Effect of Particle Size on Desalting and Bioconversion of Kelp to Methane

Abstract

ABSTRACT LARGE ocean kelp farms can potentially produce a significant amount of fuel gas, feed and food. Grinding probably would precede either bioconversion of kelp to methane or mechanical dejuicing of kelp for reduction of bulk and salt content. Grinding energy consumption varied from about 2 W-h/kg of kelp to produce material where 70% (w/w) would pass a 4.3 mm aperture (dyo = 4.3 mm) to about 6 W-h/kg for material with dyo of 1.4 mm. This equals 1-3% of the energy obtained by bioconversion of kelp to methane. In a limited test, particle sizes in the range of chopped (ca. 75 mm) to dyo of 2.1 mm had little, if any, effect on methane yield. Decreasing particle size produced relatively small decreases in salt content of pressed CaCl2-heat treated kelp, not enough in most cases to offset the increased loss of organic matter. In general, there appear to be no processing advantages to grinding to a size smaller than that needed for material handling.