Renewable energy is basic to reduce poverty and to allow sustainable development. However, the concept of renewable energy must be carefully established, particularly in the case of biomass. This paper analyses the sustainability of biomass, comparing the so-called "traditional" and "modern" biomass, and discusses the need for statistical information, which will allow the elaboration of scenarios relevant to renewable energy targets in the world. (C) 2003 Elsevier Ltd. All rights reserved.