Tag: biofuel

Way to Zero Waste

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While passing through the newly developed, urban elite settlements, the dumpsites waiting treatment are becoming increasingly common. Municipal Solid Waste (MSW) in India continues to remain a neglected area with inefficient source segregation. Further, the moisture content in waste adds to India’s challenge in solid organic waste management because of our food habits and socio-cultural habits. This is leading to environmental hazards of pollution of air and nearby water bodies, surface and subsurface soil. Added to this, decomposing organic waste generates methane which is the single largest contributor to global greenhouse gas emissions. With the Prime Minister’s Swachh Bharat Abhiyan set for a new lease of life, a crucial avenue which is now being explored is efficient urban waste management.

A team of researchers led by Prof. Brajesh Kumar Dubey from the Department of Civil Engineering at IIT Kharagpur has adapted a process called Hydro Thermal Carbonization (HTC) for Indian conditions which can effectively manage mixed MSW with high moisture content.

Through the process, most of the mixed MSW can be converted into biofuel, soil amendment and absorbents.

The current waste incineration processes adopted from the developed nations are primarily focused on treating drier waste content. This requires high energy input to combust mixed MSW with high moisture content.

“India’s tropical weather, open collection systems and mixed waste make the output yield much less fuel-efficient. Only 20-30% of the organic fraction of municipal solid waste is being recycled to biofuel. Hence there is a need to develop treatment system which can address the challenge indigenously,” opines Prof. Dubey.

Here is the goal which has been scored by the research team. They have developed a technology to convert the organic fraction of MSW into ‘Hydrochar’ by using a batch reactor. The moisture in the waste is used to the advantage of the process which uses water for the reaction. The process has increased the resource recovery yield to 50-65% of urban organic waste.

“The process novelty lies in the use of water for the reaction thus the moisture in the MSW gets used during the recycling process without requiring any removal of moisture from the segregated waste or high energy intake. This is effective for mixed municipal solid waste management in India,” explained Hari Bhakta Sharma.

For example, 1gm yard waste and 4gm water are being used in the laboratory reactor. The waste output is 1gm of biofuel with a calorific value of upto 24.59 MJ/kg, while the water remains available for reuse.

The key to the success of the technology lies in designing a proper industrial-scale HTC reactor with improved heat integration system. The technology can be deployed by municipalities at various locations within a city thus ensuring easy management of logistics of waste.

Another novelty of this technology is the zero waste scale reached through this process.

“Once the yard waste is entered into the process, the outputs generated are all usable including the water which can either be reused in the processor can be converted to biogas or methane through anaerobic digestion,” explained another researcher Sagarika Panigrahi.

The biofuel generated as the recovered output is comparable to lignite coal which could significantly address the fossil fuel depletion issue and helping to curb air pollution issues, pointed out Prof. Dubey.

The product can further be used as an absorbent to manage soil contamination.

The calorific value or energy yield and quantity yield however are inversely correlated and depends on the end-use of the product.

“So if you are looking for biofuel, the temperature at which the reaction is conducted needs to be kept very high which will increase the calorific value of the fuel however decreasing quantity yield, while in the case of the soil contamination absorbent, the low temperature will increase the product quantity yield with low energy yield,” confirms Hari Bhakta Sharma.

“This could significantly help brownfield sites or contaminated industrial sites or landfills,” added Prof. Dubey.

According to the Ministry of New and Renewable Energy (MNRE) estimates, there exists a potential of about 1700 MW of energy from MSW and sewage. Of this, only about 24 MW have been exploited, according to MNRE. Thus, less than 1.5% of the total potential has been achieved. The waste to energy mandate of Govt. of India could also be met through this innovative process.

“As of July 2017, thermal-based Waste-to-Energy plants in India have a capacity to process 5,300 tons of garbage and produce 53.5 MW/day. There is a big market on waste treatment and this technology can serve well for the organic fraction of municipal solid waste,” hoped Prof. Dubey.

Microwave for Clean Fuel

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Kitchen to Cosmos Microwaves these days ring ‘n’ number of bells. IITKGP Researchers have tapped this microwave radiation to create Clean Energy from the nitrogen-rich non-food Sunn Hemp plants.

In the wake of the ongoing initiatives to control pollution, we are often made to think of the proverb ‘prevention is better than cure’. There is an urgency to replace the use of fossil fuels like petrol and diesel which are direct causes of pollution, global warming and climate change. Various clean energy technologies have been developed. Acres of land in the country have been allocated for solar and wind energy, hydel power and geothermal projects have been deployed and expanded over the decades. But India’s fossil fuel import bill still runs high due to non-availability of renewable energy sources at mass scale. Biofuels derived from high-energy non-edible plant sources such as Sunn Hemp on the other hand have the potential of making it available in large scale for replacement of fossil fuel which can find significant use in transportation sector. The main obstacle to its large scale deployment as a future fuel is its highly crystalline structure and long polymer chains, which make the fibres inaccessible to enzymatic and chemical treatments.

Researchers from IIT Kharagpur’s P K Sinha Center for Bioenergy have exacted the issue through the use of microwave radiation. The team from the Bioenergy Lab at the Dept. of Chemical Engineering has successfully converted non-edible lignocellulosic fibres of Sunn Hemp to biofuel precursors, and that too completing the entire conversion – which otherwise takes about 8-10 hours – in only 46 minutes using the microwave reactors in the lab.

“1 kilogram of Sunn hemp fibres containing 756 gram of cellulose produces 595 gram of glucose at 160°C, and 203 gram of hydroxymethylfurfural (HMF) at 180°C, in 46 minutes. The glucose is separated and fermented using yeasts to produce 230 g of ethanol-based biofuel which is often used in automobiles as a biofuel additive for gasoline. The platform chemical HMF can also be hydrogenated to furanic biofuels such as dimethylfuran which can be used as a replacement for diesel” explained researcher Souvik Kumar Paul.

Sunn hemp is widely grown in the subtropics of Bangladesh, Brazil, India, Pakistan, Russia, Sri Lanka, USA, Uganda. It is grown in almost all states of India, especially Bihar, Orissa, Rajasthan, Uttar Pradesh and West Bengal.

The large scale availability of Sunn Hemp in India along with its fast rate of growth and high cellulose (75.6%) and high energy contents (2.5×109 MJ/year) are the key elements of listing it as a top choice for the biofuel industry. Sunn hemp fibres produce 2268 kg dry biomass/acre in only 9–12 weeks, with 19 megajoule of energy/kg dry biomass at a global production of 130,000 MT/year.

“Sunn hemp fibre has the unique potential of being converted to transportation biofuels rather than being merely used as bast fibre for weaving mats, etc. Our research will give its chemical composition the necessary stability for conversion and deployment as liquid biofuels, which can be used by the transportation industry in a large scale,” said Prof. Saikat Chakraborty, lead researcher and faculty at the Dept. of Chemical Engineering and P K Sinha Center for Bioenergy.

These chemical reactions are performed by the scientists at IIT Kharagpur in a large microwave digestion system that houses 16 high pressure reactors. By combining the dried Sunn hemp fibres with chemicals such as ionic liquid and metal catalysts, and water at high temperatures, they form large molecular structures in these microwave reactors. This supramolecular complex being polar in nature rotates under the microwave’s alternating polarity and rapidly dissipates the electromagnetic energy through molecular collisions across the reactors. These dipole rotations and intermolecular collisions help rapidly break the polymeric bonds in the Sunn hemp fibres and convert them to biofuel precursors in only 46 minutes.

“Biofuel production costs are minimized by recovering and recycling the ionic liquid,” added Chakraborty. “This conversion process, which can be used for a large spectrum of non-food lignocelluloses apart from Sunn hemp, is particularly suitable for commercialization because it results in a 10-fold decrease in the reaction time. A mixture of biomass can also be processed in these reactors rather than a single biomass without any further increase in the reaction time, which should make this process an attractive option for the biofuel industry.”

While the significant industry potential of this invention has led the scientists to file for a patent, their findings have also appeared in the globally renowned journal Bioresource Technology published by Elsevier.