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.%).
Highlights
According to the European Environmental Agency (EEA) greenhouse gas emissions in the EU-28 in 2015 were 4452 million tonnes CO2 equivalent and the share from the agriculture sector was 11.3%, mainly from ruminants [1]
The present study proposes a small-scale fluidised bed fast pyrolysis unit operating at relatively low temperature as a safe and economical way of disposing of poultry litter
In fast pyrolysis, the yield of liquid bio-oil exceeds that of the biochar, whereas fast pyrolysis of poultry litter resulted in a low liquid and high biochar yield, possibly due to the high ash content in the feedstock
Summary
According to the European Environmental Agency (EEA) greenhouse gas emissions in the EU-28 in 2015 were 4452 million tonnes CO2 equivalent and the share from the agriculture sector was 11.3%, mainly from ruminants [1]. In the EU, poultry meat production has increased by 11% in a single decade (2005–2015) reaching over 12 million tonnes of poultry meat in 2015, and it is expected to rise by another 6% by 2025 [2]. Intensive livestock production generates significant waste disposal issues and environmental impacts. The estimated accumulation of animal manure in the EU is approximately 1.4 billion tonnes/year and the share of poultry litter is about 7.9% [3]. Land application alone is no longer a sustainable solution to the growing volume of animal waste and likely to be uneconomic [5]. New waste treatment technologies addressing sustainability challenges at the nexus of food production and energy are needed to tackle the disposal problem of poultry litter
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