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Biofuels from algae: technology options, energy balance and GHG emissions: Insights from a literature review

Biofuels from algae: technology options, energy balance and GHG emissions: Insights from a literature review
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Abstract: 
During the last decade(s), algal biomass received increasing interest as a potential source of advanced biofuels production resulting in a considerable attention from research, industry and policy makers. In fact, algae are expected to offer several advantages compared to land-based biomass crops, including: better photosynthetic efficiency; higher oil yield; growth on non-fertile land; tolerance to a variety of water sources (i.e. fresh, brackish, saline) and CO2 re-using potential. The algal growth can be also integrated in wastewater (WW) treatment systems to combine the nutrient streams removal with biofuels production. In addition, a wide range of marketable co-products can be extracted from algae (e.g. chemicals, pharmaceuticals, nutritionals) along with the production of biofuels, under a biorefinery system. Considering the potential benefits, several European-funded pilot projects, under science-business partnerships, have been dedicated to the development of algae technologies in the biofuels and bioenergy sectors. Despite the extensive research and investments in the last decade(s), no large-scale, commercial algae-to-biofuels facilities were implemented yet. In fact, in the current algae cultivation sites, the produced biomass is currently exploited for production of food and feed, combined with the extraction of high added-value products, such as proteins, nutritional supplements and chemicals. We report on the current-status of technology options for the potential exploitation of algae (of both macro- and microalgae species) in the biofuels and bioenergy sectors. We presents a comprehensive review of recent advances on promising algal biofuel production pathways, in terms of technological development, opportunities and limitations to their overall effectiveness. Furthermore, we analyse the main features, assumptions, modelling approaches and results of the algal biofuel pathways considered in the LCA literature. We highlight and interpret the energy and greenhouse gas (GHG) emissions balances resulting from examined LCA studies, in view of the key parameters mainly affecting the results. A comparison of the performance associated to the proposed algal biofuels pathways with that found for conventional fossil derived fuels is also reported.