Note
The macroalga Gracilaria tikvahiae (Rhodophyta) was used in a closed system of materials to study methane production and nitrogen recycling. Twenty liter carboys served as digesters. The performance of these digesters mirrors results obtained with two- and four-litre Gracilaria digesters with respect to optimal retention times for biogas production, methane content, and bioconversion efficiency to methane. Three groups of Gracilaria were cultivated in 850-L vaults to compare growth performance under three different enrichment treatments.