Fuel from plants
All of the food we eat contains chemical energy initially derived
from sunlight. We know that it is photosynthesis that transfers
energy from light into chemical energy, and we are used to
talking about ‘calories’ in our food. You may have estimated
the amount of chemical energy in a foodstuff or a plant using
a calorimeter (see Figure 1). This instrument measures the heat
released when a sample is burnt. The greater the amount of
heat energy released, the higher the calorific (chemical energy)
content of the material. Combustion of fossil fuels to provide us
with heat relies on the chemical energy stored in plants when
they were alive (see Figure 2). With an ever-decreasing supply
of fossil fuels, however, we are constantly on the lookout for
alternative sources of energy.
