Biorefinery platforms – Biochar / Charcoal
Concept
- Biochar is a solid carbon-rich material produced by thermal decomposition of organic material at relatively low temperatures in the absence or limited supply of oxygen.
- It is the main product obtained in biomass carbonisation (slow pyrolysis) or a co-product in biomass pyrolysis and gasification.
- During these processes, carbon is not released into the air as CO2. Instead, it is stably bound in the biochar and removed from the atmosphere. When the biochar is permanently incorporated into carbon sinks (soil, asphalt…), its production can be considered as a Negative Emission Technology (NET).
- Some voices claim that the word “biochar” should be only used for agricultural applications. According to them, the voice “charcoal” is the appropriate to cover all the vast range of qualities and grades for carbonised biomass.
- Conditions like feedstock type and particle size, reactor type, residence time, heating rate… affect the physical characteristics of biochar.
- The solid carbon-rich material produced by hydrothermal carbonization (HTC) or hydrothermal liquefaction (HTL) is called hydrochar. It typically has higher H/C ratios and lower aromaticity than biochar.
- Biochar presents numerous opportunities for synergies in different areas of biomass processing. The implementation of the biochar concept is potentially attractive to reduce carbon footprint in the context of the thermochemical biorefineries.
Figure 1. Biochar platform
Applications
Biochar applications in agriculture are the most known. These three are some of them:
- Soil amendment. Due to its high specific surface and porosity, biochar has an excellent capacity to store nutrients and water and provide habitat for microorganisms.
- Feed additive. Biochar is used in silage to improve feed efficiency and intake.
- Manure treatment. It reduces unpleasant odours and improves stable hygiene.
Farmers can improve the quality of soil, save money for fertilisers and obtain additional credits from emission certificates.
Moreover, charcoal can be used in a plethora of final applications with more or less complex additional processing. The well-known article “The 55 uses of biochar” (Schmidt HP and Wilson K. the Biochar Journal 2014, Arbaz, Switzerland. ISSN 2297-1114. Version of 12 th May 2014) highlights many of them. Some relevant examples:
- Direct energy production.
- Biomass additive and slurry treatment in biogas production.
- Metal reduction in metallurgy.
- Insulation material for the building sector.
- Filler in composites, textiles and electronics.
- Active carbon filter in wastewater and exhaust gases treatment.
- Food colorant.
- Ingredient in cosmetics and painting formulations.
- Carrier for active pharmaceutical ingredient.
- Shield against electromagnetic radiation.
Figure 2. Biochar uses (taken from the EBI Consortium website)
Interesting resources and references
