Friday 6 December 2019

Bio-coal as a carbon sink and alternative raw material source

Many are looking for new green coal or bio-coal or biomass briquette. The market is predicted to grow exponentially over the next ten years. Since bio-coal is produced from biomass, it does not give rise to fossil carbon dioxide. The industry, therefore, sees this as a possible solution where fossil coal is to be phased out.

As an example, today, a number of companies in India have switched from furnace oil, fire-wood, and coal to biomass briquettes to save costs on boiler fuels. Many companies are using biomass briquettes as fuel to earn Carbon Credits, which is an indirect advantage.

The basic principle for the production of bio-coal is based on old-time coal mills, where charcoal was produced. Biomass is heated in an oxygen-poor environment to at most 700 degrees, called pyrolysis. But today's manufacturing is much more efficient. Unlike charcoal, which is only made from wood, several types of bio-based materials can be used as raw material for bio-coal. For example, leaves, food waste, or animal waste. Today's production processes of bio-coal take place in equipment with advanced process control and the opportunity to capture and utilize gas and oil formed in the process. These can then be used to produce various chemicals and biofuels, according to Maria Lundgren at The Metal Research Institute Swerim in Sweden. The interest in bio-coal has recently exploded. To date, ten Swedish plants have received state subsidies to start bio-coal production.


Bio-coal as a carbon sink

Highest hope is linked to the possibility of bio-coal forming a carbon sink. This means that some of the carbon that the plants have absorbed from the air's carbon dioxide remains in the bio-coal after the pyrolysis. If the bio-coal is then buried, the carbon can be bound in the soil for hundreds of years.

But bio-coal has more benefits. With its porous structure, it can retain nutrients and water, favoring cultivated soils. In Stockholm, bio-coal has been buried in the city's tree plantations.

Bio-carbon for metal steel and metal production

The Swedish metal industry is also interested in bio-coal. Metal powder manufacturer Höganäs, for example, hopes to be able to use bio-coal to reduce iron oxide but also as an additive when scrap is melted in an electric arc furnace.

The steel giant SSAB is investing in hydrogen to become the new reducing agent for the iron oxide, but also wants to use bio-coal in the melt in arc furnaces. Also, the company hopes that bio-coal will serve as an alloy in the future fossil-free steel.

Pilot tests will be conducted at SSAB's blast furnace in Oxelösund in spring 2020 to evaluate how it works in practical terms to inject the bio-coal with the equipment that is there. However, bio-coal has some disadvantages. So far, research is limited, but dust from grinding can be harmful. When used as soil enhancement, its absorptive ability can, in some cases, also cause the crops to decline because too little nutrients and water remain in the crops.

Issues and future of bio-coal

The most significant disadvantage of bio-coal is that it is a limited resource. It can't be enough for everything, but there is justification for some of the hopes, according to Cecilia Sundberg at The Royal Institute of Technology in Stockholm, Sweden.

- What is unique about using bio-coal as a carbon sink is that the carbon storage becomes stable in a material that can also be useful. There is a difference to bio-CCS, which is just about pumping down carbon dioxide to get rid of it. There are not many other ways to take carbon dioxide out of the atmosphere in the long term and at the same time, create benefits, says Cecilia Sundberg.

Critisism

Biomass is composed of organic materials, therefore, large amounts of land are required to produce the fuel. Critics argue that the use of this land should be utilized for food distribution rather than crop degradation. Also, climate changes may cause a harsh season, where the material extracted will need to be swapped for food rather than energy. The assumption is that the production of biomass decreases the food supply, causing an increase in world hunger by extracting the organic materials such as corn and soybeans for fuel rather than food.

Sources:
Green Biocoal: LINK
Det moderna kolet kan bli en klimaträddare, Ny Teknik: LINK
Wikipedia: LINK

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