The availability of the resources is an important factor for high shares of biomass to penetrate the electricity, heat or liquid fuel markets. We have analysed the geographical and technical potential of energy crops for the years 2050-2100 for three land-use categories: abandoned agricultural land, low-productivity land and 'rest land', i.e. remaining noproductive land. We envisaged development paths using four scenarios resulting from different future land-use patterns that were developed by the Intergovernmental Panel on Climate Change in its Special Report on Emission Scenarios: A1, A2, B1 and B2. The geographical potential is defined as the product of the available area for energy crops and the corresponding productivity level for energy crops. The geographical potential of abandoned agricultural land is the largest contributor. For the year 2050 the geographical potential of abandoned land ranges from about 130 to 410 EJ yr À1. For the year 2100 it ranges from 240 to 850 EJ yr À1. The potential of low-productive land is negligible compared to the other categories. The rest land area is assumed to be partly available, resulting in ranges of the geographical potential from about 35 to 245 EJ yr À1 for the year 2050 and from about 35 to 265 EJ yr À1 in 2100. At a regional level, significant potentials are found in the Former USSR, East Asia and South America. The geographical potential can be converted to transportation fuels or electricity resulting in ranges of the technical potential for fuels in the year 2050 and 2100 equal to several times the present oil consumption.

The regional and global geographical, technical and economic potential of onshore wind energy is assessed using a grid cell approach. For the economic potential, the regional cost -supply curves of wind electricity are presented. The global technical potential of wind electricity is estimated to be 96 PWh year À 1

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We explored the production cost of energy crops at abandoned agricultural land and at rest land at a regional and a global level to the year 2050 using four different land-use scenarios.The estimations were based on grid cell data on the productivity of short-rotation crops on the available land over time and assumptions regarding the capital and the labour input required to reach these productivity levels. It was concluded that large amounts of grown biomass at abandoned agricultural land and rest land, 130-270 EJ yr À1 (about 40-70% of the present energy consumption) may be produced at costs below $2 GJ À1 by 2050 (present lower limit of cost of coal). Interesting regions because of their low production cost and significant potentials are the Former USSR, Oceania, Eastern and Western Africa and East Asia. Such low costs presume significant land productivity improvements over time and cost reductions due to learning and capital-labour substitution. An assessment of biomass fuel cost, using the primary biomass energy costs, showed that the future costs of biomass liquid fuels may be in the same order of the present diesel production costs, although this may change in the long term. Biomass-derived electricity costs are at present slightly higher than electricity baseload costs and may directly compete with estimated future production costs of fossil fuel electricity with CO 2 sequestration. The present world electricity consumption of around 20 PWh yr À1 may be generated in 2050 at costs below $45 MWh À1 in A1 and B1 and below $55 MWh À1 in A2 and B2. At costs of $60 MWh À1 , about 18 (A2) to 53 (A1) PWh yr À1 can be produced.