Abstract
Objectives: The aim of this work was to perform a prospective life cycle assessment of the third-generation biodiesel (3G) produced from the heterotrophic cultivation of Phormidium autumnale, using sucrose as the carbon source. Materials and Methods: The study focused on the optimization of the process parameters, in the life cycle assessment and in the biofuel quality analysis in diverse microalgae-based scenarios. Results: In the best scenario, the production of microalgal biodiesel has positive energy production (50.59 MJ/kg) associated with low consumption of water (28.38 m3/kg) and low CO2 emissions (9.18 kg CO2-eq/kg). In terms of composition, this oil was predominantly saturated (45.20%), monounsaturated (34.70%), and polyunsaturated (19.90%), resulting in a biodiesel that complies with U.S., European, and Brazilian standards. Conclusion: The high potential capacity for lipid production obtained is interesting for the generation of quality biodiesel that meets or surpasses the most stringent U.S., European, and Brazilian fuel standard requirements.
Highlights
According to the International Energy Agency (IEA), more than 80% of the world’s primary energy supply derives from fossil fuels [1]
Average biomass production was 6.17 kg/m3, resulting in oil production of 1.23 kg/m3. These results show that in heterotrophic metabolism, the production of intracellular oils by Phormidium autumnale is critically affected by the carbon/nitrogen ratio in the culture medium
The condition that presented the best performance was the scenario C40, with higher values fossil energy input (27.21 MJ), energy output (50.50 MJ), energy ratio (1.85 MJ) and energy balance (-32.38 MJ), followed by the scenarios C30, C35 and C50. These results show that primary energy contained in the biomass is greater than the primary energy input in all the system (NER > 1), demonstrating that these processes have a great potential for energetic exploitation
Summary
According to the International Energy Agency (IEA), more than 80% of the world’s primary energy supply derives from fossil fuels [1]. Expanding energy demand is associated with the growth of developing economies, which represents a considerable increase in the consumption of transport fuels. This is driving a shift towards biofuels. Microalgae-based fuels are third-generation biofuels and may offer a promising biofuel option. Their high growth rates and lipid content, after extraction, are trans-esterified to obtain biodiesel, turning them into one of the most promising feedstocks [3, 4]. Some microalgae can grow heterotrophically in stainless steel fermenters on organic substances (e.g., sugars, organic acids) used as the only source of carbon and energy.
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