Substitution of renewable local charcoal for polluting coke

“The technology developed can tailor the properties of renewable charcoal to resemble coke and coal. In that way, more fossil fuel in the process industry can be replaced with renewable charcoal without affecting product quality”, says Professor Henrik Kofoed Nilsen at UiA’s Department of Engineering Sciences in Grimstad.

The professor has been main supervisor to PhD Candidate Gerrit Ralf Surup, who handed in his thesis on the use of renewable charcoal in ferroalloy industries earlier this summer, and who has developed the new technology. The work has been ongoing for three years in cooperation with the industry cluster Eyde and metallurgical companies in Agder, and it has been part of UiA’s PhD-programme with specialisation in renewable energy.

Tailoring the properties of charcoal

“The process industry uses large amounts of coal in their metal manufacturing processes. The main part of this work, therefore, has been to perform experiments to see how the properties of charcoal can be changed to resemble coal and coke and thereby replace it in various metallurgical processes”, Gerrit Ralf Surup says.

The research done in Grimstad dealt with operating parameters like primary heat treatment (500 to 1,300°C), secondary heat treatment (700 to 2,800°C), and bio-oil conditioning. By changing the parameters, the quality and properties of the charcoal changes. The process can be controlled, and the charcoal can thereby be tailored to the desired process. 

GREAT: “The potential for making the Norwegian metal industry more environmentally friendly is great”, professor and main supervisor Henrik Kofoed Nilsen (left). He and Gerrit Ralf Surup show both charcoal and bio-oil extracted from woodchips. In addition to biogas, these are products of the technology developed while conducting doctoral studies in Grimstad.

Followed closely by Eyde companies

The process industry in Agder has followed Gerrit Ralf Surup’s doctoral studies closely. His research formed part of the Eyde Biokarbon project, which was funded by the Research Council of Norway. The project was completed last year. It focused on what companies need to do to go green.

“The research done at UiA is incredibly relevant especially considering the process industry’s growing focus on sustainability. Sustainability means changing extensive well-established processes, and if renewable charcoal can contribute to this in a good way, it is of course very exciting”, leader of Eyde Innovation Centre Lars Petter Maltby says.

Great potential

If the technology is used in Norway, the potential is great. Industry produces more than 22 percent of all CO2 emissions in Norway, and emission from coal and coal used in the process industry constitutes a significant part of that. 

“Companies in Agder like Fiven Norge, Eramet and Elkem are unhappy with having to use coke in their production, and they are constantly looking for renewable substitutes”,  Henrik Kofoed Nilsen says.

“These companies don’t want to manufacture a ‘green’ product using ‘polluted’ raw materials. So, they try to replace some of the coke with renewable charcoal”, he explains.

Elkem AS in Kristiansand, among others, already replaced some of the coke in the production with renewable charcoal. Elkem’s stated goal is that it should be possible to increase this to 40 percent in a few years’ time.

Ambitious goals

A goal such as this is ambitious, however. Should the process industry in Agder and Telemark achieve a 40% substitution, it would equal around 60,000 tons of biocarbon produced from around 600,000 cubic metres wood. Even though an additional 180,000 tons of bio-oil and biogas would be extracted from the production process, it is a lot. Wood production in Agder and Telemark is reduced with around 1,540,000 cubic metres per year according to NIBIO – Norwegian Institute of Bioeconomy Research. 

In addition, price would be a challenge. Petroleum coke is cheap, almost four times as cheap as charcoal.

“Charcoal meets multiple criteria, however. First and foremost, it can contribute to making the Norwegian metal industry greener. And also, you can extract valuable by-products like bio-oil and biogas. And not least, it is a local process here in Norway where there is so much timber. So, it has a positive effect on the forestry industry as well. All in all, this is an exciting product which we now have learned to tame and tailor the use of”, Professor Henrik Kofoed Nielsen says.

Struggle over forest resources

Charcoal, or bio-coal, can deliver great environmental benefits also in other areas. One example is in agriculture. When old plant residues, trees and biomass rots, large quantities of CO2 is released. By producing bio-coal from these, greenhouse gas emissions are reduced. Also, grass and other plants grow better in poor soil when you plough bio-coal into the soil. And on a farm, by-products such as bio-oil and biogas can ideally be used for machinery and equipment rather than petroleum-based diesel and oil.

“In many ways we are at the very start of the research on how we can use our forests to improve the environment, focusing on bio-coal, bio-oil and biogas. Personally, I think there will be a struggle over these resources in the future. Research is underway in the world around us and here at UiA, and we see results even now, like Gerrit Ralf Surup’s doctoral work”, Henrik Kofoed Nielsen says.

Continues the research

The research on how charcoal can make metallurgical industry more environmentally friendly. Through a research fellowship there is now work on the pelletisation of charcoal together with bio-oil which improves the processes happening in the melting furnaces. The work is carried out in cooperation with the Eyde companies in Southern Norway.

Gerrit Ralf Surup also continues his work, but not at UiA. After completing his PhD and ending his work in Grimstad, he now moves on to a postdoctoral position at NTNU in Trondheim.

“It is going to be sad to leave Grimstad and the good research environment on environmentally friendly processes at UiA. But I have enjoyed it here, and interest in my research field has grown significantly during the three years I spent here. I am grateful for that and will carry it with me”, he says.

Producing charcoal 

Charcoal is normally produced by pyrolysis – the heating of biomass without access to air.

The produced charcoal, pyrolysis oil (bio-oil) and pyrolysis gas (biogas) can be burned and converted into electricity or processed into synthetic biofuel.

• Pyrolysis occurs at 300-700 degrees Celsius.
• Biomass without water consists mainly of 50% carbon, 44% oxygen and 6% hydrogen.
• You usually get from 5% to 50% charcoal out of the dry matter.
• The quantity of charcoal goes down as the temperature goes up.
• Carbon can also be produced using hydrothermal carbonisation of wet biomass and waste.