Introduction to biogas

The Canadian dairy industry is important to our economy.  Dairy products are consumed by most of the Canadian population and some, such as milk, are used in the preparation of most meals.  Due to the high consumption of these products, Canada has almost 13,000 dairy farms with over 1.4 million dairy cows (Canadian Dairy information centre). 

 What most people don’t realize is that the most valuable item obtained from the cow is not the milk, but the manure. That’s right, the cows' manure!  The manure from the cow can be collected to make a renewable source of energy called biogas, which can then be used to create electricity by anaerobic digestion, a biological process where microorganisms break down organic materials into their primary components.  With global warming, there is a pressing need for us to convert to renewable sources of energy, biogas being one of them.  Today, farmers dump the cows' manure into ponds or lagoons, wasting a valuable source of energy. Consider these facts on the value of this manure:

 Dairy cows produce on average 82 pounds of manure in one day.  With 1 429 400 dairy cows in Canada, that adds up to 117 210 800 pounds of manure a day and almost 43 million pounds of manure a year.  This would produce 57 176 mega watts of electricity every week and 20 869 240 mega watts every year - enough electricity to power all of New York City for almost 5 years!

 Now you must be wondering, how this electricity is created? All of the manure from the farm is collected and put into one end of an anaerobic digester tank.  The manure takes anywhere from 10-25 days to make it from one end of the digester to the other. Inside the tank, the manure is broken down by anaerobic bacteria, which separates the methane from the solid matter.  The methane rises to the top of the tank and is held in a different storage tank until it is ready to be used.  Since biogas is most commonly used to make electricity, it is used as fuel to power an engine which turns a generator- creating electricity. 

Diagram of the anaerobic digestion process.