Skip directly to content


A small proportion of the fly ash (pulverised fuel ash) produced from the combustion of coal in power stations is formed as cenospheres. These are hollow, hard-shelled, ultra low-density spheres, which form unique free flowing powders.

Cenospheres are used as a lightweight filler and in the manufacture of plastics and ceramics. They are also widely used in the aerospace industry as they are light but extremely strong and resistant to heat and acids.

They also offer low water absorption and a range of particle sizes from sub-micron to millimetres. ScotAsh Cenospheres are sold through a third-party agent who dries and processes the material. Although Cenospheres are not manufactured to any British or European Standards they are processed to very high customer and manufacturing tolerances. Examples of grading are as follows:

  • Cenospheres can be graded into the following sizes: 5 - 85 microns, 100,150, 300 or 500 microns
  • Colour: white or off-white
  • Particle density ranges: 0.6 - 0.8g/cc, 0.6 - 0.85 g/cc and 0.7 - 0.9g/cc
  • A high Alumina Grade is also available for use in refractories, foundry applications, and high temperature resistant coatings.

Cenospheres are mainly used as an inert filler. With a density lower than water (typically 0.7) cenospheres provide up to four times the bulking capacity of normal weight fillers, while their microspherical shape dramatically improves the rheology of fillers.

They can be used in plastics, GRP, lightweight panels, refractory tiles and almost anywhere traditional fillers can be used. Cenospsheres are used in many high technology industries, such as the aerospace, horticulture and offshore sectors.

Due to their resistance to heat in excess of 1300°C and their low coefficient of thermal conductivity, typically 0.09W/mK, cenospheres are often used as insulators