Nanticoke generating station, the largest coal-fired power plant in North America, is testing biomass as a replacement for coal.
The Ontario government has passed legislation that all coal plants in the province be phased out by 2014. This is spurring aggressive initiatives to find possible replacements for coal before the 2014 deadline.
Biomass is currently on the testbed for the Nanticoke station. It has been proposed to burn biomass instead of coal, as a source of energy. Biomass is plant material such as wood, husks, and switchgrass pellets. Biomass is considered carbon-neutral because it produces no net carbon emissions when burned. As a plant grows it captures carbon dioxide from the atmosphere using photosynthesis. This carbon is stored in the plant tissue. When burned it releases the same amount of carbon dioxide that it absorbed during its growth. Therefore, it is carbon neutral.
On the other hand, burning coal, or any other fossil fuel, is not considered carbon neutral because it releases carbon emissions into the air that have been “stored” for millions of years. Fossil fuels formed from ancient biomass, but their carbon has not been part of the earth cycle for millions of years, and so their release can alter the current ecological balance as we know it.
In addition to carbon dioxide, coal also emits other pollutants such as sulfur dioxide, mercury, and nitrogen oxide.
Biomass is a much safer alternative, producing no sulfur or mercury emissions, and significantly less nitrogen emissions than coal.
Biomass such as wood waste and switchgrass are currently being considered for the Nanticoke plant. Switchgrass is especially favorable due to its fast growth rate and minimal fertilization requirements. It is a robust plant that can grow even on marginal land.
How much biomass is needed?
The use of biomass for energy must be managed with a sense of sustainability. It would take a very large area of biomass growth to provide the amount of energy needed for large scale power generation. Looking at the following calculation you can see why.
Using switchgrass as an example, it can produce 6-8 tons of growth per acre every year. The energy density of switchgrass is about 19 gigajoules per ton. So for each acre of land we have 110-150 gigajoules of energy. Let’s use 110 gigajoules to be on the conservative side.
The Nanticoke station has a total power output of 4,096 megawatts. The annual energy output is about 20 billion kWh (ref: http://en.wikipedia.org/wiki/Nanticoke_Generating_Station).
20 billion kWh = 72,000,000 gigajoules.
Now, assuming a thermal efficiency of 35% (common for coal-fired plants), we need 72,000,000/0.35 = 206,000,000 gigajoules worth of switchgrass.
This is equal to 1,870,000 acres of switchgrass, which is equal to about 7,600 km2 of land. This is a very big area to grow switchgrass. I doubt this is feasible.
Below is a picture showing just how much land area would be required for switchgrass. I manually added a black colored square on to a map of Ontario which shows roughly the amount of land area needed for the Nanticoke station. The sides of the square are 90 km x 90 km.
Clearly, it’s just too large a land area.
In fact, even using wood waste (which has a similar energy density as switchgrass) is pushing the limits. You would probably need wood waste from all over Canada to satisfy the demand. But even then, it is just for one single power plant. This certainly wouldn’t be viable if all the coal-fired plants were to switch to biomass.
Biomass is best suited for small scale heating and power generation, where large areas of land aren’t sacrificed, or you’re using biomass that would otherwise go unused, such as crop residue.
There must be another solution. But what? Nuclear power is certainly possible as it produces no emissions. But there is the radioactive waste issue. And no one has yet found a way to safely dispose of it. So it just keeps piling up.
The way I see it, there’s only one reasonable replacement that is as scalable as coal or nuclear plants and with a similar installation cost. And that is wind power. Large scale wind farms can replace all the coal plants in Ontario. To replace the Nanticoke plant it would take about 3000 wind turbines, each rated at 5 MW of power, operating at a capacity factor of 30%, meaning they produce 1.5 MW of power on average. They would occupy an area of about 1000-1200 km2, much smaller than what’s needed for switchgrass. And many of them can be placed offshore, on the water. The great lakes are a rich and untapped source of wind power, so they can go a long way towards satisfying the demand for power.
The nice thing about wind turbines is that they leave a minimal “footprint” on the land. They are essentially “out of the way” to a much greater extent than most any other source of power. In other words, the land isn’t wasted. It can still be used for other things, such as growing crops.
Unfortunately, a real obstacle to something like this is of course NIMBYism (Not In My Backyard). Some claim that wind turbines are ineffective and that they kill birds. It’s true, they do kill birds, but to a small degree, roughly 1-2 bird deaths per turbine per year. The number of bird deaths can be minimized by choosing good sites.
To give you some perspective, if all the electrical generating capacity of the United States were to switch to wind power, the resulting number of bird deaths would be in the neighbourhood of 1-2 million, assuming 1 million wind turbines.
Relatively speaking, wind turbines kill much less birds than vehicles, cats, transmission lines, and the grand-daddy of them all, windows. From these, the number of bird fatalities number in the tens, or hundreds of millions in the United States alone.
But vehicles, cats, transmission lines, and windows form part of an established structure which people have gotten accustomed to and which people need. However, people also need electricity, but at the same time they don’t want to breathe polluted air or deal with hazardous waste. But wait, that’s already happening… So let me rephrase, people want electricity but they don’t want “eyesores” dotting the landscape. Uh-huh, that’s much worse. Right…
Okay, I went on a bit of a tangent here. So just to sum up, it’s time to start thinking globally and on a larger perspective than just our backyards. Renewable energy alternatives aren’t perfect, but in the long run they sure as hell beat what we’re doing now.