubbling fluidised bed reactor. Pyrolytic gases accounted for 15–22 wt.% of the product. The carbon content in biochar increased from 47 to 48.5 wt.% with an increase in the pyrolysis temperature. Phosphorous and potassium recovery in the biochar were over 75%, suggesting that it could be used as an organic soil amendment. The high ash content in poultry litter (14.3 wt.%) resulted in low bio-oil and high biochar yield. The bio-oil yield was over 27 wt.% with a higher heating value of 32.17 MJ/kg (dry basis). The total acid number of the bio-oil decreased from 46.30 to 38.50 with an increase in temperature. The nitrogen content in the bio-oil produced from the poultry litter (>7 wt.%) was significantly higher compared to bio-oil produced from the wood (0.1 wt.%).