Anaerobic digestion and co-digestion of slaughterhouse waste (SHW): influence of heat and pressure pre-treatment in biogas yield.
Mesophilic anaerobic digestion (34+/-1 degrees C) of pre-treated (for 20 min at 133 degrees C, >3 bar) slaughterhouse waste and its co-digestion with the organic fraction of municipal solid waste (OFMSW) have been assessed. Semi-continuously-fed digesters worked with a hydraulic retention time (HRT) of 36 d and organic loading rates (OLR) of 1.2 and 2.6 kg VS(feed)/m(3)d for digestion and co-digestion, respectively, with a previous acclimatization period in all cases. It was not possible to carry out an efficient treatment of hygienized waste, even less so when OFMSW was added as co-substrate. These digesters presented volatile fatty acids (VFA), long chain fatty acids (LCFA) and fats accumulation, leading to instability and inhibition of the degradation process. The aim of applying a heat and pressure pre-treatment to promote splitting of complex lipids and nitrogen-rich waste into simpler and more biodegradable constituents and to enhance biogas production was not successful. These results indicate that the temperature and the high pressure of the pre-treatment applied favoured the formation of compounds that are refractory to anaerobic digestion. The pre-treated slaughterhouse wastes and the final products of these systems were analyzed by FTIR and TGA. These tools verified the existence of complex nitrogen-containing polymers in the final effluents, confirming the formation of refractory compounds during pre-treatment.
Cuetos
M J
MJ
Institute of Natural Resources (IRENA), University of León, Avda. de Portugal 41, 24071 León, Spain. mj.cuetos@unileon.es
Gómez
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X
Otero
M
M
Morán
A
A
D000003:Abattoirs; D000818:Animals; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D006358:Hot Temperature; D013058:Mass Spectrometry; D008697:Methane / Q000096:biosynthesis*; D011200:Poultry; D011312:Pressure; D012037:Refuse Disposal / Q000379:methods*; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry
D005227:Fatty Acids; D008697:Methane