The Peninsula Daily News, Sunday, 10/10/10, page A4 reported that the Forks biomass boiler would burn 32 tons of wood chips every 2 or 3 weeks.

That is probably not year round, so “annual basis” may be meaningless. There may be considerably less burned on Saturday, Sunday, and school holidays.

Here are some calculations on a daily basis, assuming equal burning seven days per week. I believe we can assume, however, that the stuff in the air will be more concentrated on school days. My “thing” is CO2. You can develop some ratios to apply to these CO2 calculations to estimate things like SO2 and PM.

Additional Fact: From the atomic weights, the relation 44/12 can be used to calculate the amount of CO2 from the amount of carbon.

General Assumptions:

(1). The carbon content of the wood chips is 50 percent.

(2). The amount of carbon monoxide produced is low enough that it can be ignored in the calculation. An adjustment may be made, say 0.2 percent of the CO2 is CO, but it only decreases the CO2 by, say 0.03 percent. That should be on the high side!

Maximum Assumption --- 32 tons of wood chips every 2 weeks:

32 tons of wood chips/14 days = 2.29 tons of wood chips/day

2.29 tons of wood chips/day x 50 percent carbon = 1.14 tons of carbon/day

1.14 tons of carbon/day x 44/12 = 4.2 tons of CO2/day

Minimum Assumption ---- 32 tons of wood chips every 3 weeks:

32 tons /21 days = 1.5 tons/day

1.5 tons/day x 50 percent carbon = 0.75 tons carbon/day

0.75 tons carbon/day x 44/12 = 2.75 tons of CO2 per day

Conclusions: We have a range of 2.75 tons to 4.2 tons of CO2 each day of the week. Based on some calculations not shown of just a 5-day week, I believe we can say that the CO2 output each school day will be 3 tons to 5 tons, and perhaps a greater concentration of CO2 during school hours.

Perspective: Using the 2.75 to 4.2 ton range, we could say that the burner is like having 2,500 to 3,800 more adults in the area (footnote 1) or like having 167 to 255 more cars in the neighborhood (footnote 2), or it would be almost 12 to 18 cars circling the school continuously (footnote 3), or 70 to 110 cars with 2 liter engines idling at 800 rpm in the parking lot, also 24/7.

It is important to remember that the emissions will come from a smokestack whose outlet is 50 feet up and will be ejected upwards, not from ground level and horizontally.

Things get considerably worse if they add 2 megawatts of “cogeneration.” That would add something around 110 tons of CO2 per day, equivalent to another 100,000 people in the area, or 460 cars driving continuously around the school, or 2,900 cars with 2 liter engines idling at 800 rpm in the parking lot, also 24/7.

Footnotes: (1). Assumes each person exhales 11,000 liters/day containing 5 percent CO2.

(2). Assumes the average car is driven 12,000 miles/year and gets 20 miles per gallon of gasoline. A gallon of gas produces 20 pounds of CO2.

(3). Same assumptions as (2) except the vehicle is driven continuously at 20 mph.

The previous calculations that I provided were based upon what the input to the boiler was projected to be. It appears those inputs were for about one half its total capacity. If you double my previous numbers, you are close to being correct.

I just learned that the boiler is a 3 MMBtu one. (source: jhkelly.com). Assuming that to be “per hour” leads to the right calculations.

With the capacity, but without the input quantity for that capacity, I turned to a different method.

The easy method would be to just take 1/140 th of the Nippon quantities. (Nippon’s proposed boiler is 420 MMBtu/hr. I saved that as a double check).

This different method came from looking at the coal-fired plants at Boardman, OR and Centralia, WA. I tried it on Nippon and got almost identical results as the method I used there and for the previous Forks data. It would appear that sub-bituminous coal from Wyoming is about the same as bone-dry wood, which I wouldn’t have guessed.

Assume 15 days/yr downtime for maintenance; Uses the energy in sub-bituminous coal, 8,368 Btu/lb, and 49 percent carbon content like the coal plants (source: jordancoveenergy.com). CO2:C ratio of atomic weights is 44/12.

3 MMBtu/hr x 24 hr/day = 72 MMBtu/day

72 MMBtu/day x 350 days/yr = 25,200 MMBtu/yr (footnote 1)

25,200 MMBtu/yr x 1,000,000 Btu/1 MMBtu = 25,200,000,000 Btu/yr

25,200,000,000 Btu/yr / 8,368 Btu/lb = 3,011,472 lb/yr

3,011,472 lb/yr x 49 percent = 1,475,621 lbs/yr, carbon

1,475,621 lbs/yr,(C) x 44(CO2)/12(C) = 5,410,610 lbs/yr,(CO2)

5,410,610 lbs/yr,(CO2) / 2,000 lbs/ton = 2,705 tons/yr,(CO2)

2,705 tons/yr,(CO2) / 350 days/yr = 7.7 tons/day,(CO2)

This is the CO2 output of about 7,000 adults each day.

Or, it would be like having about 200 cars with 2.0 liter engines idling at 800 rpm, 24/7, year-in, year-out, nearby.

(footnote 1. Comparisons, approximate

Inputs in MMBtu/yr ---

Forks 25,200

Nippon 3,528,000

Boardman 47,000,000

Centralia 104,000,000

Nippon says there boiler is 420 MMBtu/hr. Boardman and Centralia figures are for 2007, from daily.sightline.com)

Copyright © 2010 Donald L. Beeman. All rights reserved.