garden substrate carbon capture

The value of carbon

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If in the future we will use more energy from solar and wind and electrify more processes and there will be a huge demand for carbon that is not easy to fill. The question is where should this carbon come from if we renounce the use of fossil fuels? CO2 capture to make carbon is being investigated but this technology is still in its infancy. In the short and medium term, converting biomass to biocarbon seems to be the best option.

Biocarbon not only has value for industry but can also be used for carbon storage in agricultural soils and as a soil conditioner. With this, biocarbon also plays a role as a carbon-negative option in the climate issue, according to Rian Visser, researcher at TNO. ‘That is what we mean by the value of carbon.’

Economy of scale

TNO has been researching conversions of biogenic materials, including wood and agricultural residues, to biocarbon for more than a decade. It is important to have a technology that also has advantages on a large scale, for environmental benefits and for a lower price. ‘You need an economy of scale; a technology that is affordable, robust and scalable. Developing a small installation and then duplicating it ten times does not improve efficiency nor lower costs. Small plants generally only generate their own energy and nothing extra, which means an enormous amount of energy is simply lost. We would put 25% to carbon and 75% to energy, minus some loss in the plant, with the technology we are developing. The bigger the installation the less loss of heat,” Visser says.

Bio-carbon for reducing iron

TNO researchers have proven four different technologies of which one is now scaled up to a pilot. In a project in cooperation with Tata Steel TNO explored the option to use bio-carbon for reducing iron. Other steel manufacturers such as Arcelor Mittal are also working on this, and the latter is also present at EIES 2023.

Bio-carbon as replacement of peet in potting soil

Another application lies in substrate (potting soil) for greenhouses. Potting soil is 90 to 95% peat. Peatlands store vast amounts of atmospheric CO2 which is released if the peat is harvested or the peatlands are disturbed. By growing (and not removing) peat you can keep an enormous amount of carbon stored in the ground. There are opportunities here, according to Visser. ‘A growing peat area takes more CO2 out of the air than a tropical rainforest. We could restore our peatlands as a form of climate adaptation as well as mitigation.’

TNO is concentrating on biocarbon as replacement of peat in horticulture. Gardeners have long been looking for alternatives because they know the use of peat is finite. ‘Adding 30 to 50% porous granules of biocarbon (i.e., biochar) to a potting soil can save a huge amount of peat without the grower having to change anything. After use, these carbon grains can go into the field with some compost where it will serve as a carbon sink. This is a combination of an industrial application combined with carbon storage,” Visser says.

Emerging industry

It seems like a great solution for growers but while the demand is clearly there, there are no parties willing to make the biochar on a large scale. TNO is keen to put this technology on the market and is looking for potential partners who can use the generated heat and who are willing to make biocarbon for industry. Visser: ‘Worldwide, this is an emerging industry. There are already many small companies with installations, also in the Netherlands. However, they lack the potential to supply on a large scale. Moreover, to be energy-neutral, companies must use all the energy they generate. That only works if you work on a large scale otherwise you lose too much energy.’


Besides the application in potting soil, there is also a company in the Netherlands that is working on incorporating biochar into fertilizers. By binding fertilizer to carbon, it does not wash out so easily with rainwater. In this way, fertilizers stay longer in the relevant zone near the roots of the plant. This leads to greater efficiency in the use of fertilizer.

Activated carbon

Activated carbon is another application, used as an adsorbent to capture harmful gases or to purify water. Generally, these carbons are made from peat or coal but you can also replace this with biocarbon.

Lithium-ion batteries

The fourth application under investigation is biocarbon for lithium-ion batteries, for example, for electric cars. These contain an anode made of graphite but natural graphite is a finite resource. Synthetic graphite made from fossil residues is also being used. This requires a lot of energy and chemicals. We are now looking into the possibility of developing an alternative sustainable biocarbon as a substitute for fossil-based or mined graphite.

Visser expects the carbon market to get a growth spurt as steel companies set their sights on using biocarbon. ‘This could put a floor in the market. They need so much carbon that they will dictate the price, which will likely rise.’

On Wednesday, Dec. 7, TNO will hold a session on ‘The value of carbon’ at the European Industry and Energy Summit (EIES) 2023 where Rian Visser (TNO), Leon Boerop (Rabobank), Samantha Tanzer (TU Delft), Nele Ameloot (Growing Media Europe) and Robin Post van der Burg (Torrgas), led by TNO’s Tara van Abkoude and Stephan Janbroers, will dive deeper into the topic.

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