In recent years, with the increase in standard of living, the per capita energy consumption has increased substantially. The world energy consumption is expected to increase multifold by 2025 with much of the energy growth occurring in rapidly expanding economies. Fossil fuels such as coal, oil and natural gas currently supply 86% of the world’s energy, and that will be used up in the foreseeable future. So the only way is to increase the energy availability through alternate sources of energy.

Among all crop plants, sugarcane, which efficiently converts solar energy in to biomass has been ranked as a prominent crop supporting various agro industries. Sugarcane is cultivated for sucrose production as well as for various value added by products such as feed, bagasse, alcohol, paper and electricity. Sugarcane (Saccharumspp.), a C4 photosynthetic plant, is a large-stature perennial grass that is cultivated in more than 80 countries in tropical, semi-tropical, and subtropical regions of the world, primarily for its ability to store high concentrations of sucrose in the stem. Approximately 70% of the world’s sugar supply in the form of sucrose originates from sugarcane. Sugarcane is among the most efficient crops in the world in converting energy from sunlight into chemical energy that is usable as a fuel source. Recognition of sugarcane as an important energy crop was recently heightened by the advent of large-scale sugarcane-based ethanol production in Brazil. Since sugarcane is endowed with a great potential of solar energy utilization, a drift towards energy generation is likely to occupy a prominent place in cane agriculture. Hence, quantification of energy produced by cane plant and variation among different varieties or germplasm is extremely important in commercial exploitation of sugarcane as a renewable and sustainable bio-energy crop.

 

The biomass production of a crop plant is set by its efficiency in photosynthesis. The theoretical maximum net efficiency of the photosynthetic process of converting solar energy into biomass in sugarcane and other C4 plants is estimated to be 6–7%, fairly high conversion efficiency than those of C3 plants. The relative advantage of C4 plants over C3 plants is latitude dependent: the more tropical the environment, the greater the advantage. Due to constraints like incomplete canopy closure early in the crop cycle, sub-optimum sunlight and temperature during a significant portion of the crop cycle, sub-optimum water and nutrient conditions in the soil, and losses from pests etc., the sugarcane crop has not attained the theoretical maximum productivity.

 

Sugarcane biomass is one of the main energy sources that modern technologies could efficiently utilize and fortunately the sugarcane bagasse is one of the more abundant biomass. When sugarcane is milled, the fibrous residue, bagasse, is repeatedly washed and pressed to remove all soluble solids. It reaches about a 50:50 fiber-to-water ratio as it leaves the mill to be either used directly as a fuel source in boilers to internally power the mill, or stored for future use. Sugar production is one of the few agricultural processes where the energy output is greater than the input. Only one third of the available energy in sugarcane, which is stored in sucrose, is effectively used in the production of sugar and ethanol. In the new paradigm of "energy-cane”, in future, sugarcane is cultivated for generating renewable energy. Since sugarcane cultivation is predominant in tropics and subtropics of India, it is important to explore and use the cane crop for energy generation in addition to sucrose.

 

Sugarcane crop holds promise as an energy crop since highest productivity of plant biomass is generated in tropical countries. Widening the energy crop cultivation, cane yield as well as sugar production also will be increased, which would boost the sugar industry towards more bagasse generation and other bye products. In the long term, all above-ground plant parts can be harvested for large-scale production of energy which can provide up to an estimate of about 400 GJ/ha /yr. Also, an increase in sugar % in cane might allow ethanol production to rise from the present level of 90 liters/tonne to 114 liters/tone of cane by 2030.

In a preliminary experiment, the energy production in terms of calorific value of individual plant parts (leaf, leaf sheath and stem) was assessed at different growth phases of sugarcane (formative, grand growth and maturity) in selected sugarcane varieties. The juice quality was estimated during maturity months.

 

 

The leaf and stem dry mass content was high in Co 94008 and thus the total dry mass production was also high (4.32 kg/m2) in this variety. The average partitioning of dry mass in to leaf, sheath ant stem was 16.87, 9.31 and 73.82%, respectively, suggesting greater dry mass production by stem. The energy production potential in the leaf tissue varied from a minimum of 2681 kcal/kg in Co 0314 to a maximum of 4025 kcal/kg in Co 99004 at formative phase (Fig.1). Varieties Co 94008 and Co 86032 recorded 3607 and 3228 kcal/kg, respectively. In the sheath tissue, the calorific value varied from a minimum of 2371 kcal/kg in Co 99004 to a maximum of 3805 kcal/kg in Co 86032. The stem of variety Co 99004 recorded a maximum of 3488 kcal/kg followed by Co 86032 which has recorded 3295 kcal/kg.

 

At grand growth, the energy production potential was appreciably high in stem. Varieties Co 94008, Co 99004, Co 0314 recorded more than 4000 kcal/kg. It was obvious that stem contribution towards energy production was extremely high in all cane varieties.

 

 

At harvest, leaf tissue of Co 0218 exhibited maximum energy production of 4131kcal/kg while the stem of variety Co 99004 possessed maximum energy content of 4029 kcal/kg in stem. The stem of varieties Co 86032, Co 94008, Co 62175 and Co 0314 produced 3856, 3825, 3840 and 3825 kcal/kg, respectively, at harvest. Thus in future, a drift towards energy generation is likely to occupy a prominent place in cane agriculture and identification and evolution of energy rich sugarcane varieties is the need of the hour.