Review of pre-treatments used in anaerobic digestion and their potential application in high-fat cattle slaughterhouse wastewater

Comparison of Ultrasonic and Hydrothermal Cavitation Pretreatments of Cattle Manure Mixed with Straw Wheat on Fermentative Biogas Production

“…Our study found that differences in cavitation manner strongly affected the release of organic matter form cattle manure mixed with straw wheat, and the subsequent biogas/methane production via AD. As ultrasound waves propagate through the medium, they create regions of compression and rarefaction to form cavitation bubbles [15]. Cavitation bubbles grow in successive cycles to reach a critical size at which they violently collapse creating a destructive shock wave [25,26].…”

“…These may provide to improve the methane production during the subsequent AD of pretreated lignocellulosic biomass [2]. In turn, at high frequencies (over 40 kHz) the production of free radicals (H·, OH·, HO 2 ·) prevails, which facilitate chemical reactions for organic materials [6,15]. In acoustic cavitation due to ultrasonic equipment, cavitation is produced by passage of ultrasonic waves through the liquid medium.…”

“…Ultrasonic pretreatment (UP) is a physical method, which disrupt the cell wall structure, increase the specific surface area and reduce the degree of polymerization by effect of compression and cavitation [6]. Cavitation is predominant at low frequencies and causes an intense local heating (around 5000 °C) and high pressure (around 50 MPa) on a liquid/gas interface, turbulence and high shearing phenomena in the liquid phase [11,14,15]. The physical effects of sonication leads to particles disintegration and microorganisms lyses, according to the treatment time and power [11].…”

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

“…This is particularly relevant when sludge is less active; situations where slaughterhouse waste is used in monodigestion or the AD technology does not incorporate temperature control and stirring. While FOG may be difficult to utilise as a substrate, altering the material with pre-treatment prior to entering an AD system may improve its bio-availability, and reduce either the frequency and or severity of complications [2].…”

“…Pre-treatment options of particular interest include thermobaric, chemical, thermochemical, ultrasound, and biochemical methods. Of these, biochemical methods have been investigated the least, and literature regarding bio-surfactant pre-treatment methods is scarce [2].…”