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Input-Output, More & Less Complete Studies

NOTES ABOUT THE CO₂ LIST

Many of our numbers are calculated from multiple sources. Each calculation and source is in our spreadsheet at xls.CO2List.org That spreadsheet gives complete transparency about where the data come from and what calculations were done to bring all items into comparable units.

A graph comparing CO₂ from different fuels is at CO2List.org/files/fuels.htm

ELECTRICITY

Electricity: US has five main electric grids, with much sharing inside, & little outside. CO₂ output depends on your grid, not your state's plants, which may provide little of your power. For example Idaho has mostly hydroelectric plants, with low CO₂ though possibly high methane (see below). Yet Idaho gets over half its electricity from the Western grid, which emits much more CO₂.

Emissions for the five grids (as well as states) are in our spreadsheet, The spreadsheet also shows the price charged in each state. Many electric companies itemize the cost of generating electricity separately from transmitting it and other costs. Figures here show the total.

US Government estimates refrigerators & freezers use 18% of electricity at home, air conditioning 16%, home heating & furnace fan 13%, water heating 9%, lights 9%, cooking 7%, clothes dryers 6%, TV 4%, dishwashers 3%, computers 2%, other 13%.

Electric companies compile watts and average running times of dozens of types of electric use, from toaster to pool pump: Allegheny, Cornhusker, Victoria, Bluejay

Clothes Dryers are listed as an example of heavy electricity use. Energy websites frequently say that dryers range from 1,800-5,000Watts, but list no examples. Manufacturers generally give higher numbers:

Frigidaire lists all theirs at 4,500Watts.

GE lists all theirs at 5,600Watts.

Samsung ranges from 5,300Watts to 22,000 BTU/hr (6,400Watts).

Bosch lists 18,500BTU (5,400Watts if they mean BTU/hr) and, for the same models, 15A 240V (3,500Watts).

1996 flyer from Roper (Whirlpool) lists 5,400Watts for all models, so this has been a typical level for a long time..

LG, Maytag, Sears, Siemens & Whirlpool websites do not show wattage, but require 30 Amp circuit.

Water heaters can have elements with a range of wattages. 3,500 to 5,500 are commonly available. There are two elements, but only one is on at a time. Energy use in a shower includes the hot water dripping out of the tub spigot (around 1 gallon per minute) as well as water through the shower head. There have been great efforts to adopt low-flow shower heads, but not leak-proof valves to divert water from the tub to the shower, when these share common controls.

Wave energy: We have no data yet on the CO₂ used to manufacture & maintain wave energy systems. California has summarized other environmental effects of taking energy out of waves, such as changes in location of sand, shore dwellers and bottom dwellers. http://www.resources.ca.gov/copc/docs/ca_wec_effects.pdf

Nuclear electricity creates CO₂ at each step of fuel preparation. http://www.energybulletin.net/node/15345

A study at http://www.stormsmith.nl/ notes variation in energy needed to extract ores, depending on their richness. It also criticizes industry studies for over-optimism.

Lower estimates come from Swedish and Swiss producers, but they do not itemize their estimates in any detail. Both refer substantially to ecoinvent.org, a confidential source discussed further below.

The following comments from Swedish producer, Vattenfall, say they are bound by confidentiality agreements. They cite their full study at http://www.environdec.com/reg/021/dokument/EPDforsmark2007.pdf

p. 10-11 will give you some more information on mines and the uranium amounts in the different processing steps. I can not give you any input numbers regarding our suppliers since we have promised not to do so.

You can however find a lot of information on the homepages of the mining companies and in Australia they have a public national database with a lot of information and numbers http://www.npi.gove.au/

Concrete production data have been taken from the Suisse ecoinvent database and include CO₂ from calcining. I cannot give you data from this database since we have bought a license and signed a contract not to disseminate single datasets.

We have used steel production data (excluding the end of life recycling credit) from IISI (International Iron and Steel Institute). These data you can get for free if you contact them and tell them how you will use their data.

Main construction material in our largest reactor (BWR, light water) 1170 MW is (earthquake safe, Swedish conditions)

Steel tot 29 ton/MW

Concrete 369 ton/MW

Copper 0,9 ton/MW

Here you'll find the methodology used: http://www.environdec.com/pcr/pcr0708e.pdf

Construction of transmission and distribution networks has been taken from the Suisse ecoinvent database www.ecoinvent.org

Vattenfall also told a conference they use other sources for impact of these materials:

Primary copper: ICA (International Copper Association)

Copper products: European Copper Institut (Deutsches K upferinstitut – Life Cycle Center)

Electricity: ecoinvent Data combined with IEA (International Energy Agency) statistics on

electricity generation mixes for nations, regions etc.

Fuels: ecoinvent

Aluminium: EAA (European Aluminium Association)

Plastics: PE Plastics Europe (former APME Association of Plastics Manufacturers in Europe)

Chemicals: PE Plastics Europe (former APME Association of Plastics Manufacturers in Europe), and ecoinvent

Electronic components: EIME (Environmental Information and Management Explorer) EcoBilan

Transports: NTM or regional alternatives1

Waste management, other construction material: ecoinvent

The Swiss nuclear producer, NOK, provides the answers indented below. They did not provide data on their mines or amounts of material used in construction. They did say that they omit the work of mining bentonite to protect waste permanently. Page numbers refer to the full Swiss study at http://www.environdec.com/reg/epd144e.pdf]

Generally, all emission factors for background processes (e.g. production of concrete, steel or chemicals) as well as emission factors for transport services were taken from the ecoinvent database (http://ecoinvent.org/). The database provides very detailed documentation for all modeled processes and also includes information on e.g. CO₂ emissions from concrete production.

p.18 shows grams of greenhouse gases for 10 categories. Is there any more detail about how these 10 numbers were calculated? For example what were the fuel and production at the ISL mine or the other upstream processes? Or the concrete, steel or money used in construction, with factors for greenhouse gases? Does the concrete include just heat, or also the CO2 released from calcining CaCO₃ => CaO + CO₂ ?

The CO2 released from calcining is included. Check ecoinvent documentation for details.

p.35 describes permanent waste storage in a mountain, and p.18 shows 0,51 g CO₂e/kWh for "waste treatment." Does this number include the permanent storage? Excavating the caverns as well as mining and placing the bentonite? I assume it does not include any permanent office or guards to warn people away from the area.

The number includes all aspects of the final repositories for all waste types. In addition to the excavation of the caverns and bentonite filling also the construction of storage casks as well as the construction and dismantling of an encapsulation facility is considered. The environmental impact of guards or a permanent office building is negligible compared to other activities and has therefore not taken into account.

p.9 gives the number of kilometers of transmission network for two voltages, and p.25 says grid infrastructure emits 0,151 g CO2e/kWh. Is the CO2/kilometer needed for construction the same for both voltages, or what are the factors for each voltage?

Emission factors are not the same for the all voltages as different materials in different quantities are used. Emission factors for the construction of transmission networks were taken from the ecoinvent database.

Permanent storage None of the studies includes permanently guarding or monitoring the storage of radioactive waste. Even small emissions per year for guards and monitors become noticeable when multiplied by "the tens of thousands of years during which the waste will be hazardous" or "millions of years" of radioactivity Yucca Mountain fact sheet from US Dept. of Energy.

An organization capable of maintaining maps, education about risks, and guards, requires substantial resources. Few organizations have even lasted 2,000 years: claimants include the Catholic church, some aboriginal groups and pueblos, and governments of China, Iran and Ethiopia, though one doubts if any of them could have defended poisons from all enemies for all that time, and how much CO₂ they would have used in trying.

The spreadsheet includes a hypothetical long term expense of $5 billion per year. This is 700,000,000 pounds CO₂e per year (Weber & Matthews) for 40,000 years. This adds about 0.6 pounds CO₂ per kWh, depending on the size of the waste site. Discounting future spending can be legitimate, based on inflation and increased wealth. However it is unwise to discount future CO₂, since CO₂ emissions per person will become steadily more limited and valuable if world population grows or other CO₂-releasing activities are invented.

Military Defense: Aside from a small allowance for nuclear waste, the fuel estimates exclude CO₂ for military defense. Some have argued (a) the US military spends (and so releases CO₂) heavily to defend oil supplies, (b) nuclear plants and waste repositories need to be and are defended against terrorists and conventional attack, (c) large hydroelectric dams upstream of cities have been and are military targets. For example River at the Center of the World (Winchester 1997, 2009) notes the World War II attacks on Ruhr dams and two army divisions defending the Three Gorges Dam, confirmed by the Guardian, Dai Qing and Sino Daily.

It seems beyond the scope of this website to allocate military emissions to these or other targets. Presumably coal, solar, biofuels, and wind power are less subject to attack.

Hydroelectricity: The highest greenhouse gas emissions per kilowatt hour are from shallow tropical reservoirs which flood & decay large areas relative to the power generated. Even so the highest figures shown are underestimates, since they omit gas released at turbines.

The best overview is by Farrer at http://www.up.ethz.ch/education/term_paper/termpaper_hs07/Farrer_rev_termpaper_hs07.pdf. She explains clearly where the CO₂ and methane come from and go, citing a range of studies. Larger wood of many species does not decay under water; 42% does decay. Reservoirs also convert to methane some of the flooded carbon, as well as some of the carbon coming in from detritus in tributaries. Methane forms by decay in the absence of oxygen (anaerobic). The bottom of reservoirs is often low in oxygen in the tropics because surface waters are warm, stay on top, and mix little with the bottom. Oxygen is also low under frozen surfaces. Measurements in Finland and French Guiana show more Carbon becomes methane in the tropics than in cold climates. The methane is released primarily when water runs through the turbines.

Besides the reservoir, CO₂ is also released from quarrying, earthmoving, concrete manufacture, and building the turbines, though the only study in the spreadsheet shows it is not as significant as CO₂ from reservoirs.

The Swedish hydroelectric producer, Vattenfall, uses data at odds with other researchers, to report low emissions, of 3.1 g CO₂/kWh (0.007 pounds/kWh) from flooding the land. Their full study is at http://www.environdec.com/reg/088/dokument/08_waterEPD.pdf. They give the explanation indented below. The explanation cites Adams of Oak Ridge National Lab for a figure of 10,000 tonnes of Carbon per square kilometer of Boreal soil (100 tonnes/hectare). Adams' data are at http://www.esd.ornl.gov/projects/qen/carbon12.html and actually show 129 tonnes of Carbon per hectare of Boreal soil, not 100. Later figures from Oak Ridge (Houghton & Hackler 2001).say 206 tonnes per hectare in Boreal soil. Furthermore the Carbon in surface vegetation removed before inundation also needs to be counted, since it decays or burns (a small part would have been made into products which in turn are disposed of during the 100 year time frame Vattenfall uses). Vattenfall also says their reservoirs absorb CO₂, through the action of algae, though a variety of researchers have measured gas exchanged at reservoir surfaces, and find CO₂ being generated, not absorbed. All these figures and sources are compared in the spreadsheet. Vattenfall's explanation follows:

The vegetation is removed before inundation, but there is still carbon in the ground itself and according to the ORNL database (Adams 1998), it amounts to 10 000 ton/km² in boreal areas and 50% is assumed to degenerate during 100 years (which has been assumed to be the technical service life of the dams and water storages).

Since the water flow becomes slower when building a dam there will also be an uptake of CO₂ in growing biomass (algae etc) the amount depending also on latitude and in larger storages there will also be a renewed binding of carbon in the sediments after some time. "

Adams, D. D. and Van Eck, G. T. M. (1988) Biogeochemical cycling of organic carbon in the sediments of the Grote Rug reservoir. - Archiv für Hydrobiologie, Supplement. 31:319-330.

Adams, J. (1998) An inventory of data, for reconstructing 'natural steady state' carbon storage in terrestrial ecosystems. - ORNL, Tennessee, USA: INQUA Terrestrial Carbon Commission Resource.

Axelsson, E. (1999) A life cycle assessment perspective on hydroelectric power, greenhouse gases and biodiversity. - Stockholm, Sweden: University of Stockholm; B.Sc.Thesis.

Bergström, A.-K., Algesten, G., Sobek, S., Tranvik, L. and Jansson, M. (2004). Emission of CO₂ from hydroelectric reservoirs in northern Sweden. - Archiv für Hydrobiologie 159:25-42.

Brydsten, L.; Jansson, M.; Andersson, T., and Nilsson, Å. (1990). Element transport in regulated and non-regulated rivers in northern Sweden. - Regulated Rivers Research and Management 5:167-176.

Callender, E. and Smith, R. A. (1993) Deposition of Organic Carbon in Upper Missouri River Reservoirs. - pp. 65-79. I: Kempe, S.; Eisma, D., and Degens, E. T. (eds.) Transport of Carbon and Nutrients in Lakes and Estuaries. Hamburg, FRG: Mitteilungen aus dem Geologisch-Paläontologischen Institut der Universität Hamburg; Part 6, 319 pp.(SCOPE/UNEP; v. Sonderband 74).

Egerup, J. (2001) Vattenkraftens bidrag till emissioner av växthusgaser. Kalmar, Sweden: Högskolan i Kalmar; B.Sc.Thesis.

Johansson, M. (1999) Turnover of organic matter in a hydroelectric reservoir - especially the carbon exchange between the atmosphere and the water. - Uppsala, Sweden: Uppsala University School of Engineering, Aquatic and Environmental Engineering; M.Sc.Thesis.

St.Louis, V. L.; Kelly, C. A.; Duchemin, E.; Rudd, J. W. M., and Rosenberg, D. M. (2000 ). Reservoir Surfaces as Sources of Greenhouse Gases to the Atmosphere: A Global Estimate. - BioScience 50:766-775.

Svensson, B. S. (2000) Greenhouse gas emissions from hydroelectric reservoirs - the need of a new appraisal. - Presentation made at the COP6 Conference, Den Hague, The Netherlands.

Svensson, B. S.; Kyläkorpi, L., and Blümer, M. (1996). Vattenkraftens bidrag till växthuseffekten. - Pp. 21-32 I: Zuber, A. (secretary) Klimatdelegationens årsrapport 1996. Stockholm, Sweden: Delegationen för Klimatfrågor.

DRIVING

Speeds of cars greatly affect their fuel consumption and therefore the amount of CO₂ they release per mile. Slight changes in speed can raise or lower miles per gallon and CO₂ per mile by 20%.

The slogan, 52 saves CO₂, reflects the most efficient speed for cars. Manufacturers optimize cars for 46-58 mph, since most of the EPA Highway test and 6% of the City test are at these speeds.

A study of cars popular in the 1990s showed their most efficient speeds were usually 46 - 53 miles per hour, with one car less and one car higher. We have not found more recent data, but the pattern has probably not changed much, since the EPA test has not changed.

	Speed (MPH) with Best Fuel Efficiency	Fuel Efficiency (MPG) Achieved at This Speed
Subaru Legacy	31	40
Geo Prizm	46	45
Chevrolet Pickup	46	28
Mercury Villager Van	51	33
Olds 88	53	35
Olds Cutlass	63	25

Car magazines and manufacturers need to provide similar data on MPG at different speeds for new cars. Boating magazines and builders regularly report MPG by speed for boats (fuel.BoatWakes.org), so the lack of data for cars is surprising. In your own car, a trip computer would find its best speed, and encourage you to drive frugally.

A graph and supporting data show MPG at speeds from 0 to 75 mph, for each car in the study above. The data come from West, McGill, Hodgson, Sluder & Smith, "Development and Verification of Light-Duty Modal Emissions and Fuel Consumption Values for Traffic Models," Oak Ridge National Laboratory March 1999.

Driving 52 mph also reduces stress on the car, which hits bumps less hard, and on the driver. For each hour which could be driven at 60 mph, driving 52 mph adds 9 minutes. For each hour at 70 mph, driving 52 adds 21 minutes.

EPA tests: The EPA highway test for cars is primarily at 46-58 mph, plus one start and one stop, so the average speed is 48 mph. The testing laboratory adjusts resistance on the wheels to reflect wind resistance and weight. EPA reports 78% of the lab mpg to adjust for hills, etc., which are not measured in the lab.

The EPA city test has frequent acceleration & deceleration between 0 and 30 mph. 6% of the test time is cruising at 55 mph. EPA reports 90% of the lab mpg to adjust for hills, potholes, etc., not measured in the lab.

INPUT-OUTPUT, MORE & LESS COMPLETE STUDIES

Input-Output analysis is used by economists to measure how industries directly and indirectly use the products of other industries, such as energy. It is important to use it to measure energy use, and therefore greenhouse gas emissions in many industries, since it adds indirect uses to the direct uses in those industries.

Studies using input-output (IO) analysis are more complete than others, since IO includes CO₂ from all the suppliers. Simpler studies just measure direct emissions by a manufacturer, its power supplier, and sometimes its shippers. "Direct emissions from an industry are, on average, only 14% of the total supply chain carbon emissions (often called Tier 1 emissions), and direct emissions plus industry energy inputs are, on average, only 26% of the total supply chain emissions" http://pubs.acs.org/doi/full/10.1021/es703112w

Care needs to be taken that the sector as defined in the IO model matches the work being estimated. Berkeley researchers applied the Carnegie-Mellon EIOLCA model to car manufacturing and found results similar to more detailed item-by-item estimates. An Australian researcher found much lower IO-based estimates for road construction than his item-by-item estimates, probably because the construction sector in his IO model is much wider than road construction and includes activities with lower greenhouse gases. These examples are in the spreadsheet on the Cars tab.

Carnegie-Mellon researchers using IO found much higher greenhouse gas emissions from food production than food companies using methods of the Carbon Trust. These examples are on the Products tab of the spreadsheet. In their EIOLCA.net model, Weber reports in a 16Ap'09 email,

1) Process CO₂ emissions [from calcining concrete] are included.

2) pipeline leakage methane is, but hydro reservoirs are not due to the aggregate electricity sector.

3) air travel is CO₂ only due to the uncertainty in contrail effect.

4) LUC [Land Use Change] not included due to lack of data (but it can be included in such a model; the US inventory just doesn't allow us to do it with any resolution).

5) gas flaring is included."

Ecoinvent.org is a Swiss organization with estimates of CO₂ and other impacts of many industrial processes and products. They charge 1,800 Euros for access. Ecoinvent's public documents imply they do not use Input-Output method, but try to itemize each input, and the inputs for that input, etc. Ecoinvent recognizes that CO₂ from capital goods can be substantial, and recommend it be included "where relevant! Criteria need to be defined!" (exclamation points in original). They provide a free example of their information for hard coal, which cites an internal ecoinvent report as its source. It gives 30 pounds of CO₂ per therm, higher than our other sources. Access is free for schools outside the OECD, so perhaps a researcher there can report more on how their numbers were derived and compare more of their numbers to other sources.

MEASUREMENT UNITS

The industry uses a mix of English and metric units, along with needlessly large, obscure, units. For example

Teragrams carbon per quadrillion Btu means grams per thousand BTU.

Metric tonnes or mega-grams per million dollars means grams per dollar.

Kilotonnes of CO₂ per million US$ means kilos per US$

Prefixes are defined at http://en.wikipedia.org/wiki/SI_prefix, such as

k, kilo-, thousand, 10³

M, mega-, million, 10⁶ However MBTU usually means thousand BTU, rather than million BTU

G, giga-, billion, 10⁹

T, tera-, trillion, 10¹²

P, peta-, quadrillion, 10¹⁵

Our spreadsheet converts all these to pounds of CO₂.

CARBON OR CO₂?

CO₂ is reported by weight (actually mass), since its size goes up with temperature and down with pressure. A cubic foot or gallon is not meaningful, since it is not comparable from place to place. It could be reported by the number of atoms, but the numbers would be so large they would be hard to work with.

The weight of CO₂ is usually estimated, not by capturing & weighing it, but by estimating (a) how much weight of Carbon was present to start with (in gasoline, wood, coal, etc.), and (b) what percent of the Carbon combines with oxygen to make CO₂. This is typically around 99%. Each 12 pounds of Carbon becomes 44 pounds of CO₂, because of the relative weights of Carbon and oxygen atoms.

The main exception happens when oxygen is scarce. If water is also scarce, then some Carbon may remain as soot. If water is present (such as an animal's stomach, and the bottom of a reservoir or landfill), then some Carbon may combine with water to make Methane: 2C + 2H₂O => CH₄ + CO₂. Since a pound of Methane warms the earth 25 times as much as a pound of CO₂, it is important to account for any creation of Methane.

Weights of Methane and other greenhouse gases, such as N₂O created when bacteria break down fertilizer, are usually multiplied by standard factors to reflect the amount of CO₂ which would warm the earth just as much over the next 100 years. For example pounds of Methane are multiplied by 25. Then all the gases are added up and reported as a weight of CO₂ equivalent. This has been done in our figures for meat, dairy, hydroelectric power, airplanes, and other topics.

Some websites report data on CO₂, and some report Carbon. The weight of Carbon in CO₂ is 12/44 of the weight of the CO₂ (because of chemical formulas) so either works if you're consistent.

This website uses reports CO₂ , because it is CO₂ which warms the earth. The US Energy Information Administration (EIA) explains why they sometimes use Carbon:

"Because most fossil fuels are 75 percent to 90 percent carbon by weight, it is easy and convenient to compare the weight of carbon emissions (in carbon units) with the weight of the fuel burned. Similarly, carbon sequestration in forests and soils is always measured in tons of carbon, and the use of carbon units makes it simple to compare sequestration with emissions."

http://tonto.eia.doe.gov/FTPROOT/environment/057398.pdf p.3 (p.16 of pdf)