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32 Microbiology of Biogas Production from Food Waste: Current Status, Challenges, and Future Needs

32.9

Conclusions and Future Needs

The bioconversion of food waste to biogas is known for many decades, but the

acceptability is still limited, due to lack of reliability and robustness in the anaerobic

digestion process. This is mainly due to limited and poor understanding of microbi-

ology of anaerobic digestion, which is one of the most important aspects to facilitate

the proper operation and control of the anaerobic digestion process. Further, there

is also undesirable-unavoidable issues like variation in food waste composition due

to seasonal, geographic, and temporal variations along with slower degradation

rates, lower biogas gas yield (<100 g/kg biomass/day), and higher footprint area

(<3 kg/m³/day). Further, huge operational and maintenance problems have been

continuously observed and reported in biogas plants. Hence, there is a need of

performance evaluation of the existing operational plants of multiple configura-

tions (Plug Flow Reactor/mixed) with reference to various parameters such as

linkages b/w input waste characteristics, reactor configurations, and microbial

communities on the system output. Microbial ecology and microbial interactions

in anaerobic digestion need to be rigorously assessed using both conventional and

emerging tools like metagenomics. Developing insights into kinetics of digestion

of multi-substrates, inhibition levels and interactions, and understanding the

rate-limiting steps and evolving strategies to overcome the same is also the need

of the hour. The development of a suitable mathematical model to describe the

functional relationship between input and output variables of the bioreactor

system is also desirable for better process control. The stoichiometric and kinetics

analysis of biogas formation via development of a suitable mathematical model to

describe the functional relationship between input (substrate, microbial consortia,

detention time, temperature, pH, hydrodynamic, etc.) and output variables (biogas

yield, quality) of bioreactor system along with transient analysis of the system

with response to various perturbations will also be needed to establish the stable

operation and control of anaerobic digestion systems.

List of Abbreviations

2G

second generation

3G

third generation

AD

anaerobic digestion

ALK

alkalinity

CBG

compressed biogas

CDG

city gas distribution

CST

centre for sustainable technologies

CSTR

continuously stirred tank reactor

DME

dimethyl ether

EMP

Emden-Meyerhof-Parnas pathway

GHG

green house gas