India is one of the fastest growing economies in the world, and is going through a transition phase. The country’s strong economic growth trajectory is driving the demand for more and more electricity. This has led to a search for options that are not only technologically competent, but also eco-friendly and viable in the long run. Today, India has embarked on an ambitious renewable energy path, which involves the aggressive adoption of renewable energy technologies such as solar, wind, biomass, small hydro and waste-to-energy (WtE).
India has an enormous WtE potential and, with growing public awareness about sanitation and the government’s emphasis on sustainable waste management, this segment is likely to gain more prominence in the future. However, despite being a sustainable energy solution that is not dependent on conventional fossil fuels, the WtE segment is still struggling to find a foothold in the country. Apart from challenges like a nascent technology, lack of financing and the component of criticality, a major barrier that has hampered its development in the country is apprehension regarding harmful radiations, especially from incineration technology.
Incineration with energy recovery is one of the many WtE technologies such as gasification, pyrolysis and anaerobic digestion. Incineration is a waste treatment process which involves combustion of the organic substances contained in waste material. Incineration and other high temperature waste treatment processes are also known as “thermal treatment”. The incineration of waste materials converts them into ash, flue gas and heat, and this heat can be used to generate electric power.
The ash is mostly formed by the inorganic constituents of the waste, and may take the form of solid lumps or particulates carried by the flue gas. The flue gases must be cleaned of gaseous and particulate pollutants before being released into the atmosphere.
While incineration and gasification technologies are similar in principle, the energy product from incineration is high temperature heat whereas combustible gas is often the main energy product from the gasification process. Incinerators reduce the solid mass of the waste by 80-85 per cent and the volume (already compressed somewhat in garbage trucks) by 95-96 per cent, depending on the composition and degree of recovery of materials such as metals from the ash for recycling. This means that while incineration does not completely replace landfilling, it significantly reduces the necessary volume for disposal of waste.
Apprehensions about incineration
In several countries, incineration is still considered a harmful technology that has a negative impact on the environment and public health. Many experts and local communities are vocal against its adoption. Similar problems surfaced during the construction phase of the WtE plant at Okhla in New Delhi that is based on incineration technology. The project faced strong protests and demonstrations from environmentalists, local residents and NGOs, citing harmful radiations and their impact on the surroundings. Despite this project being one of India’s most successful WtE projects till date, it continues to face opposition and demands for closure.
In some countries, incinerators built just a few decades ago often did not include material separation systems to remove hazardous, bulky or recyclable materials before combustion. These facilities posed a risk to the health of plant workers as well as to the environment due to inadequate levels of gas cleaning and combustion process control. Most of these facilities did not generate electricity.
Sustainable and secure
Continuous research on technology upgradation and efforts to bring down the emission levels of WtE plants will definitely be a catalyst for segment growth. The combinations of different technologies backed with research have made it possible to have almost nil emissions from WtE plants. The new technologies have completely eliminated the emission of dioxins and furans, among other emissions. With the development of innovative technologies, it is now possible to generate electricity and by-products from waste without any harmful impact on the surroundings. Also, the stringent norms laid down in the Solid Waste Management Rules, 2016 means that no plant can avoid strict compliance with emissions standards.
Earlier, there were only physical and chemical treatments available for flue gas. In contrast, the most advanced technologies today make use of selective catalytic reactors, wet electrostatic precipitators and bag filters, which help reduce toxic emissions to a very low level. However, the development of manual sorting and segregation of waste, and mature boiler technologies and special furnaces have resulted in limiting the formation of toxic carcinogenic compounds from “the ion family”.
The combustion of wastes may produce numerous materials that result in the formation of flue gas containing dioxins and furans, which are carcinogenic in nature. It is, therefore, the responsibility of the plant owner to ensure that these do not escape into the environment. In order to minimise these emissions, the flue gases need to be heated to 950°C and kept at the same temperature for 2.5 seconds. To eliminate or minimise secondary formations in the flue gas, there are several technologies available.
The flexibility of the system with secondary oil firing makes it possible to adjust the emission with heterogeneous waste and this can be done online. The reactions shown in the accompanying figure can be curtailed by maintaining the flue gas at higher temperatures.
A comparative analysis of dioxin and furan emissions from WtE plants using different technologies is shown in the graph. Thus, technologies and treatment can curtail emissions to almost nil in the case of scrubber, fabric filter, and scrubber, fabric filter and activated carbon. Besides dioxins and furans, there are other compounds present in the flue gas produced by WtE processing plants. The remedial technologies for each of those emissions are shown in the accompanying table.
The way forward
Although WtE projects entail huge capital investments, with attractive tariffs and grants from the government, it is possible to use sophisticated technologies. These technologies, coupled with attractive tariffs, ensure good rates of interest and internal rates of return for investors, and are environment friendly, thus making it a win-win situation for all stakeholders.
While most developed countries have WtE plants at the centre or in the vicinity of cities, in India, it is still early days for the industry and it remains a topic of debate whether to go in for WtE plants or ban them in the interest of the environment and human health. In addition, there is a lack of technological awareness and access to technologies, as well as an absence of case studies in this area.
As the world is trending towards a circular economy and sustainable solutions are the need of the hour, valorisation of waste by-products is likely to become a new business and eco-friendly alternative. WtE plants not only generate energy but also save millions of hectares of land and help in better waste management. The waste that causes environmental damage has the potential of becoming a viable energy and business solution, making way for a clean and green future.
With the help of consultants and technology suppliers, it is possible to deploy eco-friendly WtE solutions. Exhaustive desk work needs to be carried out for the selection of the most techno-commercially suitable technology. It is also time to revisit and rethink making the existing WtE plants sustainable and eco-friendly.
Perspectives need to change, and with the presence of innovative technologies, innovative financing schemes and financial aid, WtE development could be taken to the next level. The government could plan some more attractive measures under the Make in India initiative and the Clean India mission for these technologies so that these can be made available not just in WtE plants but in every plant where it is required. This could be further enhanced if Indian companies enter into MoUs with European and US companies for technology transfer under the World Trade Organization protocol.