Cement Energy and Environment

Picture 2: Algae-based lab-scale anaerobic digester developed by MCRC biomethane. Ulva typically has C:N ratio as low as 8.5. Different pre-treatment steps such as maceration, washing to remove salt debris, drying, etc., have proven to significantly increase methane production. Since most seaweeds are carbon rich, their codigestion with other N-rich substrates such as waste food or agricultural slurries has been demonstrated as a feasible and successful methodology. Codigestion of fresh Ulva with cattle manure slurry, in the proportion of 25:75, has shown to reach 93 per cent of the biomethane potential (1 70 L CH4 I kg VS) at an organic loading rate (OLR) of 2.5 kg VS m-3 d-1 . The use of seaweed for biogas production plays a significant role in reducing greenhouse gas emissions by 42- 82 per cent when compared to the use of natural gas. Furthermore, the digestate residue obtained post anaerobic digestion contains material rich in nitrogen and phosphorus, which may be reused as fertilizer. Biogas frorn seaweeds– Interesting Facts • Being mari ne form. seaweed cultivation system does not compete with food production for land space. fresh water or nutrients. It is an excellent feedstock for b lofuel production. • Carbon dioxide (C0 2 } m itigation by seaweeds : 1 .04 X 10 6 tonnes per annum • In terms of gas yield per tonnage-The largest. scale seaweed to blogas achieves yields of 22 m 3 per tonne of seaweed (Larninaria sp.). • In terms of energy yield per hectare-Current. st.at.e-of-t.he -art seaweed-to-methane achieves~ yield of 171 G.J/ha. • To meet energy requirement o f u K, only 5 ,440 km 2 of cultivation area is needed in comparison t.o maize which would require 7,700 km2 to produce same quantum of methane. Conclusion Seaweeds, undoubtedly, are a sustainable and potential source for biogas production. India, with a vast coastline can be a resourceful and renewable source for seaweed cultivation and biogas production. However, only very few seaweed digesters are operational at the commercial scale, despite identification of numerous species and pathways to produce biogas. The major long-term problems associated with use of seaweed are sand deposition in anaerobic digesters and high salinity. Certain basic factors, such as use of potential species, its cultivation method, yield per hectare, time and method of harvest, energy yield, and cost of fuel production need to be carefully researched for successful establishment of commercial biogas 50