59
Furthermore, the mechanisms of the processes in each technique are not yet well
discovered so that an optimization of the operational and technological conditions
is possible [71]. Hence, further research for the development of advanced residual
biomass pretreatment technologies with adequate reaction mechanism control, also
fitted to the particularities of various biomass and for minimal costs, are still
needed [65].
4 Biochemical Routes and Metabolic Pathways
Residual biomass generated abundantly from numerous economic sectors is a very
valuable resource through the organics content that can be recovered by bioconversion into fuel gases and a mineralized product much attractive for crop ecofertilization. Anaerobic fermentative bioprocesses such as anaerobic digestion with
biomethane generation and dark fermentation with biohydrogen production have
attracted increased interest in the research environment in the current context of the
need to replace conventional fuels with green fuels produced mainly from municipal, agro-industrial wastes and crop residuals [77].
The biological methanation involves methanogens that use carbon dioxide,
hydrogen and other simple precursors (acetate, methylamine, formate, etc.) resulted
as metabolism products from biochemical decomposition of complex biopolymers,
followed by the conversion of simple molecules into methane and other gases [78].
A schematic representation of degradation steps involved in fermentative biomass
breakdown for biogas and biohydrogen production by anaerobic digestion and dark
fermentation respectively is shown in Fig. 3.
Besides biomethane that has been largely exploited, biohydrogen produced from
carbohydrate-rich substrates through biological processes using microorganisms is
believed to be another key energy carrier for the future [79].
Anaerobic conversion of the organics-loaded substrate to produce fuel gases
takes place on very diverse and complex biochemical pathways, specific to microbial metabolism, involving a wide spectrum of fermentative microbial species (bacteria and fungi) through the enzymes they produce. The various microbial species
require specific environment conditions in terms of acidity, temperature and nutrient
concentrations that would ensure optimum growth [80].
Under metabolic interaction the fermentative microorganisms work together to
decompose the organic matter to the final metabolic products.
The full mechanism of methanogenesis is particularly complex, as some aspects
of biochemical pathways have not been elucidated so far. The biochemical processes go successively through the following four biochemical transformation steps:
hydrolysis of complex biopolymers; acidogenesis to organic acids, aldehydes and
alcohols; acetogenesis involving the formation of acetate, CO 2 and H 2 ; and methanogenesis which is the final stage of conversion having methane as product of interest, along with other gases [90, 81].
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…
Furthermore, the mechanisms of the processes in each technique are not yet well
discovered so that an optimization of the operational and technological conditions
is possible [71]. Hence, further research for the development of advanced residual
biomass pretreatment technologies with adequate reaction mechanism control, also
fitted to the particularities of various biomass and for minimal costs, are still
needed [65].
4 Biochemical Routes and Metabolic Pathways
Residual biomass generated abundantly from numerous economic sectors is a very
valuable resource through the organics content that can be recovered by bioconversion into fuel gases and a mineralized product much attractive for crop ecofertilization. Anaerobic fermentative bioprocesses such as anaerobic digestion with
biomethane generation and dark fermentation with biohydrogen production have
attracted increased interest in the research environment in the current context of the
need to replace conventional fuels with green fuels produced mainly from municipal, agro-industrial wastes and crop residuals [77].
The biological methanation involves methanogens that use carbon dioxide,
hydrogen and other simple precursors (acetate, methylamine, formate, etc.) resulted
as metabolism products from biochemical decomposition of complex biopolymers,
followed by the conversion of simple molecules into methane and other gases [78].
A schematic representation of degradation steps involved in fermentative biomass
breakdown for biogas and biohydrogen production by anaerobic digestion and dark
fermentation respectively is shown in Fig. 3.
Besides biomethane that has been largely exploited, biohydrogen produced from
carbohydrate-rich substrates through biological processes using microorganisms is
believed to be another key energy carrier for the future [79].
Anaerobic conversion of the organics-loaded substrate to produce fuel gases
takes place on very diverse and complex biochemical pathways, specific to microbial metabolism, involving a wide spectrum of fermentative microbial species (bacteria and fungi) through the enzymes they produce. The various microbial species
require specific environment conditions in terms of acidity, temperature and nutrient
concentrations that would ensure optimum growth [80].
Under metabolic interaction the fermentative microorganisms work together to
decompose the organic matter to the final metabolic products.
The full mechanism of methanogenesis is particularly complex, as some aspects
of biochemical pathways have not been elucidated so far. The biochemical processes go successively through the following four biochemical transformation steps:
hydrolysis of complex biopolymers; acidogenesis to organic acids, aldehydes and
alcohols; acetogenesis involving the formation of acetate, CO 2 and H 2 ; and methanogenesis which is the final stage of conversion having methane as product of interest, along with other gases [90, 81].
Biochemical Conversion of Residual Biomass: An Approach to Fuel Gas and Green…