CO2 capture

The CO2 extraction from the flue gas scrubbing of our energy from waste plant is highly innovative. We use this for the production of sodium bicarbonate, a substance we use to clean the flue gases in the same power plant. A small cycle of significant environmental importance!

In recent years, in collaboration with a spin-off company of the University of Twente among others, we developed a system for capturing carbon dioxide (CO2) from the dry flue gas scrubber of one of the incineration lines, and using it as raw material for producing sodium bicarbonate (‘baking powder’, NaHCO3). We use that substance to scrub flue gases in the energy from waste plant.

The plant is fully integrated. The plant produces approximately 8,000 tonnes of sodium bicarbonate annually. This amounts to a reduction of CO2 emissions of 2,000 to 3,000 tonnes per year. This is clearly beneficial to the environment and is also interesting on a commercial level. On the basis of the project’s sustainable and innovative nature, it received subsidies to the amount of almost €1.3 million from the Province, the Dutch government and the European Union. For more information about this project, visit the project website co2sbc.

CO2 emissions are a major cause of global warming. This has drastic effects on our living environment. That is why it is important to find ways of capturing the CO2 and putting it to good use.

There are many new and useful applications for carbon dioxide (CO2). We hope that recovery on a larger scale will help us take the next step in reuse. In doing so, we will prevent this inorganic compound from entering the atmosphere and we will make it available where it is needed.

All over the world, successful recovery of CO2 is still in its infancy. We share the knowledge we have acquired about this process at conferences, among other things. Interest in this knowledge of Twence comes from all corners of Europe.

Read more about the CO2 capture project here.

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Green Deal Bottom Ashes

Bottom ash is the most important solid raw material released by the energy from waste plant at Twence. This involves around 150,000 tonnes per year. For every 100 kg waste used for energy generation, around 25 kg bottom ash remains. It consists of sandy and stony material, glass, metals and ash residue from incinerated products. In 2013 and 2014, Twence built an advanced bottom ash reprocessing plant which enables us to recover even more valuable substances from the bottom ash.

Bottom ash is highly suitable as a building material, for example as foundation material for roads and dike cores. It is not a hazardous waste; the most harmful substances are already removed from the waste during the thermal processing with the flue gases and captured in the flue gas scrubbing facility. Nevertheless, bottom ash still has to be used as a construction material under protective conditions, because contamination from the substrate can occur due to metals and salts still present in the bottom ash flushing out. Because this is not desirable for the long term, the government made agreements with the Dutch energy from waste plants (Green Deal Bottom Ash, 2012) to make the bottom ash freely applicable. In order to fulfil the stricter quality requirements, the bottom ash must be cleaned, which means that it must be stripped of salts and metals which can flush out. The material can then be used in unbound form as an alternative for sand or gravel or have a quality which allows it to be used in ‘structured construction materials’, for example in the concrete and cement industry.

A project group at Twence is working on this course. Most energy from waste plants have chosen to put the bottom ash through an intensive cleaning process to achieve the quality improvement for a freely applicable construction material. Twence examined the entire chain, however, and wants to make improvements to the start of the process, before starting on quality improvement at the end of the production process. Studies have shown that the bottom ash becomes cleaner if it is drier when presented to the bottom ash reprocessing plant, because the metals then separate better.

This resulted at Twence in our own development of a ‘semi-dry’ system, which is being tested on one of the lines of the energy from waste plant. Partly due to this modification, Twence can recover almost 85% of the metal granules larger than 2 mm, which puts us among the world’s best in this field. The oxidation of the metals in the plant is also restricted, so that more metal can be recovered.

The conversion of the other two lines has been planned for 2017. Other energy from waste plants have expressed great interest in our unique concept.

Read more about the Green Deal Bottom Ashes in the factsheet.

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Retaining nutrients

Twence participates actively in the national Nutrient Platform. This platform links parties which strive to preserve valuable mineral raw materials, from manure among other sources.

We have joined the Waste2Aromatics development project, managed by TNO, to contribute to the development of biochemicals.