The newly-released EU biomass fuel action plan (earlier post) highlights the emergence of a commercial and policy-making focus on “second-generation” biofuels—biofuels created by thermochemical conversion such as gasification and Fischer-Tropsch processing, for example.
Although a variety of bio-based fuels are possible products of this route (hydrogen, methanol, ethanol, dimethyl ether (DME) and Fischer-Tropsch fuels (Biomass-to-Liquids, or BTL)), it is likely BTL diesel (which is chemically different than the methyl-ester biodiesel produced, for example, from rapeseed or soybeans) that will see the most attention over the next years, especially in Europe.
(Market development of thermochemical conversion of biomass or waste to fuels is not limited to Europe, however. Future Fuels Inc. in the US recently announced plans and funding to build a 52-million-gallon per year biomass/waste-to-ethanol facility in New Jersey.)
From the policy-maker’s point of view, second-generation biofuels offer a number of advantages:
They allow the use of a much wider range of raw material, especially waste. This can significantly lower the cost of the feedstock.
The resulting fuels are high-quality and clean-burning, with potentially a much lower well-to-wheels CO2 profile than other liquid fuel options.
The cultivation process (if any) could be less environmentally intensive than for ordinary agricultural crops. Lower intensity of cultivation will result in even lower greenhouse gas emissions from cultivation.
They can be co-produced with electricity.
Gasification and the subsequent catalytic Fischer-Tropsch processing are key technologies for producing second generation automotive biofuels. That combination of technologies, with its range of different systems and choices, however, makes the development of economically and environmentally viable systems much more complex than, say, building an ethanol plant.
There are numerous issues to work out. As summarized at the SYNBIOS conference—an event focused on biofuel production by the thermal gasification of biomass—these include:
Deciding on the appropriate gasification route and gasifier technology. These fall into two primary categories.
The first is a one-step high-temperature path (used by Shell, Uhde, Future Energy, Chemrec and others) to push the feedstock straight up to its 1,300ºC temperature. This is similar in approach to coal-based gasification systems.
The second is a two-step process (with a medium intermediate temperature (used by Choren, Värnamo/Chrisgas and others). This approach enables more optimization, and allows for intermediate gas cleaning, but also has its downsides (soot/coking).
Issues specific to the use of biomass in a gasifier (such as solids feeding, pre-treatment for entrained flow gasifiers and so on).
Optimizing synthesis gas quality.
The CO2 emission profile from these processes depends on the process technology, whether the energy source for conversion is biomass only or whether an external energy source is used, and whether the biomass is a waste product (e.g. straw) or an energy crop. This also affects the cost. Here too, significant CO2 gains and energy balance improvements are hoped for.
In Europe, Choren is developing a large-scale pilot plant (15,000 tonnes/year) in Freiberg, Germany. In addition, Choren and Shell are in the process of developing a full-size prototype commercial plant with a capacity of 200,000 tonnes/year which optimistically, depending on the experience with the pilot plant, could be operational in 2009/10.
Hybrids between first- and second-generation biofuels are also in preparation. Neste Oil in Finland is expanding its Porvoo refinery to use vegetable oil and animal fat as a raw material in a conventional hydrogenation process (using hydrogen produced at the refinery).
The resulting NExBTL synthetic has the same fuel qualities as BTL or GTL with lower investment, but higher raw material costs (closer to conventional biodiesel). The NExBTL 170,000 tonnes/year plant at Porvoo is due to come on-stream in summer 2007.
Neste has also signed a Memorandum of Understanding (MoU) with oil major Total to evaluate possibilities of jointly building a large-scale NExBTL plant adjacent to one of Total’s oil refineries, with the aim of beginning production in 2008.