Overview on biofuels production in a seaweed biorefinery

The policy makers gathered at COP27 set a goal of limiting global warming to 1.5 °C above the pre- industrial level which requires a reduction of CO₂ emissions of 43% by 2030 (relative to 2019 value). To meet this target, it is imperative to replace fossil derivatives (fuels and chemicals) with biomass derivatives. Given that 70% of planet Earth is the ocean, blue carbon can contribute significantly to the mitigation of anthropogenic carbon emissions. Marine macroalgal, or seaweed, that stores carbon, mostly, in the form of sugars rather than lignocellulosic, like terrestrial biomass, is suitable as input raw material for biorefineries. Seaweed biomass has high growth rates, does not require fresh water or arable land, and therefore does not compete with conventional food production. To make seaweed based biorefineries profitable the valorization of biomass has to be maximized through cascade processes with the production of several high-value products such as pharmaceuticals/chemicals, nutraceuticals, cosmetics, food, feed, fertilizers/biostimulants and low-carbon fuels. The composition of macroalgae, which varies depending on the species (green, red, or brown), the region in which it is grown, and the time of year, determines the variety of goods that can be made from it. Fuels must be made from seaweed leftovers since the market value of pharmaceuticals and chemicals is substantially larger than that of fuels. The following sections present a literature review on seaweed biomass valorization in the context of biorefinery with particular emphasis on low-carbon fuel production processes. An overview of seaweed's geographical distribution, composition, and production processes is also presented.