Cement Energy and Environment

.. SEAWEEDS: A RESOURCEFUL MATERIAL FOR BIOGAS Our ever-growing energy needs have forced us to look for other renewable resources such as biofuel and biogas. In this context, seaweeds have been identified as a sustainable biomass that can potentially support biofuel production demands. They have better biomass productivity, cheaper cultivation, andgreater mass farming potential. M P Sudhakar and V Shashirekha review the potential of seaweed as a source of energy. Seaweeds are marine macroalgae, which are broadly classified as red (Rhodophyceae ), brown (Phaeophyceae), and green (Chlorophyceae) based on their external colour. More than 10,000 species have been identified so far (Table 1). Seaweeds Resource Seaweeds are found abundantly in the north Atlantic coast of North America and Europe, west to southeast seaboard of South America and west and southern coast of Australia . In the Indian context, seaweeds grow in large quantities along the coasts of Tamil Nadu, Gujarat, and in certain regions of Lakshadweep, and the Andaman and Nicobar islands. There are also very rich seaweed diversity in the coastal lines of Mumbai, Ratnagiri, Goa, Karwar, Varkala, Vizhinjam and Pulicat, and Chilka . Many surveys have been conducted in various maritime states of India in the last four decades to identify the resources of seaweeds along the coast (Table 2). Table 1: Forms of seaweeds Type of Examples ·seaweeds Brown Red Green Saccharina latissima, Laminaria digitata, Fucus serratus, Ascophylum nodosum, Undaria pinnatifida, Sargassum muticum Porphyra, Gracilaria verrucosa, Palmaria palmate, Asparagopsis amata Codium tomentosum, Ulva lactuca Table 2: Seaweed resources in Indian Coasts Gujarat 1 20,000 Maharash tra - J 20.000 [Lakshadweep Islands 8,000 Goa 2 , 000 ~ erala ndaman and icobar Islands f 1 .000 120 Source: Chennubhotla VSK. 1988. Status of seaweed culture in India. In: Seminar report on the status ofseaweed culture in China, India. Indonesia, ROK, Malaysia, Philippines and Thailand. Lovatelli A and Bueno PB (Eds). FAO Corporate Document Repository Seaweeds for Commercial Applications Currently, about 700 species of marine algae are found in both intertidal and deep water regions of the Indian coast, out of which nearly 100 species of macroalgae are being cultivated for commercial use in the food , pharmaceutical , and fertilizer industries. Seaweeds have a variety of biochemical compounds, especially phycocolloids-a kind of polysaccharide-which are used for industrial production of agar, :=. Picture 1: Seaweeds in Gulf of Mannar coast (Mandapam} alginates, and carrageenans. These polysaccharides can be used for biofuel production ; bioethanol through aerobic fermentation and biomethane through anaerobic digestion. Agar yielding red seaweeds , such as Gelidiella acerosa, Gracilaria edulis, G. crassa , and G. follifera are normally collected throughout the year. However, algin yielding brown algae, such as Sargassum and Turbinaria , are seasonally 47