Anaerobic digestion of Ulva sp 3. liquefaction juices extraction by pressing and a technico-economic budget

Type Article
Date 2006-12
Language English
Author(s) Morand Berenice1, Briand X2, Charlier R3
Affiliation(s) 1 : IFREMER, CNRS, Ctr Rech Ecol Marine & Aquaculture, F-17137 Houmeau, France.
2 : Ctr Etud & Valorisat Algues, F-22610 Pleubian, France.
3 : Inst Dev Res & Enquiry Coastal Zone Studies, Chicago, IL 60641 USA.
Source Journal of Applied Phycology (0921-8971) (Springer), 2006-12 , Vol. 18 , N. 6 , P. 741-755
DOI 10.1007/s10811-006-9083-1
WOS© Times Cited 23
Keyword(s) VFA, Pressing juice, Methanisation, Green tides, Drift algae, Acidogenesis
Abstract In many countries, the algae of "green tides" are harvested in the fight against pollution. Ulva often represents the main component of the tide, and intensive research has been conducted on the possibility to use the algae as a methanisation substrate. However, methanisation is hampered by various practical obstacles, which requires a compromise between productivity and biological yield.

The process described here calls upon a pre-digestion phase of Ulva which, besides the economy of time and volume of the digestion, makes it possible to obtain a biogas of good quality. The methanisation substrate is the hydrolysis juice collected by draining, followed by pressing. The cake resulting from the pressing process can be used as organic enriching or fertilizing agent in agriculture. Various presses were tested. The screw press was found the most suitable to recover a great quantity of sufficiently loaded pressing juice after only a short hydrolysis time. For a 3 month hydrolysis period, the different fractions amounted to 158 L of hydrolysis juice, 192 L of pressing juice, and 0.075 m(3) of cake per m(3) of initial algae.

The bi-phasic anaerobic digestion with forced recuperation of juices offers interesting pollution abatement perspectives, with total and soluble chemical oxygen demand cleaning rates of respectively 79 and 95% during the methanogenic phase, for a volume productivity of 1.5 m(3) stop CH4 m(-3) digester day(-1). The quality of the Ulva juice also makes it suitable for use as substrate for industrial processes or co-substrate of methanisation in pre-existing reactors, so that subsequent investment could be avoided.
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