Simultaneous production of sugar, power generation from bagasse is environment-friendly, says IIT-Bombay study
Simultaneous production of sugar and electricity generation from bagasse -- a by-product of sugarcane -- in mills is more environment-friendly and consumes less water than undertaking these processes separately, finds a study by researchers from the Indian Institute of Technology (IIT), Bombay.
Researchers found that the production of a tonne of sugar is likely to release greenhouse gases equivalent to 324 to 834kg of carbon dioxide. Carbon dioxide, methane and nitrous oxide are the key greenhouse gases (GHGs) that can hang in the air for almost 300 to 1,000 years and trap heat in the atmosphere, thereby increasing the temperature on earth.
India is one of the leading producers of sugar in the world, and Maharashtra is the second-largest sugarcane producer in India with 82 million tonne (mt) production in 2018.
“Scenarios with only sugar production lead to more GHG emissions, water consumption and other environmental impacts than scenarios with both sugar and surplus electricity production,” said the study published on November 13 in the Journal for Cleaner Production, a peer-reviewed journal published by Elsevier.
Sugarcane cultivation alone accounts for more than 90% of greenhouse gas emissions in the entire life cycle of sugar production. Coal-based electricity consumption for irrigation and application of chemical fertiliser and cattle manure lead to this high level of emissions. Sugarcane milling accounts for 6-7% and cogeneration of electricity from bagasse accounts for 2-3% of emissions, finds the study.
Researchers from IIT-B -- Moonmoon Hiloidhari, a PhD scholar from the interdisciplinary programme in climate studies, Rangan Banerjee, professor in the department of energy science and engineering and Anand Rao, professor and head of the Centre for Technology Alternatives for Rural Areas -- set out to understand the interaction of bioenergy, climate and environment in the production of sugar.
They found that the energy return on investment (EROI) for producing sugar and using bagasse to produce electricity together was much higher than that for only sugar production or cogeneration of electricity. In simple terms, the energy generated from production of sugar and electricity surpassed the energy required for both the jobs, leaving producers with surplus electricity for sale.
“We have detailed ways to reduce the carbon footprint, water crisis of sugar production and to improve environmental sustainability of sugarcane in Maharashtra. We have also discussed how sugar factories can become cleaner energy generators,” said Hiloidhari.
The researchers suggest that sugar producers cultivate high-yielding sugarcane such as adsali or pre- seasonal to reduce environmental impact of sugarcane cultivation and increasingly use renewable energy-based irrigation systems.
“Micro-irrigation techniques such as drip and sprinkler should be preferred over the existing flood irrigation system to reduce water consumption for sugarcane cultivation. Producers should choose truck-based transportation instead of a tractor to reduce energy demand and emissions from biomass transportation. Adopting modern cogeneration technology to increase surplus electricity production is environment-friendly and will also enhance revenue of sugar mills,” said Hiloidhari.
Abinash Verma, director general, Indian Sugar Mills Association said that most sugar factories in the country were net generators of water and generated electricity from bagasse. “When the sugarcane is crushed, 70% of what we get is water. So we do not draw any water from the ground after the first day of crushing for any of our activities, including cleaning of factories. The surplus water is treated and released for irrigation,” said Verma.
With the new sugarcane season set to take off on Tuesday, Verma said that the target for the sugar industry is to replace 7.5-8% of petrol consumption in the country with ethanol, another byproduct of the sugar industry. “Currently, sugar mills in India generate around 8,000MW power from bagasse, 6,500 MW of which is supplied to the grid as surplus. In addition, we have successfully replaced 5% of petrol consumption with ethanol, which is mixed with petrol to fuel engines. Ethanol is a greener substitute of petrol and the target is to replace 20% of petrol with it by 2030,” added Verma.
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