Biochar (also called biological charcoal) is the char product that is generated by the heating of organic biomass in a very low or non-oxygen environment via a process called “pyrolysis”. The aim of creating and utilizing biochar is for mitigating GHG emissions that would have produced if the biomass had faded away naturally. Various pyrolysis process configurations have been designed, ranging from basic systems to highly advanced technologies that are allocated to a particular feedstock and for generating a special set of products, and produce gaseous streams that are very clean for electricity production in gas engines. Some examples of equipment configurations are shown in the following figures. Figure 1 show a basic burner and figure 2 shows a mobile biochar unit (source: http://energyfarmers.com.au)
Two important energy recovery options from biochar production are mentioned here. First, the steam, oil and gas by-products of biochar production for carbon sequestration. They can be recovered for their value for energy production, giving rise to a secondary revenue stream and GHG mitigation benefit. Bio-oils can be burned to generate energy for heating, or if enough volumes are available, they can be refined to transportation fuels. Similar to bio-oils, syngas can also be used for pyrolyser heating or providing energy for household and industrial applications. Moreover, syngas and bio-oils can provide steam to control turbines in centralized power systems. However, the possibility to use bio-oil relies on the level of operation, and subsequently the amount of oils that are generated.
The second energy-recovery option is direct burning of the char product as a carbon-neutral or low-carbon energy source. The production and utilization of char is more energy efficient than the burning wood directly as a heating or cooking fuel. In the context of GHG mitigation, there is also a growing interest worldwide in replacing coal with char for energy usages in industry and for application in industrial processes, like the production of steel and iron. It must be realized that industrial production procedures potentially need large volumes at centralized areas that may not be compatible with char derived from feedstock that are broadly dispersed.
All in all, the energy production and application of biochar can have both negative and positive environmental and socioeconomic consequences. Socioeconomic impacts relevant to the production and application of biochar must be evaluated and understood for sustainable use of biochar to improve food security and energy access. In this regard, four main socioeconomic topics include: employment; increased productivity of agricultural land and food security; fuel security; and health and safety. Despite the claims of widespread benefits of biochar for food security and energy access, there is currently little understanding of its real impacts. Therefore, more case studies are needed to demonstrate the socioeconomic impacts that can potentially be derived through production and application of biochar as a mitigation measure. To do so, a framework and tool(s) for evaluating the site-specific sustainability impacts of biochar related technologies is required to fit with the specific biophysical and socio-economic environment of different regions in order to enhance the economy as well as the wellbeing of the society involved.