This chapter deals with the potential, the use and the future of solid biofuels.

Biological material in the form of wood, specific crops, crop residues and organic wastes fulfil both renewable and sustainable criteria as forests and crops can be replanted and, provided these are renewed, they are sustainable. These materials are often referred to as biomass which has been defined as the yield of organic matter that may be used as a source of energy and/or chemicals. Since biomass is largely of plant origin, it can be more correctly referred to as phytomass, although biomass is the widely accepted term. When biomass is burnt it can be regarded as carbon dioxide neutral as any carbon dioxide released during their combustion has previously been fixed from the atmosphere during photosynthesis. However, in the cultivation, har­vesting, preparation, transportation and processing of biomass, fossil fuels may be required, thus making them less than 100% carbon neutral. The world’s total annual energy use has been estimated to be 425 EJ and estimates of the contribution that biomass could make vary from 7.3 to 15.0% of this total (Boyle, 1996; Venturi and Venturi, 2003; Parikka, 2004; IEA, 2005a; Faaij, 2006) (Table 4.1).

Parikka (2004) estimates that the global use of woodfuel and firewood was 3271 Gm3/year (39.7 EJ) of which 55% is used a fuel (21.8 EJ) and 45% as round — wood (17.9 EJ). As can be seen the less developed countries obtain a higher propor­tion of their energy from biomass (16.4-27.2%), as do Sweden and Denmark where efforts have been made to exploit their forest resources.