Drop‐in biofuel production via conventional (lipid/fatty acid) and advanced (biomass) routes. Part I

Abstract

Drop‐in biofuels that are ‘functionally identical to petroleum fuels and fully compatible with existing infrastructure’ are needed for sectors such as aviation where biofuels such as bioethanol/biodiesel cannot be used. The technologies used to produce drop‐in biofuels can be grouped into the four categories: oleochemical, thermochemical, biochemical, and hybrid technologies. Commercial volumes of conventional drop‐in biofuels are currently produced through the oleochemical pathway, to make products such as renewable diesel and biojet fuel. However, the cost, sustainability, and availability of the lipid/fatty acid feedstocks are significant challenges that need to be addressed. In the longer‐term, it is likely that commercial growth in drop‐in biofuels will be based on lignocellulosic feedstocks. However, these technologies have been slow to develop and have been hampered by several technoeconomic challenges. For example, the gasification/Fischer‐Tropsch (FT) synthesis route suffers from high capital costs and economies of scale difficulties, while the economical production of high quality syngas remains a significant challenge. Although pyrolysis/hydrothermal liquefaction (HTL) based technologies are promising, the upgrading of pyrolysis oils to higher specification fuels has encountered several technical challenges, such as high catalyst cost and short catalyst lifespan. Biochemical routes to drop‐in fuels have the advantage of producing single molecules with simple chemistry. However, the high value of these molecules in other markets such as renewable chemical precursors and fragrances will limit their use for fuel. In the near‐term, (1–5 years) it is likely that, ‘conventional’ drop‐in biofuels will be produced predominantly via the oleochemical route, due to the relative simplicity and maturity of this pathway. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd

Potential synergies of drop‐in biofuel production with further co‐processing at oil refineries

“…As mentioned earlier, one of the greatest challenges of upgrading lipids / biomass to drop‐in biofuels is the removal of oxygen. Although other heteroatoms such as nitrogen may be present, oxygen is the most prominent and it reduces the energy density of the fuel.…”

“…Earlier work ranked the various likely lipid / biomass feedstocks on a staircase based on their effective H/C ratio (Fig. ) . This served as an indicator of the extent of upgrading that will usually be required to produce a deoxygenated drop‐in biofuel.…”

“…However, renewable diesel (also known as green diesel, hydrotreated / hydrogenated vegetable oil (HVO), hydrotreated / hydroprocessed ester and fatty acid (HEFA), hydrotreated biodiesel, or hydrogenation‐derived renewable diesel (HDRD)) can be considered to be a drop‐in biofuel and is likely to be used increasingly by sectors such as marine and rail and as one route to biojet fuel production. Although this fuel has been used primarily as a diesel substitute, significant volumes of drop‐in biofuels, potentially as high as 426 million tonnes, will be required by a sector such as aviation where there is no other low carbon alternative such as electrification to meet climate goals…”

“…However, it is recognized that the supply of oleochemical feedstocks is constrained relative to the demands of the world's long‐distance transport sectors . Thus it is probable, building on the pioneering supply chains established by the production and upgrading of conventional / oleochemical‐based drop‐in biofuels, that complementary and still‐evolving advanced drop‐in biofuel technologies, based on lignocellulosic feedstocks, will be required to meet market demands for drop‐in biofuels.…”

“…Thus it is probable, building on the pioneering supply chains established by the production and upgrading of conventional / oleochemical‐based drop‐in biofuels, that complementary and still‐evolving advanced drop‐in biofuel technologies, based on lignocellulosic feedstocks, will be required to meet market demands for drop‐in biofuels. As summarized in earlier reports, it is likely that initial upgrading based on thermochemical‐based technologies will use pyrolysis / hydrothermal liquefaction (HTL) platforms as gasification / Fischer–Tropsch‐based technologies are challenged with issues such as economies of scale, gas clean up, etc. As will be described in more detail, the co‐location of these facilities with oil refineries should be an attractive option as processes such as catalytic cracking and hydrotreating / hydrocracking will be used to upgrade the biocrudes to fractions such as biojet fuel, renewable diesel, and biogasoline.…”