Use of wastes and by-products

The Japanese cement industry has developed technologies that enable the use of wastes as alternative raw materials or alternative thermal energy. It leads to save natural resources and extend the life of existing landfill sites.

Transition of amount of used wastes and by-products in Japan

  Figure 1 shows the types of used wastes and by-products in Japanese cement industry.
  The transition of the cement production, the total amount of used wastes and by-products and the specific amount of used wastes and by-products are shown in Figure 2. The specific amount of used wastes and by-products was 251 kg/t-cement in FY1990. But, it has increased year by year. In FY 2020 it was 468 kg/t-cement and the used total amount was 26.2 million tons.


Figure 1 Uses of wastes and by-products in Japanese cement industry

Figure 2 The transition of cement production, wastes and by-products, and the specific amount of wastes and by-products used in cement production

Table 1 shows the transition of the used amount of wastes or by-products by types.
  The amount of blast furnace slag is the total of granulated blast furnace slag and air-cooled blast furnace slag.
  The granulated blast furnace slag is mainly used for admixture of Portland blast furnace slag cement and the air-cooled blast furnace slag is used for one of raw materials of clinker.
  Figure 3 shows ratio of used amount in cement industry to amount of blast furnace slag from steel works. In FY 2019, the rate was 33.1 percent.
  The amount of coal ash is the total of fly ash and clinker ash. The produced amount of Portland fly ash cement in specified by JIS R 5213 was only 46,000 ton in FY 2020, and the ratio of Portland fly ash cement to total amount of produced cements was only 0.09 percent. So, the coal ash is mainly used for a raw material of clinker in Japan. Figure 4 shows ratio of used amount in cement industry to amount of coal ash generated from power plants. In FY 2019, the rate was 67.5 percent.

Table 1 The amount of wastes or by-products used for cement production

(Units：thousand tons)

Type Use for1) 1990 2000 2010 2015 2017 2018 2019 2020
Coal ash ARM, MIC 2,031 5,145 6,631 7,600 7,750 7,681 7,593 7,286
Blast furnace slag ARM, MIC 12,213 12,162 7,408 7,301 7,398 7,852 7,430 6,981
Sludge ARM 341 1,906 2,627 2,933 3,255 3,267 3,091 2,950
By-product gypsum ARM(Additive) 2,300 2,643 2,037 2,225 2,179 2,229 2,091 2,032
Incineration ash (excluding coal ash),Soot,Dust ARM 468 734 1,307 1,442 1,524 1,530 1,554 1,482
Waste soil from construction2) ARM − − 1,934 2,278 1,823 1,531 1,214 1,241
Waste plastic AF 0 102 445 576 543 517 746 746
Non-ferrous slag ARM 1,559 1,500 682 722 795 811 740 725
Woodchips AF 7 2 574 705 643 718 450 437
Steel slag ARM 779 795 400 395 374 387 411 364
Foundry sand ARM 169 477 517 429 446 455 407 336
Recycled oil AF 51 239 195 179 209 223 236 282
Waste activated clay AF,ARM 40 106 238 311 287 264 260 260
Waste oil AF 90 120 275 293 314 335 322 245
Cullet ARM 0 151 111 129 130 152 165 154
Meat and Bone meal AF,ARM 0 0 68 57 59 60 63 71
Waste tire AF,ARM 101 323 89 57 63 70 65 69
RDF,RPF3) AF 0 27 48 37 37 40 46 46
Coal mining waste AF,ARM 1,600 675 0 0 0 0 0 0
Others − 14 253 408 382 502 459 506 447
Total（thousand ton）   21,763 27,359 25,995 28,053 28,332 28,583 27,422 26,155
cement production（thousand ton）   86,849 82,373 55,902 59,074 60,202 60,074 57,978 55,894
Total /cement production（kg/t-cement）   251 332 465 475 471 476 473 468

Note 1) ARM : Alternative raw materials of clinker, MIC : Constituent of blended cement or Portland cement, AF : Alternative fuels

Note 2) “Construction soil” has been categorized into “Others” before FY 2002.

Note 3) RDF：Refuse Derived Fuel,RPF：Refuse derived paper and plastics densified Fuel

Figure 3  The ratio of used amount in cement industry to amount of blast furnace slag from for steel works
  Total amount used in FY2019 : 22.803 Mt
  Amount used for cement production : 7.546 Mt (33.1%)

[Source]
  “Annual report for iron and steel slag statistics”
  (published by Nippon Slag Association)

Figure 4  The ratio of used amount in cement industry to amount of coal ash generated from power plants
  Total amount generated in FY2019 : 8.407 Mt
  Amount used for cement production : 5.673 Mt (67.5%)

[Source]
Japan Fly ash Association

Transition of use of alternative thermal energy in Japan

  Wood chips, waste plastic, waste oil, etc.al are used as alternative thermal energy at burning process. Figure 5 shows the ratio of alternative thermal energy at burning process. Over the past several of years, the ratio has come to some 20.3%. And, wood chips and other waste have used as alternative thermal energy for on-site power generations Figure 6 shows the ratio of alternative thermal energy for on-site power generations.
  The use of alternative thermal energy contribute to save natural resources and extend the life of existing landfill sites.

Figure 5  Ratio of alternative thermal energy at burning process

Figure 6  Ratio of alternative thermal energy for on-site power generation

Extending the life of landfill sites

  In Japan, it is becoming difficult to find new landfill sites, because Japanese land area is very small. The cement industry has helped to extend the life of existing landfill sites by using industrial wastes. The estimated result of extending the life of existing landfill sites is shown as follows.

- The remaining capacity of industrial landfill sites in Japan at April 1, 2019 was 158,649,958 m3(A)*.
- The remaining life of industrial landfill sites was estimated to be 17.4 years(B)*.
- The annual volume of industrial waste disposed is estimated to be 9,117,814 m3(C=A/B).
- The volume of wastes and by-products taken by cement plants in FY 2019 is estimated to be 19,858,294 m3(D)**.
- If the cement industry will not use wastes and by-products at all, the remaining life of industrial landfill sites are estimated to be 5.5 years(E=A/(C+D)).

  The comparing of estimated value B(17.4 years) and estimated value E(5.5 years) shows that the use of large amount of wastes and by-products in Japanese cement industry surely helps to extend the life of existing landfill sites.

(*) Source : Ministry of the Environment
(**) This volume is estimated with the amount of wastes or by-products shown in Table 1 and these bulk densities.
 
 
   
 
 

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