Addition of carbon capture and storage (CCS) technologies to reduce emissions could stress water resources in a vast proportion of coal-fired power plants in India that are already exposed to water scarcity, a study has warned.
A study by University of Berkeley researchers reveals that as much as 32% of the world’s coal-fired power plants (CFPPs) are exposed to water scarcity for at least five months per year and 43% face regional water scarcity for at least one month per year. Of these 32%, 56% are located in China, 15% in India and 11% in the US, said study author Lorenzo Rosa.
“CCS technologies are energy and water-intensive processes. Retrofitting CFPPs with CCS will lead to a substantial increase in freshwater consumption for India. Irrigated agriculture is still by far the largest water use in India, but CCS will further strain water resources,” said Rosa.
“To reduce vulnerability it is necessary to develop water-efficient CCS technologies or locate CCS technologies in regions not affected by water scarcity,” he added.
CCS is considered a crucial strategy for meeting carbon dioxide emission reduction targets. It consists of the separation of carbon dioxide from industrial and energy-related sources, transport to a storage location and long-term isolation from the atmosphere.
Post-combustion CCS, where carbon dioxide is first captured from the flue/fuel gases, is a preferred, economically viable technology to reduce carbon emissions because it can be retrofitted to existing power plants without decommissioning them.
Coal continues to be the mainstay of India’s power mix, contributing to more than 50% of it. With its policies, the national government also makes it clear that this will remain the scenario at least for several years even as the emphasis on renewable grows. India currently has no commercial CCS projects at large scale.
Rosa and co-authors explain that energy-producing facilities such as coal-fired power plants consume large amounts of cooling water. The type of cooling method used in a power plant (wet cooling towers, once-through cooling, or air-cooled condensers) affects water consumption.
Installing CCS at these facilities requires that they produce additional energy to compensate for the energy used by the CCS process. With that comes additional consumption of cooling water. In addition, the CCS process itself adds to the overall water consumption in a fashion that depends upon the CCS technology deployed, they said.
Factoring in four types of CCS systems, Rosa analysed the potential impacts on water resources that would result from retrofitting large (greater than 100 MW gross capacity) CFPPs with the CCS systems. They are absorption, adsorption (with temperature and pressure swing processes), and membranes.
The finding that 32% of CFPPs are exposed to water scarcity for at least five months per year suggests that these coal-fired units might not be well suited for retrofitting with CCS unless alternative water sources are available, said Rosa.
China, with 48% of the world’s CFPP capacity, also consumes the greatest share of freshwater, followed by India and the United States. In China, more than 30% of the installed CFPP capacity faces water scarcity from March to October while more than 40% of India’s CFPP capacity faces water scarcity in the dry season (December–June).
“We mapped 218 coal-fired power plants in India with a capacity greater than 100 MW,” said Rosa, adding that CFPPs located in other Asian countries are not particularly exposed to water scarcity, because of high water availability and being constructed along the coast to use seawater as a cooling medium.
Agreeing with the findings, coal chemistry scientist Binoy Saikia, who was not associated with the study, also underscored the water footprint in coal washeries for removing high ash content before transport of coal to the power plant.
“Currently, India also faces big water pollution from coal mining activities like acid mine drainage, groundwater contamination. Indian coal washeries require water and also generate a large amount of contaminated water after beneficiation to produce clean coal,” he said.
“The process (CCS) requires high energy consumption and drastic treatments. In India, CCS is not yet fitted commercially in large scale, as far as I know. In a few Indian power plants, fluidised bed combustion is used to reduce the sulphur dioxide emission in few Indian power plants,” Saikia of CSIR-North East Institute of Science & Technology told Mongabay-India.
Ahead of the 2015 Paris Climate Agreement, India had pledged to unconditionally reduce the emission intensity of its Gross Domestic Product (carbon dioxide emissions per unit of GDP) by 30-35% from the 2005 level by 2030, and achieve 40% of its installed power capacity from renewables.
In a 2018 notification, the Ministry of Environment, Forest and Climate Change defined strong limits on the usage of water for inland thermal power plants (TPP). It mandates all old and new inland TPPs to be based on cooling tower technology from 2017 onwards and also proposes a limit of 3 cubic metres per megawatt hours (m3/MWh) for specific water consumption of all inland thermal power plants.
Vaibhav Chaturvedi, an economist who leads the Council on Energy, Environment and Water’s (CEEW) work on low-carbon pathways said the notification on water withdrawal limits for power plants has significant potential to reduce pressure on India’s water resources.
“A failure to implement this policy will result in continuous increase in withdrawals and will put more pressure on India’s water resources. In the long run, however, withdrawals will increase across scenarios due to the growth in underlying electricity generation, but will still be comparable to current withdrawals,” Chaturvedi said.
Disputes over water with India’s neighbouring countries are likely to compound the water stress issue, according to CEEW research. For example, their study states that TPPs dependent on the Brahmaputra for meeting their water needs can expect water stress in a regional rivalry scenario as China is upstream in the river basin.
“India does not have a CCS power plant and so there is no India-specific data on CCS. For India, at this moment what we know from our research is that nuclear power plants have a higher water footprint compared to coal power plants,” said Chaturvedi.
“CCS is nowhere right now in India’s discussions. But we have been saying that we should never close ourselves to any technology. Technological innovation has an important role in making technologies less water and energy-intensive,” said Chaturvedi.
Chaturvedi and co-authors highlight that India might need to think about the importance of dry cooling technology for addressing the trade-offs of the electricity generation – water nexus. The dry cooling technology eliminates almost all the need for water for thermal cooling in power plants, though this is a highly energy-intensive technology. The extra investment required for dry cooling might be worth it if the increasing pressure on water availability in arid regions for India can be exacerbated, they add.
Innovations to remove emissions from power plants is the need of the hour. “We should design new advanced materials to absorb the emitting gases instead of minimising the use of water. Or, conversion of those gases into value-added products by means of a novel catalyst,” Saikia added.
Source: science.thewire.in
