450

29 Zero-Waste Biorefineries for Circular Economy

only five genera of seaweeds are responsible for annual bulk production which

are brown algae such as Laminaria [53]. Cultivation of other seaweed species like

Kappaphycus alvarezii and Eucheuma denticulatum (carrageenophytes) as well as

Gracilaria species (agarophytes) is done by countries such as Philippines, Indonesia,

Tanzania, and India [54]. Cultivation site, type of season, and methodology used

during cultivation are the governing factors for the growth rate of various species.

For example, K. alvarezii growth rate varies daily between 3% and 12%, and that of

Gracilaria spp.

Out of 221 species, for food purposes, 145 species are used and phycocolloid

production can be done using 110 species. However, macroalgae are known for

nutrition and economy builders for some countries [55]. The most important global

contribution of algae is the conversion of algal carbon to biofuel in terms of CO2

sequestration. Dependency on fossil fuel for transportation and chemical feedstock

purpose can be reduced by both macro- and microalgae. Lipid content in both algal

types can be converted into fuel like ethanol and chemical feedstocks (Figure 29.4)

[56]. Another development in which red algal pulp can be used as an alternative

to the tree for pulp production and hence deforestation can be controlled. Thus,

conservation of ecological damage by converting fossil fuel into atmospheric CO2

and conservation of terrestrial forest which play an important role in the carbon

cycle can be done by bringing algal-based fuel and algal-based pulp [57]. There has

been a change in macroalgal distribution and diversity along with photosynthetic

and physiological performances with the change in climatic conditions. This can

directly contribute to CO2 sequestration. Under present-day CO2 levels, some

species are already CO2 saturated, and no further performance increment can be

seen in the future.

Case 2. Biomethanation Since the 1950s, the oldest, cheapest, and exploited tech-

nology of India is the production of biogas from organic waste. Until 2013, about

45 lakhs of domestic-type biogas have been installed by the Indian Government

with an estimation potential of 36.85%. India being a huge country holds around

1.5 billion of the population and about 70% of energy comes from fossil fuel of the

total energy consumption by the country. Around 53% of energy import increment

is expected by the end of the year 2030. To avoid food versus fuel conflict in 2008,

Indian biofuel policy was made. The aim is to focus on nonfood feedstocks for

bio-based energy/fuel rather than exploiting limited natural resources by importing

fossil feedstock and refined petroleum products. From the same context, between

2002 and 2010, increment in renewable energy share from 2% (11 628 MW) to 11%

(18 155 MW) is seen in the Indian market. Presently, biomass is the source respon-

sible for providing 32% of primary energy [58]. Biofuel is another new sustainable

dimension that can open doors for waste management and energy generation.

Biofuel has lower GHG emission as compared to fossil fuel and therefore becomes

the priority for bio-based economy development.

According to the reports published by the Ministry of New and Renewable

Energy (MNRE), waste as a resource can never be diminished. Waste to electricity

conversion accounts for 1700 MW from municipal solid waste (MSW), 225 MW from

Department of Science and Technology (DST), and 1300 MW from the industrial