By Dr Pradip D. Narale, Deepak Kumar, and Ayush Ranjan, College of Agricultural Engineering and Post-Harvest Technology, Central Agricultural University, Imphal
Bioenergy is the energy derived from biomass and is a renewable form of energy. It is obtained from thermo-chemical conversion of biomass and is one of the many diverse resources available to help meet our demand for energy. This renewable energy can be used as transportation fuels, and for heat and electricity. Bioenergy has great potential for application. It also provides waste management benefits as it can be generated from various waste materials such as animal waste, agricultural field waste (straw), sugarcane bagasse and other biodegradable wastes. Biomass is also capable of providing firm energy. About 32 per cent of the total primary energy use in the country is still derived from biomass, and more than 70 per cent of the country’s population depends on it for energy needs.
The Ministry of New and Renewable Energy (MNRE) has realised the potential and role of biomass energy in the Indian context. Accordingly, it has initiated a number of programmes for the promotion of efficient technologies for biomass use in various sectors of the economy, to ensure the derivation of maximum benefits. As such, bagasse-based cogeneration in sugar mills and biomass power generation have been taken up under the biomass power and cogeneration programme. The programme is being implemented with the primary objective of promoting technologies for the optimum use of the country’s biomass resources for grid power generation. Biomass materials used for power generation include bagasse, rice husk, straw, cotton stalk, coconut shells, soya husk, de-oiled cakes, coffee waste, jute wastes, groundnut shells and sawdust.
Keeping in mind India’s future prospects, demand, and aim of becoming carbon-neutral by 2070, biomass application will become a key industry trend for energy generation, at the policymaking level. Earlier, it was limited to being a rural energy generation resource. The total estimated energy generation potential from urban and industrial organic waste in India is approximately 5,619 MW.
Targets and plans
According to a study sponsored by the MNRE, biomass availability in India could translate to a potential of about 28 GW. In addition, about 14 GW of additional power could be generated through bagasse-based cogeneration in the country’s 550 sugar mills. However, India has not scaled its ambition in the biomass sector despite its potential, instead focusing on the solar and wind power sectors. India has scaled its ambitious plans to 280 GW of solar and 140 GW of wind by 2030, to reach 450 GW of installed renewable energy capacity.
The ministry has been implementing biomass power as well as cogeneration programmes since the mid-1990s. More than 800 biomass power, and bagasse and non-bagasse cogeneration projects, aggregating 10.7 GW, have been installed in the country for feeding power to the grid. The states that have taken a leadership position in implementing bagasse cogeneration projects are Maharashtra, Karnataka, Uttar Pradesh, Tamil Nadu and Andhra Pradesh. The leading states for biomass power projects are Chhattisgarh, Madhya Pradesh, Gujarat, Rajasthan and Tamil Nadu. In 2015, at the Paris Climate Summit, India announced its Intended Nationally Determined Contributions and climate goals. These included a target of 175 GW of renewable energy by 2022, of which 15 GW was to come from biomass power, small-hydro power and waste-to-energy plants. Six years later, in 2021, India had already achieved the 10 GW target for biomass power. The current installed capacity of biomass power is 10.7 GW, compared to 4.4 GW in 2015.
Various reports have been published on rural biomass usage, as non-commercial energy sources, primarily fuel wood, chips and dung cakes, contribute to around 30 per cent of the total primary energy consumed in rural areas in the country. It has been reported that 46 per cent of households using firewood and chips in rural India obtain these fuels at zero cost. Meanwhile, about 21.14 per cent of households depend on home-grown stock, and 23.7 per cent make cash purchases.
Bioenergy as biogas
Biogas is produced when organic materials, such as cattle dung, are digested in the absence of air. It is an excellent energy source for individuals as well as institutions that own cattle. Biogas can be used in a specially designed burner for clean cooking without indoor air pollution. A biogas plant of 2 m3 capacity is sufficient for providing cooking fuel to a family of five (the standard family size in India as per the Census of India, 2001). It can also power gas lamps. For example, a gas lamp with an equivalent power of 60 W needs 0.13 m3 of gas every hour, according to MNRE data from 2010.
There is ample potential for setting up biogas plants, considering India’s livestock population of 512.06 million. This includes about 300 million bovines (cattle, buffaloes, mithuns and yaks). The dissemination of biogas technology is a boon for Indian farmers with its direct and collateral benefits. The MNRE has promoted the installation of biogas plants by implementing two central sector schemes under off-grid and decentralised renewable power.
Bioenergy as power and heat through biomass gasification and cogeneration
Biomass gasification involves the incomplete combustion of biomass, resulting in production of combustible gases consisting of carbon monoxide, hydrogen and traces of methane. This mixture, known as producer gas, is used to run internal combustion engines, generating power. In sugar growing areas, there is a possibility of cogeneration (heat and power) from bagasse, a by-product of sugarcane processing.
Biofuels for transportation
Biofuels are transportation fuels produced from biomass as a substitute for fossil-based fuels. First-generation biofuels can be produced from various types of biomass via numerous technologies and pathways, which are often separated into “generations”. First-generation biofuel technologies are in commercial production and utilise sugar, starch, animal fats and vegetable oil. Biomethane, produced through anaerobic digestion, can be upgraded for use as transport fuel and is also regarded as a first-generation biofuel. Biodiesel can be produced from waste fats and oils, tallow, and oilseed energy crops such as mustard, jatropha seed, canola and palm seed through various processes. Biodiesel can be mixed with diesel, or used unblended in many modern diesel engines.
Bioethanol is categorised as a second-generation biofuel. Bioethanol is produced through fermentation of sugars and starches extracted from agricultural waste or crops, including sugarcane, wheat and corn. Brazil produces around 80 per cent of the world’s ethanol from sugarcane. Bioethanol is typically blended with petrol at rates of 5-10 per cent. E85 engines, specifically designed to run on 85 per cent ethanol and 15 per cent petrol, have been in use for decades.
Third-generation biofuel technologies include hydrogen production from biomass and algae production for biofuels. Algae used for biofuel can be sorted into two categories:
- Microalgae are microscopic, photosynthetic organisms that produce substances such as lipids, which can be harvested and converted into a range of products, including biodiesel. Many technical challenges need to be overcome to reduce the high cost of algae-based biofuel production. Other potentially high-value by-products can be extracted from some algae species, thereby reducing overall production costs.
- Macroalgae, such as seaweed, can potentially be grown and converted into heat and power, such as via biodigestion to produce biomethane, or fermentation to produce ethanol. Macroalgae technologies are still at an early stage of development.
Current status of deployment
As of July 2022, a total capacity of 10.7 GW has been installed in the biomass power and cogeneration segment, with bagasse cogeneration contributing 9.4 GW, non-bagasse cogeneration accounting for 772 MW, and the rest coming from waste-to-energy. The instability of oil prices, surging energy demand in developing countries, and greater awareness about climate change threats due to fossil fuel usage have evoked interest regarding bioenergy amongst policymakers in India as well as international development agencies.
Recent years have also witnessed the development of more efficient and cost-effective bioenergy technologies such as smokeless chulha technology. Modern bioenergy technologies such as biomass combustion and gasification for power, production of biodiesel and ethanol as liquid fuels, and production of biogas as gaseous fuel provide opportunities for meeting energy needs in a sustainable manner, improving quality of life and protecting the environment (while addressing climate change). On average, labour-intensive biofuels can generate about 100 times more workers per joule of energy content produced in comparison to the capital-intensive fossil fuel industry. Recent advances in bioenergy technology are also expected to provide locally produced bioenergy for local agriculture, industrial and household usage at a lower cost than fossil fuels.
Bioenergy can offer renewable, low-carbon energy systems, sequestering atmospheric carbon, and generating numerous environmental and socioeconomic benefits, thereby supporting global climate change targets and wider environmental, social, economic and sustainable targets. There is scientific evidence of the benefits of bioenergy, but results are often subject to variation and uncertainty. Additionally, it is important to consider the various sustainable aspects of bioenergy systems beyond carbon. Treating bioenergy only as part of the energy sector would fail to ensure sustainable biomass production and sourcing, clean applications with low health impacts, and fair and affordable energy vectors.
In order to ensure that bioenergy offers the required holistic emissions reduction, context-specific and long-term approaches are necessary to understand the synergies and trade-offs of bioenergy and related agricultural and forestry systems. To assess the environmental and wider sustainable impacts of bioenergy, full supply chains as well as direct and indirect stakeholders, their drivers, benefits and challenges need to be considered. Moreover, we have to assess and evaluate bioenergy in the context of the specific system it is part of, and its direct and wider impacts on the environment, economy and society.