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Coal and biomass cofiring: fundamentals and future trends 137

5.9 Concluding remarks

Biomass cofiring in coal plants can play an important role in increasing the share of
biomass and renewable sources in the global energy mix and reducing emissions of
GHGs and, therefore, it is an attractive option of energy generation from both econom-
ical and environmental points of view. The investment required to adapt or retrofitan
existing conventional coal-fired power plant for biomass cofiring is lower than the cost
of building a new dedicated biomass power plant. Generally, biomass cofiring levels
are still within 5%e10% (as energy content) on a continuous operational basis, which
appears to be no great issues. In this case, direct cofiring of coal and biomass is the
most common approach owing to its low investment costs.
Biomass handling still requires solutions in relation to milling, pretreatment, and
transport. The higher content of volatiles as well as lower carbon content of the
biomass indicate that it provides a lower heating value compared with other traditional
fossil fuels. Combustion behavior significantly depends on chemical and physical
properties, and combustion of biomass therefore provides severe challenges due to
its inherent characteristics that need to be considered properly to have a solution to
implement future improvements. Thus, a better understanding of the characteristics
of biomass for the design of combustion facilities is highly important. In addition,
biomass fuels have a wide range of different physical and chemical properties, which
will determine the type of combustion facilities. Particle deposition, unburned carbon
in ash, and all other related issues, as well as slagging, require further research and
development. There are still huge gaps in the knowledge about the thermal, chemical,
and physical properties of different complex elements which influence the combustion
performance in cofiring conditions. CFD modeling is being progressively used, and it
is a very promising option to determine the flow characteristics, temperature mapping,
and emissions level for different combustion cases.

Acknowledgments

Authors are grateful to the Gobierno del Principado de Asturias (PCTI-GRUPIN14-079) and to
the CSIC (PIE-201780E057) for funding.

References

Agbor, E., Zhang, X., Kumar, A., 2014. A review of biomass co-firing in North America.
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Alvarez, L., Yin, C., Riaza, J., Pevida, C., Pis, J.J., Rubiera, F., 2014. Biomass co-firing under
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