Green Power - A Consumer Guide to Green Power in Canada

WHAT TO KNOW

What are Green Power Technologies?

BIOMASS

Biomass is organic matter and includes trees and plants; crop residue, including corn stalks and wheat straw; forestry waste, such as sawdust, timber slash and mill waste; and municipal organic waste. For thousands of years, biomass dominated the global energy economy and it remains important today, particularly in developing countries. It qualifies as Green Power because it can be greenhouse gas neutral — when converted to energy it does not add more carbon dioxide to the air than it sequestered when it was growing.

There are several ways of turning biomass into heat and electricity:

Direct combustion

Any organic material can be burned if it is dry enough. The heat from the combustion boils water to produce steam, which turns a turbine attached to a generator to create electricity. The heat produced is often a lost source of energy. In some cases, heat from the boilers is diverted to heat buildings and water in a process called co-generation. There are several successful direct combustion projects in Canada, including a generating station in Williams Lake, British Columbia fuelled by wood waste from nearby sawmills, and a plant in Charlottetown, Prince Edward Island that converts 30,000 tonnes of municipal waste annually into steam to generate electricity and heat more than 80 buildings.

Anaerobic digestion

When organic waste decomposes in a landfill, tank or other container with no oxygen present it produces a combustible gas in a process called anaerobic digestion. This biogas, composed mainly of methane and carbon dioxide, is a reasonably clean fuel that can be used to generate electricity and heat. Other by-products of the digestion process are useful as fertilizer and soil conditioner.

At an increasing number of municipal and regional landfills, buried pipes collect naturally-occurring methane gas, which is used to power a generator. The technology at these landfill gas facilities is relatively simple, and many operations will produce a fairly constant supply of electricity for decades, even after the landfill is closed. A more proactive biogas process involves building mechanical digesters that accelerate decomposition to produce commercial quantities of methane gas. These anaerobic digesters can be built as alternatives to new or expanded landfill sites, thereby easing the ongoing problem of finding sites for new landfills.

Pyrolysis and gasification

These are thermo-chemical processes used to convert solid biomass into liquid and gaseous fuel, which are easier to store, transport and burn than solid waste.