By Julie Smith, Golden, Colorado

These equations and references support the Glass Recycling post.

Equations

1. We would increase recycled glass to RMBC by 267,180 tons per year.

RMBC – 750 tons/day total production, 30% cullet (225 tons/day), 40% local (90 tons/day), 60% out-of-state (135 tons/day)

Windsor – 800 tons/day total production, 16% cullet (128 tons/day), 95% local (121.6 tons/day), 5% out-of-state (6.4 tons/day)

Total Production (both plants) = (750+ 800) tons/day x 365 = 565,750 tpy (tons/year)

Current Cullet (both plants) = (225 + 128) tons/day x 365 = 128,845 tpy

Current Local Cullet (both plants) = (90 + 121.6) = 211.6 tons/day = 77,234 tpy

Current Out-of-State Cullet (both plants) = (135 + 6.4) = 51,611 tpy

Ultimate Goal – 70% Cullet (both plants) = 565,750 tons/year x 0.70 = 396,025 tpy

Total Cullet Increase to Meet Goal = 396,025 – 128,845 = 267,180 tpy

2. Carbon footprint of electricity and natural gas would be decreased by 35,106 tons CO2 per year.

For every 10% increase in cullet, there is a 2.5% reduction in electricity and natural gas to produce glass.1

Total glass produced in U.S. in 2018 was 12.3 million metric tons.2

Total fuel to generate electricity used to produce glass in the U.S. in 2018 was 135 Tbtu (terabtu, 1012 btu).3

Total natural gas used within process to produce glass in the U.S. in 2018 was 123 Tbtu.3

CO2 emissions for fuel as natural gas is 53.60 kg CO2e/mmBTU x 2.2 LBS/kg = 116.7 LBS/mmbtu.4

Increase in cullet = (267,180 tpy increase in cullet)/(565,750 tpy total glass production) = 47.23% increase

Reduction in electricity and natural gas = 47.23% x (2.5/10) = 11.81%

Electricity Reduction:

135 Tbtu x (116.7 LB CO2e/mmbtu) x (106 mmbtu/Tbtu) x (1 ton/2200 LBS) x (mmt/106 ton) = 7.161 mmt CO2e

(7.161 mmt CO2e/12.3 mmt Glass) = 0.582 x 267,180 tpy (tons/year) cullet = 155,499 tpy CO2e total electricity x 11.81% = 18,364 tpy CO2e reduction

Note – CO2e means CO2 equivalent – this is all sources of greenhouse gas emissions normalized to equivalent units of CO2, so their combined impacts can be added.

Natural Gas Reduction:

123 Tbtu x (116.7 x 106)/(2200 x 106) = 6.524 mmt CO2e

(6.524 mmt CO2e/12.3 mmt Glass) = 0.530 x 267,180 tpy cullet = 141,605 tpy CO2e total x 11.81% = 16,724 tpy CO2e reduction

Total electricity and natural gas reduction = 18,364 + 16,724 = 35,088 tpy CO2e

3. There’s a 9.5% reduction in raw materials for every 10% increase in recycled glass,1 so the additional recycled cullet from within Colorado would offset 281,242 tons of raw materials, which is a carbon footprint savings of 25,562 tons CO2e per year to mine the raw materials.

Sand – 0.71 mmBTU/ton5 x 116.7 LB CO2e/mmbtu x 1 ton CO2e/2000 LB CO2e x 0.645 = 0.0265 ton CO2e/ton glass

0.0265 ton CO2e/ton glass x 271,637 tpy glass = 7,198 tpy CO2e

Soda Ash – 5.25 mmBTU/ton5 x 116.7/2000 x 0.225 x 271,637 = 18,306 tpy CO2e

Limestone – 0.09 mmBTU/ton5 x 116.7/2000 x 0.205 x 271,637 = 285 tpy CO2e

Feldspar – 1.37 mmBTU/ton5 x 116.7/2000 x 0.105 x 271,637 = 2,172 tpy CO2e

Total – 26,562 tpy CO2e/year

4. There’s a 10% decrease in sulfur dioxide (SO2), 6% decrease in nitrogen oxide (NOx), and 17% reduction in carbon dioxide (CO2) for every 10% increase in recycled glass, which works out to 49,166 tons of carbon footprint reduction per year.

Total CO2 emissions from chemical reactions in glass production in 2020 was 1.858 mmt CO2e. CO2e is calculated based on emissions of SO2, NOx and CO2, which are converted to equivalent CO2 emissions.6

Total U.S. glass production in 2018 was 12.3 mmt.7

Total U.S. glass industry revenue in 2018 was $30 billion, and in 2020 it was $25 billion.8

U.S. glass production in 2020 is estimated at 12.3 mmt x (25/30) = 10.25 mmt.

Note: 2020 glass is estimated based on industry value because the EPA doesn’t have 2020 production available from gpi.org yet, and to get this information from gpi.org, a membership is required. Total industry market value is available on the internet (sort of) so I used that to estimate 2020 production from 2018, so that total emissions from EPA and total glass production were from the same year.

1.858 mmt CO2e/10.25 mmt glass = (0.181 LB CO2e/LB glass x 2000 LB glass/ton glass) =

362 LB CO2e/ton glass

Note: Steps were eliminated by going directly from mmt/mmt to LB/LB because the ratio doesn’t change for like units.

362 LB CO2e/ton glass x 271,637 tons raw materials = 49,166 tpy CO2e

5. Carbon footprint from transporting cullet and raw materials from out of state would be reduced by 4,100 tons per year.

Cullet Transportation:

Current cullet transported from out of state is 51,611 tons/year.

From Google Maps, mileage from Colorado to each state from which cullet is currently shipped is:

Wisconsin – 1044 miles

Oregon – 1093 miles

Michigan – 1277 miles

Average = 1138 miles

Note: Google Maps gives mileage from center of state if there is no specific address. Also, taking the average assumes that an equal portion of cullet comes from each state. These numbers can be improved with more specific information on cullet quantities and shipping addresses.

Transportation by rail is 310 btu/ton-mile.9

Diesel fuel is 163 LBS CO2e/mmbtu.10

Rail Emissions = (310 btu/ton-mile) x (163 LB CO2e/mmBTU) x (1 mmBTU/106 BTU)

x (1 ton/2000 LB) = 2.2526 x 10-5 ton CO2e/ton-mile

Transportation of cullet by rail = 2.2526 x 10-5 ton CO2e/ton-mile x 1138 miles

x 51,611 tons/year = 1,323 ton CO2e/year

Raw Materials Transportation:

Every 10% increase in cullet offsets 9.5% raw materials, so

267,180 tons of cullet/0.95 = 281,242 tons raw materials offset.

Assume soda ash comes from Wyoming by rail, from middle of state, 339 miles.

281,242 tons x 0.22 x 339 miles x 2.2526 x 10-5 ton CO2e/ton-mile

= 472 tons CO2e

Assume limestone and feldspar come from Wyoming by rail, 339 miles.

281,242 tons x 0.3 x 339 miles x 2.2526 x 10-5 ton CO2e/ton-mile

= 644 tons CO2e

Assume sand comes from Oklahoma, middle of state, 736 miles.

281,242 tons x 0.64 x 736 miles x 2.2526 x 10-5 ton CO2e/ton-mile

= 2984 tons CO2e

Total CO2e offset = 472 + 644 + 2984 = 4,100 tons CO2e/year

Total Transportation CO2e saved per year = 1,323 + 4,100 = 5,423 tons/year

6. All these carbon footprint savings add up like a shopping list – totaling a whopping 115,329 tons per year!

35,088 + 25,562 + 49,166 + 5,423 = 115,239 tons CO2e/year

References

1. www.gpi.org – states that for every 10% increase in cullet, energy decreases by 2 – 3%. I took an average and used 2.5%.

8. https://www.statista.com/statistics/886956/us-selected-figures-glass-product-manufacturing-industry/

9. "The Green Freight Handbook", Environmental Defense Fund, Mather, Jason, Craft, pHd, Elena, Norsworthy, Marcelo, Wolfe, Christina, www.edf.org/freight.