In this paper we consider electromagnetic wave scattering by aggregated fibres using a multiple scattering approach. Scattering by particles of complex shape such as concave particles, torus, or clusters of fibres can not normally be computed using the T-matrix method. In this paper we are proposing a decompositioning approach to handle this scattering problem. A scattering particle is decomposed into a number of basic units and scattering by such an ensemble of basic constituents is computed using a multiple scattering T-matrix approach. The range of validity of this approach is investigated by providing exemplary computation results for single fibres and aggregated fibres.