77
are still many aspects that should be closely investigated for further improvements
of fuel gas production [14, 157]. In Fig. 9, important research directions which
require further prospects and some innovative developing optimization strategies
for biomethane/biohydrogen production processes are summarized.
The biogas production technologies have reached a technological maturity level
which makes them feasible for large-scale application; the future goals of research
in the field should be more focused on controlling biochemical process stability,
increasing feedstock availability and lowering production costs, as well as on biogas
upgrading to make it suitable as transport fuel [158].
Compared to anaerobic digestion which has been more widely investigated, dark
fermentation is still a rather immature practice, not sufficiently developed to be
commercially available. The main challenge in dark fermentation is that the conversion efficiency of the process as a whole is still low in comparison to theoretical
data. Since about 67–85% of the substrate leaves the reactor before being decomposed, many efforts still need to be made to increase the conversion efficiency of the
substrate and thus the production of biohydrogen [34]. Scaling-up the biohydrogen
production systems and developing continuous pilot-scale or industrial-scale bioreactors are currently still a challenge. Improvement of dark fermentation energetic
yields requires a deeper knowledge of microorganisms’ biology and interactions,
selection of appropriate substrates and pretreatment strategies. Also, further
Fig. 9 Research directions for advances in biochemical conversion to fuel gas and by-products
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…
are still many aspects that should be closely investigated for further improvements
of fuel gas production [14, 157]. In Fig. 9, important research directions which
require further prospects and some innovative developing optimization strategies
for biomethane/biohydrogen production processes are summarized.
The biogas production technologies have reached a technological maturity level
which makes them feasible for large-scale application; the future goals of research
in the field should be more focused on controlling biochemical process stability,
increasing feedstock availability and lowering production costs, as well as on biogas
upgrading to make it suitable as transport fuel [158].
Compared to anaerobic digestion which has been more widely investigated, dark
fermentation is still a rather immature practice, not sufficiently developed to be
commercially available. The main challenge in dark fermentation is that the conversion efficiency of the process as a whole is still low in comparison to theoretical
data. Since about 67–85% of the substrate leaves the reactor before being decomposed, many efforts still need to be made to increase the conversion efficiency of the
substrate and thus the production of biohydrogen [34]. Scaling-up the biohydrogen
production systems and developing continuous pilot-scale or industrial-scale bioreactors are currently still a challenge. Improvement of dark fermentation energetic
yields requires a deeper knowledge of microorganisms’ biology and interactions,
selection of appropriate substrates and pretreatment strategies. Also, further
Fig. 9 Research directions for advances in biochemical conversion to fuel gas and by-products
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…