Sunday, October 30, 2011

USA Export land model analysis for food energy production and consumption: Part 1

I am not going to re-hash old ground explaining how I derived the food energy contents for the various food items reported by the FAO and how these aggregated data can be used to estimate overall food energy production, consumption and export/import rates for individual countries regions or the world.  This has all been covered before in the most recent four blog entries.

I am also not going to spend time explaining what the export land model (ELM) is—this was discussed in the context of oil production and consumption in many of my past post; you can find an introduction and further references to that here.

Definitions of some important parameters

I do, however, want to cover how I define net food production, net consumption and net exports.

As discussed in the previous posts on this topic, the spreadsheets published by FAOSTAT report several food categories: gross Production (P), Imports (I), Stock Variation (SV), Exports (E), and the domestic food supply (DS).  See the handbook for further details.

DS is derived from the other categories, as shown in equation (1):

                        (1)                    DS = P + I + SV – E

rearranging equation (1) gives net exports (E – I):

                        (2)                    (E – I) = (P + SV) - DS

For any give year, SV is a small positive or negative number relative to P.  However, in order for equations (1) or (2) to be balanced, which is important when considering relative changes, SV need to be accounted for.   

Therefore, for the purposes of this analysis, I have taken production plus stock variation (P+SV) as being net production (i.e., annual production after correction of increases or decreases in food stocks), and I have taken net consumption as being equal to the domestic supply of food available (DS). 

Net consumption (i.e., DS), in turn, is composed of several subcategories that are also reported in the FAO Food Balance sheets: Human Food Supply (Hs), Feed (Fd), Seed  (Sd), Processing (Pr) and Other Utilization (Ot):

                        (3)                    DS = Hs + Fd + Sd +Pr + Ot

The Human Food Supply, refers to the plant and animal food directly available for human consumption, that is, food actually consumed plus that thrown away by humans.  Feed for animals and Seed for replanting are self explanatory.   Processing refers to the "commodity in question used during the reference period for manufacture of processed commodities for which separate entries are provided in the food balance sheet either in the same or in another food group."  Since processing is listed in the food balance tables as, processed, is a positive number, I take this as reflecting gains in food energy due to the food manufacturing process.  The handbook defines Other Utilization as food consumed by tourists and for non-food purposes.  

Alright, with these definitions in mind, let get on with the data reported for the USA.  All food energy units are expressed as Peta Joules per year (PJ/yr)

Net Food Energy Production
Figure 1 shows the time course of the changes in total net food energy production (blue), and the two major subcategories of plant-derived and animal derived net food energy production.

The USA's total annual net production rate (blue circles), has increased 2.4 times, from about 3246 PJ/yr in 1961, to about 7871 PJ/yr in 2007.  Plant-derived and animal-derived food production both increased by above the same amounts (2.5 and 2.2 times, respectively).  As a percentage of total food production, plant-derived food production has gone up from 87 to 90 percent with the animal-derived production correspondingly going down from 13 to 10 percent.

Also shown in FIG. 1 is the USA's population, as reported by the FAO, over this same time period (black Xs).  Since 1961, the population has increased about 1.6 times from 189 to 308 million.   

As the plots in FIG. 1 illustrate, the increase in net food energy production has far outstripped the population increase. 

However, the rate of food production increase is much more variable. 

For instance, the average annual change in population equals 1.1 ± 0.2 percent, while the average yearly change in net food energy production equals 2.0 ± 3.9 percent. 

Figure 2 shows the 5-year averages of the year-to-year percent changes in net food energy production (total, animal and plant), and the population change.     

These 5-year averages further illustrate the high variability in food production, ranging from +4% to -0.5%; the increase in animal-derived food more stably ranges from +1 to +2.5%.  In comparison the 5-year average year-to-year change in population (black cross hatched bars) has been fairly steadily growing at about 1% per year from 1961 to 2007.

A large portion of the variability in food production can be traced to some particular hard years having large downturns in cereal production.  For instance, 1974, 1983, 1988, 1993, and 1995 had annual cereal production declined -14, -38, -26, -27 and -22 percent, respectively.  Many of these years coincided with draught conditions in the mid-west USA, causing large year over year declines in corn production (see e.g., Corn Yield Trends for Indiana)

Figure 3 presents the same data as in Figure 2, but as a scatter-plot of the 5-year averages of the year-to-year percent changes in population and food energy production as function of the mid-year of each 5-year averaging period.  The solid lines show the linear regression best fits.

Figure 3 again illustrates that there are no substantial linear trends for the percentage changes in population growth rate to be changing with time.  There is a trend for the percentage change in net total food energy production rate to decelerating with time but the scatter and r2 is so low that I can’t make much of the cross over at about 2012, compared to the population growth trend line, and zero growth at about 2045. 

Contributors to Net Food Energy Production
Figures 4-7 presents major food items that contribute to the plant-derived and animal-derived net food energy production rates.

Figure 4 illustrates that, as noted above, as a percentage of the total food energy production, total plant-derived food energy increased from about 87% in 1961 to 90% by the mid 70s to 2007, with the corresponding inverse trend for total animal-derived food energy illustrated in Figure 7 below.

Of the seven subcategories of plant-derived food energy depicted in Figure 4, cereals stands out as THE major food produced in the USA.  Although there is a slight downward trend, cereal-derived food production accounts for 65 to 59 percent of total net food energy production.  Most of the 5 percent decline in the relative contribution from cereals can be accounted for by the relative increase in the oil crops (e.g., soyabeans) increasing from 10 to 16 percent from 1961 to 2007.  All of the other food types make relatively minor contributions to net food production.

Figure 5 focuses on relative contributions of four plant food items that were important in my previous post analyzing the world production trends: maize (corn), wheat and rice, and, soyabean plus oil from soyabean. 

The relative contribution of these four items have increased from 61 to 76 percent of total net food energy production from 1961 to 2007.  But, really we are talking about two or maybe three items because the relative contribution of rice production in the USA is less than 1 percent of total net production and the relative contribution of wheat production has stayed declined from 13 to 10 percent.

The relative contribution from soyabean and soyabean oil to total production has risen from 9 to 19 percent of total net food energy production, while the relative contribution from maize(corn) has risen from 38 to 45 percent.  In other words just soyabean and corn production accounted for 64% of total net food energy production in the USA.  Add in wheat and you are at 74%.  Just amazing. 

This nicely illustrates the consequence of America's industrial food complex:  great efficiency in production (i.e., a 2.4 times increase in net production from 1961 to 2007) at the cost of high dependency on just three food types: corn, soyabean, and wheat for almost three-quarters of production. 

To further drive home the importance of corn, Figure 6 shows the relative contributions from the nine different cereal items, Wheat, Rice, Barley, Maize, Rye, Oats Millet, Sorghum and Other Cereals, that are reported as separate items by the FAO

Even among the cereal crops resiliency has dramatically declined.  The relative contribution from wheat declined 4 percent from 21 to 16 percent—all the other cereal types have similarly declined with, only corn increasing.  The relative contribution from corn has increased from about 59 to nearly 76 percent of the total cereal food energy production, and as shown above in Figure 4, cereal food account for about 65-59 percent of total net production.  It follows therefore that corn alone presently accounts for about 45 percent of total food energy production, up from about 38 percent in 1961. 

Figure 7 shows that the total animal-derived food energy has slightly declined from 14% to 10% of the total food energy from 1961 to the mid 70s and has stay fairly steady to 2007.

Major animal-derived food items include meat (steady at about 4%), milk (down from 4% to 2.5%),  animal fats (down from 3% to 2%) and sea food (steady at about 0.2%).   Together these four food types account for most of the animal-derived food energy in 2007.

Consumption of Food Energy
Figure 8 shows the distribution of the Domestic Supply of food energy.  That is, the proportions of major domestic consumptive uses of domestic food energy. 

Surprisingly, to me at least, is that the major domestic use historically has not been for the Human food Supply, but rather for Feed, although this is declining.

Food energy for Feed in 1961 accounted for 49 percent of domestic consumption, but in 2007 that was down to 34 percent.   Presumably feed is animal feed for live-stock.  The decline in the proportion of food energy devoted to Feed to the mid 70s tracks with the decline in animal-derived net food energy production—although the continued decline in Feed thereafter is a bit puzzling to me, since animal-derived food production since then has stayed stable at 10 percent. 

The domestic supply of food energy for the Human Supply has been fairly steady at 30-33 percent from 1961 to 2007.  The consumption of food energy as Seed has also remained steady at about 2 percent. 

“Other Uses” are up from 4 to 7 percent.  Presumably this reflects an increase in non food uses of food (e.g., soaps, fuels etc), but this also include food consumed by tourists.   The separate category “alcohol non-food” has gone up 65 times from 0.38 PJ/yr (1961) to 24.5 (2007), but, this still only accounts for a very small proportion of total net energy production (0.3 percent in 2007).

What has gone up most is Processing, from 13 to 27 percent of the domestic supply.  Processing, as I noted above, refers to the “manufacture of processed commodities” having separate entries in the food balance sheet.  I believe that this doubling in the proportion of processed food commodities is another reflection of the American fossil-fuel dependent industrial food complex: instead of providing the raw food (e.g., corn-on-the-cob) the raw food is “manufactured” into something else (e.g., fructose-corn-syrup).

Well, that is it for the USA’s production and consumption. In part 2, I will discuss the USA’s imports and exports, the relative importance of the USA to the global food supply, and give my summary and conclusions.  I hope that you will join me.


  1. "I believe that this doubling in the proportion of processed food commodities is another reflection of the American fossil-fuel dependent industrial food complex: instead of providing the raw food (e.g., corn-on-the-cob) the raw food is “manufactured” into something else (e.g., fructose-corn-syrup)."

    And slowly killing many of us...but that's a whole other issue.

    Good report, as always.

  2. Yes Bill, you are probably right. I became aware of this when I watched the "King Corn" movie.

    But putting it together myself with the FAO data, and then finding the dominance of few crops with corn at the top, really drives home the point for me.

    And the clear trend is for more and more processed food, because no doubt that is more efficient, long as there are cheap fossil fuels to keep the machines running.

  3. I am hoping the same best effort from you in the future as well. In fact your creative writing skills has inspired me.
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