1.3 Extracting Energy from Biomass
• Photosynthesis produces glucose and oxygen from
carbon dioxide, water and light energy
• Not all organisms undergo photosynthesis, but all
organisms get energy from glucose
– Single celled bacteria to complex life forms like humans
• For organisms to release and use the energy,
the glucose has to be broken down
• Once glucose is broken down, cells can extract
the energy to complete the processes that are
essential to life
• There are two main processes through which
organisms extract the energy from glucose:
• Cellular Respiration which occurs when
oxygen is present = aerobic conditions
• Fermentation which occurs when oxygen is
absent = anaerobic conditions
Cellular Respiration
• The most common and efficient method for
extracting the energy from glucose is cellular
respiration.
• Plants, animals, fungi use cellular respiration
Cellular Respiration
• In cellular respiration, as well as in fermentation,
the glucose that was assembled by photosynthesis
is broken down to make the energy available to
body cells
• Remember: solar energy from the Sun is converted
into chemical energy called glucose by a process
called photosynthesis
• The chemical formula for cellular respiration:
C6H12O6 + 6O2
Glucose
Sugar
Oxygen
6CO2 + 6H2O + energy
Carbon
Dioxide
Water
• In contrast to photosynthesis, cellular respiration
consumes oxygen and produces carbon dioxide
Extracting Energy from Food
• Most organisms require oxygen to extract energy
from food = aerobic conditions
• In cellular respiration, organisms take in oxygen
which reacts with the glucose in cells to produce
carbon dioxide, water and energy
• If conditions are anaerobic = no oxygen,
then fermentation is used
• Even though plants produce their own food
through photosynthesis, they still have to
break down glucose to get energy from it
• Plants break down the glucose through
cellular respiration
– During day and night, need energy all the
time to live
• Photosynthesis is active only during the day
though
WHY?
CO2 and Other Greenhouse Gases
• Greenhouse gases are atmospheric gases that
prevent heat from leaving the atmosphere,
therefore increasing the temperature of the
atmosphere
• Ex: water vapour, carbon dioxide, methane
• Without greenhouse gases, Earth’s
temperatures would average less than 0oC
– natural insulator
Greenhouse Effect: the warming of the Earth as a
result of greenhouse gases
Biomass and Fossil Fuels
• Scientists have concluded that single celled
organisms used photosynthesis to generate
biomass more than 3 billion years ago
• Most of the matter in this biomass has been
cycled through the biosphere countless times
Biomass and Fossil Fuels
• Small amounts escaped the biosphere’s
cycling system when the remains of organisms
settled in places where there was not enough
oxygen to decompose them
• Over time, with pressure and heat, the
biomass changed into fossil fuels such as:
Coal, Petroleum and Natural Gas
Biomass and Fossil Fuels
• Fossil fuels come from biomass that was produced
by photosynthesis millions of years ago
• Therefore it is not surprising that burning them has
an effect that is similar to cellular respiration
• Both processes consume oxygen, release energy
and produce carbon dioxide
Enhanced Greenhouse Effect
• Fossil fuels have been accumulating for many
millions of years
• Significant portions of Earth’s reserves have been
burned by humans in a span a few centuries
• Since humans have “suddenly” released much of
the carbon dioxide that was converted to
biomass by ancient plants
= the net result for the atmosphere is added CO2
Enhanced Greenhouse Effect
• Since the Industrial Revolution in the 1700s,
the concentration of CO2 in the atmosphere
has increased
• This era marked the start of an increased and
widespread burning of fossil fuels as a source
of energy
Enhanced Greenhouse Effect
• Many scientists believe that the increased
concentration of CO2 in the atmosphere along
with an increase in other greenhouse gases, such
as methane, is the cause of global warming
• Global warming is the increase in Earth’s average
surface temperature
• Video
Reducing CO2 in the Atmosphere
• There are many ways to reduce the amount
of CO2 being released into the atmosphere,
including:
– International initiatives by governments from
around the world
– Initiatives by the federal, provincial and local
governments of Canada
– Efforts by individuals!
Reducing CO2 in the Atmosphere
Example: Kyoto Accord
• International agreement to reduce greenhouse
gas emissions, signed by over 180 countries in
1997
Example: Protecting existing forests
• In 2008, Ontario announced that half of its
forests will be protected
• 225 000 km2 of forest will be protected from
logging, mining and fossil fuel exploration
• The Boreal forest in Ontario is a carbon sink
= absorbs about 12 million tonnes of CO2/year
Example: Recycling Programs
• Recycling helps to reduce carbon dioxide
emissions because less energy is needed to make
something from recycled materials than from
new materials
• Ex: energy input is reduced by
95% when an aluminum product
is made from recycled aluminum
rather than a raw material