During 2009 or 2010, bakers will be asked by the government, insurance companies or other organizations to calculate and report the carbon footprint of their plant(s). Carbon dioxide is a major contributor to Greenhouse Gas (G.H.G.). G.H.G.s are implicated in the destruction of the ozone layer and climate change. Common greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and some refrigerants.
The focus of the calculation for most food plants will be the carbon dioxide and other products from the burning of fossil fuels such as diesel, petroleum and natural gas both on-site and from the purchase of electric power. In addition, wastewater treatment gases such as methane and refrigerants such as the release of hydrofluorocarbons (H.F.C.s) could be in the count. Methane and refrigerants are converted to a carbon dioxide equivalent.
Carbon emissions are measured in metric tons. For example the carbon equivalent of 1 tonne of methane equals 21 tonnes of carbon dioxide.
For government reporting, fuel for cars and trucks will probably be counted by refineries, not individual plants. Biogenic sources such as carbon dioxide emissions from fermentation and from trees will not be counted.
According to the Environmental Protection Agency, industry in the United States was responsible for about one-third of G.H.G. emissions in 2002, and the food sector accounted for about 5% of that, or 106 million tonnes of carbon equivalents. Nationally, transportation accounted for about 27%. The carbon footprint of an individual was about 10.4 tonnes of carbon equivalents each year.
Current legislative proposals require facility action at 25,000 tonnes per year of carbon equivalents.
In an example that follows, the bakery’s carbon footprint is 6,371 tonnes of carbon equivalents. For this illustration, the carbon footprint of a bakery is calculated using a realistic, but still fictional, operation. Generic Bakery in Ohio employs 100 people baking bread and rolls. The bakery operates three ovens and two boilers. Refrigerant is used to cool the mixers, and the plant features a small wastewater lagoon.
The calculation will be for the year 2008 when the bakery operated three shifts five days a week. The identification of the state indicates how the electricity is produced for example, coal or nuclear.
One program to calculate a carbon footprint for energy use may be found at the web site Carbon Footprint http://www.carbonfootprint.com/businesscalculator.aspx.
Bakers may use the tool to calculate their energy carbon footprint by entering the gas usage in U.S. dollars from their bill or the British Thermal Unit (B.T.U.) rating of their equipment in therms. An oven rated at 4 million B.T.U.s per hour is shown as 4 MMBTU. A therm is 100,000 B.T.U.s. For example, Oven 1, at 4 MMBTU = 40 therms x 6,240 hours = 249,600 therms. The bakery also has Oven 2, 5 MMBTU; Oven 3, 6 MMBTU; Boiler 1, 4 MMBTU; and Boiler 2, 4 MMBTU.
However, because equipment does not run full-on, the bakery only used 31,973 thousand cubic feet (MCF) of natural gas. Multiplying 31,973 MCF times the conversion factor 10.25 and entering 327,723 therms in the computer calculator yields carbon equivalents of 1,974 tonnes.
When the cost of the electric bill or the kilowatt hours (kWh) are entered (4,048,230 kWh), carbon equivalents of 3,307 tonnes are generated.
The bakery has a glycol system to cool the mixers. The glycol is cooled by the refrigerant R-404A. During the year the bakery had leaks totaling 500 lbs of R-404A. The web site www.carbonissues.com gives the carbon equivalent of 3,922. Multiplying 500 times 3,922 generates 1,961,000, divided by 2,204 lbs (which equals 1 tonne) and equaling 890 tonnes of carbon equivalents. The refrigerant with the best energy efficiency and capacity with the lowest global warming potential is R-407A.
The bakery sends 3,650,000 gallons of wastewater a year to a small lagoon for treatment. The lagoon is not aerated so the methane from the biological activity in the lagoon is released. Methane emissions may be modeled using E.P.A. Water 9 found at www.epa.gov/ttn/chief/software/water/index.html#support. Emission estimates may also be based on Biological Oxygen Demand (B.O.D.) using conversion factors.
To estimate the methane, bakers may use the B.O.D. produced with a conversion factor of one kg of B.O.D. equating to .25 kg of methane. The B.O.D. produced is 83,713 lbs or 37,972 kg per year. Multiplying 37,972 kg by .25 equals 9,493 kg or 9.5 tonnes of methane. When 9.5 is multiplied by 21, a carbon equivalent of 200 tonnes is generated.
Emission coefficients for fuel oils and other substances may be found at www.eia.doe.gov/oiaf/1605/coefficients.html.
Sample bakery carbon footprint:
• Burning natural gas — 1,974 tonnes
• Electricity — 3,307 tonnes
• Refrigerant loss — 890 tonnes
• Methane — 200 tonnes
This bakery’s carbon footprint is 6,371 tonnes of carbon equivalents. Should production have been higher, the carbon footprint may have been close to 10,000 tonnes.