Changes in agar and other chemical constituents of the seaweed Gracilaria tikvahiae when used as a substrate in methane digesters

An alternative energy source currently under consideration is the production of ethanol or methane (biogas) from different kinds of biomass. Among potential sources are marine plants, some of which have been shown to be highly productive [1,2]. One particular seaweed under consideration as an "energy crop" is the agarophyte, Gracilaria tikuahiae. Previous research has demonstrated that this species can be successfully cultivated in a mariculture system [2] and fermented to produce methane gas [3]. Furthermore, in the interest of maximizing the economic benefits of producing fuels from biomass, the residues left in the digesters can be used as a source of recyclable fertilizer [4].