CharcoTec has developed a sustainable process to make charcoal from vegetable residual flows. Originally intended for Asia and Africa, the company is now looking for high-quality applications in Europe with a pilot plant.
Charcoal was in vogue as a fuel in Europe until the 1930s. For production, coal burners heat wood in so-called charcoal stoves. Pyrolysis, a chemical reaction, produced charcoal in about a month.
In some African and Asian countries, charcoal production still takes place in a similar manner in covered pits. 'We saw in such countries that when heating the wood, stinking, black smoke is produced,' explains chemist Joep van Doorn. 'That is bad for health and the environment. Moreover, the use of wood as fuel in developing countries leads to deforestation and desertification.'
Together with expert in the field of alternative energy Jacques Poldervaart, Van Doorn had previously ended up in the Philippines through the Broadcast Managers Program. Experts from the Netherlands work as volunteers with SMEs in emerging markets with the aim of helping the local economy, environment and society.
“Our pyrolysis process can produce valuable raw materials from grass clippings,” Joep van Doorn, Charcotec chemist
The pair have developed an alternative process for the production of coal from locally available residual biomass. The pyrolysis oven from their company CharcoTec is affordable, has a high yield and can largely be produced locally. But the most important thing is that the oven has no harmful emissions and that the gases released can serve as an energy source for the pyrolysis process, which prevents deforestation.
"We tried to sell our technology in developing countries, but unfortunately potential customers were unable to finance it," says Poldervaart. That is why he and Van Doorn chose to start in Europe. The aim is to convert agricultural residual flows, which now often serve as compost, into coal, including in the form of briquettes to replace classic charcoal briquettes.
Pilot plant
The two started a pilot plant in Bosnia in 2014. When the process turned out to work well, they built a demo plant in Groningen in 2015. This is now located in Purmer. Poldervaart and Van Doorn use the demo plant to investigate how high-quality coal can be made from different types of biomass.
The pyrolysis installation in Purmer consists of a burner and two insulated sea containers. In one of them, the drying of biomass takes place at a relatively low temperature – less than 80 degrees Celsius – which is achieved with residual heat from the second container.
The second container contains an oven with a reactor in the form of a barrel to carbonize the dried biomass, in the case of grass in the form of briquettes. This starts at temperatures from 200 to 250 degrees. This releases some carcinogenic hydrocarbon molecules and tar, which cause the black, smelly smoke in the classic process.
The CharcoTec process directs this smoke back to the oven, which burns the harmful substances into harmless gases. This means no polluting emissions are created and the energy released during combustion can keep the carbonization process at the desired temperature. This means that only drying and the start of pyrolysis require heat from an external source.
Once charring has begun, this external source is no longer needed. By allowing drying and carbonization to take place alternately in the two reactors, the process can continue and virtually no external heat is required.
Grass clippings as biomass
As biomass, CharcoTec in Purmer uses residual biomass from different sources and with different sizes and residual flows from agriculture such as straw, reed, hay and clippings. "We have little wood in the Netherlands," says Poldervaart. 'But every year around 1 million tonnes of grass clippings come from railway edges, river and canal banks and sports fields.'
Van Doorn adds: 'Almost all of this is now composted, while with our process we can turn it into a valuable raw material and nitrogen emissions are up to eight times lower. Unfortunately, this cannot yet be expressed in market value. Moreover, the removal of clippings is expensive, 20 to 30 euros per tonne and it also consists of 60 percent water.' With the emerging market for CO2 rights, the duo expects to keep up with the times.
The researchers continue to look at new applications for charcoal from residual biomass. They are considering, among other things, use as a soil improver, raw material for asphalt or insulation material and an ingredient for animal feed.
They have also not forgotten the origins of their design: in the Philippines, Van Doorn and Poldervaart see possibilities for pyrolyzing rice hulls, which are now usually burned after the rice harvest. This also applies to the shells of cashew nuts that a Dutch company produces in Gambia and Senegal. They see this as a promising opportunity, because oil can also be extracted from those nutshells.
"In any case, we want to reduce deforestation and damage to the environment," says Van Doorn. 'When you know that 85 percent of the world's population cooks with wood or charcoal, there is still a lot to be gained,' Poldervaart adds.
Biocharcoal can potentially replace peat in potting soil
The use of peat as a raw material for potting soil has been controversial in recent years due to the CO2 emissions released during extraction. CharcoTec is collaborating in an Interreg project with Releaf, a research and development company from East Flanders specializing in the valorization of green residual streams. The goal is the development of biochar as an alternative to peat in substrates, particularly for greenhouse horticulture. This application places strict demands on the composition of the charcoal, such as the content of minerals and impurities. In the project, CharcoTec and Releaf are investigating the possibilities of meeting these requirements through the pre- and post-processing of biomass and biochar. The market for peat in Belgium and the Netherlands amounts to approximately 1,4 million tonnes per year. If biochar replaces 10 percent of this, it means an annual reduction of about 125.000 tonnes of CO2 emissions.
Source: Nieuweoogst.nl, text: Hanneke de Jonge
