How Energy Is Produced - The Renaissance of Renewable Energy - page 144

Figure 4.49. Breakdown of global bioenergy sources compared with the global primary
energy mix. Renewable energy (RE) accounts for roughly 13 per cent of primary energy
supply. Bioenergy is the most important of all renewables and represents roughly 10 per
cent of total primary energy supply (almost 80 per cent of renewables). Of this, almost 80
per cent comes from forestry and agriculture, the rest is recovered wood, charcoal, wastes,
and residues. See Table 4.8 for details. Source: IEA website, IEA Bioenergy ( 2009 ),
Chum et al. ( 2011 ) .
The current global crop (cereals, oil crops, sugar crops, roots, tubers, and pulses) is
about 60 EJ/year, while global forestry production comes to 15-20 EJ/year (Chum et
al. 2011 ) . We can see straightaway from these figures that if bioenergy is to rise from
its current 10 per cent and become a major source of future primary energy supply, the
human appropriation of plant life on Earth will have to increase substantially. This would
entail expanding agriculture and forestry across a greater share of the world's landmass
and increasing agricultural productivity through fertilizer, irrigation, and mechanisation.
Meanwhile, world primary energy demand is expected to rise from its current 530 EJ to
between 600 and 1,000 EJ by 2050 (IEA Bioenergy 2009 ) .
The land requirements of the bioenergy economy are daunting. The annual global
demand for liquid transportation fuel is equivalent to roughly two million tonnes of crude
oil. Were all transportation based on biofuel crops grown in highly productive tropical
regions such as Brazil, Indonesia, or Central Africa, 600 million hectares would be needed,
more than the current total of tropical land under cultivation (Smil 2010 , 100). Moreover,
if we wanted to meet global primary energy production with sugarcane ethanol, we would
need the entire global area currently under cultivation, and using biofuels from soy we
would need the entire land surface of the Earth (Andrews et al. 2011 ; see Section 6.2 in
Chapter 6 ). In short, we would need another planet: one for food production, the other for
biofuels.
Table 4.8. Breakdown of global bioenergy sources compared with the global
primary energy mix