According to the recent book by Dr. D. Thrän, “Smart Bioenergy: technologies and concepts for a more flexible bioenergy provision in future energy systems” (2015), the currently developing energy system (in Germany, but more generally, in Europe) based on renewable energy sources, could be built on the following pillars:
- solar and wind energy (heat and/or electricity);
- balancing/residual power load, e.g. from biomass and waste;
- upgrading/storage of excess energy with heat, gases/accumulators (batteries);
- rely on system control solutions, e.g. grid stabilization and security;
- bio-refineries for the production of refined fuels, for specific applications (i.e. heavy duty vehicles, ships and aviation) as a synergy with electric mobility, and for feedstock conversion to materials;
- (renewable) heat provision (e.g. standalone CHPC units, co-generating heat, power and cold) for households, public buildings and industry.
Among the contribution to such regional, distributed and interconnected energy system, solid biomass could play a significant role: for residual power balancing (e.g. flexible electricity generation from thermal conversion technologies) and heat/cold production in standalone applications.
For the development of such framework, a strategic question which arises is: “Which solid feedstock is suitable for which conversion technology?” If matching feedstock type and conversion technology with a simplified (and didactic) approach, the following scheme could be considered (r.t. reaction time; own elaboration).
As indicated in the proposed scheme, high hydrogen (H), oxygen (O) and nitrogen (N) to carbon contents in the fuel, identify the biological conversion technologies (with respect to thermochemical) as better suited options for the fuel conversion. Yet, the answer to this question is far from being comprehensive and it is rapidly evolving as the technological options develop. However, it seems clear the strategic interest of coupling the specific feedstock with the suitable technology, in order to efficiently valorise solid fuels in the modern, renewable based, energy system.