Hey guys,
Returning from work this morning I drove by the local 401 Power Plant when I noticed a yellow/brown smoke coming out of the two stacks. I knew it was a natural-gas power plant before I bought the place here, but I always assumed natural gas was a clean burning fuel – Seeing the smoke I became curious, if not slightly alarmed.
]I searched this message board for any other threads; some noise but nothing informative so I bit the bullet did my own research. I’ll leave the results below for any one else curious. I’ll start with a quick summary and continue on with details/sources if you're interested in further reading.
Summary:
Natural-Gas is definitely not clean; however, out of all the other possible fossil fuels available for power generation, it's a good choice here (cheap and efficient).
The yellow/brown smoke I saw is largely Nitrogen Dioxide (NO2). It can be nasty stuff at high enough concentrations but not at the levels this plant is dishing out. I.E. It's safe.
Just to put it in perspective, based on my rough estimation, the 7.7Km stretch of highway that runs through Milton, generates roughly an equal amount of NOx.
Now the Details:
Plant Name: Halton Hills Generating Station
Rated: 683 MW (Mega Watt).
Plant type: Combined Cycle 2X1
Fuel: Natural Gas (Tapped from the Union Gas pipeline).
Owner: TransCanada.
http://www.powerauthority.on.ca/clean-energy/halton-hills-generating-station-6415-mw-halton-hills
http://www.transcanada.com/docs/Key_Projects/HH_Fact_Sheet.pdf
How it works:
Two gas turbines (think jet engine) fueled by natural gas (instead of jet fuel) burn a gas-air mix at very high pressure. The super heated pressurized exhaust is used to spin a massive electrical generator.
The remaining hot exhaust from each gas turbine is channeled into a heat recovery exchanger which generates steam.
The steam from both exchangers is combined and fed into another turbine (steam powered) which spins an additional electrical generator. The remaining steam is cooled / condensed back into water. Remaining exhaust is expelled out of the smoke stacks.
http://en.wikipedia.org/wiki/Combined_cycle
Emissions / Exhaust:
Almost all the exhaust gases from this plant are invisible except Nitrogen Oxides (NOx) [translucent yellow/brown] and Steam (Water) [white opaque plumes] which you may see from time to time.
The exhaust makeup is as follow (figures based on a EU study):
CO2 (Carbon Dioxide) 99.804% (56100 g/GJ [grams per Giga Joule])
SO2 (Sulfur Dioxide) 0.001% (0.68 g/GJ)
NOx (Nitrogen Oxides) 0.166% (93.3 g/GJ)
CO (Carbon Monoxide) 0.026% (14.5 g/GJ)
Other (Organic compounds / particles) 0.003% (1.68 g/GJ).
All these gasses can be toxic in high enough concentrations and as such are considered pollutants especially Nitrogen Oxides - which can cause respiratory problems such as asthma, acid rain etc. Even at low concentration.
Monitoring:
Fortunately, Environment Canada sets strict emission limits. Atmospheric pollutant concentration must be lower than allowable maximum safe limits (See: Health Canada).
The plant’s emission is monitored by Environment Canada and is posted in their NPRI Database. 2010 report for our plan can be found here (NOTE: the data available to the public is 2 years old).
The data is collected by the plant operator and is than submitted to Environment Canada's database through a web portal (Called the Single Window System).
Environment Canada will monitor reported emissions and will also periodically audit the whole data-collecting/reporting process in order to keep the operator in-line (QA/QC process).
Pollution Impact:
Anyway, assuming all these systems / processes work as advertised:
Total release of Nitrogen Oxides for our plant in 2010 was 179 metric tonnes. To put it into perspective (when compared in volume to liquid water); we’re looking at about 6 average size swimming pools of this stuff being released into surrounding atmosphere (over the course of 1 year).
179,000 [kg] / 1443 [kg/m^3] (Density of NO2 in liquid form) equates to 124 m^3 (cubic meters).
124[m^3] / 20 [m^3] (aprox volume of a standard 5m by 3m pool) = 6.2.
Though that may seem alarming, lets compare that to Highway 401:
Traffic volume for Milton in 2008 was 114,900 cars (daily). Figures pulled from Ministry of Transportation here.
For simplicity I’ll generalize each vehicle’s emission and use the Canadian Medium Duty NOx emissions average (2005) of 0.33g/mile (0.53g/km) pulled from here.
The stretch of highway starting at 5 Line to Tremaine Rd is 7.7 KM.
Sum result gives us ~171 metric tonnes per year
0.53[g/km]*7.7[km]*114900 [vehicles/day]*365[day/year]
One thing to note though is: that environmental impact from a single concentrated source (plant), and a dispersed source like the 7.7km stretch of highway, has a different impact in immediate vicinity of said plant.
Conclusion:
NOx emissions from this plant no longer bother me. It would be nice to see/read the original Environmental Study submitted to the Ministry and/or City (?) for this Particular plant before its construction was approved - but personally, I'm content for now.
However, what this entire exercise has truly opened my eyes to is; The gigantic amount of CO2 emissions we're spewing into out into the atmosphere as a species
. Environment Canada (in my opinion) is doing a satisfactory job tracking this crap in our own backyard, I doubt that the majority of the world is doing the same. I don't see how the Earth's atmosphere can not sustain such levels for long...Edit: Spelling/Grammar corrections.
