Biofuel co-products as livestock feed - Opportunities and challenges

Utilizing co-products of the sweet sorghum-based biofuel industry as livestock feed in decentralized systems 239 Nutrient digestibility and nutritive value of sweet sorghumbagasse in graded Murrah buffalo bulls and Deccani ramsNutrient componentDigestibility (%)Buffalo bulls Deccani rams Notes Source et al., 201020 kg within the first 15 days. Farmers appreciated thatfresh sweet sorghum bagasse and leaf residue was wellaccepted by the buffaloes, but pointed out that choppingwould have further improved the intake and reduced therefusal of thick stalk pieces. Interestingly, farmers observedthat the milk of the fresh BLR fed animals was creamierthan those on the previous grass diet due to increased fatcontent (Kumar et al., 2010).Other usesSweet sorghum bagasse, other than for animal feed, canbe used as raw material for a range of purposes, includingbiofertilizer production, paper making and co-generation.One of the options for bagasse utilization is as organicsoil amendment. However, the direct incorporation intothe soil of raw wastes such as the bagasse is not usuallysuitable because they may cause undesirable effects, suchas phytotoxicity and soil nitrogen immobilization. It is wellknown that composting is one of the most suitable waysof transforming wastes into more stable products that aresafe and beneficial to plant growth. The finished composthas a low C/N ratio of 13, compared to 90 in the originalsubstrate bagasse, and also has improved levels of macroandmicro-nutrients (Negro et al., 1999).For the paper industry, cereal straw and sugar canebagasse are two abundant raw materials in addition towood from the forest. However, these raw materials are inshort supply due to restrictions on cutting trees in the forest,electricity generation from bagasse and residues, and residueuse as livestock feed. Hence, sweet sorghum bagassewas assessed for its suitability for paper making (Belayachiand Delmas, 1997). The quality of the pulp obtained fromsweet sorghum bagasse is excellent for the paper industry.The pulp exhibits a degree of cohesion higher than 80 percent;a low kappa number, indicating good delignification;a high degree of polymerization; and exceptional physicomechanicalproperties, meeting the requirements of thepaper industry, and is expected to be the best alternative tosugar cane bagasse and cereal residues.Co-generation is the simultaneous production of electricityand process heat from a single dynamic plant.Globally, biomass-based co-generation has been widelyapplied in forest industries and agro-industries such assugar factories, rice mills and palm oil factories. The30 KLPD Tata Chemicals Limited (TCL) plant at Nanded,Maharashtra, India, has a 2 MW per hour power generationcapacity using bagasse, thus making it self-sufficientin energy.Sweet sorghum bagasse, with a bulk density of70–90 kg/m 3 and ash levels of 4–5 percent, is highly suitablefor gasification (Rajavanshi and Nimbkar, 2005).UTILIZATION OF FOAM, VINASSE AND STEAMLiterature is scanty in these areas. The foam, froth andvinasse that is taken out during concentration of juice tosyrup is rich in nutrients and can be used in compostingof bagasse as well as directly as organic fertilizer. Vinasseneeds to be subjected to nutrient analysis. Similarly thesteam generated while boiling can be captured and usedas a source of heat. This heat can be channelled to warmwater when the DCU is aiming for more juice extractionefficiency. Alternatively, it can be used for pre-heating ofthe juice before boiling.ECONOMIC IMPORTANCE OF BAGASSE FORTHE SWEET SORGHUM VALUE CHAIN IN THEDECENTRALIZED SYSTEMThe current rate of conversion of a tonne of sweet sorghumstalk to juice is 26.9 percent (269 litres) with 700 kgavailable as wet bagasse. After drying, about 30 percent(210 kg) of that wet bagasse (700 kg) is available as fuelor as fodder for livestock. In DCUs, about 45 percent ofthe dry bagasse (95 kg) is utilized as fuel (heating thepans) for converting juice to syrup, and the remaining55 percent (115 kg) of the bagasse can be used or soldas fodder for livestock. During the early phases of DCUdevelopment, bagasse was sold direct to fodder traderswith no value addition, and at a low price. However, duringsubsequent seasons, based on feedback from traders, driedbagasse of sweet sorghum was chopped to realize a highervalue. Accordingly, efforts were made toward choppingsweet sorghum bagasse, doubling returns to Rs. 1/kg(US$ 0.0022) for chopped sweet sorghum bagasse. Thisvalue addition through change in physical form of thebagasse increases the overall income from sweet sorghumin the ethanol value chain under the decentralized system.Additionally, sweet sorghum bagasse sold as fodder inthe region of sorghum-based crop-livestock systems alsohelps in meeting the fodder requirements for the growingpopulation of milch animals.