Sunday, April 22, 2007

Ag Energy Compared to Oil Production Per Day

As I work to translate how much energy we use to grow, make and move the food we eat I decided to correlate the energy to the amount of oil that OPEC and non-OPEC nations produced each day.

To do this I had to simplify some numbers and I did this mainly be equating all energy use to gasoline. I expect that some people would call this way to much simplification for a very complex set of variables. For many others, however, this can help make sense, bring home, and simplify this complexity. Also, gasoline has a middle of the road energy rating, with diesel having more British Thermal Units (Btu), and propane having less (see BPA's Conversion table), so it is arguably the best vehicle for this work (pun intended).

Using the percentages of energy use discussed in a previous posting about Energy Use in Food, I calculated the number of days of the world's daily oil production across each segment of the ag and food sector:
  • Ag Production: 5.1 days of world oil production
  • Transportation: 3.4 days
  • Processing: 3.9 days
  • Packaging: 1.7 days
  • Food retail: 1.0 days
  • Restaurants & catering: 1.7 days
  • Home preparation & storage: 7.6 days
Here is a screenshot of the worksheet I used to make these calculations. Click on the image for a bigger version. If we just use OPEC's daily output there are almost twice the number of days for each segment.

Thursday, April 19, 2007

Obesity Factoid

Good quote:

“Obesity is associated with a 36% increase in inpatient and outpatient spending and a 77% increase in medications, compared with a 21% increase in inpatient and outpatient spending and a 28% increase in medications for current smokers.”
Source: Strum, R., 2002, "The effects of obesity, smoking, and drinking on medical problems and costs", Health Affairs, 21(2), 245-253

Sunday, April 1, 2007

Ag Emissions and GWP, part 2

I am trying to uncover more Global Warming Potential (GWP) impacts from our food system. Some segments of agriculture are already tracked by the EPA (discussed in Part 1 of this chain): enteric fermentation in domestic livestock, livestock manure management, rice cultivation, agricultural soil management, and field burning of agricultural residues. There are some gaps that need addressing, and would best be aligned with other research like Heller/Keoleian's report and the resulting breakdown of energy use by segment: ag production (EPA), transport, processing, packaging, food retail, restaurants, home refrigeration, and then waste disposal (but not in Heller report).

Let's start with what we know. The US DOE's Energy Information Administration's (EIA) Emissions of Greenhouse Gases in the United States 2005 report details Carbon Dioxide (CO2), Methane (CH4), and Nitrous Oxide (N2O) emissions as well as other GHG gases.

CH4 is produced as part of normal digestive processes in animals(1). It is also a byproduct of landfills and decomposition, and landfills have already been tapped for this energy source. The EIA methane report shows that from what we measured in 2005 for anthropogenic methane emissions we know:
  • Methane has a GWP rating of 23.
  • Total U.S. Methane Emissions were 26.6 million metric tons
    • 611.9 million metric tons CO2 equivalent (CO2e)
  • Agriculture released 173.4 million metric tons CO2e
    • 28.3% of total emissions
Of note: "emissions increases from enteric fermentation and animal waste management more than offset small decreases in emissions from rice cultivation and crop residue burning. Of total estimated methane emissions from agricultural activities, 93 percent (170.9 MMTCO2e) results from livestock management, of which 68 percent (115.6MMTCO2e) can be traced to enteric fermentation in ruminant animals and the remainder (55.3 MMTCO2e) to anaerobic decomposition of livestock wastes. A small portion of U.S. agricultural methane emissions result from crop residue burning and wetland rice cultivation."(2)

We need to calculate the other ag and food emissions from other data sets.

Nitrous Oxide
N2O is found in ag primarily from fertilizer application and management of solid waste from animals . If applied properly as a fertilizer, nitrogen is taken up by the plants, but "Indirect emissions from nitrogen fertilization result from adding excess nitrogen to the soil, which in turn enriches ground and surface waters, such as rivers and streams, and results in emissions of nitrous oxide."(3)

What we do know:
  • Nitrous oxide has a GWP rating of 296.
  • Total U.S. N2O emissions for 2005 were 1.2 million metric tons
    • 366.56 million metric tons CO2e
  • Agriculture (what is measured) released 279.9 million metric tons CO2e
    • 76.4% of total emissions

Of note: "
Nitrogen fertilization of agricultural soils accounted for 78 percent of U.S. agricultural emissions of nitrous oxide in 2005. Nearly all the remaining agricultural emissions (22 percent) can be traced to the management of the solid waste of domesticated animals."(4)

This means that nitrogen fertilization adds 218.3 million metric tons of nitrous oxide emissions, which is 60% of total U.S. nitrous oxide emissions from this one act. Now, nitrogen is a critical component to plant fertilization. The question is: how do we make that fertilizer, and are we applying efficiently?

Another question that arises is: why the increase in nitrous oxide in the last couple years? Is our land yielding less and therefore requiring more fertilizer?

(2) ibid.
4) ibid.

Ag Emissions and their Global Warming Potential, part 1

There is a lot of buzz about carbon emissions and their impacts on global warming. But what other emissions are heating up the planet?

The UN's Intergovernmental Panel for Climate Change (IPCC) has become the trusted international body for much of this info. They track different gases in relation to their Global Warming Potential (GWP). The DOE's Energy Information Administration (EIA) has a very good definition about GWP and which gases are considered.

The main item I want to highlight right now is that the GWP ranks gases according to their carbon dioxide equivalent, the "radiative efficiency (heat-absorbing ability) of each gas relative to that of carbon dioxide (CO2 ).(1)". So, while CO2 while has a GWP rating of 1 (against itself), Methane (CH4) has a GWP of 23, and Nitrous Oxide (N2O) a GWP rating of 296. There are ten other gases that are tracked, but these three are the more commonly discussed .

The EPA's U.S. Greenhouse Gas Inventory Reports tracks the gas emissions and sinks (where GHG gases are taken in/reduced), and has a chapter devoted to agriculture impacts. It has a graph of GHG emissions from 2004 and states that "In 2004, the agricultural sector was responsible for emissions of 440.1 teragrams of CO2 equivalent (Tg CO2 Eq.), or 6 percent of total U.S. greenhouse gas emissions. " The report, though, only measures a few ag components: enteric fermentation in domestic livestock, livestock manure management, rice cultivation, agricultural soil management, and field burning of agricultural residues. There is a lot more that needs to be included to understand the full GHG impacts of our food system, and then what potential solutions exist for reducing our carbon equivalent footprint.
(1) US DOE EIA website page Global Warming Potentials, viewed April 1, 2007.