Turning low grade biomass into syngas

Torrefaction

Working on biomass for over 15 years produced a valuable lesson: biomass is far too variable in quality to be used as feedstock in an industrial process. It can be too wet, too dry or too fibrous and cluttering up the equipment. Torrgas learned these lessons the hard way, but also found a solution.

That’s why Torrgas developed a pre-treatment called torrefaction. This mild version of pyrolysis removes all moisture from the biomass and then partially cracks the hydrocarbons, removing the low-energy hemicellulose fraction and leaving the cellulose and lignin. 

Two-step process

This so called torrefied biomass is then turned into syngas, using a patented two-step process in which the char is removed. Char is a problem in the production of syngas, as it causes sintering inside the plant. By removing it, Torrgas can also sell this engineered carbon in a wide variety of high-end applications for example for usage in the purification of water or flue gas. 

The syngas can be used in different ways: as a feedstock for the chemical industry, e.g. in the synthesis of bio-methanol or acetic acid, as a source of green hydrogen or the carbon and hydrogen can be recombined into methane. All three solutions could be useful in Delfzijl.

Demonstration plant

Torrgas is currently running a demonstration plant at DNV-GL in Groningen, which has an input capacity of 1 Megawatt hour. In the near future, this plant will be moved to Delfzijl, to be tested in a production setting which includes users of their end products. In due time, a 25 Megawatt hour facility will be built, producing synthetic natural gas (methane). 

It is the conviction of Torrgas that high quality biomass should not be used to produce syngas. With the application of torrefaction, they can produce a stable and high quality feedstock for the gasification process from low-quality materials like twigs and leaves.  A process, capable of processing grass or straw, has progressed.

Torrefaction could be done locally, even at farm level. The light and energy-dense ‘coals’ which are produced can then be transported to a central gasification plant. Even rice stalks, which are often burned in the field, could be utilized this way. Calculations show that nature captures enough carbon and hydrogen to substitute enormous quantities of fossil fuels, without competing with food production or endangering nature conservation.