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19 Increasing biofuel production on agricultural lands in tropical island nations will likely result 20 in increased deforestation [1], and also inflate food prices, especially in net food importing 21 countries like the Philippines [2-4]. Compounding problems associated with promotion of 22 biofuels in southeast Asian countries are the technical efficiencies of bioethanol production, 23 including poor energy balances from terrestrial crops that are close to, or less than unity, 24 unless bagasse is used as the distillation heat source [1]. As the increase in terrestrial biofuel 25 2 production in Pacific island nations is potentially less sustainable than is publically stated, 26 alternative feedstocks are required which retain the regional development benefits, while 27 reducing the negative ecological and food security impacts [1,5]. This work presents the 28 potential of farmed macroalgae chemical substrates as a bioethanol feedstock supply, 29 explores macroalgae-to-bioethanol yields, and details prospective non-food macroalgae 30 species, specific to the Philippine coastal region. Leveraging off the existing capability of the 31 macroalgae farming industry (producing 1.7 million wet tonnes annually in the Philippines 32 alone), a significant new market for non-food macroalgae stimulated by bioethanol producers 33 can be developed to avoid problems related to food/feed grade ethanol feedstocks. 34