79
trace gases are required. Regarding the latter, various techniques for gas upgrading
have been employed, whether physico-chemical, biological or combined techniques, but there are still some inconveniences that need to be surpassed. For
instance, membranes employed in gas separation are costly and fragile, while catalysts in chemical hydrogenation process are easily degenerated and need periodical
replacement [110].
Other exploitable directions could be the reduction of handling cost associated to
the fermentation effluent and mitigation of its potentially hazardous influence on the
environment. In this purpose, several approaches could bring proper results:
advanced separation of useful chemicals, low-energy-consuming concentration
techniques for further use as fertilizer, improved recovery techniques for water savings, etc. [162].
Further expectations in the fuel gas production using anaerobic digestion and
dark fermentation processes rest also on engineering and scientific advances in the
sector of feedstock supply. Although fermentation can be conducted on a wide variety of possible substrates out of which organic wastes are preferred, ensuring continuous feedstock to the processes may be sometimes a challenge for constant fuel
gas production. Catch crops, which are plants not intended for food but grown intercropped with food crops, contributing to the enrichment of the soil, have been previously investigated for bioethanol productions; their degradation to biohydrogen and
biogas should also be considered. The selection of new substrates and their subsequent processing to make them suitable for fuel gas production should take into
account some criteria such as availability, biodegradability, cost (of production/processing/transportation), chemical composition and contaminants, etc. [157, 163].
Developing effective pretreatment techniques of lignocellulosic biomass which is
recalcitrant to degradation is also a key point in widening substrates choices for
biomass-to-fuel gas conversion processes [40].
To summarize, there are still multiple directions for possible improvements of
anaerobic digestion and dark fermentation to be approached towards increasing
global process efficiency, so as to bring important contribution to developing sustainable bio-based fuel gas industry while supporting the circular economy.
9 Conclusions
Residual biomass is an inexhaustible energy resource derived from human, animal
and plant waste. It contains organic matter that stores the energy produced in plants
by photosynthesis, energy that is transferred through the food chain to animals and
human beings and finally to their waste. Energy recovery from residual biomass
may partially replace fossil fuels but also help in maintaining environmental balance by reducing greenhouse gas emissions and soil and water pollution.
Biomass biochemical conversion technologies can provide environment-friendly
option for producing gaseous and liquid fuels with the help of specific enzymes as
biological catalysts to break down biopolymers from biodegradable waste into
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…
trace gases are required. Regarding the latter, various techniques for gas upgrading
have been employed, whether physico-chemical, biological or combined techniques, but there are still some inconveniences that need to be surpassed. For
instance, membranes employed in gas separation are costly and fragile, while catalysts in chemical hydrogenation process are easily degenerated and need periodical
replacement [110].
Other exploitable directions could be the reduction of handling cost associated to
the fermentation effluent and mitigation of its potentially hazardous influence on the
environment. In this purpose, several approaches could bring proper results:
advanced separation of useful chemicals, low-energy-consuming concentration
techniques for further use as fertilizer, improved recovery techniques for water savings, etc. [162].
Further expectations in the fuel gas production using anaerobic digestion and
dark fermentation processes rest also on engineering and scientific advances in the
sector of feedstock supply. Although fermentation can be conducted on a wide variety of possible substrates out of which organic wastes are preferred, ensuring continuous feedstock to the processes may be sometimes a challenge for constant fuel
gas production. Catch crops, which are plants not intended for food but grown intercropped with food crops, contributing to the enrichment of the soil, have been previously investigated for bioethanol productions; their degradation to biohydrogen and
biogas should also be considered. The selection of new substrates and their subsequent processing to make them suitable for fuel gas production should take into
account some criteria such as availability, biodegradability, cost (of production/processing/transportation), chemical composition and contaminants, etc. [157, 163].
Developing effective pretreatment techniques of lignocellulosic biomass which is
recalcitrant to degradation is also a key point in widening substrates choices for
biomass-to-fuel gas conversion processes [40].
To summarize, there are still multiple directions for possible improvements of
anaerobic digestion and dark fermentation to be approached towards increasing
global process efficiency, so as to bring important contribution to developing sustainable bio-based fuel gas industry while supporting the circular economy.
9 Conclusions
Residual biomass is an inexhaustible energy resource derived from human, animal
and plant waste. It contains organic matter that stores the energy produced in plants
by photosynthesis, energy that is transferred through the food chain to animals and
human beings and finally to their waste. Energy recovery from residual biomass
may partially replace fossil fuels but also help in maintaining environmental balance by reducing greenhouse gas emissions and soil and water pollution.
Biomass biochemical conversion technologies can provide environment-friendly
option for producing gaseous and liquid fuels with the help of specific enzymes as
biological catalysts to break down biopolymers from biodegradable waste into
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…