1 3 Extracting Energy from Biomass Photosynthesis produces

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: C 6 H 12 O 6 + 6 O 2 Glucose Sugar Oxygen 6 CO 2 + 6 H 2 O + 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?

CO 2 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 0 o. C – 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 CO 2

Enhanced Greenhouse Effect • Since the Industrial Revolution in the 1700 s, the concentration of CO 2 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 CO 2 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 CO 2 in the Atmosphere • There are many ways to reduce the amount of CO 2 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 CO 2 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 km 2 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 CO 2/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