# The Perspective of Large-Scale Production of Algae Biodiesel
## 1 Introduction  
Fossil fuel is an unsustainable source of energy and directly linked to air, water, land degradation, and climate change. A large proportion of fossil fuels is consumed as motor fuel in various means of transportation, power plants, and agriculture. On the other hand, as the number of transport facilities increases significantly and, thus, the amount of fuel they consume, the world faces the challenge of finding alternative fuels, since the reserves of fossil fuels are reduced. In 2018, the energy end-use in the EU-28 showed three dominant sectors: industry (25.8%), households (26.1%), and transportation (30.5%) [1]. In the European Union, the transportation sector contributes to 25% of greenhouse gas emissions [2], 36.48% emission of NOx, and 10.67% emission of PM2.5 [3]. Therefore, one of the strategic goals is to reduce emissions from transportation. To achieve this, it is essential to gradually substitute fossil fuels with renewable energy sources. In that sense, biofuels can play a remarkable role. Besides this, biofuel production can increase employment in rural areas and, thus, help their development. In this regard, one of the energy alternatives is biodiesel. Globally, biodiesel is mostly produced from palm oil (31%), soybean (27%), oilseed rape (20%), and used cooking oil (10%). In the EU biodiesel is produced from oilseed rape (44%), palm oil (29%), used cooking oil (15%), and soybean oil (5%). The rests represent sunflower, coconut, peanuts, hemp, jatropha, corn, and algae [4]. Algal biodiesel is an alternative to decrease the consumption of fossil fuels. Compared to classical bioenergy crops, algae cultivation gives much higher yields, which is a significant advantage. Particular algae species (_Schizochytrium_ sp., _Nitzschia_ sp., and _Botyococcus braunii_) contain over 50% of the oil reduced to dry biomass, which can be extracted and processed into fuel [5; 6]. Several fuel types can be produced from algae, such as bioethanol, biodiesel, methane, aircraft fuel (kerosene), biobutanol, biogas, and green diesel. Microalgae grow in fresh or saltwater [7], but also in extreme conditions [5]. Therefore, they are present in diverse ecosystems, like dormant and liquid aquatic ecosystems [6]. Microalgae can yield significant amounts of lipids that are the basis of biodiesel production, as opposed to macroalgae that tend to produce sugars and other carbohydrates instead of lipids. The macroalgae oil content is less than 5% of their dry weight, so they are not economically viable feedstock for biodiesel production [6] and are not be further analyzed in this paper. Algae convert sugars into oil and biomass from which, in addition to biofuels, various chemicals, pharmaceuticals, foodstuffs, and cosmetics can be obtained [8]. Obtaining biodiesel from algae is technically feasible and sustainable, thus putting this technology in an excellent position to potentially and methodically replace oil-derived fuel [9]. Although many reports state that obtaining biodiesel from algae has a perspective [10; 11; 12], the production of large-scale biodiesel from algae is not yet commercially viable. In the production of biodiesel, only those microalgae that contain a high proportion of oil and have a high productivity of biomass and are resistant to various environmental influences can be used. So far, no known microalgae species have these properties [13]. This paper overviews the outline of elements of sustainability and the algae potential for large-scale production of biodiesel. The SWOT (strengths, weaknesses, opportunities, and threats) analysis was conducted to facilitate the study. The structure of the work is as follows. Section 1 introduces the topic and briefly addresses the issues. Section 2 describes the methods and material of the study. In Section 3, the data regarding the technical aspects of biodiesel production from algae are presented.