Char: the “black gold” of CSS1
July 26, 2022

Authors: Vittoria Benedetti, Lorenzo Menin, Francesco Patuzzi, Marco Baratieri

In CSS1, low-quality wood packaging residues are gasified in order to obtain renewable thermal energy to provide heat to industrial and domestic utilities. However, during gasification, not only gas is produced, but also char, a black powdery material representing up to 10 % of the initial mass of the feedstock.

Nowadays, char is considered a full-fledged by-product and treated as an industrial waste, which means that it is an actual economic loss for the plant owners and an environmental threat whenever disposed of in an improper way. Therefore, it is crucial to find alternative and innovative applications for char to decrease its costs and its environmental impacts and consequently, the profitability of the gasification plants under a circular economy perspective can be increased. Indeed, char shows remarkable properties and many similarities with more traditional activated carbon (AC), such as a high carbon content up to 90%, a high surface reactivity, a large specific surface area of approx. 600 m2/g and a well-developed micro-porosity, that make it suitable for different industrial applications.

More specifically, during the FRONTSH1P project, the char obtained after gasifying the wood packaging residues will be characterised in detail through different techniques and its suitability in agriculture and in the plastics industry will be assessed. As far as the agricultural sector is concerned, char will be tested as an additive in composting, a process during which the organic matter of biodegradable waste is converted into a product rich in nutrients that acts as a slow-release fertilizer. Indeed, char addition in composting could allow accelerating the process, reducing greenhouse gas emissions, reducing ammonia loss, serving as a bulking agent for the compost and reducing odour. Regarding the plastics industry, char will be tested as filler and black pigment due to its intense black colour.

Fillers are the inorganic or organically modified materials added to polymers not only to strengthen the composite either by improving or introducing other functional properties, but also to reduce the production cost and the environmental impacts of a high-cost fossil-based matrix such as plastic. Recently, carbon-based fillers have been exploited in the plastic industry for enhancing the tensile properties, thermal stability, and electrical properties of the composites. However, materials such as carbon black, carbon fibres, carbon nanotubes, graphene, etc., are usually associated with high production-costs, fossil fuel-based feedstocks and the need of chemicals for their synthesis. Due to its similarities with traditional carbon-based material, char represents a renewable and low-cost alternative in the view of minimizing costs and increasing sustainability.

In conclusion, valorising gasification char as foreseen in the FRONTSH1P project could not only alleviate the issues associated to its management and disposal, but also minimize waste, preserve resources, and produce materials with enhanced properties suitable for a plethora of different applications. Moreover, its utilisation will allow an increase of gasification plant revenues and decreasing the costs of the processes in which it is exploited, making char the “black gold” of CSS1.