Flex-Fuel Humans

[An updated treatment of some of this material appears in Chapter 20 of the Energy and Human Ambitions on a Finite Planet (free) textbook.]

If you’re one of those humans who actually eats food, like I am, then a non-negligible part of your energy allocation goes into food production. As an approximate rule-of-thumb, each kilocalorie ingested by Americans consumes 10 kilocalories of fossil fuel energy to plant, fertilize, harvest, transport, and prepare. The energy investment can easily exceed a person’s household energy usage—as is the case for me. But much like household energy, we control what we stick in our mouths, and can make energy-conscious choices that result in substantial reductions of energy consumption. I now call myself a flexitarian, a term acknowledging that my body is a flex-fuel vehicle, but also that I need not be rigid about my food choices in order to still make a substantial impact on the energy front.

An earlier post on how many miles per gallon a human gets while walking or biking touched on the fact that fossil fuels undergird our food supply. As a result, walking to the grocery store effectively uses as much fossil fuel as would a typical sedan. The lesson is not to walk less, but to change that 10:1 ratio for the better by eating more smartly. Once upon a time, we put less than one kilocalorie of energy into food production per kilocalorie obtained (or else we and our draft animals would have starved to death). So the 10:1 ratio is not at all inescapable, and depends strongly on the foods we choose to eat.

My Flex Transition

Several years back, I engaged in a broad spectrum of energy reduction strategies. I had learned enough to know that our energy future was not likely to follow an ever-growing trajectory. The back-side of the fossil fuel age could bring with it challenges unimagined by our many-generation boom society. Technology can play an important role over the long term. But tech solutions generally do not hold a candle to voluntary reduction when it comes to having enormous short-term impacts. I was curious to know how life would be if I reduced energy use by something like a factor-of-two across-the-board. As a result, I not only have the personal satisfaction of knowing that it can be done without drastic changes in lifestyle, but I am also much better-prepared to adapt to a world where energy reduction may not be as much a choice as an imposition foisted on us by failing supply.

I had heard from multiple sources that eating meat carried a large energy tax, amounting to as much as 8× for beef, 5× for pork, and something like 2× for chicken and fish. I have not been able to track down this original source, but the sentiment was almost certainly correct if not the numerical factors. In any case, I switched to a primarily meat-free diet.

That’s not to say I don’t enjoy eating meat products. I personally have no ethical problems with eating meat, and still enjoy meat on special occasions or even by accident. I imagine many vegetarians feel sullied when a piece of beef slips into their otherwise vegetarian burrito. Not me. Meat treat! Accidental/unexpected bits of bacon happen surprisingly often, but do not go unappreciated. When I go to someone’s house for dinner, I’ll happily eat whatever is being served. On holidays I enjoy the traditional fare: Thanksgiving turkey (for which I am thankful), July 4th hot dog or hamburger, etc. And sometimes it can be hard to hew to the plan when traveling, so sometimes I switch over to meat when that’s the only reasonable option.

My approach is to not let my no-meat preferences become an undue impediment to myself or to others. When I have control over the situation, and have good vegetarian options available (almost always), I’ll go meatless. Otherwise I’ll go with the flow. One trick I’ve learned in meat-centric restaurants is that I can often order a few side dishes that result in generous portions at a lower price than a “normal” meal.

Being semi-quantitative about it, although based on questionable numbers, I figured that maybe I got a quarter of my food energy from meat, which probably averaged 4× the energy impact of vegetarian fare. Playing this game, let’s say that 75 units of energy went into my 75% vegetable-based diet, and another 100 units for the 25% meat portion. Going full-veggie would require 100 units rather than 175. So roughly speaking, I figured I was having about a factor-of-two impact. The occasional meat treat might constitute 1% of my dietary intake, and at 4× the impact, this turns 100 units of energy into 103 (99% vegetarian plus 4×1% meat). Not a big deal for the occasional deviation.

I have to admit that I have never been a big fan of vegetables themselves. But somehow I really like being a flexitarian. It feels like a responsible choice, and between pasta, bread, rice, beans, cereals, dairy products, and nuts, I do not spend my days feeling deprived of good things to eat.  An alternate approach of moderation is to use meat as an accent, or garnish in a meal—constituting a very small portion of the caloric value.

An Aside About Protein

Somewhere along the way, our culture developed something of a fixation on protein. It’s not as important to a healthy diet as many assume. In fact, read The China Study for a fascinating and compelling story recounting mountains of evidence to the contrary—especially exposing the deleterious effects of animal protein. It’s not hard to get plenty of protein from plant matter. You don’t really even have to be vigilant—rice and beans will do you well. Unless you’re a body builder or actively increasing muscle mass, maintaining your physique requires just 10% of your calories in protein form. Billions test the idea daily, without shriveling up from lack of protein.

Other Considerations

Energy is not the only component to the story, even though it’s the one I focus on here.  Livestock practices in the U.S. have become ever-more industrialized, packing animals into giant feedlots, raising chickens too top-heavy to walk properly, and feeding grains to naturally grass-eating cows resulting in chronic stomach pain.  Genetic engineering, waste pools, rampant antibiotics, heavy water use, and wholly unnatural lives of animals all make the modern meat industry a twisted enterprise.  Although it’s not a primary motivation for me, I am relieved to bear less personal responsibility for this mode of feeding ourselves.

Digging Deeper: Energetics of Food Choices

Eventually, I felt I should learn more about the impacts my choices were having. Was I fooling myself? Was I making poor choices based on erroneous information? How reliable were these 8×, 5×, etc. factors? I was pretty sure that my diet was at least going in the right direction with regard to energy, but should I fine-tune it based on more solid analysis?

I ran across a fascinating work by Gidon Eshel and Pamela Martin that consolidates a variety of research inputs into an assessment of the energy requirements of various diets. Much of the data comes from a book edited by Pimentel and Pimentel called Food, Energy, and Society, which has seen editions in 1996, 2005, and 2008.

First, a few numbers to lay the groundwork. Excluding exports, the U.S. produces 3774 kcal of food energy per person in the U.S. Not all of this is eaten: 2100 kcal is a more typical diet. Yes, food is wasted in the U.S. The total share of national energy devoted to food production, distribution, and preparation ranges from 10% to 17%, depending on what is included in the summation (see Heller, DoE, and Horrigan references in the Eshel & Martin work referenced above, and this USDA report). Ignoring the household portion (refrigeration, cooking), food tends to end up consuming around 11% of our energy inputs. Using the handy—if not alarming—number that each American’s total energy share zips by at a rate of 10,000 W, this means 240 kWh/day is expended per person, so that food comes out to about 27 kWh/day per person in the U.S. Meanwhile, we typically metabolize 2100 kcal/day, which turns into 2.44 kWh/day. There’s our 10:1 ratio: put in 27 kWh of energy, eat 2.44 kWh in exchange.  (We can also get to 10:1 quickly by realizing that 11% of 10,000 W is 1100 W, while the human metabolism runs at about 100 W.)

Next, the typical American diet is broken down (calorically) as 72% plant-based, 11.5% dairy, 9% red meat, 5% poultry, 1.5% eggs, and 1% fish, in round-ish numbers.

Now for the magic part. What is the output-to-input energy ratio for producing various types of food? The following table is excerpted from the Eshel & Martin paper, much of which derives from the Pimentel & Pimentel work. One caution: don’t take these numbers as absolutely authoritative. I suspect the uncertainties are quite large, but they nonetheless convey a general sense.

Food Type Energy Out/Energy In
Shrimp 0.009
Lamb 0.012
Pork 0.037
Salmon (farmed) 0.057
Tuna 0.058
Beef (grain fed) 0.064
Eggs 0.112
Chicken 0.181
Milk 0.206
Tomatoes 0.6
Herring 1.1
Apples 1.1
Potatoes 1.2
Peanuts 1.4
Dry Beans 1.8
Rice 2.1
Wheat 2.2
Corn 2.5
Soy 4.15
Oats 5.1

Even if the uncertainties are sizable, the obvious trend is that plants and grains tend to produce more energy than is contained in the fossil fuel inputs. These numbers are for U.S. production practices, and tend to be larger by factors of two or three when manual techniques are employed.

How can eggs cost more energy than the whole chicken? Well, how long must a chicken live and be fed before it produces the equivalent of its edible body weight in eggs? Apparently longer than it needs to live and be fed to find its way to the frying pan.

Having laid some groundwork, we can now have some fun imagining various diet scenarios and computing the production energy of each set of choices. Let’s use an energy factor of 2 as representative of plant-based food. Obviously then, a strict vegan (no animal products) can get by with only 1.2 kWh of fossil fuel investment to produce a day’s worth of food (2.4 kWh)—becoming 2.2 kWh if we allow the typical U.S. ratio of produced/consumed food. At present, we’re only talking about production and processing—later we’ll address other required energy inputs for distribution, refrigeration, preparation, etc.

Meanwhile, the typical American diet has a weighted energy expenditure of 0.72/2.0 (plant) + 0.115/0.206 (milk) + 0.09/0.05 (red meat) + 0.05/0.181 (chicken) + 0.015/0.112 (eggs) + 0.01/0.05 (fish), amounting to 3.3 times as much fossil energy as food energy. In case you are confused about where these numbers come from, the dietary fraction of any particular intake is in the numerator of each term (e.g., 11.5% from milk/dairy), and the factor of energy output/input is in the denominator (sometimes approximating a mix of inputs from the table). The vegan calculation by the same method is 1.0/2.0 (100% of food from plants, at a 2:1 output:input ratio), for a factor of 0.5×.

So from a pure production point of view, the vegan uses one-sixth the energy resources that the typical American does to grow/raise food. What about someone like me who has not given up dairy/eggs? I’m not replacing all of the normal 28% animal product with dairy/eggs: I make up a good deal of the difference via grains, etc. Let’s say that I am 15% dairy and 2% eggs, just for the sake of getting some numbers down. My math looks like 0.83/2.0 (plant) + 0.15/0.206 (dairy) + 0.02/0.112 (eggs) for a production energy requirement of 1.3 times the fossil fuel input. So I’m not below the magic 1:1, but more than a factor of two less than the typical diet. I would drop to 1.15× if giving up eggs, or all the way to 0.5× if I dropped all animal products.

The Rest of the Energy

There is more to the food energy story than production and processing alone. We also have transportation (actually not that large), packaging, refrigeration, retail operations, and preparation. If the average American diet uses a production energy input that is 3.3 times the metabolic energy output of the food, and total energy inputs amount to ten times the metabolic energy, then production/processing accounts for one-third of the total expenditure. We’ll call the non-production aspects “overhead,” and assess this at 6.7 times the metabolic energy, so that the average American diet—consuming 3.3 times the metabolic energy for production—adds to the familiar 10× total.

If the overhead costs are the same for all types of food, then the vegan diet comes to 0.5× for production, plus 6.7× for overhead, in the end only managing to shave 30% off the energy requirements of the average American diet.

But this is likely not true. Vegan-friendly foods, for example, tend to require less packaging (see produce section of grocery store), and less refrigeration (grains, etc.). If we make a crude guess that vegan diets require half the energy in the overhead sectors, the net effect is 0.5× for production, plus 3.3× for overhead, amounting to about 40% as much energy going into food delivery as for the typical diet. It’s just a rough guess, but it looks like roughly a factor-of-two in any case.

The sort of diet I’m on (allowing eggs and dairy) will likely fall in between vegan and average American on the energy overhead front. If my diet requires 75% of the overhead that a typical diet would, then I’m at 1.3× for production, plus 5× for overhead. In this case, my diet choices result in 63% of the energy that the average American consumes. Given that I tend to waste little food, perhaps I am operating below 60% on the energy scale. I am less sure of the food being wasted on my account before it ever makes it to my hands: otherwise I would claim a bigger share of savings in this sector—after all, using 2100 out of every 3774 kcal corresponds to a 44% waste.

The Net Effect & Perspective

Put in more familiar terms, we saw before that the food enterprise in the U.S. consumes 27 kWh/day per person—turning into about 75 kWh per household. Compare this to American household average daily consumption of 30 kWh of electricity (typically demanding ~90 kWh of thermal energy in power plants), 37 kWh of natural gas consumption, and 2.9 gallons of gasoline amounting to 105 kWh. Dietary choices can obviously have a sizable effect on our total energy budget.

As with many such adaptations, it is easy to make the claim that the change is too inconsequential to make a difference: that if the U.S. spends 10–15% on food practices, no game-changers are possible on the food front. “So I’ll keep eating beef, thank you very much.” In truth, our energy use is diverse, so game changers are only possible in across-the-board reduction strategies.

In other Do the Math posts, I have described cuts to our household energy amounting to about 20 kWh/day in natural gas, about 8 kWh/day in utility electricity (becomes > 20 kWh/day in source energy), and comparable cuts in gasoline use. Add to this the savings from two people each consuming 60% of the average 27 kWh of food energy, and our household saves another 22 kWh of energy per day. Clearly, our dietary choices represent a substantial component of our total energy reduction strategy.

Operating at about 60% of the typical food-energy allocation isn’t quite the factor-of two cut that I typically like to achieve, but it’s still pretty significant (and may in fact reach 50% given the large uncertainties in my crude calculation). I could go the vegan route and be more assured of making a factor-of-two difference, but this feels too restrictive given prevalent choices in today’s society. Plus, I have the unfortunate pleasure of being essentially a vegetarian who doesn’t actually like vegetables very much. It’s not as dire as it sounds: bread, beans, rice, pasta, polenta, etc. form the foundation of my diet, and I don’t struggle through life yearning for better.

Flexitarian Reflections

I try to strike a balance: mindfulness without rigidity; disciplined minus judgment; sacrifice without dismal deprivation; flexibility without wanton rationalization.

The main idea is what a nerd-type might call establishing a low duty-cycle for eating energy-intensive foods. If 2% of my meals share the profile of an average American diet (about right for my habits), then my computed 63% energy impact turns into a trivially-different 64%. At one normal American diet day per week (14% duty-cycle), it would turn into a 68% impact. I like the “Meatless Monday” movement, but would like the inverted situation of “Meat Treat Monday” even more.

The numbers sketched above indicate that big reductions are not seriously jeopardized by the occasional allowance. The biggest impact stems from changing the “normal” behavior. Even though the numbers are a little fuzzy, the approximate magnitude (and direction) of the impact is obvious enough.

This is an evolving process for me. I would like to take a deeper look at the numbers, if I get the chance. I certainly no longer view tuna and chicken as equivalent.  I may need to evaluate whether or not to drop eggs (small impact, given the small share of my diet), or whether to cut back on dairy products. Should I get some chickens and feed them scraps to get my eggs for “free”—in the process learning what it really means/takes to enjoy eggs? We’re growing vegetables this year. Should we expand this operation and try to get a greater fraction of our diet from home-grown food (assisted by my rainwater catchment system)?

I want to have a greater awareness of the energy cost of my food, and take a greater responsibility for the choices I make. A growing number of people are doing the same, and it will be very interesting to see where the movement leads.

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78 thoughts on “Flex-Fuel Humans

  1. Various remarks:

    The source for all the various food:energy ratios is Pimentel and Pimentel (I own a copy, 3rd edition). My cousin (who grew up at Cornell, where I think P&P work) has some quibble with their production-energy accounting, but it’s not a huge quibble.

    Be careful of statistics that count kilocalories of protein, versus kilocalories of food. I think the table you quoted IS consistent (out:in of 100% beef protein is 1:40, or 0.025, but fat has so much energy that out:in of 85% lean beef is 20:1, so it looks like they are using 80% lean).

    Apropos of previous paragraph, note that a lot of our “food waste” may be comparatively high-calorie fat trimmings and drippings. I don’t know this for sure, but I know how people prepare food, and there’s a lot of energy in fat (about the same density as gasoline, if you cook out the water).

    With the exception of shrimp, notice that pretty much the bigger the fish, the worse the EROEI. Top of the food chain also concentrates mercury and other pollutants. (Too bad about shrimp….)

    As Eshel and Martin point out, there are other costs besides energy. The non-energy GHG effects of beef and pork and their food supply are (if I recall correctly) about as large as their energy-related GHG costs. These include CH4 from both ends and manure decomposition, and N2O from fertilized crops and manure.

    A useful link for helping with this: http://ndb.nal.usda.gov/index.html

    For very high EROEI foods (e.g., oats, 5.1:1), it is easy for processing energy to cut the efficiency a lot. I did a sanity check on this once, and discovered:

    “If you heat 300 kCal of dry oats (1 cup) in 400mL (1-3/4 cup) of water from 10C (50F) to 100C (boiling point; but do not boil) it requires 90 times 400 equals 36000 calories, or 36 kCal. Since the input energy was only 59 kCal, this adds quite a lot to the energy input, and gives you a delivered-to-your-mouth energy return on energy invested (ERoEI) of only 3.15.”

    Inspired by this, I did once cook a batch of oatmeal on the top of a wood stove (wood cut as a byproduct of dropping a dangerous tree; hand split with ax and hydraulic ram). It was slow.

    It might not be valid to extrapolate from our current diet to what we would eat if we expended more human energy in transit. I burn about 2500 kCal/week on not-driving; in the summer, that rises to 4000+ kCal, and I get HUNGRY, but I get especially hungry for high-cal treats — i.e., fat and carbs, not protein. This might hold for people in general, though it’s hard to say.

    Regarding the appeal of a veggie diet, Trader Joe’s soy chorizo is astonishingly good. A friend of mine once took me to a fake-meat-Chinese restaurant in SF, and I had to rely on his assurance that I was in fact eating plants, because I could not tell the difference at all.

    • The Pimentel work definitely suffers from a protein-centric focus. The numbers in the Eshel & Martin table correct for total caloric content (and thus my table as well).

      Good point about food waste perhaps being slanted toward the unsavory bits.

  2. Congratulations on your choice of going meatless most of the time! I wished you touched on something else that is food related: bottled drinks. I’m talking about all forms of bottled drinks from bottled water, to aluminum cans to red bull, pepsi, and bottled fruit juices.

    I rarely drink any of those things. Clean water in an aluminum bottle is fine for me. Clean water is so precious that the vast majority of people in the world do not have access to it. Yet here in the western world we waste a tremendous amount of oil turning water into sugar water. Yes all those drinks are essentially a form of oil (plastic/aluminum) containing water and sugar.

    My second point is that the the industrialized farming of the US is possible only because of cheap corn. And corn subsidies make cheap corn possible. The corn lobby and the US government are directly responsible for the sorry state of farming.

  3. Tuna and herring are both caught, right? So why the huge difference? Catching tuna is equivalent to farming salmon? And is the shrimp figure farmed or caught?

    It’d be nice to know how much difference organic food, or grass-fed beef, make.

    • My understanding is that tuna and herring are so different because the former is long-haul, while the latter is near-shore. Not sure why shrimp is so high, but I presume this is caught rather than farmed.

      • Tuna is higher on the food chain so the opportunity cost of a pound of tuna is the 10 pounds of herring, mackerel etc that it ate. This doesn’t affect the fossil fuel energetics, but reflects limits on how much the resource can be exploited. Industrial farming of shrimp increases yield per land mass by increasing fossil fuel inputs to pump large amounts of water to flush waste, aeration, preparing special food pellets etc.

    • Feeding beef grass instead of grain makes a massive difference. I had a disagreement a few years ago over the energy costs of production for meat versus plants in my home country (New Zealand), and dug up the numbers from maf.govt.nz (Ministry of Agriculture and Forestry).

      Roughly, the energy ratios for non-solar input:output calories were 1:3 for plants, and 1:2 for meat/dairy (and no, I’ve haven’t got those numbers around the wrong way). The difference is that the vast majority of cattle and sheep here are grass fed their entire lives, and don’t winter in heated barns – albeit with the usual exceptions during exceptionally bad weather.

    • The Pimentel & Pimentel work suggest a factor of 3.5 less fossil fuel input for range beef vs. feedlot/grain-fed beef.

  4. The company I work for has a handy CO2 impact calculator based on percentages of diet dedicated to different food groups:

    Our data source for emissions: http://data.brighterplanet.com/food_groups

    We also did a study on food impact that includes impacts from cooking, packaging, and breaks fuel use into transportation from farm to store and transportation of materials to the farm: http://attachments.brighterplanet.com/press_items/local_copies/52/original/carbon_foodprint_wp.pdf?1271438613
    It turns out that food-miles have a much smaller impact than agricultural inputs, packaging, and preparation.

  5. There was a bit of folk wisdom I heard often when I was a little kid (1940’s), and have not heard since: “If you eat Sunday dinner every day, not just your purse will feel the pain.” (I do not know the provenance.)

    A popular bit of humor in my wife’s native country of Honduras is a shaggy dog story of a conversation between a pig and a dog. The pig brags to the dog, “This Christmas, they’re going to make me [into] nacatamales!” (The play on words does not translate well.) Nacatamales are a delicacy associated with Christmas, wedding feasts, etc. that are made with a very modest amount of pork (as an ingredient, not as a condiment).

    For most people I am aware of, for most of «history», meat has been a luxury. I think it was Mark Twain who observed that “When our luxuries become necessities, we make ourselves poorer.”

  6. I’ve heard the number that ammonia synthesis accounts for 1% of global fossile fuel consumption. Not irrelevant, but the by far biggest part of energy spent on food production seems to be the fuel operating land machines.
    Regarding this, i would suggest not to be too adversive towards pesticide usage, especially herbicide usage, because they can effectively reduce the need for plowing(Useful for energy saving, but also useful to counteract soil erosion). Being a citizen of the European Union, i feel sorry for the marginal part soil-conservating farming here compared to US and South America, because pesticides are evil,uncontrolable health hazards that “accumulate in the food chain and will contaminate our soil, water, air and bodies for an unknown period of time”
    to a big part of the public and also policy makers.
    These people just didn’t recognize any progress that was made in the last fifty years.
    The pesticide on the market today are readily biodegradable, and many don’t have chronic toxicity either.

    • …the by far biggest part of energy spent on food production seems to be the fuel operating land machines.

      This is not true, at least for the United States. According to the 2004 Congressional Research Service report “Energy Use in Agriculture: Background and Issues,” in 2002 US agricultural production consumed 1.7 quadrillion BTUs of primary energy both directly on the farm and indirectly through agrochemical production. This is actually down 28% from the peak use in 1978, despite substantial growth in agricultural production.

      The largest single item in the 2004 energy budget is fertilizer production, at 29% of the total.

      Then it is:
      Diesel fuel, 27.3%
      Electricity, 20.7%
      Gasoline, 8.5%
      Pesticides, 6.3%
      LP gas, 4.5%
      Natural gas, 3.6%

      Liquid fuels come to 35.8% of the agricultural production primary energy cost. This is about the same as the 35.3% share for agrochemicals.

      • 1.7 quad btus comes out to about 200 watts/person — of fossil fuel investment, plus unstated solar input, to produce 100 watts of food.

  7. I’d love to see you do the math for a combination of cost savings, choosing grass-fed meat which has almost 0 oil use in its production, and equivalents of local versus globally sourced vegetables. You’d also have to factor in the energy used in providing healthcare services to people that are ostensibly eating vegetables but are actually eating underripe vegetables shipped from China and treated with chemicals to make them appear ripe (not to mention the pesticides ect) or the energy cost of treating tens of millions of people with cancer in 20 years after the mass adoption of GMO foods.

    • Good points. I’m curious as to the impact of home gardening and “farming”. We have chickens (fed local feed store using local grain), dairy goats (grass fed as well as hay cut from our own fields…could use horses if I were younger), and a large solar-heated greenhouse and coldframes. Only energy used in gardening is tilling the beds in the spring. Organic fertilizers and animal manure only (no pesticides…not even “organic”).

  8. Great post. I would take any of the purported results of the China Study with a massive dose of salt though. I would at the very least take a look at the cricisms of the apparent cherry-picking and uneven application of statistical measures rampant in the study. A good basic critique, along with responses from the study’s author, can be found here: http://rawfoodsos.com/2010/08/03/the-china-study-a-formal-analysis-and-response/

    Also, I feel that this point: “Vegan-friendly foods, for example, tend to require less packaging (see produce section of grocery store), and less refrigeration (grains, etc.). If we make a crude guess that vegan diets require half the energy in the overhead sectors” may not be quite accurate, or at least requires a little more deliberation. For instance, produce may require slightly less packaging than meat from the butcher (not by a whole lot though), the processed vegan food found throughout the grocery store have every bit as much packaging as their meat-containing counterparts.
    Also, on the refridgeration aspect, grain may not require that much refridgeration, but those low-packaging produce section occupants (and the myriad vegetables and vegan-friendly processed foods in the freezer) require large amounts of it. It seems a stretch to immediately jump to a factor of two energy consumption gap in light of such ambiguous indications.
    Of course, there is absolutely no argument that vegan diets use far less energy than meat-intensive diets, but the referenced crude guess doesn’t seem well supported to me.

  9. A friend of mine, familiar with my passion for energy conservation/reduction said to me once, “If you’re really serious about reducing your energy footprint, you should grow some of your own food.” I thought about it for some time and realised he was absolutely right. I’ve since devoted a few weekends each year to converting my existing ornamental garden and lawn to an edible food forest. Don’t get me wrong. I don’t like gardening and the thought of tilling and planting a garden each year is no more appealing to me than I expect it is to most people. My goal is a self sustaining low maintenance edible landscape. Think blueberries, saskatoons, strawberries, blackberries, cherries, apples, pears, plums, rhubarb, asparagus, etc, right outside your door. The energy to produce and maintain such a garden is no more than that for the equivalent ornamental garden or lawn that it can replace, but the benefits in terms of energy savings (not to mention food quality, and the satisfaction of providing for yourself) are immense.

    So if you want to reduce your food related energy footprint, think not only about your purchasing choices but about what food you could be growing on your own property, or in a community garden, or in a gorilla garden. Many edible perennials can take years to reach their potential. That should be taken as a call to action rather than, as seems more often the case, a reason not to start at all.

    Those interested in more information on this form of low effort, high yield gardening should try searching on food forestry, forest gardening or permaculture. Some of the classics on the subject are “Permaculture: A Designers’ Manual” by Bill Mollison, “A Forest Garden” by Robert Hart, “Gaia’s Garden” by Toby Hemenway, and “Food not Lawns” by H.C. Flores, though there has been a proliferation of many good books on the subject in recent years.

    PS. I noticed one typo you may wish to correct: “I suspect the uncertainties are quite large, but they nonetheless coNvey a general sense.”

    • I’d also recommend Eliot Coleman’s books, especially “Winter Harvest Handbook”. We grew all of our fresh vegetables this winter in a passive solar green house and coldframes. (No water/stone heat storage…just floating row covers.) Temperatures hit a low of 14 degrees in the greenhouse, with no damage whatsoever to the 20 or so different crops we grew.

  10. After reading your detailed post I have one simple question. Should I turn the engine off when I’m waiting for my quarter pounder with cheese at the drive-thru or let the engine idle ?

    A question from real America

  11. Apparently, this report by the FAO
    claims that the total overhead required by livestock (as represented by GHG emmisions) is slightly bigger than all of transportation combined. thus the impact of diets leaning toward vegan/vegetarian seems to be significant.

    • Considering GHGs rather than energy (as I would — energy isn’t nearly as pressing of a problem) changes the calculations a little, mainly by making dairy much worse than pork or poultry. I drink less milk than I used to but there is no good substitute for it. You’d think of all the things I consume that would be the easiest one to recreate in a lab.

      • I’d think blood and plasma would be easy to cultivate, and in demand given all the begging for donations, but it seems not…

  12. I think the topic of this post is particularly close to concept of emergy (with an M). It’s an energetic accounting method for normalizing and tabulating inputs and comparing competing methods for product generation. In essence, not all ears of corn are equal. It can cost more to generate an ear of corn in a dry desert than on a rainy plain. However, when other less simplistic situations arise, (What about a dry desert with excellent soil vs. a rainy plain with poor soil that needs heavy amending?) making conclusions can become more difficult.

  13. What we call “grains” are really grass seeds. Are humans made to live on grass? Do other great apes eat “grains”?

    • Modern humans evolved to eat almost anything. Incidentally this seems to have been our key advantage over the Neanderthals, who were almost exclusively meat-eaters. The other great apes eat mostly fruit and shoots and leaves if I’m not mistaken. But that is irrelevant since they stayed in the trees while we evolved on the grassy plains of Africa.

    • Mountain gorillas eat primarily leaves, shoots, and stems, which are, broadly speaking, less calorically dense than grass seeds. So the answer is Not Necessarily, But Paleo-Diet Misunderstands Basic Precepts Of Evolutionary Constraints On Diet.

      • Why did paleo-diet suddenly get mentioned?

        Grains, AIUI, are rather modified grass seeds, to be even starchier than usual. Not to mention how we process them.

    • Our digestive system is like neither the ruminant (obviously), or the gorilla (hind gut digester). The gorilla has a much larger hind gut (colon) than ours, and can absorb a significant amount of calories from the digestion of vegetable fiber. Humans cannot, since we have a very short digestive tract, such as most carnivores possess. We are simply not well suited for digesting grains, although we have been making a brave attempt for the last 300 generations or so, in spite of the reduction in brain size and skeleton that has produced. Interestingly, our near relative, the chimpanzee dines on meat rather frequently, and its favourite prey is a ruminant primate – the colobus monkey.

      • Actually chimpanzees eat very little meat. Sure they catch prey, but it’s a minor part of their diet. They largely eat fruit, which is supplemented with other items such as termites.

        We do not have a carnivore gut.

        It’s OK to like meat, but don’t justify it with false science.

        • Termites are kind of also meat.
          And chimp hunting may be greater than that. Also, seasonal, a good way of getting through the dry season: http://www-bcf.usc.edu/~stanford/chimphunt.html

          As for guts, AIU in descending length its
          herbivores (ruminants, gorillas), omnivores (humans), carnivores (cats), scavengers (vultures). We don’t have a carnivore gut, but it’s also true we don’t have herbivore guts or adaptation to live entirely on greens; we need high energy food, whether plant or animal.

  14. I didn’t really realize that the ratio of energy inputs between meat and grains was reduced by the sum of all its stages, such as hauling, packaging, refrigeration, the liquid fuels for driving it home and again, for refrigeration. Still, though, meat can become way more efficient… if it is grown (and if we are willing to eat the cultured meat)…
    (This is basically just the first link I found under searching “growing meat”).

    As for canning foods, this one gives hope…
    Living the Frugal Life…(This is not the first link from search of “energy costs canning food”). Kate says
    “… I could can salsa for about one-sixth of a fossil fuel calorie for every calorie of preserved food…”

  15. I note a fair number of women I know have stopped being vegetarian/vegan due to health reasons, like anemia or weight control. This despite living in a heavily veg*n social group.

    • Damien –

      I’ve noticed a similar trend (not among friends, though), and I think it might be due to a combination of factors: a) poor eating habits as a vegetarian and b) misinformation from poorly researched books (particularly from the “paleo” camp). The first factor is very common—it’s easy, especially when switching to a vegetarian diet, to not get the right mix of nutrition. Michael Pollan’s guideline—eat food, not too much, mostly plants—is excellent advice. The key aspect that’s ignored, I think, is “eat food” combined with “mostly plants”. It’s easy as a new vegetarian (or when feeling lazy) to eat lots of processed soy meats and cereal and bread and cheese and pasta, instead of veggies and fruits and beans and eggs and lentils and nuts.

      I used to be in Tom’s camp about vegetables. What I’ve found is that when prepared properly, many are actually really tasty. Winter squash are great when roasted with garlic and herbs. Beets can be great fresh when blended into a soup. Kale and garlic makes a great topping on thin-crust pizza. And so on.

  16. Tom, you can find a concise treatment of the energy subsidies to the modern food system in Vaclav Smil’s excellent book “Energy in Nature and Society”, full of interesting quantitative evaluations and references to the main scientific literature on the subject. Here we discover, for example, that the grand total of energy subsidies used by global crop farming at the beginning of the 21st century is about 13 exajoules per year (2 EJ to produce and maintain agricultural machinery, 5 EJ to power it, 5 EJ to produce fertilizers, 0.5 EJ for herbicides, the rest goes to irrigation systems). But Smil correctly points out that energy considerations alone (e.g. the ratio of energy invested to energy of the harvested food) are somewhat misleading when food is concerned. This is because crops are clearly not grown just for their gross energy content but for their unique combination of nutrients, processing potential, storability, etc. Moreover, the idea that the energy subsidies of modern agriculture are converted into food is wrong. The relevant energy conversion is photosynthesis, and its efficiency has not improved. The subsidies remove or moderate some factors that limit plant growth and help to channel the photosynthetic products into target harvest tissues.

  17. No waste=No waist
    How about an alternate that doesn’t require giving up so much meat? Dietary restriction to 30% of usual caloric intake has been shown to significantly extend lifespan across species, from worms to mammals. Most Americans are overweight or obese; think about the embodied energy in all that fat that is only serving to shorten lives. Not to mention that a heavier body takes more energy to move around. Not to let the thin off the hook–how many get there by going to the gym to run off their extra caloric intake? Surely this cannot be an ideal way to conserve energy.
    Of course, it is not an easy thing to do. But at least one can enjoy a surf’n’turf without feeling guilty.

    • To further this thought, the 2100 kcal per capita average that Tom uses underestimates current consumption significantly. According to the USDA the average was around 2700 kcal and climbing back in the year 2000 (page 2 in the following link):


      So we could drop our food energy use 20-25% by collectively eating a healthy amount. And that reduction in energy use would be accompanied by increased quality of life and less health care spending. Win win.

  18. Great post. A few notes on meat: FAO (faostat.fao.org) estimates that in the American diet, despite its heavy use of meat, meat constitutes only 12% of dietary energy. FAO estimates 3kg of grain are needed for each kg of meat and the energy content of meat is about half that of grain, so the energy conversion 1:6. That depends of course on the type of meat and other factors. A few references:
    • UNEP: World Food Supply – http://www.grida.no/publications/rr/food-crisis/page/3562.aspx
    • Pimentel and Pimentel (2003). Sustainability of meat-based and plant-based diets and the environment. http://www.ajcn.org/content/78/3/660S.full

    • I took a look at faostat.fao.org. It claims that meat makes up 12% of dietary energy, dairy 11.4%, and “fats” (including butter, lard, and vegetable oil) at 20.5%.

      In order to know exactly how much animal products are contributing to the American diet, we’d need to know the exact breakdown of the “fats” category. However it appears that the Americans get around 28% of their total calories from animal sources.

      At the 1:6 ratio you mentioned, this implies that the average american consumes 2.4x more energy than if he ate a vegan diet.

  19. I helped my brother with his backyard chickens all last year. From what I can tell, you don’t even have to give them much in the way of scraps, as long as your backyard’s not sterile; they find all the bugs they want, along with grass seed, dandelions, whatever. Do not let them near your strawberries. Some of the chicks even managed to eat the leaves of one of the kinds of potatoes.

    Anyway, the two adult hens produced about a half dozen eggs a week between them all summer (except when broody) for the cost of two bags of chicken feed (added supplementally, and split among up to thirty chickens at once). Those backyard eggs were delicious and much better than what you buy at supermarkets.

    So off the top of my head, $35 for a 50lb bag of organic scratch (so $70 for two), 13 weeks of 6 eggs, and a single hen eating 1/10 of both bags over that time; about $14 for 78 eggs, maybe $2.16 to the dozen? Also, you can turn however many cockerels you ended up with into meat.

    Also, there are no ticks on the chickens’ side of the yard. Dog poop gets taken care of by chickens scratching it apart for beetles. They are composting machines that mostly take care of themselves.

    An appropriate adage here: People who raise cows are really grass farmers (or should be); the cow is just the way to put the grass in a form humans can eat.

  20. “As a result, walking to the grocery store effectively uses as much fossil fuel as would a typical sedan.”

    Um… I don’t see how this is possible. Are you talking about a sedan that grew on a tree? A sedan without a person in it (who is of course metabolizing food)? A sedan that does not require parking space or elaborate highway and road system? What sedan are you talking about, and how in the heck is it typical?

    • Good points. If you have a sedan in the driveway, roads between you and the store, and a parking lot at the far end there already, then the marginal decision of whether to walk or drive is surprisingly not hard-over in favor of walking, if on a typical American diet. Of course you make a strong argument that our collective decision to build a mobile infrastructure is not accounted in my narrower argument.

      • I disagreed with that before and I still disagree with it. Counting marginal calories burnt from walking a few steps more might make a bit of sense in a scarce society where every calorie is accounted for. Given however that somewhere between 30 and 40% of US calories just go to waste, that analysis is pointless. It is quite likely that people who drive when they could just as well walk are also more wasteful in their food habits. And when you carry your groceries you probably buy less stuff that you don’t need. Moreover, the same person who drives to the store might also go to a gym specifically to burn calories. When you think about this for more than two seconds, you realize that the “marginal” analysis cannot capture how people actually behave. Humans are not machines whose energy expense can be precisely predicted based on the physical work they perform.

        I neglected to spell out that that driver also has a two-thirds chance of being overweight. Would that person really eat more for every step walked? Possible but not likely.

        • Toni:
          “Given however that somewhere between 30 and 40% of US calories just go to waste, that analysis is pointless.”

          That’s a red herring. Walking is still not much more energy-efficient than driving.

          “It is quite likely that people who drive when they could just as well walk are also more wasteful in their food habits. And when you carry your groceries you probably buy less stuff that you don’t need.”

          That may be true, but it doesn’t matter. If you wish to reduce your energy impact, you should continue to drive, but stop buying food that you won’t eat.

          “‘marginal’ analysis cannot capture how people actually behave.”

          It’s not trying to capture how people actually behave. It’s trying to capture _what you should do_ if you wish to reduce your energy impact.

          There may be other good reasons to walk rather than drive but energy conservation is not among them, unless you would walk that distance _anyway_ for health reasons.

      • tmurphy,

        The only problem I can see with your MPG analysis is that you are calculating the energy cost of transporting the _person_ to the grocery store and back, but not of transporting the _food_.

        Suppose I load the car with 15 bags of food which would have required 5 walking round-trips to transport. Also suppose that the additional weight of 15 bags degrades fuel economy in the car by only a negligible amount. In this case, driving is far more energetically efficient (more than 5x as efficient) per unit of food transported.

        Perhaps the best way to conserve energy is to consolidate trips.

        • But if you don’t take the energetic cost of car construction (and I guess shoe construction) this doesn’t make a lot of sense to me.

          I do get the point: driving with all other costs externalized is no more energetically intensive than walking with all the other costs internalized.

  21. I would argue that it is possible to eat a meat based diet that requires less energy from fossil fuels and is less environmentally destructive than a grain based vegetarian diet. This is accomplished by simply letting ruminants be ruminants. Ruminants have the amazing ability to convert plants that can’t be eaten by humans and require no fertilizer, irrigation or pesticides into meat for humans. If we converted the millions of acres of grain, now dedicated to growing food for animals, into properly managed grassland we could drastically reduce the energy cost of meat and begin restoring a more natural and less destructive environment. Growing grain requires massive inputs and has huge environmental consequences. A properly managed pasture can actually build soil and serve as a carbon sink, not to mention allowing native species to thrive (which is impossible on a massive grain monoculture). I don’t think this is a replacement for our current system (there is no way that we could produce the massive amounts of cheap meat available today), I just bring this idea up because I think it should be considered in any discussion comparing the cost of meat vs grain based diets. Eating grains is destructive and requires huge amounts of fossil fuel.

    • Thanks for saying making these points – I found “The Vegetarian Myth” by Lierre Keith to provide a very insightful counter to the meme that meat is necessarily environmentally bad.

      • Here’s the most charitable thing I could say about ‘The Vegetarian Myth’: that it tries to generalize from a personal experience to vegetarianism vs. meat eating in general. The less charitable take on it is that it’s a horribly researched book (just check the references—most are are random websites and non-scientific sources), gets numerous basic facts wrong, and isn’t well argued. It’s not a book to use to make an informed decision about eating meat vs. not.

        A better and wiser book vaguely in the genre, if you want to read one, is Kerasote’s book Bloodties. (My friend Adam had a nice post on the book and the broader notion of “fossil-fuel vegetarianism”.)

    • “there is no way that we could produce the massive amounts of cheap meat available today”

      Agreed on the “cheap” point, but industrially farmed meat is only cheap because we haven’t yet paid the full cost. Factor in soil degradation, soil errosion, GHG emissions, polution, energy footprint, etc, and industrial meat is not so cheap afterall. Pastured animals, raised, butchered, and sold to consumers all within a short distance of their pasture may cost a little more to the consumer now, but the full cost is much less. It’s been estimated that close to 1/3 of the world’s arable land has been lost since 1950 due to errosion and salination resulting from current farming practices. The rate of soil loss is a much scarier prospect to me than the rate of fossil fuel depletion. It’s not yet clear to me whether it will be the lack of soil or the lack of oil that will factor most heavily in our future.

      However, at least there are viable alternatves to current farming practices. Permaculture methods of raising food crops and intensive methods of raising grass fed meat have been shown to be capable of producing as much or more food per acre than current standard practices, while at the same time improving rather than degrading the soil, and utilizing far less energy. Joel Salatin’s Polyface Farm (described in Michael Pollan’s “In Defense of Food”) is the classic example, but there are many. The worry is whether there will be enough soil remaining to avoid a famine by the time we figure out how we should have been farming all along.

      Unfortunately, as we run out of oil, we’ll likely see an even greater rate of soil degradation/errosion from production of biofuels.

    • Your points are excellent.

      Looking at cattle solely as a food source greatly underestimates their importance. They are one of the key original contributors to civilization; see Jared Diamond’s “Guns, Germs and Steel”. If we are looking to build a sustainable, non-oil-based culture, we might appreciate a food source that can also be used to pull wagons (oxen)–truly sustainable transportation. They provide hides that are made into leather for shoes, clothing, harnesses, storage pouches, even tipis. Their collagen can be made into glues, paints and fillers; their hair into brushes, felt for clothing and blankets, upholstery and insulation. Rather than thinking of cattle as being food, it might be more accurate to think of them as a sustainable source of many useful products, with the wonderful added value of providing milk, butter and meat.

    • I thought so too – 2100 is how much thin (but not starving) people in poor countries eat. But then Hall et al. (Hall KD, Guo J, Dore M, Chow CC (2009) The Progressive Increase of Food Waste in America and Its Environmental Impact. PLoS ONE 4(11): e7940. doi: 10.1371/journal.pone.0007940) estimate 1400 kcal food waste per capita. That would correspond to about 2400 kcal actually consumed. That figure sounds low to me – can you really get overweight from that? Of course lack of exercise might be an important factor. I am just not so sure that our data are that reliable.

  22. Seems you need to start a garden Mr Tom. That should get you below the 50% you want. Enabled by your change in diet.

  23. Thought it over.
    If a person eats ~2000 kcal a day (eq. ~250g Gasoline),
    and every calorie requires ten times its energy for production
    this makes 1t of gasoline-equivalent a year, with a year having 400 days.
    300 Million Americans will need 300 million tons a year, a third of their total oil consumption.
    If fertilizer (mostly ammonia) production is 30 percent of that, we have ~100 million tons (CH2)n going into ammonia.
    Global annual ammonia production takes 1-2% of the worlds energy supply
    Probably that’ more in the industrialized agriculture countries…
    I was surprised.
    For energy reduction, switching to a diet lower in nitrogen (protein) might make quite a difference.
    Peanuts are an alternative. They’re rich in the amino acids tryptophan and lysin, rare in most plants, which nitrogen is caught directly from the air, and certain vitamins that can be scarce when living mainly off grains.

  24. Healing our land and keeping it healthy is essential to growing food. In short plants need animal wastes to recycle key nutrients, starting with nitrogen, which is too often replaced with chemical nitrogen omitting the balanced nutrients in manure. This has been the life work of many – Alan Savory, for example, has won many major awards for his efforts working to heal land with grazing animals –

    Plants and animals depend on each other. Vegetarianism, in general, is the wrong path for planet Earth. We are not as efficient grazers as cows and ruminants. We are omnivores. Millions of acres of Georgia farm land were healed – returned to productivity – using chicken manure as I was reading at the chicken building at the Georgia National Fair (Great Fair!)

  25. Industrial meat do demand a lot of energy to be produced but meat can actually be a net plus of energy. Traditionally cattle and other animals have roamed fields not suitable for any food crop such as stone hills, forests with unsuitable soil and so on. If meat is produced this way during the life time of the animal, it will produce a net benefit of energy available.

    I want to add that industrial meat is raised on grains, hence the big energy cost. However it is worth to remember that not all grain in the harvest reached human consumable quality and is only worthy as animalfeed.

  26. I think we have a huge problem in America with food waste largely because food purchasers expect beautiful waxed “perfect” looking food that is developed and raised to be transportable and because our food systems are linear instead of circular. So much good food is thrown away or left to rot simply because it doesn’t look nice, or might have a bug on or in part of it or got a little bruised in shipping and the company selling it can’t be bothered to find alternate uses for it. As an anecdote, I live in the part of the country that grows 95% of the apples and pears for the rest of the country. Fruit packing houses tell the growers when they can pick based on when the packing house can transport. Last fall, at least one whole orchard worth of pears (hundreds of acres of bearing trees) rotted on the ground because the packing house didn’t have room to take the fruit when it was ready to be picked, and when it did have room, the pears were slightly too soft to transport. The packing house wouldn’t take them. The grower couldn’t sell them, so didn’t bother to pay workers to pick them. A whole growing season of fertilizer, pesticides, tractor diesel, and pumped irrigation water resulted in virtually no food for people to eat. That’s waste. The other aspect about producing meat however, is that a lot of this kind of food waste could be recovered by integrating animals back into our agricultural processes. Several orchardists in my area are experimenting with running sheep or pigs or chickens through their orchards in spring/summer/fall. The animals mow the grass around the trees, eat the fallen fruit, eat bugs that affect the trees and keep disease loads and weeds down, as well as produce meat for consumption. In addition, the same piece of land can result in many more calories (and more farm income) through managing the systems better. It does require a change of thinking and additional thought and observation to run the system well.

  27. Any idea how shellfish measure out? Farmed oysters and mussels don’t require any fertilizing or feeding. Plus, they actually improve water quality and the environment.

  28. Australia’s foremost science body, CSIRO, published a pie chart fairly recently showing the energy footprint of a typical Australian household, including embodied energy components.

    Energy to power the household and its appliances and so forth came to 17 percent of total household energy footprint. Our food footprint came in at 29 percent.

    This is very valuable information because it demonstrates that when a person makes some simple decisions about what they eat and where they get it from that effort is likely to be much more advantageous than when he / she undertakes traditional and very costly measures such as putting solar panels on roofs.

    Too many people look to purchasing sexy technologies when there are vastly more beneficial things to do, mostly at little or no financial cost.

  29. There are some utterly delicious dishes that use meat («FLESH!») as a condiment rather than an ingredient. What comes to mind is the Puerto Rican «Arroz con Gandules» (in English, «Rice with Pigeon Peas» — but while I lived in PR I never heard Anglos call those delicious things Pigeon Peas, instead calling them by their name in Spanish). A young Honduran immigrant friend of ours wondered why the Arroz con Gandules bought in a Hispanic supermarket tastes so much better than the dish fixed by a Puerto Rican friend of hers. It turns out that the friend (plus her family) are members of a religion that mandates veganism. Leave out the pork, and your taste buds will be severely disappointed.

    I highly recommend Arroz con Gandules. Warning: it is not as easy to fix as the recipes could lead one to believe. I suggest buying it in a place recommended by a Puerto Rican you trust. Anyway, it uses only a miniscule amount of pork. And it is awesomely nutritious — serve it, and there is no need for any meat. Goes great with a full-bodied beer or a gentle Tempranillo. Or with H₂O.

    Kinda like, you don’t need much ham to make a great split-pea soup!

  30. I was discussing this blog topic with one of my kids yesterday, she works for a large agrochem company. They are looking at energy use as a critical future constraint on crop production, clearly less for more is better, but overall, they see it as a race between running out of energy and running out of water. And apparently, the crops favoured for vegetarian diets are significantly more consumptive of water than others e.g. soya. Now I should go check on that…

    • Do you have data on water consumption of plants? It seems like animals generally must be more intensive for energy/water, simply because you are having do to double work: first put water/energy into plants, then put those outputs into animals. Neither is efficient, so it’s hard to see how you could waste more water on plants than animals.

      Most of the soya used here in the UK is imported for cattle feed from South America, which are responsible for rainforest destruction and nasty pesticide use (causing illness in locals). See FOE report: foe.co.uk/resource/briefings/gm_animal_feeds.pdf

      • Plants obviously vary a lot in water needs; rice and cactus, say. They can also differ in whether one applies water or relies on rainfall. Cattle eating rain-fed arid grass can use less applied water than heavily irrigated human crops.

        • Sure. But I find it hard to believe that even rice uses more water per calorie than cattle on grass, but I would be interested in seeing the figures.

          • Applied water, not just water in general. The rangeland grass is growing on rainwater. It’s not taking water away from any other use; the rain would have fed grasses anyway, which would have in turn fed antelope or rabbits or bison if not cattle.

  31. Very fascinating post.

    II think, however, that the benefits of eating less meat have the potential to be even greater, when we look at to what is possible if meat is thought of as a vital small portion of our diets. Diets with a moderate amount of animal products have the potential to be more energy efficient than a vegan diet. There are man niches where animals can vastly improve the energy efficiency of food production:

    -As noted, many small farmer, including the college farm where I work, are able to produce modest amounts of eggs, chicken and pork with little or no grain by utilizing food wastes.
    -Carefully managed, much of the rangeland in the US can sustainably produce animal protein with minimal energy input and no harm (or even some benefit) to the local ecology.
    -The best way to cut a quarter to a third of the energy use out of growing corn is get rid of nitrogen fertilizer by reintroducing biennial and perennial legumes (clover, alfalfa) into crop rotations. This only ends up being financially feasible if the farmer has ruminants which can graze this and/or eat the hay from these crops. Brood cows can also be maintained for much of the winter on corn stalks.

    The issue is, however, that if we want to eat as much meat as we do now, these systems are probably not going to be sufficient. If we accept meat as a treat, we can keep our consumption to a level where meat production fits into the niches where it belongs, and is at least as energy efficient as vegetable foods.

    • When I lived in Puerto Rico (1962, studying engineering at the CAAM in Mayagüez), several times a day one could hear teenagers pulling barrel-laden carts through my residential area. They would cry out, “¡Fregados! Fregados!” (Slops!) They collected uneaten food and fed it to pigs, which they sold when appropriate.

  32. I would be very interested in the energy consumption for entirely grass fed beef. Locally raised about 40 miles away from my home.

    I find myself reading these analyses and not knowing hoe to apply them to my situation because I do indeed avoid feedlot beef (or any other animal) quite carefully. If it turns out to be true for grass fed beef too then I would be willing to try to change my diet. In the meantime, my gut tells me that grass fed beef is good for me.

    • According to Pimentel & Pimentel, range-fed beef uses 3.5× less fossil fuel energy than grain fed beef. So that puts it at about 0.2 on the scale: similar to chicken or eggs. Indeed it’s a big improvement. And I’m sure there can be large variations in practices among range beef operations. If low energy is a goal, it can probably be quite good on this score (as with many things).

  33. Interesting! So, I too will continue to cut back on my less energy efficient foods. I started a similar program when I retired and my income dropped 40%. Meat was no longer a daily item in my diet. I live where meat is very expensive and the recipes have little or none. The choice is 5 lbs of rice at $1.50 or 8oz of beef for the same price. On occasion, I have the beef, but much more often, I have the rice.

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