The present study evaluated the action of endogenous bioethanol produced during solid-state fermentation of Ulva spp. on subsequent hydrothermal liquefaction (HTL). HTL of raw biomass (RB) was compared with HTL of the fermented biomass after bioethanol separation (F-Aqua) and HTL of the whole fermentation broth containing the bioethanol (F-Eth). Optimization of fermentation conditions increased the ethanol yield efficiency (Y_eff) and specific ethanol yield (SEY) from 23.55% and 0.120 g g⁻¹ sugar consumed to 43.97% and 0.224 g g⁻¹ sugar consumed, respectively. TGA and FTIR analysis confirmed noticeable changes in the thermal profile and functional groups of the fermented residue with increased volatiles and lower ash content. Among different HTL treatments, F-Eth showed the highest bio-oil yield of 24.96% at 250 °C, which was 37.7% and 39.0% higher than that of RB and F-Aqua, respectively. In addition, hydrocarbons and esters in the bio-oil represented the dominant compounds in F-Aqua and F-Eth, altogether 28.28% and 68.58%, respectively, compared to 17.96% in RB. Economic analysis for a proposed 100 ton year⁻¹ plant confirmed that HTL of the whole fermentation broth containing endogenous bioethanol enhanced the gross energy output to 8.152 GJ ton⁻¹, which represented 4.2-time, 51.1%, and 23.3% higher than individual bioethanol production, individual bio-oil production, and sequential bioethanol/bio-oil recovery, with the highest net annual profit of 29553 US$ compared to 23391 US$ for the sequential production.

本研究评估了石莼属固态发酵过程中产生的内源性生物乙醇的作用。随后的水热液化（HTL）。将原料生物质 (RB) 的 HTL 与生物乙醇分离后的发酵生物质 (F-Aqua) 和含有生物乙醇的全发酵液 (F-Eth) 的 HTL 进行比较。发酵条件的优化将乙醇产率（Y _eff）和比乙醇产率（SEY）从 23.55% 和 0.120 g g ^-1糖消耗提高到 43.97% 和 0.224 g g ^-1分别消耗的糖。TGA 和 FTIR 分析证实，随着挥发物增加和灰分含量降低，发酵残渣的热分布和官能团发生了显着变化。在不同的 HTL 处理中，F-Eth 在 250 ℃时的生物油收率最高，为 24.96%，分别比 RB 和 F-Aqua 高 37.7% 和 39.0%。此外，生物油中的烃类和酯类在 F-Aqua 和 F-Eth 中占主导地位，分别占 28.28% 和 68.58%，而 RB 为 17.96%。^{拟建的 100 吨年-1}工厂的经济分析证实，含有内源性生物乙醇的整个发酵液的 HTL 将总能量输出提高到 8.152 GJ 吨^-1，分别是单项生物乙醇产量、单项生物油产量和顺序生物乙醇/生物油回收率的 4.2 倍、51.1% 和 23.3%，最高的年净利润为 29553 美元，而 23391 美元顺序生产。