Coal combustion products
Coal combustion products (CCPs), also called coal combustion wastes (CCWs) or coal combustion residuals (CCRs),[1] are categorized in four groups, each based on physical and chemical forms derived from coal combustion methods and emission controls:
Regulation[edit]
United States[edit]
Following the 2008 Kingston Fossil Plant coal fly ash slurry spill, EPA began developing regulations that would apply to all ash ponds nationwide. EPA published the CCR rule in 2015.[54] Some of the provisions in the 2015 CCR regulation were challenged in litigation, and the United States Court of Appeals for the District of Columbia Circuit remanded certain portions of the regulation to EPA for further rulemaking.[56]
EPA published a proposed rule on August 14, 2019, that would use location-based criteria, rather than a numerical threshold (i.e. impoundment or landfill size) that would require an operator to demonstrate minimal environmental impact so that a site could remain in operation.[94]
In response to the court remand, EPA published its "CCR Part A" final rule on August 28, 2020, requiring all unlined ash ponds to retrofit with liners or close by April 11, 2021. Some facilities may apply to obtain additional time—up to 2028—to find alternatives for managing ash wastes before closing their surface impoundments.[95][96][97] EPA published its "CCR Part B" rule on November 12, 2020, which allows certain facilities to use an alternative liner, based on a demonstration that human health and the environment will not be affected.[58] Further litigation on the CCR regulation is pending as of 2021.[98]
In October 2020 EPA published a final effluent guidelines rule that reverses some provisions of its 2015 regulation, which had tightened requirements on toxic metals in wastewater discharged from ash ponds and other power plant wastestreams.[99][100] The 2020 rule has also been challenged in litigation.[101] In March 2023 EPA published a proposed rule that would reverse some aspects of the 2020 rule and impose more stringent wastewater limitations for some facilities.[102]
India[edit]
The Ministry of Environment, Forest and Climate Change of India first published a gazette notification in 1999 specifying use of fly ash and mandating a target date for all thermal power plants to comply by ensuring 100% utilisation.[103] Subsequent amendments in 2003 and 2009 shifted the deadline for compliance to 2014. As reported by Central Electricity Authority, New Delhi, as of 2015, only 60% of fly ash produced was being utilised.[104] This has resulted in the latest notification in 2015 which has set December 31, 2017, as the revised deadline to achieve 100% utilisation. Out of the approximately 55.7% fly ash utilised, bulk of it (42.3%) goes into cement production whereas only about 0.74% is used as an additive in concrete (See Table 5 [29]). Researchers in India are actively addressing this challenge by working on fly ash as an admixture for concrete and activated pozzolanic cement such as geopolymer [34] to help achieve the target of 100% utilisation.[105] The biggest scope clearly lies in the area of increasing the quantity of fly ash being incorporated in concrete. India produced 280 Million Tonnes of Cement in 2016 . With housing sector consuming 67% of the cement, there is a huge scope for incorporating fly ash in both the increasing share of PPC and low to moderate strength concrete. There is a misconception that the Indian codes IS 456:2000 for Concrete and Reinforced Concrete and IS 3812.1:2013 for Fly Ash restrict the use of Fly Ash to less than 35%. Similar misconceptions exists in countries like US[106] but evidence to the contrary is the use of HVFA in many large projects where design mixes have been used under strict quality control. It is suggested that in order to make the most of the research results presented in the paper, Ultra High Volume Fly ash Concrete (UHVFA) concrete is urgently developed for widespread use in India using local fly ash. Urgent steps are also required to promote alkali activated pozzolan or geopolymer cement based concretes.
In the geologic record[edit]
Due to the ignition of coal deposits by the Siberian Traps during the Permian–Triassic extinction event around 252 million years ago, large amounts of char very similar to modern fly ash were released into the oceans, which is preserved in the geologic record in marine deposits located in the Canadian High Arctic. It has been hypothesised that the fly ash could have resulted in toxic environmental conditions.[107]