Today, bioethanol and biodiesel are produced from agricultural raw materials also used in the production of food. Consequently, beyond a certain level, their development will begin to compete with food production. So, to achieve the incorporation rate target set by the European Union - 10% renewable fuels in 2020 - the current biofuel offer will need to be supplemented.
The idea is to transform the whole plant, and, in particular, lignocellulose, the main component of plant walls which is available in large quantities in various forms: straw, hay, wood, etc.
The thermochemical conversion of lignocellulosic biomass into gas oil and kerosene fuels involves hightemperature processes. There are several different conversion
Direct processes using flash pyrolysis or hydroliquefaction
Flash pyrolysis is a purely thermal treatment used to obtain a bio-oil, volatile compounds (gas) and tar. Hydroliquefaction consists in transforming biomass with water in conditions close to its critical point (374°C and 221 bar) to obtain a biocrude.
In both cases, the properties of the liquid fraction must be enhanced by treatment under hydrogen pressure.
Indirect Biomass to Liquid (BtL) process
It involves a sequence of individual steps: gasification of the biomass, purification of the syngas produced, Fischer- Tropsch synthesis and hydro-isomerization to produce hydrocarbons.
Technologies exist for all these steps but they are variable in terms of maturity and are generally only used to treat fossil feeds. So they first need to be adapted to biomass and then the various technological obstacles that still exist need to be overcome before they can be used on an industrial scale. In order to be economically viable, this BtL process requires large-scale units, in which securing supplies is one of the major challenges. From this point of view, flexibility of the sequence of processes in terms of the feeds to be treated would be a major advantage.
IFPEN is specifically examining the possibility of treating both plant-derived and fossil feeds in the same BtL-type facility; a route known as coprocessing B-XtL process. This B-XtL process is the focus of the collaborative BiotfueL project, bringing together industry and research centers among which IFPEN, which aims to develop process for the thermochemical conversion of lignocellulosic biomass and fossil feeds with a view to producing diesel and kerosene fuels.
The process will incorporate the entire biomass transformation sequence: drying and milling, torrefaction, gasification, gas purification and Fischer- Tropsch synthesis.
Lignocellulose, the main component of the non-edible parts of plants, consists of a complex assembly of two sugar polymers — cellulose and hemicellulose — and one polymer composed predominantly of aromatic moieties: lignin. The primary difficulty when it comes to transforming this raw material resides in making the sugars fermentable to ethanol without excessive degradation.
IFPEN's research is seeking to resolve this problem and develop new processes for each of the steps in the lignocellulosic ethanol production process:
The economic viability of these processes depends on optimization of the operating conditions of all of these steps. Recycling of byproducts is also taken into account with, for example, the use of nonfermentable sugars as a carbon source for enzyme production and combustion of lignin to produce energy. IFPEN's research in this field is being carried out primarily within the Futurol project.
Some of the properties of butanol - higher heating value, lower vapor pressure and lower miscibility in water - mean that it has greater potential than ethanol for incorporation in gasoline. In the last few years, there has been a resurgence of interest in butanol produced biologically since it can be obtained from biomass, including lignocellulosic biomass. The process follows the same steps as those used for the production of cellulosic ethanol. However, the fermentation yield and productivity are lower and the distillation costs much higher.
In addition, some sugars contained in the hemicelluloses may be converted into butanol. It is this last aspect that IFPEN is examining in the context of the European project Biosynergy which seeks to make the best possible use of the process byproducts, thus fitting squarely with a biorefinery concept.
Some micro-algae are capable of synthesizing fats or hydrocarbons from CO2 with a potentially higher productivity than that of land-based oil crops. These are chemical factories that use solar energy. However to make effective use of them and improve their potential, in addition to biological selection and crop studies, it is also necessary to optimize the oil and hydrocarbon separation and conversion steps.
IFPEN is currently involved in lifecycle analysis and environmental impact studies on this route.