As bulk density is the same as density (except that it takes air spaces into account), the units are also the same.
Units of bulk density therefore include g/m3, kg/m3 and t.m3.
Use of bulk density
If the amount of space in a coal bins is known, the weight of coal it will hold can be calculated from the bulk density of the coal. We can also estimate the weights of stocked coal, by measuring and multiplying the volume by the bulk density of the coal. In the laboratory g/m3 is probably the most convenient unit but for estimation of large stocks of coal t/m3 is probably more appropriate. Sales of coal or coke usually use kg/m3.