Wood chips for biofuel
In part two of our look at energy production and climate change, Energy IQ breaks down the greenhouse gas emissions associated with renewable energy sources and looks at their part in Canada’s energy policy.
The term “climate change” is used to describe shifts in global temperature and long-term weather patterns caused by excessive greenhouse gas emissions. Greenhouse gases, or GHGs, include carbon dioxide, methane, nitrous oxide and fluorinated gases, and are released into the atmosphere through both natural processes and human activities...
The term “climate change” is used to describe shifts in global temperature and long-term weather patterns caused by excessive greenhouse gas emissions. Greenhouse gases, or GHGs, include carbon dioxide, methane, nitrous oxide and fluorinated gases, and are released into the atmosphere through both natural processes and human activities.
Carbon dioxide is the primary GHG emitted by human activities. Canada is one of the highest GHG emitters in the world. Of the 704 million tonnes of GHGs emitted in Canada in 2016, the oil and gas sector and transportation sectors accounted for almost 50% of total emissions.
Hydro emits 35 times less greenhouse gases than natural gas electricity-generating systems, and 70 times less than coal. However, when reservoirs are created for hydro projects, trees and plants become submerged in water, and the decomposition that occurs from this process releases carbon dioxide into the atmosphere. Methane is also released as plant matter decomposes, and emissions of carbon dioxide and methane usually peak between two and four years after a reservoir is filled. In addition to flooding land to create reservoirs, constructing a hydroelectric dam also creates greenhouse gas emissions.
Most of the greenhouse gas emissions associated with solar power come from transporting solar panels (fossil fuel), and the manufacturing process. Photovoltaic solar panels are made from crystalline silicon, which is energy and carbon intensive to mine and refine. Crystalline silicon (in the form of sand or quartz) must first be mined from the Earth’s surface, then refined at high temperatures and subjected to intense chemical processing to be suitable before it is used in a photovoltaic cell. There is much debate over the actual size of a solar panel’s carbon footprint, but generally, after a few years, solar panels payback their carbon debt. However, with production of solar panels moving to cheaper markets in Asia, there are concerns about the regulations around emissions and chemical byproducts being more lax than in Europe or North America.
Wind turbines having a 20 to 30 year lifespan, during which they are able to payback the carbon emissions that occur before they are operational. Most of the associated emissions occur during construction, with offshore wind farms having higher lifecycle greenhouse gas emissions than on-shore farms since more concrete is used for underwater supports.
Wind energy emits less carbon dioxide equivalent than any other major renewable energy source. Most estimates of wind turbine emissions during their lifecycle are between 0.02 and 0.04 pounds of carbon dioxide equivalent per kilowatt-hour.
Biomass power generating plants release nitrogen oxides, sulpur dioxide and carbon dioxide. However, the carbon dioxide it releases may not result in a net increase of atmospheric carbon dioxide, especially if the biomass resources originate from a sustainable source. If sustainably managed, biomass is considered to be a carbon neutral, renewable energy source.
It is difficult to measure the exact carbon footprint of biomass and bioenergy, as the resource can come from dedicated land, such as crops grown specifically for biomass, or undedicated land, such as forest or landfill sites. In general, bioenergy collected and burned from dedicated land is less sustainable than bioenergy from wastes, such as landfill gas or animal waste.
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