The world’s energy demand has been steadily increasing as the population grows and economies develop. According to the International Energy Agency (IEA), global energy demand increased by 2.9% in 2019, which is the fastest annual increase since 2010. The IEA has projected that global energy demand will continue to increase in the coming decades, although the rate of growth is expected to slow down. In 2019, the world’s total primary energy demand was around 168,860 terawatt-hours (TWh). The majority of this energy demand was met by fossil fuels, such as coal, oil, and natural gas, which accounted for approximately 84% of the world’s total primary energy supply. Renewable energy sources, including hydropower, wind, solar, and bioenergy, accounted for approximately 11% of the world’s total primary energy supply, while nuclear energy accounted for approximately 5%. Overall, meeting the world’s growing energy demand while transitioning to a cleaner and more sustainable energy system is a significant challenge facing policymakers and the energy industry.
Bioenergy potential in India
India has significant potential for bioenergy due to its abundant availability of biomass feedstock. According to the Ministry of New and Renewable Energy (MNRE), India’s total biomass potential is estimated to be around 18,000 MW, which includes both grid-connected and off-grid power generation. Agricultural residues, such as rice husk, wheat straw, and sugarcane bagasse, are the most widely available biomass feedstock in India. In addition, forest residues, energy crops, and urban waste can also be used as feedstock for bioenergy production as shown in Fig. 1. In terms of electricity generation, biomass power plants have been installed across India with a total capacity of around 10,000 MW. The government has set a target of increasing the installed capacity of biomass power plants to 14,500 MW by 2022, which would contribute significantly to India’s renewable energy targets. In addition to electricity generation, bioenergy is also being used for other applications, such as cooking and heating. In rural areas, where access to modern energy services is limited, bioenergy-based cooking stoves and biogas plants are being promoted to improve energy access and reduce indoor air pollution. Overall, bioenergy has significant potential in India and can contribute to achieving the country’s energy security and sustainable development goals. However, there are several challenges that need to be addressed, such as the availability and quality of biomass feedstock, technology and infrastructure, and policy and regulatory frameworks.
Densification technology
Densification technology refers to the process of converting loose biomass materials into denser forms, such as pellets, briquettes, or cubes, to improve their handling, storage, transportation, and combustion characteristics. Densified biomass has a higher energy density and can be used as a renewable energy source for various applications, such as heating, power generation, and transportation.
There are several types of densification technology available, which can be broadly classified into the following categories:
- Pelletizing: Pelletizing is a process that involves compressing biomass material into small cylindrical pellets using a pellet mill. The biomass is fed into the pellet mill, where it is forced through a die to form pellets of a specific size and shape. The pellets are then cooled and screened to remove any fines and oversized particles. Pelletizing is commonly used for wood waste, agricultural residues, and energy crops.
- Briquetting: Briquetting is a process that involves compressing biomass material into larger blocks or briquettes using a briquette press. The biomass is fed into the press, where it is compacted under high pressure to form a briquette of a specific size and shape. Briquetting is commonly used for agricultural residues, such as rice husk and wheat straw.
- Cubing: Cubing is a process that involves compressing biomass material into small cubes using a cube press. The biomass is fed into the press, where it is compacted under high pressure to form a cube of a specific size and shape. Cubing is commonly used for biomass materials with irregular shapes, such as sawdust and wood chips.
- Extrusion: Extrusion is a process that involves forcing biomass material through a die to form a specific shape, such as a rod or tube. The biomass is fed into an extruder, where it is heated and compressed to form the desired shape. Extrusion is commonly used for energy crops and agricultural residues.
Electricity generation through gasification process
Gasification is a thermochemical process that converts biomass into a gas mixture, known as syngas, consisting mainly of carbon monoxide, hydrogen, and methane. The syngas produced can be used as a fuel for electricity generation or as a chemical feedstock for the production of chemicals and fuels. Biomass pellets are a common feedstock for gasification because they have a high energy density and are easier to handle and transport than raw biomass. There are various types of biomass pellets, including wood pellets, grass pellets, and agricultural waste pellets. Electricity production through gasification process using biomass pellets involves the conversion of biomass feedstock into a combustible gas called syngas, which is then used to generate electricity through a gas engine or a gas turbine. The process of gasification involves heating biomass pellets in the absence of oxygen, which causes the biomass to break down into a mixture of gases, including hydrogen, carbon monoxide, and methane. The resulting gas mixture, or syngas, has a high energy content and can be used as a fuel for electricity generation.
The gasification process typically involves four stages: drying, pyrolysis, gasification, and combustion. In the first stage, the biomass pellets are dried to remove any moisture content. In the second stage, the dried pellets are heated to a high temperature in the absence of oxygen, which causes them to break down into a solid char and a volatile gas. In the third stage, the volatile gases are converted into syngas through a series of chemical reactions, which take place in the presence of a gasifying agent, such as steam or air. In the final stage, the syngas is combusted to generate electricity. The electricity generation process using gasification can be configured as a standalone power plant or integrated into an existing power generation facility.
Gasification-based power plants have several advantages over traditional power plants, including the ability to use a variety of biomass feedstock, such as agricultural and forestry residues, and the ability to produce low-emission energy. However, there are several challenges associated with the gasification process, such as the variability of biomass feedstock, the need for high-quality pellets, and the cost of gasification technology. Therefore, the feasibility of electricity production through gasification process using biomass pellets depends on several factors, such as the availability and cost of biomass feedstock, the efficiency of the gasification process, and the cost of electricity production.
Conclusion
Gasification process using biomass pellets for electricity generation is a promising technology that can provide a sustainable and renewable source of energy. The process involves the conversion of biomass into a gas fuel through high temperature and pressure, which is then used to generate electricity. The advantages of using biomass pellets for gasification and electricity generation include the availability of a renewable and sustainable fuel source, reduced greenhouse gas emissions compared to fossil fuels, and the potential for localized energy production.
However, there are also challenges associated with this technology, such as the high capital cost of the gasification equipment, the need for consistent and high-quality biomass feedstock, and the potential for environmental impacts if the waste products of gasification are not properly managed. Overall, gasification using biomass pellets has the potential to play an important role in the transition to a low-carbon energy system, but it will require further research and development, as well as policy support, to overcome the challenges and maximize the benefits of this technology.
Reference
Tezer, O., Karabag, N., Ongen, A., Çolpan, C.O. and Ayol, A., 2022. Biomass gasification for sustainable energy production: A review. International Journal of Hydrogen Energy
Abolee Jagtap is a Ph. D. Scholar. She is connected to the Department of Unconventional Energy Sources and Electrical Engineering, Post Graduate Institute, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola.
