The human carbon budget: an estimate of the spatial distribution of metabolic carbon consumption and release in the United States

Abstract

Carbon dioxide is taken up by agricultural crops and released soon after during the consumption of agricultural commodities. The global net impact of this process on carbon flux to the atmosphere is negligible, but impact on the spatial distribution of carbon dioxide uptake and release across regions and continents is significant. To estimate the consumption and release of carbon by humans over the landscape, we developed a carbon budget for humans in the United States. The budget was derived from food commodity intake data for the US and from algorithms representing the metabolic processing of carbon by humans. Data on consumption, respiration, and waste of carbon by humans were distributed over the US using geospatial population data with a resolution of *450 9 450 m. The average adult in the US contains about 21 kg C and consumes about 67 kg C year -1 which is balanced by the annual release of about 59 kg C as expired CO 2 , 7 kg C as feces and urine, and less than 1 kg C as flatus, sweat, and aromatic compounds. In 2000, an estimated 17.2 Tg C were consumed by the US population and 15.2 Tg C were expired to the atmosphere as CO 2 . Historically, carbon stock in the US human population has increased between 1790 and 2006 from 0.06 Tg to 5.37 Tg. Displacement and release of total harvested carbon per capita in the US is nearly 12% of per capita fossil fuel emissions. Humans are using, storing, and transporting carbon about the Earth's surface. Inclusion of these carbon dynamics in regional carbon budgets can improve our understanding of carbon sources and sinks.

Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

“…Although individually, lateral transport may not be a very large flux, the sum of individual contributions is significant in the calculation of regional carbon budgets (Cole et al, 2007;Ciais et al, 2008;Raymond et al, 2008;Battin et al, 2009;West et al, 2009;Bastviken et al, 2011). Outgassing of CO 2 , originating from terrestrial ecosystems, by freshwater systems, is a significant CO 2 flux to the atmosphere, impacting regional CO 2 budgets.…”

Urban Emissions of CO2 from Davos, Switzerland: The First Real-Time Monitoring System Using an Atmospheric Inversion Technique

“…House heating emissions originate from the combustion of fuel oil at 98.5%, whereas electricity, thermal heating, wood, geothermal, and natural gas represent only 1.5%. Similarly, human respiration from the city represents about 3% of the total direct emissions based on the population of about 12 000 people and using human respiration factor from West et al (2009). Although the inventory provides annual emission estimates for each energy source, no spatial or seasonal references are available.…”

Atmospheric inversion of surface carbon flux with consideration of the spatial distribution of US crop production and consumption

“…The livestock consumption data were calculated in a similar way but also considered different feed consumption rates of different animal species. The consumed amount was assumed to be released back into the atmosphere within the same year as CO 2 through respiration, excretion, and flatus (West et al, 2009). Excretion typically entered the waste treatment facilities within the county, and the emissions were taken into account in the consumption term above.…”

“…Therefore, experiments that adjust for production only are prescribed a 10 % uncertainty in annual NPP distributed over the production regions and weighted with the original matrix Q. Experiments that adjust for both production and consumption use the above method to include production uncertainty as well as an additional 1 % of annual total human consumption (West et al, 2009) and 20 % of the annual total livestock consumption distributed over consumption areas . Additionally, the χ 2 test (Eq.…”