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food_energy.tex

@@ -113,13 +113,13 @@ The point of these energy calculations is not to give students an eating disorde
 One feature of the aught's ``homesteading'' culture \cite{homesteading} is the idea that a person should probably be able to move to the country, eat a lot of peaches, and grow all their own food.  Learning that farming labor is \textit{skilled} labor can be brutal and disheartening. Eating $3000kcals$ each day means planting, weeding, harvesting, and storing more than a million kcals each year \cite{Haspel}.  Where will those Calories come from? Is your backyard enough to homestead in the suburbs \cite{backyard_homestead}?
 
 At some point between 1920 and 1950, US chemical manufacturers realized that in the post-war period, they could repurpose processes developed for manufacturing munitions and chemical warfare agents, to produce chemicals that would kill insects and increase the nitrogen levels in the soil. 
-As figures \ref{corn_and_potato_yields} and \ref{ag_yields} show, the epoch of ``Better Living Through Chemistry'' produced a dramatic increase in per-acre yields across all comodity food crops, particularly corn and potatoes.  
+As figures \ref{corn_and_potato_yields} and \ref{ag_yields} show, the epoch of ``Better Living Through Chemistry'' produced a dramatic increase in per-acre yields across all commodity food crops, particularly corn and potatoes.  
 
 \begin{figure}[ht!]
 \centering
 \includegraphics[width=\columnwidth]{corn_potatoes_raw_production_per_acre.pdf}
 \caption{
-USDA per acre Corn and Potato production figures, plotted over time.  Data is given in harvet units, $56lbs$ bushels per acre for field corn and hundred-weight (CWT) for potatoes.  By mass, corn is about $4.5$ times more calorie dense than potato which results in a nearly equal $kcal/acre$ values for both crops in figure \ref{ag_yields}.
+USDA per acre Corn and Potato production figures, plotted over time.  Data is given in harvest units, $56lbs$ bushels per acre for field corn and hundred-weight (CWT) for potatoes.  By mass, corn is about $4.5$ times more calorie dense than potato which results in a nearly equal $kcal/acre$ values for both crops in figure \ref{ag_yields}.
 Details on the data source and conversions are given in \ref{how_yield_plot_is_made}.
 }
 \label{corn_and_potato_yields}
@@ -167,29 +167,20 @@ The choice of operation is difficult to make without seeing the units present, w
 What does the answer of $2.3$ acres mean?  The university's $91m\times49m$ football field has an area of about $1.1$ acres, so you could say that a football field planted in potatoes will probably feed a family through the winter \cite{Deppe}.  Can a person enjoy the benefits of urban living and grow all their own food?  The population density of New Jersey is $1,263~people/mile^2 \approx1.97~people/acre$ and our 4 person family needs $2.3$ acres for their potatoes.  
 Unless the social model is one of a country Dacha or an endless suburb with no duplexes or apartment buildings, urban living and food self-sufficiency seem mutually exclusive.
 
-% This is interesting, but probably a weak argument because organic yields can be as high as ~ 140bu/acre BUT must be grown in a 3 or 4 year rotation vs corn's 2-year rotation.
-%
-% https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjswtTZo8X8AhXkjokEHW-yD74QFnoECA8QAQ&url=http%3A%2F%2Fextension.agron.iastate.edu%2Forganicag%2Fresearchreports%2Fn-kltar98.pdf&usg=AOvVaw2mLZB25pv44LX_EBAR5kXU&cshid=1673638241316994
-%
+
 More emotionally charged conversations can be had about converting the United States to all organic agriculture, which, for corn, typically has a yield penalty of about $20-40bu/acre$ when compared to conventional production.  The 1917 data isn't directly applicable, but it relates. At $180bu/acre$ conventional corn requires $\approx 24~million~acres$ (half of Wisconsin, or all of Indiana) to feed the US population ($350$ million people) corn for a year.  The remainder of the corn belt can be devoted to animal feed, ethanol, and export.  If the corn belt was devoted to producing organic corn at lower yield \cite{organic_corn_yield}, we probably wouldn't starve, but cheap meat and ethanol vehicle fuel would likely disappear.   
 %WI 42M acres
 %IN 23M acres
-%
-%1917: 35 bu/acre
-% 350M ppl*1M kcal / (3.1Mkcal/acre) = 113M acres
-% 2022
-% 180bu/acre / 35bu/acre = 5.1x (less)
-% 113M acres / 5.1 ~= 22M acres
 
 \clearpage
 
 \section{Example: How big could Tenochtitlan have been?}
-The questions described thus far have largely been centered within a physics context.  The paper closes with two more examples that leverage this food energy picture to make historical claims.  The first example relates to the pre-Columbian capital of the Aztec Empire, Tenochtitlan, now known as Mexico City.  Tenochtitlan was built on and around a endorheic lake, Texcoco.  Crops were grown in shallow parts of the lake via chinampas \cite{national_geo}, floating patches of decaying vegetation and soil.  Given the proximity to water and decaying vegetation, these fields were very fertile \cite{HortTech_2019,Chinampas_1964} and some continue to be used in the present day \cite{google_earth}.  
+The questions described thus far have largely been centered within a physics context.  The paper closes with two more examples that leverage this food energy picture to make historical claims.  The first example relates to the pre-Colombian capital of the Aztec Empire, Tenochtitlan, now known as Mexico City.  Tenochtitlan was built on and around a endorheic lake, Texcoco.  Crops were grown in shallow parts of the lake via chinampas \cite{national_geo}, floating patches of decaying vegetation and soil.  Given the proximity to water and decaying vegetation, these fields were very fertile \cite{HortTech_2019,Chinampas_1964} and some continue to be used in the present day \cite{google_earth}.  
 
 
 Estimates of Tenochtitlan's population in 1500CE vary widely, from 40,000 \cite{40k} to more than 400,000 \cite{400k} inhabitants, comparable in size to Paris at that time. These estimates come from oral and written records and estimates of archaeological building density and land area.   While cannibalism was part of Aztec religious ritual and practice \cite{Aztec_Cannibalism}, the staple Calorie sources for the Aztecs were corn and beans.
 
-Few if any Native American cultures made use of draft animals for food or power before the Columbian Exchange.  This means that the food that fed Tenochtitlan must have been brought to the city center by foot or canoe.  How much land must have been devoted to chinampas to feed the population, or conversely, how many people could be supported by the land within walking or paddling distance from the city center?
+Few if any Native American cultures made use of draft animals for food or power before the Colombian Exchange.  This means that the food that fed Tenochtitlan must have been brought to the city center by foot or canoe.  How much land must have been devoted to chinampas to feed the population, or conversely, how many people could be supported by the land within walking or paddling distance from the city center?
 
 A 1964 paper in Scientific American \cite{Chinampas_1964} gives a general outline of the chinampas in the area of Tenochtitlan in 1500CE.  This map seems to be the basis for the similar figure in Wikipedia \cite{chinampas_wikipedia}.  Descriptions of chinampas agriculture indicate that as many as $7$ successive crops could be grown and harvested from the same plot of soil each year, two of which could be maize (corn).  This is truly amazing productivity, given that in the midwest United States corn is normally grown, at most, every other year because of it's extreme nutrient demands on the soil.
 
@@ -212,7 +203,7 @@ This crop productivity is in remarkable agreement with the 1917 USDA yields, $35
 
 
 \section{Example: Was the Irish Potato Famine a Natural Disaster?}
-In contrast to native cultures of the Americas, Ireland's population boomed with the Columbian Exchange and the introduction of the potato. \cite{potato,little_ice_age}.  Figure \ref{ireland_population} shows that from about 1700 onward there was a dramatic growth in the island's population.  There's never just one reason for historical events, but unlike grains, potatoes thrived in Ireland's cool damp climate and potatoes, kale, and milk form a nutritionally complete diet that greatly reduced hunger-related mortality among the poor working-class in Ireland.  If you look closely at the data in figure \ref{ireland_population} you might believe that there were \textit{two} weather and potato related famines, the most obvious 1845-49 and the second, with much smaller effect on population in 1740-1.  Both famines were precipitated by poor weather, but an important difference is that in 1740, Ireland was a sovereign state but by 1845 the island was effectively an economic colony of the British Empire \cite{little_ice_age}.  
+In contrast to native cultures of the Americas, Ireland's population boomed with the Colombian Exchange and the introduction of the potato. \cite{potato,little_ice_age}.  Figure \ref{ireland_population} shows that from about 1700 onward there was a dramatic growth in the island's population.  There's never just one reason for historical events, but unlike grains, potatoes thrived in Ireland's cool damp climate and potatoes, kale, and milk form a nutritionally complete diet that greatly reduced hunger-related mortality among the poor working-class in Ireland.  If you look closely at the data in figure \ref{ireland_population} you might believe that there were \textit{two} weather and potato related famines, the most obvious 1845-49 and the second, with much smaller effect on population in 1740-1.  Both famines were precipitated by poor weather, but an important difference is that in 1740, Ireland was a sovereign state but by 1845 the island was effectively an economic colony of the British Empire \cite{little_ice_age}.  
 
 As the story goes, the two main commodity crops in Ireland were potatoes (for humans), and oats, which as horse feed, were something like gasoline in today's economy.  A sovereign government can halt the export of food to feed English horses, which is what happened in 1741 (and 1782). The grain was diverted back as relief to starving people in Ireland, reducing the famine's mortality. However, by 1845 most of Irish farmland was economically controlled by foreign (English) markets, and grain traders typically refused to divert oats (horse feed) as famine relief for the sake of their investment income.
 
@@ -263,28 +254,14 @@ A class about Energy and Social Policy and the author hasn't mentioned climate c
 How many tons of carbon does your car release in a year? How many shiploads of iron oxide will we have to dump into the ocean for phytoplankton to eat up the equivalent about of carbon?  Every question in a class like this is, to at least some extent, informed by numerical calculation and it's pretty arrogant to assume that ``those students'' don't need to (or can't) do the math.  If you're going to have success talking about numerical calculations, you might as well start with examples that everyone can relate to, and everyone eats!  Along the way you might find fascinating historical questions to investigate.   
 
 
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-%\begin{acknowledgments}
 \ack
 The work was influenced and improved by discussions with 
 Diane Dahle-Koch, 
-Larry Moore, 
 John Deming, 
 Carl Ferkinhoff, 
+Larry Moore, 
 and Sarah Taber.
-%\end{acknowledgments}
 
-%The command \appendix is used to signify the start of the appendices. Thereafter
-%\section, \subsection, etc, will give headings appropriate for an appendix. To obtain
-%a simple heading of ‘Appendix’ use the code \section*{Appendix}. If it contains
-%numbered equations, figures or tables the command \appendix should precede it and
-%\setcounter{section}{1} must follow it
 \clearpage
 \appendix
 \section{Creating the historical kcal/acre figure from USDA data}
@@ -307,10 +284,6 @@ In 2022 the USDA reported an average production of $172.3$ bushels of corn per a
 \label{example_calculation}
 \ee
 Obviously the result is only reasonable to two significant figures!
-%grams_per_lbs=453.592
-%corn_lbs_per_bu=(56.0/1.0)
-%corn_kcal_per_gram=(365/100)
-%corn_kcal_per_acre = corn_bu_per_acre*corn_lbs_per_bu*grams_per_lbs*corn_kcal_per_gram
 
 \begin{table}
 \caption{\label{label}