Evaluation of chemical, thermobaric and thermochemical pre-treatment on anaerobic digestion of high-fat cattle slaughterhouse waste

Abstract

This work aimed to enhance the anaerobic digestion of fat-rich dissolved air flotation (DAF) sludge through chemical, thermobaric, and thermochemical pre-treatment methods. Soluble chemical oxygen demand was enhanced from 16.3% in the control to 20.84% (thermobaric), 40.82% (chemical), and 50.7% (thermochemical). Pre-treatment altered volatile fatty acid concentration by -64% (thermobaric), 127% (chemical) and 228% (thermochemical). Early inhibition was reduced by 20% in the thermochemical group, and 100% in the thermobaric group. Specific methane production was enhanced by 3.28% (chemical), 8.32% (thermobaric), and 8.49% (thermochemical) as a result of pre-treatment. Under batch digestion, thermobaric pre-treatment demonstrated the greatest improvement in methane yield with respect to degree of pre-treatment applied. Thermobaric pre-treatment was also the most viable for implementation at slaughterhouses, with potential for heat-exchange to reduce pre-treatment cost. Further investigation into long-term impact of pre-treatments in semi-continuous digestion experiments will provide additional evaluation of appropriate pre-treatment options for high-fat slaughterhouse wastewater.

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

“…Improving CH 4 yield and increasing the possibility of potentially recovering nutrients from the AD process are directly connected to all aspects of AD (chemical, microbiological and operation aspects) [63]. Recent studies have demonstrated the interrelationship and variation between these three aspects of AD [67,[77][78][79][80][81][82][83][84][85]. The necessity to investigate this interconnectivity and dissimilarity as a priority for advancing the energy recovery potential of AD processes has also been established.…”

“…These include operating parameters (such as temperature, pH and alkalinity, carbon to nitrogen ratio, particle size, retention time and loading rate) and their influence in AD processes; feedstock moisture content; feed rate, and process conditions including co-digestion of different feedstocks [62,86]. Others are fluid flow patterns (such as unstirred and stratified fluid flows) [87][88][89][90]; retention time; carbon to nitrogen ratio and organic loading rates as well as types of digesters and their influence in digestion processes [61,62,[79][80][81][82][83][84][85][86][87][88][89][90][91][92][93]. Although a host of other issues have been addressed by previous investigations, which could not all be captured in this review.…”

Bovine bile as a bio-surfactant pre-treatment option for anaerobic digestion of high-fat cattle slaughterhouse waste

“…In comparison with the financial implications considered in Harris et al [14] With respect to the volume of bile generated per day, around 200 L, the treatment of 1 ML of such waste would bring the value of bile up to around 1102 AUD/day based on these values. In comparison with the collection and preparation of bile for sale to the pharmaceutical industry, bile for wastewater treatment is dosed directly to the waste stream with no other treatment, reducing the effort and energy investment.…”

“…The substrate was dissolved air flotation (DAF) sludge, a concentrated source of FOG residues produced by the DAF process that is representative of the fatty material entering the anaerobic digestion system of red meat facilities [14]. Substrate was collected from the outlet of a DAF unit, and refrigerated at 4°C until use.…”

Opportunities and challenges in sustainable treatment and resource reuse of sewage sludge: A review

“…Biogas comprises of 60 -70 % methane, and 30 -40 % of carbon dioxide, trace amounts of other gases (e.g. hydrogen, hydrogen sulfide and nitrogen), with a relative density of around 0.85, and calorific value of about 13 -21 MJ kg -3 , which is lower than that of coal (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) ), but equivalent to lignite's (12 -16 MJ kg -3 ) [8].…”