Assoc. Prof. PhD. Truong Duy Nghia
Reporter: Dear Sir, how many tons of ash and slag annually discharged from coal-fired power plants in Viet Nam?
Assoc. Prof. PhD. Truong Duy Nghia: Total amount of ash, slag from coal-fired thermal power plants is currently about 12 million tons/year. Under the adjusted Power Plan VII, by 2030, this figure will reach about 20 million tons/year.
Reporter: There are many comments considering ash and slag from thermal power plants as hazardous waste, what is your assessment on this issue?
Assoc. Prof. PhD. Truong Duy Nghia: I have written many scientific articles as well as given speeches in forums and stated that, coal ash slag from coal-fired thermal plants is not hazardous waste. It has been reported that coal-fired thermal power generated a large number of toxic heavy metals such as mercury, selenium, arsenic, lead, cadmium, etc. Through actual testing, comparing with regulated values in QCVN 07:2009/BTNMT, the concentration of heavy metals in ash, slag is less than a few tens to thousands of times over permissible ones. The concentration in ash, slag is even lower than that in animal body. Thus, is there anything to worry about?
Reporter: Currently, many disposals of ash, slag in Viet Nam have been full or nearly full. So in your opinion, how to treat this ash, slag?
Assoc. Prof. PhD. Truong Duy Nghia: According to calculation, 10 million tons of ash, slag per year will be able produce 5 billion standard-size thick bricks or 10 billion air bricks. By 2030, Viet Nam needs 40 billion unfired bricks, but the meeting capacity only reach 10-20 billion. There is a large amount of ash and coal that has not totally burned in domestic coal, accounting for 15% of ash, slag. This type cannot be used as building materials, but it can be decarbonized to produce beehive charcoal. Additionally, fly ash can be used for cement additives. If all BM enterprises involve for turning ash, slag into useful products, we do not need to worry about them anymore. Moreover, because imported coal is almost totally burned with very little ash left, so if by 2030, coal imports increase and account for ¾ coal used for power generation, ash disposals will be almost removed in many plants.
Reporter: There are opinions that ash, slag from coal-fired thermal power plants cannot be used as ground fill material?
Assoc. Prof. PhD. Truong Duy Nghia: I would like to reiterate that ash, slag is not hazardous substances but resources, it will be very favorable if ash, slag is used for construction of traffic road such as foundation reinforcing (sand is currently used) in the form of roller compacted concrete, reducing the amount of stone as well as sand mined from rivers that causes bank erosion and waste of national resources. This is the fault of the Transport sector when they do not make use of such cheap and good material while sand is very expensive. I commended in a forum on highway construction for Phan Thiet - Nha Trang section, ash, slag of Vinh Tan Thermal Power Center should be used, it would be very favorable and saved a lot of money.
Currently, ash, slag disposals in some plants are only used within 2 years, some of them have been almost full, the Government should issue “hard” regulations for the Sectors of Transport, Construction using ash, slag as leveling materials, reusing them but not calling, exhorting like current period.
Reporter: What is the use of ash, slag from coal-fired thermal power plants in the world, Sir?
Assoc. Prof. PhD. Truong Duy Nghia: Britain annually imports millions of tons of ash, slag to produce BM. In China, coal-fired thermal power accounts for 79% of the system’s installed capacity (more than the national capacity of America) with huge ash, slag content up to hundreds of millions of tons and are mostly used as BM. Particularly, since 2003, the Chinese Government has issued regulation on banning the use of burned bricks, and each year, the country needs 600 billion bricks mainly produced from thermal power ash, slag. They argue that if they do not use ash, slag, their country will have to mine a huge amount of clay to produce bricks.
Such other countries as Japan, they use 100% ash, slag, South Korea uses 97% (the remaining 3% is low-quality coal). In Europe, some countries with large proportion of coal-fired thermal power such as Germany, Poland and the Czech Republic also use most of ash, slag, without wasting like our country. I find it odd that while ash, slag is a precious material, many people consider it a hazardous waste.
Reporter: Thanh you so much, Assoc. Prof. PhD.!