BtL Technology: The Future of Biofuels?

Attaining and expanding energy resources are a great challenge to the economic sustainability of a rising number of countries. Furthermore, biofuels have become crucial for the energy security and the diversification of energy supply for almost every nation.

Biomass to Liquids (BtL) technology is maybe at the most vital phase of its evolution with escalating investments in biomass gasification and Fischer Tropsch technologies. This is combined with an increase in financing for biorefinery research and development. Today, BtL economics seems to answer the quest for sustainability.

BtL fuels are synthetic fuels derived from biomass by means of a thermo chemical process. Probably the biggest advantage relies upon the ability to be tailored for specific purposes and requirements. The goal is to yield fuel compounds which are identical to those of existing fossil-derived petrols like conventional gasoline and diesel fuels. Consequently, they can be used as “drop in replacement” in available systems of fuel distribution and with customary engines. Fuels made by BtL technology are also called synfuels.

BtL fuels may be prepared by any kind of low-moisture biomass, organic wastes or residues like short rotation trees, persistent grasses, forest thinning, straw, bark from paper-pulp production, fibre-based composites, waste paper, shattered wood, bagasse…

It is projected that each year, a hectare of land can yield more than 4.000 liters of BtL-fuels. Thus, in future, a substitution of 20-25 % of the current liquid transport fuel is feasible, if 4-6 million hectares are cultivated to grow energy crops.

The benefit of the BtL route to liquid transport fuels relies in the ability to make use of almost any kind of biomass, with little pre-treatment other than moisture control. Most commonly, BtL fuels are produced by gasification of the raw material to gain hydrogen and carbon monoxide. These two gases (syngas) are then processed by the Fischer Tropsch process.

Fisher-Tropsch process

The Fischer-Tropsch process is a chemical reaction in which syngas (hydrogen and carbon monoxide) is converted to liquid hydrocarbons of different forms using catalysts. Iron and cobalt-based catalysts are generally used for the following reaction:

(2n+1)H2 + n(CO) -> CnH2n+2 + nH2O

This is a well-established technology and has been used for decades on a large scale for the processing of coal or natural gas.

Currently, the biggest drawback is the high capital cost as this is a multistage process. Practically, by using biomass as a feedstock, the cost will escalate due to the transportation of the biomass to the plant.

The Choren Carbo-V® Process

However, in Europe BtL RD&D is gathering momentum, and in Frieberg Saxony, the world’s first commercial BtL Plant using the Choren Carbo-V® Process is constructed for the annual production of 13.500 tons. The Carbo-V® Process is a three-stage gasification method to produce syngas. Subsequently, the Fischer Tropsch process is used to fabricate an automotive fuel called “Sundiesel®”.

CEA Bure Saudron Pilot Plant

Last December 2009, the construction of a pilot BtL plant in Bure Saudron was announced by CEA (the Atomic and Alternative Energy Commission) in France. The plant will process 75.000 tons of agricultural and forestry waste to generate approximately 23.000 tons of biofuel (diesel, kerosene and naptha) every year. To optimize the ratio with carbon monoxide, the Bure Saudron method will inject hydrogen throughout the synthesis.

NSE Biofuels Demonstration Plant

At Stora Enso’s Varkaus Mill in Finland, a BtL demonstration plant was launched by NSE Biofuels Oy. This project is a joint venture between Neste Oil and Stora Enso. The annual productivity is 656 tons from a 12 MW gasifier. NSE Biofuels with the partnership of Foster Wheeler and VTT intends to extend a commercial production plant at one of Stora Enso’s mills with an expected output capacity of 100.000 tons per year. This facility will presumably be launched in 2016.

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