The bioliq process can be used to produce a sustainable second-generation biofuel from straw in three steps. In future, it might also be possible to produce chemicals in a biorefinery from the biomass-based synthesis gas, although this still remains a far-off vision. The method is attracting a huge amount of attention due to the fact that first-generation biofuel (biodiesel and bioethanol) is considered to be less sustainable and is constantly losing market share.

The bioliq approach is not really new. What is new is the way the process is implemented. It would be a pity to use biomass, the only available carbon-containing regenerative energy source, purely for the production of heat and electricity. Dinjus is convinced that biomass needs to be economically processed into high-quality energy carriers (i.e. designer fuels) and basic chemical  materials via energy-rich intermediary products. Moreover, the bioliq process is not in competition with food as it uses only waste from agriculture and forestry, i.e. straw and waste wood. Quoting the German Science Minister, Dinjus highlighted that bioliq would be the "best measure for maintaining freedom" for China, where around 700 million tons of straw (which would make around 120 mio. t fuel) are burnt every year on the fields. In addition, the burning of such huge quantities of straw also poses a considerable threat to the environment. Countries in South Asia, South Africa and South America have also expressed huge interest in the bioliq process.

Bioliq is a three-stage process consisting of flash pyrolysis, entrained-flow gasification and the production of synthetic fuel (synfuel). The attractiveness of bioliq is based on the first stage, i.e. the conversion of biomass into a transportable liquid intermediate product using flash pyrolysis (increase of energy density). This solves the problem of having to transport huge volumes of low-energy biomass to the bioreactors. This decentralised solution was developed very early on in the discovery process on the basis that transportation costs have to be kept at a minimum in the search for economic, large-scale production opportunities. A centralised solution would have involved around 20 million tons of straw.

In cooperation with Frankfurt-based Lurgi AG, the flash pyrolysis pilot plant has since been erected on the premises of the Karlsruhe Research Centre with funds from the Ministry of Agriculture. The plant became operational in summer 2007 and has since been optimised. The plant has a capacity of 500 kg biomass per hour. This type of pyrolysis is suitable for liquidising almost any type of biomass. Dinjus and his team have tested "almost everything that grows around the world" (throughput: 20 kg/h), including bamboo, soy, palm leaves and cotton residues.

Little research has been carried out with the intermediary product, the pyrolysis oil. This mixture has the potential to be turned into other materials that can then be used separately. Dinjus envisages using the oil that is used for the production of fuel and coke for other purposes. The bioliq inventor believes there are many more developments to be made in this area.

The crushed biomass is heated to 500°C in a double drive disc reactor with warm sand (steel spheres would be even better due to the lack of abrasion). Under hermetic conditions, this biomass is converted into gases and coke within seconds. The majority of the gas condenses into fluids upon cooling and the coke formed is mixed with the fluid (oil/coke slurry). This results in an energy-rich, technically easy-to-manage mixture that can be transported by boat, train and lorry. Moreover, it can be transferred to the next processing step without requiring too much energy.

The decentralised pyrolysis process has already been simulated. It is known, for example, that three to four flash pyrolysis plants would be necessary to cope with the biomass accumulating in Baden-Württemberg. Viticulture companies are very interested in the conversion of biomass because they are unable to leave their vine residues in the vineyards. Dinjus expects that around 200 to 250,000 t of vine residues accumulate in a 25 km radius around the city of Obrigheim. He also expects that about 20 decentralised plants would be required to enable the large-scale production of fuel.

If it were possible to find a temporary solution until decentralised facilities can be established, the mixture could easily be combusted in cement factories or biomass heating power stations. Flash pyrolysis does not generate any residues, has a closed heating cycle and has to overcome a temperature difference of only 50 degrees during ongoing processes. Dinjus has had numerous conversations with the Karlsruhe-based mineral oil refinery in order to identify the synergy effects of using pyrolysis oil.

This energy-rich mixture is fed into a high-pressure entrained-flow gasifier, which will also be put in place by Lurgi AG on the premises of the Karlsruhe Research Centre in 2011. The gasifier is based on a technique developed by the GDR-Fuel Institute for bad quality brown coal. High temperature and high pressure ensure a complete and rapid conversion into a tar-free gas. During the process, the ashes melt and form a slag layer on the inner wall of the gasifier. This coating prevents the gasifier from corroding; excessive slag drops off and is discharged at the bottom. This means that all pyrolysis products, with the exception of the gases that cannot be condensed and are used for heating the processes, can be directly processed in the gasifier. Since the normal purification of gas is carried out at low temperatures, researchers at the KIT Institute of Thermal Waste Treatment have developed a new method for cleaning the gas at high temperatures. Pressure and temperature are tailored to the requirements of the downstream synthesis process.

Originally, it was planned to implement the entire synthesis process with three industrial partners. However, in the end the KIT had to implement the process alone and decided to use a one-tier DME (dimethyl ether) synthesis (which does away with the need to isolate methanol) rather than the established Fischer-Tropsch method for which the KIT would not have received funding. Dinjus is now carrying out the synthesis with a medium-sized company that hopes to be able to set up a new business field.

The entire pilot line was expected to be in place by 2010. However, Dinjus estimates that it will take two to three more years before the process is ready for use in refineries. The reasons for this read like a didactic play about the confusion of who is responsible for what in energy policy and an industrial sector that is afraid of taking risks.

It is planned to erect the 5MW entrained-flow gasifier in 2011. Dinjus is convinced that it will be both possible and easy to develop the synthesis into a large-scale process. He also believes that once the pilot line is up and running effectively, the bioliq technology will "soon be used" by industrial partners and other interested parties.

"The problems experienced during the development of the bioliq process finally made the Karlsruhe Research Centre decide to construct the entire pilot line in order to show that the method functions well in converting biomass into fuel and chemicals," said Dinjus. In terms of quantity, the majority of the biomass is used for the production of fuel and hence energy. However, this does not mean that smaller amounts of chemicals cannot be produced in smaller plants. A German chemical company is evaluating the possibility of producing the pyrolysis products abroad and processing them into chemical products at its German headquarters.

Dinjus explains that the processing industry hopes to use the bioliq process to tackle the waste problem. In Malaysia, huge quantities of biomass on palm oil plantations are ready to be exploited; palm oil leaves are left on the plantations for up to ten years, without being used for anything. The same is true for empty palm oil capsules. The chemistry giant Dow Chemical, which uses biomass originating from a Peruvian SRC plantation to produce energy, plans to use flash pyrolysis to convert the biomass and process it further in Germany. The sugar industry is also looking for alternatives for using cane trash, for which no suitable form of exploitation has yet been found.

The KIT is also seriously considering establishing a new institute to deal with growing research and development activities. Originally Eckhard Dinjus planned to retire, but has now decided to stay in his job for another two years in order to complete the pilot plant. The KIT announces on its homepage that it plans to take the process to marketability by 2015.

According to a paper published by K. Bullis in Technology Review (TR 10: Solar Fuel. Designing the perfect renewable fuel May/June 2010; https://www.biooekonomie-bw.dewww.technologyreview.com/energy/25077/), the biogenic raw material basis is also undergoing a change. The paper highlights the fundamental progress of an American company in the production of biofuel, in which the company uses genetically modified photosynthetic microorganisms to convert carbon dioxide into ethanol and diesel in photo bioreactors, without the need for water and grown on normal biomass substrates. The paper points out that the yield was hundreds of times greater than that produced by fermenting maize and ten times greater than that of biogenic waste.

Literature/Sources:

International Energy Agency (ed.): Sustainable Production of
SECOND -Generation Biofuels. Potential and perspectives in major economies
and developing countries, Paris 2010.

A. Wille: Biokraftstoffe - eine langfristige Energiequelle, in: Chemie Ingenieur Technik 2007, 79, No. 5., p. 613-616

S. Fürnsinn/H. Hofbauer: Snythetische Kraftstoffe aus Biomasse: Technik, Entwicklungen, Perspektiven, in: Chemie Ingenieur Technik, 2007, 79, No. 5, p. 579-590

H. Schöne/M. Rüsch gen. Klaas: Biogene Kraftstoffe - Potentiale und Grenzen, in: Chemie Ingenieur Technik, 2009, 81, No. 7, p. 901-908