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.%).

Biorefineries at poultry farms: a perspective for sustainable development

“…In contrast, the long residence time of slow pyrolysis produces a high yield of solid product 57 . Elements like N, H and O decrease in the biochar with an increase in pyrolysis 1, while the C content increases 56 …”

“…The fraction of nutrients recovered in biochar is about five times higher than that in incineration ashes with better plant availability, especially for P 54 . Pyrolysis is considered a technically feasible and environmentally friendly alternative method for poultry waste management 55,56 …”

“…However, such ash may contain heavy metals, which are hazardous for human health if used as substitute of synthetic fertiliser. Pandey et al 56 . recommended that fly ashes from PL gasification need post‐treatment if utilised as a fertiliser due to the presence of higher concentrations of Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb and Se in the fly ashes, being classified as a hazardous material.…”

“…53 The fraction of nutrients recovered in biochar is about five times higher than that in incineration ashes with better plant availability, especially for P. 54 Pyrolysis is considered a technically feasible and environmentally friendly alternative method for poultry waste management. 55,56 Fast and slow pyrolysis processes are distinguished by the residence reaction time and the heating rate. Fast pyrolysis has a short residence time and a high heating rate, which favour a high yield of liquid product.…”

“…57 Elements like N, H and O decrease in the biochar with an increase in pyrolysis 1, while the C content increases. 56 Agblevor et al 46 used PL from broiler chicken and turkey houses, as well as bedding material (hardwood shavings) to convert into biocrude oil in a fast pyrolysis fluidised bed reactor. The conditions for the reaction are presented in Table 2.…”