Photosynthesis in past geological eras has provided the dominant contribution to today’s energy supplies: the fossil fuels (oil, coal and natural gas) on which we currently so heavily depend were laid down by the decay of plant matter and marine organisms in the Carboniferous Period between 345 and 280 million years ago. Photosynthesis also provides an often-underrated contribution to world energy resources today by creating biomass, the organic matter associated with living or recently living organisms. Traditional plant and animal biomass-mainly fuelwood and animal dung-are important sources of non-commercial energy, currently providing about 14% of the world’s total final energy consumption and nearly twice that in the developing world, as shown in Table 1.1. Traditional plant biomass is, however, often gathered and burned unsustainably, leading to deforestation, soil degradation and net COz emissions. Only better land management techniques throughout the developing world can prevent this.
‘New’ biomass in the form of energy crops (crops grown specifically for energy production) have only a small commercial presence today, but could make an important contribution to future, more sustainable energy supplies. Indeed. many experts see biomass as providing the dominant renewable energy resource in the postfossil fuel era. Production of biomass and energy crops represents one of the few ways of turning solar energy-a fluctuating, intermittent and dilute source of energy-into a compact, storable chemical form that can provide energy on demand. Energy crops can simply be dried and burned to provide heat or generate electricity. More value is added, though at a cost that is likely to be uneconomic at times of low fossil fuel prices, by converting biomass or energy crops into biofuels by biological, thermal or chemical means such as fermentation, pyrolysis and gasification.
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