The development of sustainable liquid transport fuels is essential to guarantee a reduction of the carbon footprint and the future security of energy supply in Europe. As with all industrial processes, production of biofuels requires energy input and has an environmental impact. When measuring the overall sustainability of biofuels, a range of factors need to be taken into account, including competition with food production, the release of stored carbon, and the impact on biodiversity, as land is cleared to grow energy crops. Thus, a carbon-neutral process which uses residual biomass as feedstock for carbon-based fuels that are irreplaceable by electrification, such as aviation fuel, is urgently needed. The current proposal addresses this need.
The production of advanced biofuels from waste lignocellulosic biomass, to be used as alternatives to traditional fuels, is a challenge. In this project we will address the need by developing a process to produce jet fuel from the lignin fraction of biomass. Jet-fuel is composed by linear alkanes, cycloalkanes and aromatics compounds. Nowdays, the feedstock of bio-jet fuel are vegetable oils from which only linear alkanes can be obtained, so a blending with traditional fuel is needed to have the complete range of the jet-fuel compounds. Thus, the goal is to obtain a jet fuel made up not only of alkanes, but also of cycloalkanes and aromatics in order to be used as a direct substitute for a conventional jet fuel. Lignin is the best candidate due its aromatic structure and furthermore, it is the main waste product of second generation bio-ethanol production plants.
To achieve this goal, the project will focus on a novel catalytic hydrothermal liquefaction process and on the development of the appropriate catalysts, which will produce a stable bio-crude, which means low O/C ratio to decrease the oil polarity, which will be a perfect precursor for the production of aromatics and cycloalkanes for bio-jet fuel.
Liquid biofuels have a long history in transport, energy and climate policies in Europe, Brazil and North America. Governments have created supporting policies for biofuels driven by an array of objectives relating to the fight against climate change, oil import reduction, and agricultural and rural development.
Over the last two decades, climate concerns have become an increasingly strong motivation for policies promoting biofuels. This has resulted in growing support for biofuels and the production of biodiesel and fuel ethanol. These policies triggered a substantial investment boom, which peaked in 2007 when several sustainability concerns relating to the impacts of biofuels on food security, food and feed prices, and direct and indirect land use became an integral part of the international climate and energy debate.
The food-vs-fuel debate, particularly, mobilised the scientific community, governments and non-governmental organisation (NGOs) and led to studies on the carbon intensity of various types of liquid biofuels. Consequently, regulators in the largest markets, particularly in the US and the EU, reset their biofuels targets, blending mandates and support policies considering fuel distinctions by feedstock and associated carbon intensities. This discussion brought to the fore the need to develop advanced biofuels, or (2nd generation) 2G biofuels, which are made of lignocellulosic feedstock such as corn stover, straw, wood waste, rapidly growing grasses and short rotation trees, municipal waste, and waste oils, fats or algae, all of which have few non-energy uses, and some of which can be grown on less productive and degraded lands or in seawater (algae), thus involving a smaller impact in terms of land-use.
Investments in biofuels started to decline after the peak year of 2007 for 1G biofuels and 2011 for 2G biofuels. The production of biofuels has continued to grow, however, utilising the existing biofuel refinery capacity and its annual increments. The industry as a whole, however, including both conventional and advanced biofuels, demonstrates a limited, or at best moderate, appetite for new investments. Barriers affecting investments in advanced biofuels are numerous and reflect the complex nature of the business environment.
Not only the technology needs improvements, reflected in the operational problems of the first-of-its-kind projects and high costs, but the challenges also include an array of environmental, infrastructure-related, social and political issues.
Despite the advantages of a transition to producing and using 2G biofuels, the emergence of the advanced biofuel industry has been sluggish due to early-stage technology development and numerous barriers such as high production costs, immature supply chains, dependence on government support schemes that are subject to political influences, and consequent uncertainty around market size. This becomes even more evident when the focus switches to drop-in fuels, considered to be a key element of the transport sector decarbonisation. In fact, advancing beyond the ethanol and biodiesel blend wall and supplying for heavy-duty transport, aviation and marine sectors requires fuels that can power engines alone and/or in very high blends.
High-quality drop-in biofuels are currently produced from lipids from vegetable oils, oily wastes, used cooking oils (UCO), tall oil and animal fats via an oleochemical processing route (HVO/HEFA). This has already become a thriving new business, which paves the way for drop-in fuels as part of the transport sector decarbonisation.
However, the feedstocks used may not be available in sufficient quantities to cover all the projected biofuel demand from the transport sector, especially the rising aviation sector.
Therefore, other pathways for drop-in fuel production using lignocellulosic feedstocks, which are cheaper and more readily available, must be at the centre of the scientific research. Several economic and technical challenges concerning improving yield and maintaining stable processing exist with some of these technologies, and this project has been conceived to be a first step to overcome part of these challenges. In fact, to pursue the objective to obtain a drop-in fuel from waste biomass the first step of the waste depolymerization is of crucial importance to decrease the overall cost of the plant.
Hydrothermal liquefaction is not yet a completely mature technology, few demonstrative continuous plants are present but the quality of the oil produced is still low needing a strong up-grading process after the bio-oil production.
The development of a process using heterogeneous hydrogen producers directly inside the HTL reactor will open the possibility to obtain a partially up-graded oil. Furthermore the process let to use as hydrogen producer iron ore valorizing a waste product.