The sulfite pulping industry produces nearly 2.7 million kg of organic waste material annually in the form of lignin and other water soluble organic compounds. For every 1,000 kg of sulfite pulp manufactured, approximately 8,800 liters of desugared spent sulfite liquor (SSL) are produced. This SSL contains the lignin molecule (lignosulfonate) dissolved from wood fibers during the pulping process. It has been estimated that the calorie value of the organic wastes in the SSL produced annually is about 97 trillion cal or the equivalent of 1.1 billion M³ of natural gas/year (38, 137).

CEBTech has past experience with a project involving the conversion of organics and sulfur in SSL, classified as pollutants from sulfite pulp mills, into synthetic methane and protein by means of a combination chemical-biological process. Ozonation was used to break the high molecular weight lignosulfonate molecules present in SSL into lower weight fractions which could be metabolized by methane-producing bacteria and protein-producing yeast. Ozonation experiments showed that this treatment is effective in partially oxidizing and fragmenting lignosulfonates into fermentable substrates. This process is initiated at low ozone concentrations and proceeds rapidly until nearly 30% of the Chemical Oxygen Demand (COD) has been consumed. The conditions under which ozonation is conducted greatly affect the degree of oxidation and the molecular weight of the cleaved fragments (38, 77, 137).

Ozone Generator with 1.8 Meter Reaction Column

Two Flasks Showing Ozone Reactor Influent & Effluent

Chemical Engineer Posing with Four Anaerobic Reactors

Gram Stain of Methanobacterium ruminatium

Methanogens in an Anaerobic Roll Tube Under Room Light

Methanogens in an Anaerobic Roll Tube Under UV Light

Fig. 1 Process Flow Diagram of Ozonation & Fermentation of SSL

Process Table 1 of Ozonation & Fermentation Results

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References