# The Perspective of Large-Scale Production of Algae Biodiesel
## 3 Production of Algal Biodiesel
### Production Cost Analysis  
The cost of farming algae for biodiesel production varies significantly from research to research. The production cost of one liter of oil varies from $0.43 to $24.60, making it challenging to predict biodiesel prices in the future [63]. Algae biodiesel production technology is still under development, and prices are considerably higher than competitors in the market. Considerable effort has been placed into automating the production system to cut labor costs. If the price of crude oil rises and technological advances are made in the production of algae biodiesel, the biodiesel price in the future could compete with the price of conventional diesel [63]. Algae biodiesel production has increased since 2010, but low oil and natural gas prices have slowed further development [63]. The high costs of growing and harvesting algal biomass represent a significant barrier to cost-effective biofuel production. Harvesting represents 20% to 30% of the production costs of biomass [64; 65]. The high cost of harvesting is due to the small concentration of microalgae in the water [64; 66]. Open-pond farming systems may be a more economical option for mass production of algae, but low biomass productivity and high water consumption further increase the operating costs [63; 67]. The biomass production depends on the water speed in the channel. Low water speed gives laminar flow and low pond productivity. If the speed of water increases, so does productivity, but the power to run the paddlewheel increases cubically. This condition is especially pronounced for water velocities greater than 30 cm/s, which is especially evident in the increased energy costs. Closed photobioreactors, however, have higher biomass productivity and less contamination, but capital and operating costs are high. The highest share of energy consumption during the cultivation phase relates to the transport of media in the PBR and overcomes the friction loss. It is therefore unclear whether PBRs can become competitive with open-pond systems [68]. Figure 1: Scheme of the biodiesel production system (adapted from [PERSON] et al., 2011 [62]). Most studies agree that the production of algal biodiesel is an energy-intensive process [9; 62; 69]. Thus, the current systems for algae biodiesel production are not energy sustainable, that is, they result in a negative energy balance [70]. As an indicator of the energy sustainability of a product's production, energy efficiency factor (EER) is used, which is defined as the ratio of energy produced and energy intake. EER higher than one indicates the net positive energy produced, and vice versa. The EER values are greater than one in the production of biodiesel from oilseeds [71], as depicted in Table 3.  
Furthermore, it was found that energy consumption in algae biomass production and processing is crucial in assessing the life cycle impact in all the categories evaluated. Especially, biomass drying and lipid extraction are the most energy-intensive processes, requiring the improvement of existing technologies or the adoption of new technologies to achieve a positive balance of energy and CO\({}_{2}\). An increase in biomass productivity reduces the energy consumption in the production of biomass from microalgae, and this is also one of the areas where improvement efforts are being made. Due to the lack of large farms, there are no large-scale farming data available. Laboratory data are often extrapolated, which is unrepresentative of a larger-scale application. Several researchers note that sustainable microalgae farming for large-scale biodiesel production is impossible in the short- and medium-term and further development is needed [72]. However, regardless of the required period, a key factor is minimizing production and maintenance costs, along with maximizing production [73]. The significant barrier to the market of algae biodiesel is the high cost of algae growing and harvesting [74; 75]. According to Reference [76], farming and harvesting account for 50% to 65% of the production cost.