The effect of nitrogen content on methane production by the marine algae Gracilaria tikvahiae and Ulva sp

The rhodophyte Gracilaria tikvahiae and the chlorophyte Ulva sp. were grown under three different nitrogen enrichment regimes producing plants of each species with three different concentrations of tissue nitrogen. Each was then digested in batch-mode fermentation experiments. Both biogas and methane production were initially greater in Ulva but persisted longer in Gracilaria, resulting in similar performances for the two species over the entire time course of the experiment.