Renewable, low-carbon biofuels offer the potential opportunity to decarbonize marine transportation. This paper presents a comparative techno-economic analysis and process sustainability assessment of four conversion pathways: (1) hydrothermal liquefaction (HTL) of wet wastes such as sewage sludge and manure; (2) fast pyrolysis of woody biomass; (3) landfill gas Fischer–Tropsch synthesis; and (4) lignin–ethanol oil from the lignocellulosic ethanol biorefinery utilizing reductive catalytic fractionation. These alternative marine biofuels have a modeled minimum fuel selling price between $1.68 and $3.98 per heavy fuel oil gallon equivalent in 2016 U.S. dollars based on a mature plant assessment. The selected pathways also exhibit good process sustainability performance in terms of water intensity compared to the petroleum refineries. Further, the O and S contents of the biofuels vary widely. While the non-HTL biofuels exhibit negligible S content, the raw biocrudes via HTL pathways from sludge and manure show relatively high S contents (>0.5 wt %). Partial or full hydrotreatment can effectively lower the biocrude S content. Additionally, co-feeding with other low-sulfur wet wastes such as food waste can provide another option to produce raw biocrude with lower S content to meet the target with further hydrotreatment. This study indicates that biofuels could be a cost-effective fuel option for the marine sector. Marine biofuels derived from various feedstocks and conversion technologies could mitigate marine biofuel adoption risk in terms of feedstock availability and biorefinery economics.

中文翻译：

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海洋运输可持续生物燃料的技术经济分析


可再生低碳生物燃料为海洋运输脱碳提供了潜在机会。本文对四种转化途径进行了技术经济比较分析和工艺可持续性评估：（1）污水污泥和粪便等湿废物的水热液化（HTL）； (2)木质生物质的快速热解； (3)垃圾填埋气费托合成； (4) 利用还原催化分馏从木质纤维素乙醇生物精炼厂生产的木质素-乙醇油。根据成熟的工厂评估，这些替代海洋生物燃料的模拟最低燃料售价为每加仑重质燃料油 1.68 美元至 3.98 美元（按 2016 年美元计算）。与炼油厂相比，所选途径在水强度方面也表现出良好的工艺可持续性表现。此外，生物燃料的O和S含量差异很大。虽然非 HTL 生物燃料的硫含量可以忽略不计，但通过HTL 途径从污泥和粪便中获得的原始生物原油却显示出相对较高的硫含量 (>0.5 wt%)。部分或全部加氢处理可有效降低生物原油中的S含量。此外，与其他低硫湿废物（例如食物垃圾）共同进料可以提供另一种选择，生产具有较低硫含量的生物原油原料，以满足进一步加氢处理的目标。这项研究表明，生物燃料可能是海洋部门一种具有成本效益的燃料选择。来自各种原料和转化技术的海洋生物燃料可以减轻原料可用性和生物炼制经济方面的海洋生物燃料采用风险。