This chapter is part of a publication, commissioned by the Netherlands Agency for Energy and the Environment (Novem) on the status and perspectives of research and development in the field of high-tech biological production of methane and hydrogen. Chapter 4 gives a short but precise introduction the technological aspects of waste treatment by anaerobic digestion and the reuse of the produced biogas.MES, T.Z.D. de STAMS, A.J.M. ZEEMAN, G. (2003): Chapter 4. Methane production by anaerobic digestion of wastewater and solid wastes. In: REITH, J.H. ; WIJFFELS, R.H. ; BARTEN, H. (2003): Biomethane and Biohydrogen. Status and perspectives of biological methane and hydrogen production. 58-94.