Featured Research

from universities, journals, and other organizations

Carbon hitches a ride from field to market: Agriculture's mobile nature makes predicting regional greenhouse gas impacts more complex

Date:
August 3, 2011
Source:
DOE/Pacific Northwest National Laboratory
Summary:
New research that tracked carbon's movement in US crop production found that regional carbon sinks and sources are created because agricultural crops are consumed far away from where they're grown.

Based on US crop production, scientists determined which American regions are carbon sinks, or those that take in more carbon than release it, and carbon sources, or those that release more carbon than they take in. Their calculations showed that the most agriculturally active regions, shown in blue, are carbon sinks while the regions with larger populations, shown in red, are carbon sources.
Credit: PNNL

Today, farming often involves transporting crops long distances so consumers from Maine to California can enjoy Midwest corn, Northwest cherries and other produce when they are out of season locally. But it isn't just the fossil fuel needed to move food that contributes to agriculture's carbon footprint.

New research published in the journal Biogeosciences provides a detailed account of how carbon naturally flows into and out of crops themselves as they grow, are harvested and are then eaten far from where they're grown. The paper shows how regions that depend on others to grow their food end up releasing the carbon that comes with those crops into the atmosphere.

"Until recently, climate models have assumed that the carbon taken up by crops is put back into nature at the same place crops are grown," said the paper's lead author, environmental scientist Tristram West of the Department of Energy's Pacific Northwest National Laboratory. "Our research provides a more accurate account of carbon in crops by considering the mobile nature of today's agriculture."

West works out of the Joint Global Change Research Institute, a partnership between PNNL and the University of Maryland. His co-authors are researchers at PNNL, Oak Ridge National Laboratory and Colorado State University.

Carbon, carbon everywhere

Carbon is the basis of life on Earth, including plants. During photosynthesis, plants take in carbon dioxide and convert it into carbon-based sugars needed to grow and live. When a plant dies, it decomposes and releases carbon dioxide back into the atmosphere. After eating plants, animals and humans release the plants' carbon as either carbon dioxide while breathing or as methane during digestion.

But the geography of this natural carbon cycle has shifted with the rise of commercial agriculture. Crops are harvested and shipped far away from where they're grown, instead of being consumed nearby. As a result, agriculturally active regions take in large amounts of carbon as crops grow. And regions with larger populations that consume those crops release the carbon.

The result is nearly net zero for carbon, with about the same amount of carbon being taken in as is released at the end. But the difference is where the carbon ends up. That geography matters for those who track every bit of carbon on Earth in an effort to estimate the potential impacts of greenhouse gases.

Digging into data

Agricultural carbon is currently tracked through two means: Towers placed in farm fields that are equipped with carbon dioxide sensors, and computer models that crunch data to generate estimates of carbon movement between land and the atmosphere. But neither method accounts for crops releasing carbon in areas other than where they were grown.

To more accurately reflect the carbon reality of today's agricultural crops, West and his co-authors combed through extensive data collected by various government agencies such as the Department of Agriculture, the U.S. Census Bureau and the Environmental Protection Agency.

Looking at 17 crops -- including corn, soybeans, wheat and cotton -- that make up 99 percent of total U.S. crop production, the researchers calculated the carbon content of harvested crops by county for each year from 2000 to 2008.

Next they used population numbers and data on human food intake to estimate, by age and gender, how much carbon from crops humans consume. On the flip side, the co-authors also calculated how much carbon humans release when they exhale, excrete and release flatulence. They did the same analysis on livestock and pets.

But not all food makes it to the dinner table. The researchers accounted for the crops that are lost due to spoilage or during processing, which ranges from 29 percent of collected dairy to as much as 57 percent of harvested vegetables. Beyond food, they determined the amount of carbon that goes into plant-based products such as fabric, cigarettes and biofuels. And they noted how much grain is stored for future use and the crops that are exported overseas.

National crop carbon budget

Combining all these calculations, the researchers developed a national crop carbon budget. Theoretically, all the carbon inputs should equal the carbon outputs from year to year. The researchers came very close, with no more than 6.1 percent of the initial carbon missing from their end calculations. This indicated that the team had accounted for the vast majority of the carbon from America's harvested crops.

The team found overall that the crops take in -- and later return -- about 37 percent of the U.S.'s total annual carbon dioxide emissions, but that amount varies by region. Carbon sinks, or areas that take in more carbon than release it, were found in the agriculturally active regions of the Midwest, Great Plains and lands along the southern half of the Mississippi River. Regions with larger populations and less agriculture were found to be carbon sources, or areas that release more carbon than they take in. The calculations indicated the Northeast, Southeast and much of the Western U.S. and Gulf Coast were carbon sources. The remaining regions -- the western interior and south-central U.S. -- flip-flopped between being minor carbon sinks or sources, depending on the year.

Informing policy decisions

Next, West would like his team's methods applied to forestry, which also involves the movement of carbon-containing products from one locale to another. Comprehensive carbon calculations for agriculture and forestry could be used in connection with previous carbon estimates that were based on carbon dioxide sensor towers or carbon computer models.

"These calculations substantially improve what we know about the movement of carbon in agriculture," West said. "Reliable, comprehensive data like this can better inform policies aimed at managing carbon dioxide emissions." This research was funded by NASA through the North American Carbon Program.


Story Source:

The above story is based on materials provided by DOE/Pacific Northwest National Laboratory. Note: Materials may be edited for content and length.


Journal Reference:

  1. T. O. West, V. Bandaru, C. C. Brandt, A. E. Schuh, S. M. Ogle. Regional uptake and release of crop carbon in the United States. Biogeosciences, 2011; 8 (8): 2037 DOI: 10.5194/bg-8-2037-2011

Cite This Page:

DOE/Pacific Northwest National Laboratory. "Carbon hitches a ride from field to market: Agriculture's mobile nature makes predicting regional greenhouse gas impacts more complex." ScienceDaily. ScienceDaily, 3 August 2011. <www.sciencedaily.com/releases/2011/08/110803151228.htm>.
DOE/Pacific Northwest National Laboratory. (2011, August 3). Carbon hitches a ride from field to market: Agriculture's mobile nature makes predicting regional greenhouse gas impacts more complex. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2011/08/110803151228.htm
DOE/Pacific Northwest National Laboratory. "Carbon hitches a ride from field to market: Agriculture's mobile nature makes predicting regional greenhouse gas impacts more complex." ScienceDaily. www.sciencedaily.com/releases/2011/08/110803151228.htm (accessed April 17, 2014).

Share This



More Earth & Climate News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Great British Farmland Boom

The Great British Farmland Boom

Reuters - Business Video Online (Apr. 17, 2014) Britain's troubled Co-operative Group is preparing to cash in on nearly 18,000 acres of farmland in one of the biggest UK land sales in decades. As Ivor Bennett reports, the market timing couldn't be better, with farmland prices soaring over 270 percent in the last 10 years. Video provided by Reuters
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Change of Diet Helps Crocodile Business

Change of Diet Helps Crocodile Business

Reuters - Business Video Online (Apr. 16, 2014) Crocodile farming has been a challenge in Zimbabwe in recent years do the economic collapse and the financial crisis. But as Ciara Sutton reports one of Europe's biggest suppliers of skins to the luxury market has come up with an unusual survival strategy - vegetarian food. Video provided by Reuters
Powered by NewsLook.com
How Mt. Everest Helped Scientists Research Diabetes

How Mt. Everest Helped Scientists Research Diabetes

Newsy (Apr. 15, 2014) British researchers were able to use Mount Everest's low altitudes to study insulin resistance. They hope to find ways to treat diabetes. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins