Monday, August 14, 2017

Which EROI do we need to collect berries?



My wife, Grazia, collecting berries in the woods of Tuscany in a hot day of August. Maybe her ancestors were doing exactly the same, more or less in the same place, hundreds or thousands of years ago. Here, I present some reflections and some calculations showing that the EROI of this simple way of collecting food may be over 100, better than almost anything we have nowadays. Of course, no empire in history was based on hunting and gathering, but was that a bad thing?


The question of EROI - the energy return on energy invested - is raging nowadays, with some people insisting that a civilization cannot exist without an EROI of at least variously estimated values, at least 10 and higher (image on the right by Charles Hall). And that is said to mean we absolutely need sophisticated technologies, such as nuclear, in order to survive.

Yet, this morning I had been collecting berries in the wood with my wife and wondering: 'what is the EROI of what we are doing?' A reasonably good EROI, I am sure, enough for what our ancestors needed when they survived on hunting and gathering. All you have to do is to walk in the woods, find the berries and pick them up (and watch your step, you don't want to fall into a thorn bush).  If our hunter-gatherer ancestors used this method, and if we are here today - their descendants - it means it was an effective strategy for survival. Collecting what you can find is an ancient and tested strategy that goes under the name of "gleaning" and it has accompanied humankind for millennia. It is a good strategy just because it is so simple: no tools, no written laws, no overlords, no police, no fences. And it works.

As I was collecting berries, I started thinking things. How to program a drone to collect berries, for instance. Sure: a perfect way to bring down the EROI of the whole thing to nearly zero. And to destroy the bushes forever. Humans are like this, with their attempt of "improving" things they always pull the levers in the wrong direction. And that means making things more complicated, needing more and more energy to keep them running, and then complaining that we don't have enough.

Of course, with more than seven billion humans on this planet, it is hard to think that we can go back to gleaning to feed them all. But for how long we can trust the expensive, complex, delicate, and terribly inefficient enterprise we call "industrial agriculture"? I can't say. What I can say is that collecting berries is a big satisfaction, as you see below.





And now some approximate calculations: Today we collected 2 kg of berries. According to the available data, berries contain 125 kJ/100g. So, the total collection was about 2500 kJ, about 700 Wh.

Now, it was about one hour of low-intensity work for two people, so let's say it involved a total of 50x2x1h = 100 Wh of human work. Then, I found values of 20-25% for the human metabolic efficiency of converting food to mechanical energy, it means we consumed some 400-500 Wh of food energy in order to collect 700 Wh.

Very approximate, or course, but the final result is an EROI = 1.4-1.7. Not comparable to crude oil, but probably more than enough for our ancestors to enjoy berries as a seasonal treat.

But, of course, no one ever lived on berries alone, not even in paleolithic times. The energy content of several kinds of foods that you can find in a natural environment may be more than an order of magnitude larger than that of blackberries. Walnuts are reported to have more than 10,000 kJ/100 g. If you can collect one kg/hour, as we did for berries, it means an EROI of more than 100 (!!). Larger than the mythical EROI of crude oil of a hundred years ago. Wheat and cereals, in general, have also high energy content, wheat is reported to have 15,000 kJ/kg, showing how gleaning could be an extremely efficient food gathering strategy.

So, life was simple and easy, once, until we decided to make it complicated and difficult.






40 comments:

  1. Sorry to disappoint you, even if I can't find a scientific reference, I believe that berry collection i almost below 1 in EROEI. Which is the reason for why noone collected them in the the Swedish forests for food, just for fun and for the nice taste, or for exports to Italy where they taint red wine with blueberries! I know there has been some study on it, but I can't find it. It is sugar cultivation that was the breakthrough for berries. A bit cynical you can see them as sugar flavorants.....

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    1. Well, at this point we really need a calculation. Let's see. Today we collected 2 kg of berries. According to http://apjcn.nhri.org.tw/server/info/books-phds/books/foodfacts/html/data/data2a.html, berries contain 125 kJ/100g. So, the total collection was about 2500 kJ. Translated into Wh, it is about 700 Wh.

      Now, it was about one hour of low intensity work for two people, so let's say it involved a total of 50x2x1h = 100 Wh. Then, I found values of 20-25% for the human metabolic efficiency of converting food to mechanical energy, it means we consumed some 400-500 Wh of food energy in order to collect 700 Wh.

      Very approximate, or course, but the final result is an EROI = 1.4-1.7. Not comparable to crude oil, but probably more than enough for our ancestors.

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    2. Note also that my wife collected more berries than me - she was more patient. She chose a bush, and picked it systematically. In my case, I tried to find the best bush, I walked more and I collected less. Her EROI was better than mine. There have to be reasons why women were more gatherers and men more hunters!

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    3. What strikes me about the process and your post is how we live in a mindset of evaluating everything relative only to our own position. Debating EROI makes sense but only if we disregard the greater networks around us. Every single calculation could be higher than 1.0 (or even 10.0) and the end result is disaster.

      While this calculation must be above 1.0 for the work to make since to the individual the calculation is irrelevant in the grander system. The problem with EROI is that the calculation is only made on a basis on how the energy flow relates to an individual. In paleolithic times (and today too) the harvesting of berries would have also accompanied an enormous number of environmental network effects. The harvesting would have involved the humans relocating the seeds to other areas for fertilization (both in feces and spillage), it would have involved the fertilization of the soil, and a host of other interactions totally beyond a simple energy in/out calculation among a thousand different species.

      The effect is dynamic of course and it actually makes sense in this kind of arrangement for specific species to do work that has an EROI below 1.0 if the overall network gain from interactions in the chain benefit the species at another point in the cycle --- symbiosis.

      One problem that we see is that the industrial process for agriculture essentially destroys the entire network and replaces it with only those interactions that are direct and measurable. Essentially anything not directly involved in the EROI calculation of the human individual is left to die --- species depopulation, mono-culture, and food source vulnerability through environmental change is the result.

      With no network the moment the inputs into the calculation decline the output must fall. And with no network there is no natural limit to that decline.

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    4. Sorry, but your EROI calculation is fundamentally flawed--because it ignores baseline maintenance requirements. Should you and your wife have chosen to lay around the campfire rather than pick berries you would have expended X calories digesting breakfast and replacing all the night's cells whose telemeres have grown too short. By going berry picking you expended X+A calories to generate a gross income of 2500 kJ. The EROI of berry picking should be computed based upon the marginal energy cost (A) of the activity, not the total of X+A.

      If one wants to refine the calculation a bit further one should calculate the heath benefits of a walk in the woods and shared activity vs laying around the campfire and getting on each other's nerves. (its well known that too much of the latter can lead to heart attacks which definitely have a quantifiable economic cost.)

      ps: I doubt if one of the challenges facing the future biosphere will be that there are still 7 billion humans all trying to pick the last berry and expending too much energy doing so---. And thankfully the remaining half billion won't have time to waste posting stuff like I just did!

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    5. That's another kind of measurement, called indeed "MEROI" Marginal EROI - it has been proposed first, I think, by Douglas Reynolds. Standard EROI, however, is calculated more or less the way I did for collecting berries. These measurements are useful for comparing one activity with another - the mistake that many people make is to compare one kind to another and then conclude that some technology they don't like (typically, photovoltaics) is useless.

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    6. A lot of good points emerging, and number crunching (sorry for being lazy myself and letting others do the counting). An EROEI on food production/collection below 2 is very low. People need food energy also for dependants and sick, repairing their implements etc. So even for foragers not having the burden of complex civilzation berry collection (and most mushrooms) is barely feasible. Nuts and wild grains is something quite different, they are very energy dense.

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    7. Ragelle - wonderful response. The whole picture always.

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    8. Berries likely have some vitamin C, which nuts and grains don't have, so the time spent gathering them could have value greater than their calorie content. You are presumably using the energy of a complete diet to hunt and gather with, so you need to compare the energy to hunt and gather a complete diet to get a proper comparison.

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  2. I prefer to define EROI as a difference, rather than a ratio. In the present case 700 Wh - 500 Wh is > 1. In my opinion any positive number is satisfactory, unless negative number is accompanied with pleasure.

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  3. I was picking berries in Raymond Washington yesterday with my partner and coworker. It is a good time indeed and the berries and wine that it will become require very little to enjoy. It isn't a grand solution as you said, but it is a pleasant bit of survival at a human scale. My gratitude that you took the time to remind us to breathe as it were.

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  4. Too many berries and you will get a negative EROI. You can count on someone turning it into alcohol and work will come to a dead stop till it is all got!

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  5. On a decades-ago backpacking trip in Michigan, my kids (then 5 & 7 years old) kept finding patches of wild strawberries. Off came the packs. They kept exclaiming that strawberries from stores never tasted this good. My wife suggested they gather some for the following morning's breakfast (oatmeal). Patch after strawberry patch, none lasted until the packs went back onto the backs.

    The 7-year-old observed that each tiny strawberry had more flavor and sweetness than an order-of-magnitude bigger strawberry from the store. He wondered whether nutrition was also independent of per-strawberry volume. They both complained that it was impossible to eat enough wild strawberries to fill the tummy.

    I pointed out that bears eat immense quantities of berries (various kinds) that help them fatten up for the forthcoming long winter's nap. Both kids testily told me they were human children, not bear cubs.

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  6. Ugo
    If you look at the work of the Land Institute in Salina, KS, USA, you will find that the domestication of grains resulted in a 20 to 50 times increase in EROEI. This permitted the growth of what we label 'civilization'.

    There is no question that hunting and gathering can be a pretty good way to live.
    Marshall Sahlins wrote about The Original Leisure Society a long time ago. But the domestication of grains was what permitted the initial large increase in the population of humans on the Earth. And grains, being an annual crop, are what created the ecological disasters that turned the Fertile Crescent into a desert. We are still wrestling with the Deal With the Devil of annual grain crops.

    Humans are exquisitely adapted to foraging for raspberries, but that doesn't sustain the city of Rome, or much less Lagos or Mexico City.

    The takeaway for you is to stop belittling the work of the EROEI people and treat it with the serious respect that it deserves.

    Don Stewart

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    1. Exactly. With such large EROIs, our ancestors surely had a lot of leisure time. Too bad they used some of it for pleasant activities which, unfortunately, resulted in large numbers of them spreading around.

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    2. hihi yeah and copping trees down for bad unfortunately for nut collectors. i once heard about taking account that most wheat fields have a lower EROEI than a oak or chestnut forest, when take account that most soils degraded etc...

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  7. Gleaning – Wikipedia
    Gleaning is the act of collecting leftover crops from farmers’ fields after they have been commercially harvested or on fields where it is not economically profitable to harvest. It is a practice described in the Hebrew Bible that became a legally enforced entitlement of the poor in a number of Christian kingdoms.

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    1. https://en.wikipedia.org/wiki/The_Gleaners_and_I

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    2. Great movie. And I have something in the pipeline about gleaning, too.

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  8. The fact that you can have such high EROI levels from gathering berries and specially high energy content nuts (as you say 100 or more) might explain why many hunter gatherer societies spent little of his time gathering food and much simply doing other tasks (inclding a great deal of free time as some anthropologista report). I have the feeling this was somehow inverted with the agricultural revolution whete most of the population was condemend to support the landed classes and the few artisans, doctors... With the start of capitalism and at the beginnimgs of the industrial revolution many would simply have to work for countless hours in very poor conditions...

    I think I'd be interesting to have more studies on the time invested in several activities of different hunter-gatherer based groups. They could help understand better how ro build up a low-energy consuming society...

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  9. Berries are not about calories or even recreational eating. Nutritional science is complicated, but berries continue to get a good press even for populations living modern industrial styles. http://www.mdpi.com/1420-3049/21/2/169/htm
    best
    Phil

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  10. @ Ugo Bardi et al

    Dear Sir,

    Since almost every commentator is addressing exclusively the numbers' side of your post (apparentely, that's the way minds are shaped into in tech societies: first you somehow learn how to turn everything into some sort of quantity, and then proceed to monetize it), I dare to bring readers' attention to other (provocative) thought-inducing phrase from Mr. Bardi (and breaking some netiquette by doing so):

    "Collecting what you can find is an ancient and tested strategy that goes under the name of "gleaning" and it has accompanied humankind for millennia. It is a good strategy just because it is so simple: no tools, no laws, no hierarchy. And it works."

    Thank you for reading.

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  11. I can collect about 350lb. of acorns per day. In a month I can collect enough to feed three pigs for a year .The three pigs produce fat that can be made into biodiesel . The biodiesel produced is adequate to plow and cultivate about two acres of garden. So foraging , raising pigs and gardening a couple acres can result in a positive EROEI. Combined with solar for electrical demands of water pumping and transport there is the potential for a small scale farmer to produce food( meat and vegetables )and fuel. Foraging is also a pleasurable adventure off the farm .

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    1. Let's see.. you can collect 160 kg of acorns in one day, which means 20 kg/hour. Wikipedia lists acorn energy content at 1,619 kJ/100 g. That means you can collect some 90 kWh in one hour. If you do all that by hand, it is an EROI around 200-300. Then, of course, you can't eat the acorns directly, so the whole thing would need an LCA calculation. But this kind of farming may be very efficient

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    2. http://www.humanpowerplant.be/
      Human energy. Fun and efficient.

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    3. What about the wildlife that depends on those acorns? Take away their food and you decrease the local biomass and diversity.
      It's a zero sum game. Every winner means there's one or more losers.
      Scale it up enough and everyone loses

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    4. I use a rake and a dust pan. Mowed lawns , sidewalks and curbside are flat and easy to harvest. My goal is to use the energy from a silvoculture crop to fuel tractors that can turn forest crops into food and energy. Pigs transform the calories into fats that power the tractor, the tractor multiplies the energy and can result in very high EROEI . We currently rely upon fossil fuels and replacing that energy by one that is annually produced and results in very low carbon emissions . Trees are much better at sequestering carbon than the mono crop techniques that dominate our current food systems ( farms ). The Spanish Dehesa is one of the most advanced silvopasture methods ever developed IMO. I am make progress in urban environs . The city cats and dogs take care of squirrel problems . Farmers don't compete with squirrels and you can look into how mono crop farmers deal with them.

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  12. When you see that today we need 10 calories to produce 1 calorie of food, or that in average food travels about 2.000 km from "factory" to the "table", then is easy to imagine that any other "natural" way to get food should be much, much more efficient.

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  13. this is why aboriginal peoples could not build cities and empires.

    not enough surplus energy in the system to support all the necessary labour to divert into such activity

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  14. I did a similar experiment with raspberries a few years ago. I also got about two kg of berries in two hours. Raspberries are a bit more energy dense than blackberries at about 520 Calories/kg. I didn't do any EROI calculation at the time, just a adhoc calculation that I would have to pick berries for 6 hours each day to go even.

    But here's my stab at a EROI-calculation. Lets assume that I burn 200 calories per hours of berry picking and 100 calories at rest. Every hour of picking would produce 520 calories gross or 320 calories net. Given these numbers I would have to pick for:
    5:43 hours per day to get an EROI of 1
    15:00 hours per day to get an EROI of 2

    A long-term calculation should also account for increased efficiency as one gains experience in picking berries and also reduced efficiency as the best/closest bushed are depleted.

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  15. Ugo’s post was clear that collecting berries is not a long term solution for the survival of 7 billions of us. And yet some commenters chose to make calculation as if that was proposed. It was just a reminder of one of the tricks that was available to our ancestors and they had a whole bag of tricks to help them through the year’s seasons. There is one big mistake in calculations about berries. They are not only rich in fructose but also contain important antioxidants that protect us from diseases. Energy and calories are not the only thing we need for survival.

    Modern industrial man’s diet contains a lot of sugar but produces a lot of diseases too, both body and mental. See some films by Antonioni. Or read biography of Mario Monicelli. Modern man (they say) lives longer than primitive but modern man is ill. It’s not only length (statistics, numbers, data) that counts. For humans the quality of life is important too. In the case of Monicelli, 95 years can be too much if the motivation is lost.

    Read again:
    http://discovermagazine.com/1987/may/02-the-worst-mistake-in-the-history-of-the-human-race

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  16. Ugo
    Following up with the raspberry EROEI discussion. I read somewhere recently from a biophysical economist about the importance of phase changes. For example, fossil fuels and internal combustion engines and highways permit a phase change wherein 'local food' is phased out and 'global food' is phased in. If we try to calculate the EROEI of local food vs. global food, we have to make some sort of assumption about the phase we are either in or anticipate being in. It's like trying to measure the 'hardness' of water....is it frozen or liquid or gas?

    With raspberries, the EROEI for some scattered hunters and gatherers with a huge natural ecosystem generating berries, the phase is highly favorable to human gathering. But if calculated from the standpoint of the average person living in Lagos, the EROEI would be miserable indeed. Curiously, in many very rich urban cities, gathering unwanted fruit from the trees in rich people's yards can be a high EROEI endeavor.

    It becomes maddeningly difficult to give any really sensible advice. Local food makes eminent sense if the fossil fuels and internal combustion engines and highways disappear...either because of depletion or political developments. But today, with fossil fuels and internal combustion engines and highways everywhere, coupled with the trillions of dollars of subsidy that the IMF says that fossil fuels are receiving, and excluding other externalities, then local food is economical only in a very small niche.

    I have to plead guilty that I haven't read Charles Hall's latest book on EROEI. But I suspect that his pyramid relates somewhat to the notion of phase changes.

    Don Stewart

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  17. Not to diminish your argument (which is essentially correct) but it is simply not true that there are no laws, rules, or hierarchies in hunting/gathering. It is my job to scold you on this, as a person who studies foragers. This is a little like an anthropologist who studies foragers showing up on an energy blog and saying "Just put a windmill on your car, and when you drive, that will generate the energy needed to run the car!"

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    1. You are right Greg, but let me reformulate my argument as "there are no FORMAL laws, rules, or hierarchies" I think even an anthropologist would agree with that!

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    2. Closer to what I wanted to say, that sentence should read "no written laws, no police, no fences" - and thanks for noting this point.

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    3. And I think it was such a good point that I modified the post accordingly.

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  18. This post and list of comments partially ignores that eroei is a relative measurement. It helps decide, should I invest in solar pv, nuclear, fracking, or wind turbines to get the most dollars or joules for my investment. But what we need to know is that for a system of x people, located in y environment, living with z services, with no enemies or competitors (think space station with no resupply) will that community be viable for say 400 years using present technology. Here is a 10 minute video that shows how to calculate the answer. Sustainable Civilization Analysis Project https://www.youtube.com/watch?v=EEqCabuiHJM

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  19. Gathering berries is less energy-efficient than buying the equivalent industrial product.

    Which means that if you do buy the industrial product, you will have to get rid of the excess energy in other ways (in the gym, for example), or face consequences for your health and fall ill.

    So can it be that, at the current level of industrialization, gathering berries is overall more efficient than buying?

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  20. Ugo
    Have you any thoughts on EROI of internet?
    I have a feeling bitcoin may not be just one special case. Could be an energy parasite?
    https://realinvestmentadvice.com/salt-wampum-benjamins-is-bitcoin-next-a-primer-on-cryptocurrency/

    BTW Pwople round here motor out to pick blackberries of a weekend ... hmmm
    best
    Phil

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  21. Slow is the rasberry's growth. fast(er) is the picking of the man, so goes the rasberry's cliff... 8-))

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Who

Ugo Bardi is a member of the Club of Rome and the author of "Extracted: how the quest for mineral resources is plundering the Planet" (Chelsea Green 2014). His most recent book is "The Seneca Effect" to be published by Springer in mid 2017