H.N. Chanakya

Biogas plant dissemination: success story of Sirsi, India

Dissemination of alternative energy technologies such as biogas in various parts of the world has rarely led to a success rate of 90%. This study in Sirsi block, Karnataka, south India, revealed that 43% of rural households (HH) had dung resources to operate biogas plants and 65% of them had already built biogas plants. 100% of the plants built were functioning satisfactorily and 85% of HH with biogas plants met all their cooking energy needs with biogas, improving the quality of life of women. The presence of multiple agencies in the dissemination network, participation of entrepreneurs competing to assist households in all aspects of biogas plant construction, commissioning, procuring subsidy, guaranteed performance and free servicing contributed to the high rate of success (of 100% of biogas plants being functional). Most biogas plants built had excess plant capacity, with cost implications. An observed shift in the design choice from mild steel floating drum design to fibre reinforced plastic-based floating drum design and then to a less expensive fixed dome model shows that rural households respond quickly to technological developments. The paper discusses the roles of various factors and their implications for future dissemination programmes.

Bioremediation and lipid synthesis through mixotrophic algal consortia in municipal wastewater

Algae grown in outdoor reactors (volume: 10 L and depth: 20 cm) were fed directly with filtered and sterilised municipal wastewater. The nutrient removal efficiencies were 86%, 90%, 89%, 70% and 76% for TOC, TN, NH4-N, TP and OP, respectively, and lipid content varied from 18% to 28.5% of dry algal biomass. Biomass productivity of ∼122 mg/l/d (surface productivity 24.4 g/m(2)/d) and lipid productivity of ∼32 mg/l/d were recorded. Gas chromatography and mass spectrometry (GC-MS) analyses of the fatty acid methyl esters (FAME) showed a higher content of desirable fatty acids (bearing biofuel properties) with major contributions from saturates such as palmitic acid [C16:0; ∼40%] and stearic acid [C18:0; ∼34%], followed by unsaturates such as oleic acid [C18:1(9); ∼10%] and linoleic acid [C18:2(9,12); ∼5%]. The decomposition of algal biomass and reactor residues with an exothermic heat content of 123.4 J/g provides the scope for further energy derivation.

Two-phase anaerobic digestion of water hyacinth or urban garbage

Abstract Diphasic fermentation of water hyacinth or garbage to biogas was tried by coupling a solid-phase acidogenic system (TS 20–30%) to an upflow, anaerobic packed-bed, methanogenic digester. A daily sprinkling of the biomass bed with an aqueous suspension of biodegrading bacteria resulted in accumulation of intermediate volatile fatty acids (VFA) in the sprinkling liquid which gradually lowered the pH to about 5 and suppressed methanogenesis in the biomass bed. A part of the VFA-bearing leachate (following sprinkling) from the acidogenic reactor was fed to the methanogenic reactor for methane production. Clear phase separation was obtained only in the digester fed with garbage. Phase separation occurred when the total VFA levels were 5–6 g litre −1 (pH 5). In the case of fresh- and dried-water hyacinth significant levels of gas production occurred from the decomposing biomass bed and phase separation could be achieved only for short periods (25 days). Low rates of acidogenesis (therefore moderate pH levels) from these substrates encouraged methanogenesis within the biomass bed. Results indicated that the biomass bed may be used alone as a packed-bed digester to obtain high biogas production rates. In the present study specific gas yields between 146 and 181 litres kg −1 TS were obtained for the substrates tested. Solid-phase fermentation is feasible with these substrates and could reduce digester volume and costs of operation. This process overcomes problems associated with feeding, control of floating scum and continuous/semi-continuous operation normally encountered when untreated-biomass feeds are used in conventional biogas digesters.

Fermentation properties of agro-residues, leaf biomass and urban market garbage in a solid phase biogas fermenter

he decomposition and gas production pattern of eight unprocessed biomass feedstocks representing annual weeds, leaf litter, agro residues and market wastes were monitored in this laboratory study. Solid phase fermentation was effected with a weekly fed biomass bed sprinkled twice daily with recycled fermentor liquid to initiate and sustain biogas production from the decomposing biomass bed. Fermentors were fed from the top with gradually increasing feed rates to determine maximum feed rates sustainable. Feed rates of 1 g total solids

Plug Flow Digestors for Biogas Generation from Leaf Biomass

(TS) 1^{-1}d^{-1}

Assessment of treatment capabilities of Varthur Lake, Bangalore, India

was possible which lead to pseudo steady state gas production rates between

Environmental Issues and Management in Primary Coffee Processing

0.26-0.98 11^{-1}d^{-1}

Biomass based energy system for a South Indian village

at specific gas yields of

Solid phase fermentation of leaf biomass to biogas.

0.18–0.44 \hspace{2mm} 1 \hspace{2mm} g^{-1}TS

Field experience with leaf litter-based biogas plants

at 35-75% volatile solids (VS) destruction. Feedstocks such as paper mulberry (Broussenetia), Parthenium, Synedrella and urban garbage lost >50% VS in 30 d while paddy straw, bagasse and sugarcane trash exhibited lower VS loss (\geq 35%) in this period. During decomposition, bulky biomass feedstocks underwent compaction and obviated the need for a pretreatment step. Bulk densities rose manifold to reach between