The carbon footprint of cooking is determined by cooking method, cooking time, and cooking location. Carbon footprint calculators for cooking are presented for the following cooking methods:
- Electric Ovens
- Gas Ovens
- Electric Frying
- Gas Frying
- Electric Water Boiling
- Gas Water Boiling
- Microwaving
The calculators assume the average grid electricity for the US, so certain regions will provide more or less carbon emissions for the same energy use. In order to calculate average emissions in the US from cooking, the average mix of natural gas, propane, and electricity for cooking will be assumed. Assumptions of average cooking time will be anchored to the literature whenever possible. The average emissions from cooking are 97.68 g CO2e/MJ, with assumptions outlined at the end of this document.
Carbon Footprint by Household Size
The carbon footprint of cooking depends on how many meals are being cooked at a time. A large share of the energy used from cooking is due to heating the stove or hot plates, so increasing the number of servings of food cooked at a time will increase the efficiency of cooking. The number of servings that can be prepared depends on the size of the cooking instrument, so cooking times or number of pots will depend on the number of servings prepared.
The efficiency of cooking depends on how many people are being served in a meal. The following table was adapted from the US Census Bureau (2018) to determine the number of servings prepared in a meal:
| Household Size | # Households | Total People | Proportion (%) |
|---|---|---|---|
| 1 | 35,740,000 | 35,740,000 | 11.38 |
| 2 | 44,038,000 | 88,076,000 | 28.05 |
| 3 | 19,333,000 | 57,999,000 | 18.47 |
| 4 | 16,468,000 | 65,872,000 | 20.98 |
| 5 | 7,442,000 | 37,210,000 | 11.85 |
| 6 | 2,851,000 | 17,106,000 | 5.45 |
| 7 | 1,714,000 | 11,998,000 | 3.82 |
| Total | 127,586,000 | 314,001,000 | 100 |
Carbon Footprint of Energy Used for Cooking: 97.68 g CO2e/MJ
- The United States emitted 2,046.15 Million US Tons of CO2e in 2016, which generated 4.075 Billion MWh of electricity (EPA, 2018). This yields an average of 0.5021 US Tons of CO2e/MWh, or 126.53 g CO2e/MJ.
- 907.185 kg / US Ton
- 3600 MJ/MWh
- Natural Gas emits 117 Pounds of CO2e/Million BTU (EIA, 2018A), which equals 50.30 g CO2e / MJ.
- Propane emits 18.8% more CO2e/BTU compared to natural gas (EIAA), which equals, 59.75 g CO2e / MJ. Propane cooking will be assumed as a 1:1 substitute for natural gas.
- 61.48 percent of US residences use electric stoves, 32.59% use natural gas stoves, 5.09% use propane, and 0.83% use an assumed 50% mix of propane and natural gas (EIA 2018B). Given these proportions of appliances, the general US cooking carbon intensity is estimated at 97.68 g CO2e / MJ.
Carbon Footprint of Baking in an Electric Oven
To find the heat capacity of specific foods, please see: Engineering Toolbox
Based on a room temperature of 72 degrees. Energy use calculator adapted from Sonnesson et al. (2003) in a validation study modeling 122 electric stoves in Sweden.
Carbon Footprint of Baking in a Gas Oven
To find the heat capacity of specific foods, please see: Engineering Toolbox
Energy use calculator adapted from Sonnesson et al. (2003) in a validation study modeling 122 electric stoves in Sweden. Based on a room temperature of 72 degrees. Converted energy use from an electric oven to gas by the Efficiency Factors stated by Hendron (2006, US Department of Energy), where electric ovens are 11.07% efficient (average of 3 designs) and gas ovens are 6% efficient (average of 2 modern designs). Electric values are thus converted by the ratio of efficiency, which is 1.844:1 for energy used by Gas:Electric ovens. i Canals et al. (2007) states a ratio of efficiency of 1.39:1, which appears ambiguously sourced from another study (unable to locate number referenced from their source). Foster et al. (2007), who makes generalized estimates widely cited by LCA studies for cooking, claims that there is a 1:1 ratio of energy used in gas and electric stoves, however this is contradicted by experimental observation by the US Department of Energy, and thus their value of 1.844:1 is used for this model.
Carbon Footprint of Frying on an Electric Stove
To find the heat capacity of specific foods, please see: Engineering Toolbox
Energy Use calculator adapted from Sonnesson et al. (2003) in a validation study of 14 experiments at various temperatures and pan sizes. The values reported are for a recessed ceramic stovetop instead of a raised cast iron enclosure that is not commonly seen in residential stoves. Temperature elevation of the pan is assumed from 72 degrees to 329 degrees, the median value used in Soneccon et al. (2003). Sonnesson et al. (2003) also erroneously reports their model for pan area, when they used pan circumference to validate their model to experimental observations. Despite this, the model is still valid for real cooking conditions.
Consumer Ecology added a section for heating the food, not included in the model. This is relevant because if a food is being heated from a refrigerator or freezer, the energy required to heat the food will significant raise, however so will the cooking time, as authors of the model suggested. Heat capacity of the food is normalized for 72 degrees room temperature, so if a food started colder than this temperature, the difference must be added to the cooking temperature.
Carbon Footprint of Frying on a Gas Stove
Carbon Footprint of Boiling on an Electric Stove
To find the heat capacity of specific foods, please see: Engineering Toolbox
Energy use calculator adapted from Sonesson et al. (2003) based on 16 boiling experiments and 10 cooking experiments. Based on a room temperature of 72 degrees. Results are valid for water amounts between 300-4000 ml and food amounts between 0-400 grams. A saucepan weighing 560 grams was used for experiments between 150-1000 ml experiments. A saucepan weighing 596 grams was used for experiments between 1001-2000 ml. A saucepan weighing 1480 grams was used for experiments between 2001-4000 ml. There is no section included for the weight and size of the pan because only 3 pans were used to calibrate the models. Models shown only for ceramic heating elements.
Carbon Footprint of Boiling on a Gas Stove
Energy use calculator adapted from Sonesson et al. (2003) based on 16 boiling experiments and 10 cooking experiments. Based on a room temperature of 72 degrees. Results are valid for water amounts between 300-4000 ml and food amounts between 0-400 grams. A saucepan weighing 560 grams was used for experiments between 150-1000 ml experiments. A saucepan weighing 596 grams was used for experiments between 1001-2000 ml. A saucepan weighing 1480 grams was used for experiments between 2001-4000 ml. There is no section included for the weight and size of the pan because only 3 pans were used to calibrate the models. Models shown only for ceramic heating elements.
Converted energy use from an electric oven to gas by the Efficiency Factors stated by Hendron (2006, US Department of Energy), where electric ovens are 75.2% efficient (average of 3 designs) and gas ovens are 41% efficient (average of 2 modern designs). Electric values are thus converted by the ratio of efficiency, which is 1.834:1 for energy used by Gas:Electric ovens. i Canals et al. (2007) states a ratio of efficiency of 1.51:1, which appears ambiguously sourced from another study (unable to locate number referenced from their source). Foster et al. (2007), who makes generalized estimates widely cited by LCA studies for cooking, claims that there is a 1:1 ratio of energy used in gas and electric stoves, however this is contradicted by experimental observation by the US Department of Energy, and thus their value of 1.834:1 is used for this model. In addition, the electric burner model accounts for heating up the cooking element, which is not present in gas stoves because a direct flame is used to heat the pan. The model has been calibrated to experimental observations only for electric burners, so the gas model will assume the same energy requirements, but but in reality the expected energy requirements for gas should be lower.
Carbon Footprint of Microwaving
To find the heat capacity of specific foods, please see: Engineering Toolbox
Energy use calculator adapted from Sonesson et al. (2003) based on 16 microwaving experiments with 4 different microwaves and 2 food types. Results are to reach a desired temperature of the food, so sensor cooking would best approximate the results. To calculate temperature elevation, frozen foods are stored at 0 degrees, refrigerated foods are stored at 40 degrees, and otherwise a room temperature of 72 degrees can be assumed. Most microwaved products will be elevated to near the water boiling temperature of 212 degrees, while some experiments only reached a temperature of 149 degrees. The US Department of Agriculture (USDA, 2011) recommends cooking foods from 145 degrees up to 160 degrees for food safety. The calculator defaults at raising refrigerated food to boiling temperature: 172 degrees.
Data for water evaporation is not readily available. Sonesson et al. (2003) calculates water evaporation by weighing the food before and after cooking. Sonesson et al. (2003) reports an average moisture loss of 15.3% for meat loaf, and 5.0% moisture loss for potatoes. This can be a starting point to approximate moisture loss, but experimental results are needed for all foods.
References
Carlsson-Kanyama, A., & Boström-Carlsson, K. (2001). Energy use for cooking and other stages in the life cycle of food. Stockholm, Sweden: Stockhoms universitet.
EIA: US Energy Information Administration (2018,A) How much carbon dioxide is produced when different fuels are burned? See Link to Source
EIA: US Energy Information Administration (2018,B) Residential Energy Consumption Survey (RECS). See Link to Source
EPA: US Environmental Protection Agency. (2018). Emissions & generation resource integrated database (eGRID).
Hendron, R. (2006). Building America performance analysis procedures for existing homes. National Renewable Energy Laboratory.
i Canals, L. M., Muñoz, I., McLaren, S., & Brandão, M. (2007). LCA methodology and modelling considerations for vegetable production and consumption. Centre for Environmental Strategy, University of Surrey: Surrey, UK.
Foster, C., Green, K., & Bleda, M. (2007). Environmental impacts of food production and consumption: final report to the Department for Environment Food and Rural Affairs.
Sonesson, U., Janestad, H., & Raaholt, B. (2003). Energy for preparation and storing of food: models for calculation of energy use for cooking and cold storage in households. SIK Institutet för livsmedel och bioteknik.
US Census Bureau (2018). Historical Household Tables. Table HH-4. Households by Size: 1960-Present. See Link to Source
USDA (2011) Microwave Ovens and Food Safety. See Link to Source
