Press-cake is residue matter which remains as a by-product after oil extraction from the Jatropha seeds. The cake is made up of the seed husks and kernel and contains mainly proteins and carbohydrates. About 50-75 % of seed weight remains as press — cake (Staubmann et al. 1997; Singh et al. 2008). Press-cake contains oil which is about 9-12 % of its weight (Achten et al. 2008). Press-cake has about 18.2 MJ kg-1 gross energy value (Achten et al. 2008). Press-cake contains 6 % nitrogen 2.8 % phos­phorus, and 0.9 % potassium respectively (Del Greco and Rademaker 1998). Out of total 94 % solids present in press-cake, 93 % are volatile solids. One hectare

Jatropha plantation can produce about one ton of press-cake which can supply about

18.2 GJ of energy.

The press-cake has high organic content making it a good potential entity for production of biogas that can be used to supply electricity, process steam, heat, and methanol. Biogas is produced by digestion of adequate amounts of carbohydrates and proteins present in press-cake by anaerobic bacteria (Staubmann et al. 1997; Singh et al. 2008). Staubmann et al. (1997) using pig manure as inoculums, obtained 0.446 m3 of biogas containing 70 % methane per kg of dry seed press-cake. Singh et al. (2008) observed J. curcas press-cake produced 60 % higher biogas than cattle dung and contains 66 % methane. Jatropha press-cake via pyrolytic processes can be materialized for biofuel production (Demirba§ 2002). Cellulose, hemicellulose, and lignin, which are major components of press-cake during pyrolysis are broken down to produce char, bio-oils, and gas which are important energy carriers. Press-cake if present in large quantities can be as a fuel for steam turbines to generate electricity.