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18 Advancements in Bio-hydrogen Production from Waste Biomass

Table 18.1

Comparison of the catalytic and biological route of hydrogen production.

S. No.

Catalytic route (steam reforming)

Biological route (fermentation)

1.

It is an endothermic reaction and

requires high temperature (800–1000 K)

and pressure (10–30 bar). The control of

this high temperature is a difficult task,

and it adds to the operational cost and

capital cost of the reactor

It can be operated at ambient

temperature and pressure (upto

maximum 40 ^∘C)

2.

The impurities present in feedstock

(water, ash, or lignin) may affect the

chemical reaction and lead to the

decrease in the overall cost of the

process, as the refining stage of would

be eliminated

The impurities present in feedstock do

not have any adverse effect on hydrogen

production. Some impurities such as

methanol, fatty acids, and salt are

reported to be beneficial for the growth

of microorganisms

3.

The cost for reactor design and catalyst

is higher, making the process less

economical

The zero cost of biological catalyst and

modest reactor design makes it an

efficient process

4.

The selectivity of the steam reforming

process is low due to the side-products

such as methane, which hinder the

production as well as the purity of

hydrogen

The side-products of the fermentative

route are butyric and acetic acids, which

are a part of the pathway and are further

utilized to form butanol and ethanol,

which are also alternative fuels

5.

The process also deals with the

formation of coke/carbon during the

process. This carbon/coke acts as a

poison and clogs the pores of the

catalyst and hence deactivates the

catalyst, thus affecting the process as

well as the yield and purity of hydrogen

No such coke is formed in this process

Source: Adapted from Sarma [3].

various processes such as gasification or partial oxidation, supercritical water, ther-

mal, and steam reforming of hydrocarbons. But, these catalytic routes of H2 produc-

tion are fossil fuel-based and have limitations, which have paved the way toward

the search of biological routes of H2 production. Table 18.1 depicts the advantages

of the biological route over the catalytic conversion of H2 production [3]. Biological

routes are based on microbial pathways that have the ability to metabolize various

carbon sources through a series of enzymatic reactions to produce biohydrogen and

other value-added products. These microbial entities act as cell factories containing

various pathways specific for the production of targeted products. A wide variety of

renewable feedstock serves as the source of carbon for the growth of these microbial

factories that can be channelized toward the production of biohydrogen. It includes

feedstock such as biomass, wastewater, food waste, microalgae biomass, etc.

This chapter outlines various routes of biological H2 production, substrates, and

utilization of various biomasses as feedstocks for biohydrogen production. It also

provides information on different process parameters affecting fermentative H2 and

strategies to enhance its production.