By David Waltner-Toews
Eating is the most intimate experience we have with other living beings on the planet, more intimate even than sex. When we eat, we are taking parts of the planet into our bodies; they become one with us. They become us. That is true for all animals. Eating at its best is one long orgasm.
We could also say that, in eating, the prey is reincarnated as the predator, and we are all predators, if not of other animals, then certainly of plants and bacteria. If we view it this way, eating is one great religious experience.
Both of these are true.
But there is something missing from these romantic and religious notions of eating. There is a part of eating we rarely talk about: the leftovers. Eeeew, some would say. But I say finish your dessert, have a sip of cognac, and let’s talk about it.
From your lips to your butt, your intestines are a tube through which the environment of the outside world moves through your body. This is true of most warm-blooded animals. The muscles and organs inside animal bodies, including those of people, are sterile, and the interactions between the environment moving through the gut and those sterile organs are carefully regulated. That is why surgeons have to wash their hands and wear masks. If an appendix ruptures, or the surgeon nicks the intestine, you are in big trouble. The bacteria and food wastes in the intestine spill into the sterile field. This is why, from a food safety point of view, a rare steak is pretty safe; the inside of the muscle is sterile and you just need to burn the bacteria off the surface.
If we were so bold as to look inside our bodies or to travel there on an incredible journey, we would see the individual cells draw in oxygen and various elements and excrete what they don’t use. The cells lining the intestine try to keep out as many toxins as they can and only absorb what is necessary for fueling the other cells that make up our bodies. Our own cells produce waste that could kill us if it were not carried away in the blood and then out of the body through urine, shit, bile, sweat and breath. Some substances undergo special processing in the liver or kidneys before they are released.
Many of the materials in the food that are not allowed across the intestinal walls into the more intimate secret places of your body are used as food for the trillions of bacteria that are born, live, breed, and die in your gut. Mostly these are beneficial bacteria, which do their best to keep out the pathogenic bacteria, the disruptive hooligans of the bacterial world. Babies are born sterile inside and out and are only colonized by bacteria as they emerge into the wider world. Most of the hundred bacterial species, representing forty genera, that colonize a newborn baby’s intestines in the first few months are either harmless or beneficial. They help us digest our food and stimulate our immune systems. As we get older, we acquire more bacteria from the parts of the environments we eat, or otherwise interact with. There are somewhere in the vicinity of 1011 bacteria (that is ten with eleven zeroes after it) per cubic millimeter of adult human feces, a number that exceeds my capacity to imagine, but is typical of other animals’ feces. These bacteria represent some 500 to 1,000 different species, most of which we don’t know much about. These include a wide range of micro-organisms, including bifidobacteria and lactic acid bacteria (which predominate in breastfed babies and yogurt), coliforms (which scientists look for when measuring water contamination), and even archaea (which prefer an atmosphere devoid of oxygen, much like that of the early Earth).
Some of the wastes from these bacteria also provide further nourishment for your body in the form of certain vitamins. Finally, every day tens of billions of our own cells commit suicide, an act referred to scientifically as apoptosis, or programmed death. Other cells, especially those that line the intestine, are scrubbed away by the passage of food and come out in our feces. Every day, parts of you are replaced. Have a look in the toilet. That’s not just a stool sample: that’s the old you. That’s life.
You are part of a larger living web. Every life form, as the result of consumption and respiration, uses nutrients and energy from its surroundings and (re)cycles various kinds of modified or unused nutrients and energy back to the environment around it. Some of these byproducts of life are toxic to the organisms that dump them, some toxic to competitors or predators, and some are merely not used, for a whole variety of reasons. They may not be digestible by the animals that ingest them. Or they may be more than the animal can digest at a given meal.
Excrement may also be described in terms of its content of phosphorus, nitrogen, potassium and water. This is the viewpoint generally taken by those interested in the sustainable management of manure; in particular, the chemicals in excrement may be thought of as nutrients for other species, and as fertilizer supplements to soil. Animal manure could probably replace most of the commercial nitrogen fertilizer in the world. The nutrient content of manure, like the labels on canned foods, tells us a great deal not just about what is being eaten, but also what we might be able to do with the leftovers.
We can also think of the energy content of manure. If half the livestock manure in the world were used to produce energy, it could replace about 10 percent of current fossil fuels, and save billions of dollars. This energy – in the form of methane gas – can be produced from manure and other organic materials through a process of decomposition and bacterial fermentation in a relatively simple apparatus called an anaerobic (oxygen-free) biodigester. The methane can then be used as fuel directly, or used to run engines to produce electricity. The slurry left over from this process can still be used for fertilizer; since about one percent of the world’s energy consumption is used to produce fertilizer, this is a rare win-win-win situation.
So how much of this stuff is there? Is this really something worth talking about? Each person on the planet (the average one, somewhere between starving children in the Sudan and obese adults in the U.S.) puts out 150 grams of excrement per day. That’s about 55 kilograms in a year. This is likely an underestimate, but at least it gives us a reasonable number to work with.
In 10,000 BCE there were about a million people on the planet. That’s 55 million kilograms of human excrement scattered around the globe in small piles, slowly feeding the grass and fruit trees. In 1800, there were about a billion people on the planet, so about 55 billion kilograms. By 1900, we had a world human population around 1.6 billion, which would have been 88 billion kilograms of human shit.
By 2013, with more than 7 billion people on Earth, the total human output was close to 400 million metric tons (400 billion kilograms) of shit per year. That is about eighty million large bull elephants’ weight of crap! Okay, I can’t imagine that either.
Now let us consider all the other animals with whom we share this planet. Many are going extinct at dizzying rates, but this does not mean that the overall number of animals is decreasing. For instance, beetles, bats, and frogs are disappearing, but the numbers of commercially raised pigs and chickens are dramatically increasing.
There are about 1.4 billion cattle, 19 billion chickens, a billion pigs, and 1.8 billion sheep and goats on the planet. Using low-end of average estimates we arrive at the following: in 2010, the amount of manure produced by all the cattle, sheep, goats, pigs and chickens in the world added up to 14,136,450,000 metric tons (multiply by 1000 to get kilograms). That’s 35,341,125,000 million cubic meters. If we take an average soccer field to be about 60 meters wide and 100 meters long, we could cover almost 3 million fields to a depth of 2 meters — enough to bury everyone on the field. (I left out the human manure, because we want somebody to be able to watch this spectacle.) If you want a more homey way to think about it, that’s 141,365,000,000,000 one-cup servings — enough for 2000 one-cup servings a year (more than five cups a day) for every person on the planet.
And then we can throw in the dogs and cats and rats and coyotes and the deer and elephants and robins and pythons and the bird shit on your car’s windshield. Animals that are well adapted to human settlements, such as cockroaches and raccoons, are also increasing, although these are not as carefully counted, and cockroach frass is not easily quantified. Overall, I am guessing we are facing a grand total weight of about 400 million tons for people, and more than 14 billion tons from the other animals — every year.