Abstract
This study investigated the role of liquid nitrogen (LN2) in increasing microbial accessibility of wool proteins for biogas production. It involves a mechanical size reduction of four different types of raw wool fibres, namely, Blackface, Bluefaced Leicester, Texel and Scotch Mule, in presence of liquid nitrogen, followed by the determination of the methane production potential of the pre-treated wool fibres. The highest methane yield, 157.3 cm3 g−1 VS, was obtained from pre-treated Scotch mule wool fibre culture, and represented more than 80% increase when compared to the yield obtained from its raw equivalent culture. The increase in biogas yield was attributed to the effectiveness of LN2 in enhancing particle size reduction and the consequent increase in wool solubility and bioavailability. Results also showed that LN2 pre-treatment can enhance size reduction but has limited effect on the molecular structure. The study also showed that the biogas potential of waste wool fibres varies with the type and source of wool.
Highlights
Wool is natural fibre material obtained majorly by shearing sheep and generally used in the textile manufacturing
The sheep population in the European Union (EU) area is constantly increasing and now is the second largest, amounted to about 90.4 million, with the majority of the sheep located in the United Kingdom (UK) [4]
This study has shown that pre-treatment of wool fibres can enhance the amenability of wool fibres to anaerobic biodegradation, thereby contributing to increased biogas yield
Summary
Wool is natural fibre material obtained majorly by shearing sheep and generally used in the textile manufacturing. The world textile industry has largely amplified the production due to the increasing global need for manmade fibres estimated from 52.6 million tonnes in year 2000 to 70.5 million tonnes in 2009 and surpassed the volume of 100 million tonnes in 2016, where wool is 1.56% from the total world fibre production [1, 2, 3]. In the UK in 2009 only the clothing industry generated 164,984 tonnes of wool waste, sourced from fibre production, processing, garment production, distribution and import, retail, use and end-of-life [5]. There is an increasing interest in treating wool for energy production. Anaerobic digestion offers a sustainable technology for treating wool waste, which has a great potential to both reduction of waste and energy generation
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