미세조류 바이오매스의 열수액화공정을 통한 바이오크루드 생산

학위논문(박사) - 한국과학기술원 : 생명화학공학과, 2016.2 ,[vii, 116 p. :]Biofuels are one of renewable energies that are actively developed in order to solve global climate change and fossil fuel depletion. Among the biofuels, microalgal biofuel is considered promising due to high productivity and lipid contents. However, conventional conversion method involving lipid extraction suffers low extraction efficiency from wet microalgal biomass. Hydrothermal liquefaction (HTL) is a promising method of converting wet microalgal biomass into biocrude. Especially, the potential HTL of microalgae to produce biocrude regardless of the types of microalgae (biomass-agnostic) has been highly noted. However, the quality of biocrude and the Energy Return On Investment (EROI) of HTL have not been investigated in detail, and only the high yield of biocrude tends to be emphasized. Here we report that the yield as well as the quality of biocrude is directly dependent on the lipid contents of microalgae, and the importance of high lipid content in HTL is revealed using statistical analysis and Energy Return On Investment (EROI) calculation. HTL was conducted with Nannochloropsis oceanica (30.2% lipid content) and Golenkinia sp. (17.3% lipid content), and various operation conditions were tested. The quality of HTL was assessed in terms of asphaltene/non-asphaltene contents, heteroatom (O, N, and S) concentrations, and the effective hydrogen-to-carbon ratios $(H/C_{eff})$ of the biocrudes. N. oceanica with high lipid content produced biocrude more suitable for catalytic upgrading to transportation fuels than the biocrude from Golenkinia sp. with low lipid content. It is shown that carbohydrate and protein in microalgae mainly contributes to formation of asphaltene, which is not suitable for catalytic upgrading due to excess amount of heteroatoms and polyaromatic structure. Based on analysis of components in aqueous phase and biocrude, a general reaction pathway diagram was suggested. Multivariate statistical analysis (redundancy analysis) with the data gathered from the literature confirmed that lipid content has strong positive correlations with biocrude yield as well as quality, represented by H/Ceff. As the result of EROI calculation, low temperature $(200^\circ C)$ is beneficial for HTL of high-lipid microalgae such as N. oceanica, while high temperature $(300^\circ C)$ is suitable for low-lipid microalgae such as Golenkinia sp. The result also shows that production of transportation fuel is only feasible with high-lipid microalgae. These results strongly support that the choice of microalgae with high lipid content is still a key factor that must be considered for biocrude production as much as it is regarded important for biodiesel production using microalgal biomass.한국과학기술원 :생명화학공학과

Method for Extracting Lipid from Microalgae Using Cationoid Polymer and Method for Preparing Biodiesel Using the Extracted Lipid

본 발명은 양이온성 고분자를 이용한 미세조류로부터 지질의 추출방법 및 추출된 지질을 이용한 바이오디젤 제조방법에 관한 것으로, 보다 상세하게는 미세조류의 건조 과정 없이, 음전하를 띠고 있는 미세조류의 세포벽을 파괴할 수 있도록, 말단에 양전하기와 지방족 사슬을 포함하는 고분자를 이용한 미세조류로부터 지질의 추출방법 및 추출된 지질을 이용한 바이오디젤 제조방법에 관한 것이다.본 발명에 따른 미세조류로부터 지질의 추출방법 및 추출된 지질을 이용한 바이오디젤 제조방법은 미세조류의 건조 과정 없이, 미세조류로부터 지질을 추출할 수 있으므로, 바이오디젤의 에너지 및 생산단가 절감에 효과가 있다. 또한 처리 과정에서 소모되는 화학물질이 없고, 별도로 투입되는 에너지 없이 고분자 코팅과 미세조류 세포벽 사이의 상호작용만으로 처리가 이루어지므로 친환경적인 바이오디젤 하부공정을 실현할 수 있다