Evaluation of microalgae biodiesel for carbon neutrality based on the waste treatment by the autotrophic and heterotrophic combination

Microalgae aid in addressing environmental pollution and climate change by enabling carbon sequestration as part of CCUS, which offers a promising solution to reduce fossil fuel dependence and mitigate emissions. This study uses the combination of autotrophic and heterotrophic methods to enhance the benefits of biodiesel based on waste treatment. The study demonstrates that by integrating autotrophic and heterotrophic biodiesel production, it is feasible to attain substantial economic advantages while maximizing carbon sequestration and reducing emissions. It shows a 62.73 % cost reduction for 1 ton of biodiesel produced using the coupled heterotrophic method over traditional photobioreactors. Additionally, compared with the corresponding heterotrophic proliferation, the carbon emissions of biodiesel under autotrophic coupled heterotrophic proliferation were reduced by 21.16 % and 24.08 %, respectively. The total economic benefits of biodiesel under autotrophic coupled heterotrophic proliferation increased by 2.12 % and 3.10 % compared to heterotrophic proliferation. However, it should be noted that due to the high carbon emissions caused by the heterotrophic proliferation of microalgae, biodiesel does not achieve negative carbon emissions. This study provides a new development strategy for waste resource utilization and microalgae bioenergy production phase. It will provide a theoretical and practical framework for utilizing microalgae biodiesel to achieve worldwide carbon neutrality.