The trouble is that you can’t start gleefully smearing untreated sewage across crops you intend to eat later: you’ll simply complete the life cycle of numerous human pathogens and trigger widespread outbreaks of disease. Indeed, although preindustrial China enjoyed productive agriculture, gastrointestinal diseases were endemic among the population. The proper treatment of human waste is of such crucial importance in ensuring a healthy society that you’ll need to consider it right from the start as you begin to rebuild civilization. (At the very least, a post-apocalyptic settlement could dig privy pits, which should be sited at least 20 meters away from any well or stream that anyone uses as a source of drinking water.)
Disease-causing microbes and parasite eggs can be killed by heating above 65°C, or 150°F (a theme we’ll come back to in the context of food preservation and health), so if you want to fertilize the fields using human manure, the problem to be solved now becomes: How do you pasteurize large volumes of your own excrement?
On a small scale, feces can be treated by sprinkling with sawdust, straw, or other non-leafy vegetative matter (to rebalance the carbon and nitrogen levels, as well as soak up moisture) before piling them in a regularly turned compost heap for several months to a year. As bacteria partly decompose the organic matter in the compost they release heat (just as our bodies’ metabolism does), and this can naturally raise the heap’s temperature enough to kill troublesome microorganisms. It’s also best to separate urine and feces—practically achievable by simply building toilets with a funnel toward the front—to avoid a waterlogged sludge. Urine is sterile and so can be diluted and applied directly to the land.
But with a little more ingenuity, some of the human and farmyard waste can be turned into something altogether more useful with a bioreactor. In a compost heap the objective is to keep everything well aerated so that oxygen-needing bacteria and fungi can readily decompose the matter. But if instead you hold the waste in a closed vessel, blocking oxygen from getting in, anaerobic bacteria thrive and partly convert the organic material into flammable methane gas. This can be piped into a simple gas storage facility constructed from a concrete-lined pool filled with water with an upturned metal container fitted snugly within it. As the methane bubbles up into the storage tank, the water forms an air seal, and the metal gas collector rises. The weight of the floating storage tank provides gas pressure, and the methane can be piped off to supply stoves, gas for lighting, or even, as we’ll see later, fuel for vehicle engines. A metric ton of organic waste can produce at least 50 cubic meters of flammable gas, equivalent to the energy of a full tank of gasoline. (It is not surprising that such biogas digesters became common across fuel-starved Nazi-occupied Europe during the Second World War.) The microbial growth slows considerably at lower temperatures, so it’s important to keep the bioreactor insulated, or even siphon off some of the methane produced to heat it.
As the population of the post-apocalyptic society begins to grow again, larger-scale methods for dealing with waste will be required. Enteric bacteria, including potentially pathogenic strains, thrive in the warm internal conditions of the human body, but are poorly adapted for rapid growth outside. So the principal trick of sewage treatment is to force human enteric bacteria to compete with environmental microorganisms in a pool of poo—a survival struggle they will lose. Modern treatment plants accelerate this process by bubbling air through the sludge to encourage oxygen-needing bugs.
Although fertilizing fields with human waste may seem anathema to many of us in the Western world, it is proving to be very effective in some places. In Bangalore, India’s third largest city with around eight and a half million inhabitants, euphemistically named “honey-sucker” trucks empty urban septic tanks and transport their load to surrounding agricultural areas. The waste is treated in pools before being spread on the fields. There are even commercially available products that contain processed human sewage sludge. Dillo Dirt, a fertilizer sold by the City of Austin, Texas, uses a composting process to ensure waste is naturally heated to pasteurizing temperatures to eliminate pathogens.
Aside from nitrogen, plants also need phosphorus and potassium. Bones are very rich in phosphorus—together with teeth, they are biological deposits of the mineral calcium phosphate—and so sprinkling bone meal, which is just boiled and crushed animal skeletons, is another good way of restoring failing land. Reacting the bone meal with sulfuric acid (see Chapter 5 on how to produce this) makes the phosphate much more absorbable for plants and so produces a far more effective fertilizer. In fact, the first fertilizer factory in the world was set up in 1841 to react sulfuric acid from London’s gasworks with bone meal from the city’s abattoirs and sell the “superphosphate” granules to farmers. Potassium for fertilizers is present in potash, which we will see in Chapter 5 is easy to extract from wood ashes; in 1870 the vast forests of Canada were the main source for fertilizers for Europe. Today we gather potassium and phosphorus for fertilizers from particular rock and mineral deposits, and identifying these in a post-apocalyptic world will require the rediscovery of geology and surveying.
Modern fertilizers provide an optimal balance of these three required nutrients (not unlike the carefully designed diets of top athletes). Using the more rudimentary methods discussed in this chapter, you won’t achieve yields as high as the enriched soils of today, but you will be able to preserve the fertility of the land to a good degree during the recovery period.
ONE FEEDING TEN
For a post-apocalyptic society to progress, it absolutely must secure this solid agricultural foundation. If a brutal cataclysm wipes out a great majority of humanity along with the knowledge and skills they hold, the surviving population could be knocked back to a bare subsistence existence, hanging by its fingertips on the cliff edge of extinction. It doesn’t matter how much industrial knowledge or scientific inquisitiveness persists through the apocalypse if the survivors are preoccupied with the struggle for mere survival. With no food surplus, there is no opportunity for your society to grow more complex or to progress. And because growing food is so vital, you’re much less willing to change what is tried and tested when your life depends on it. This is the food-production trap, and many poor nations today are caught in it. Thus, post-apocalyptic society may stagnate, perhaps for generations, while the efficiency of agriculture is slowly improved until a critical threshold is surpassed when society can begin clawing its way back up to greater complexity.
On the most basic level, a growing population size means more human brains, which can find solutions to problems more quickly. But efficient agriculture offers an even more important opportunity for progress. Once basic food security is assured by efficient means, a civilization can release many of its citizens from toiling in the fields. A productive agricultural system enables one person to feed several others, who are then free to specialize in other crafts and trades.* If your brawn is not demanded in the fields, your brain and hands can be put to other uses. A society can economically develop and grow in complexity and capability only once this basic prerequisite has been met—agricultural surplus is the fundamental engine for driving the advancement of civilization. But the benefits of productive agriculture for a rapid reboot of civilization after the apocalypse can be realized only if the excess food can be stored reliably and doesn’t rot away uneaten: we’ll now turn to food preservation.
CHAPTER 4
FOOD AND CLOTHING
Burg-places broken, the work of giants crumbled.
Ruined are the roofs, tumbled the towers,
Broken the barred gate: frost in the plaster,
Ceilings a-gaping, torn away, fallen,
Eaten by age . . .
UNKNOWN EIGHTH-CENTURY SAXON AUTHOR
LAMENTING ROMAN REMAINS, “The Ruin”
COOKING IS THE ORIGINAL CHEMISTRY in our history—deliberately directing the transformation of the chemical makeup of matter. The crispy browning on the outside of a grilled st
eak and the golden crust of a loaf of bread are both due to a particular molecular change known as the Maillard reaction. Proteins and sugars in the food react together to create a whole host of new, flavorsome compounds. But cooking serves far more fundamental purposes than simply making food taste more appetizing, and it will form the crux of keeping the survivors healthy and well nourished after the apocalypse.
The heat of cooking kills any contaminating pathogens or parasites, preventing food poisoning from microbes or infection with tapeworm from pork, for example. Cooking also helps to soften tough or fibrous food, and breaks down the structures of complex molecules to release simpler compounds that are more easily digested and absorbed. This increases the nutritional content of much food, allowing our bodies to extract more energy from the same volume of edible matter. And in some cases, such as taro, cassava, and wild potato, prolonged heat inactivates plant poisons, which in the extreme example of cassava would otherwise be lethal from a single meal.
Cooking is only one kind of processing that we apply to food before consumption. The capability to keep food safely for protracted periods beyond its immediate collection is a fundamental prerequisite for the support of civilization. It allows produce to be transported from the fields or slaughterhouses into cities to support dense populations, and enables the stockpiling of reserves for leaner times. Food is spoiled by the action of microbes—bacteria as well as molds—breaking down its structure and changing its chemistry, or releasing waste products distasteful or even outright toxic to humans. The purpose of food preservation is to prevent this microbial spoilage occurring, or at least to delay the process for as long as possible. You pull this off by deliberately modifying the conditions in the food to push them outside the sweet spot for microbial growth. We’ll come in a second to a more detailed explanation of how this is actually achieved, but you are essentially trying to exert control over the food’s microbiology: preventing any microorganism growth, or even employing some microbes to block other, undesirable strains from gaining a foothold. In some cases, fermentation from microbial growth is encouraged to decompose the complex molecules in food and make nutrients more readily accessible for our own consumption. Biotechnology, therefore, is far from a modern innovation; it is, in fact, one of humanity’s oldest inventions.
The development that first endowed us with all of these capabilities—cooking food thoroughly by boiling or frying, fermentation processing, and long-term preservation—was the innovation of firing clay into earthenware pots. This had profound ramifications for us as a species. The human digestive system, unlike the multiple stomachs of ruminants like cows, for example, is unable to break down many food types particularly well, and so we have applied technology to supplement what our bodies can naturally do. Pottery vessels, used as receptacles for food during fermentation or cooking to release further nutrients, therefore serve as additional, external “stomachs”—a technological pre-digestive system.
Modern cuisine—the height of civilized sophistication with all its marinades, confits, and drizzles of reductions—is no more than a superficial adornment upon these fundamental necessities of stopping food from poisoning you and unlocking as much of its nutritional content as possible. This isn’t a cookbook, so we won’t go into recipes or detailed instructions, but the general principles behind preservation and processing methods are crucial knowledge for a post-apocalyptic recovery.
FOOD PRESERVATION
Preserving food takes into account the environmental conditions that microbes, and indeed all life, need to thrive. But the traditional techniques we’ll look at were all developed over long periods by trial and error, long before the discovery of invisible microorganisms causing decay (even the modern practice of canned food was adopted before the demonstration of the germ theory). These techniques were found to work, but without any underlying theory as to why. Retaining this kernel of understanding after the apocalypse (see here for how to build a microscope capable of revealing these microbes) will be enormously beneficial to maintaining a reliable food supply and avoiding infectious disease—both critical to sustaining a population increase after a cataclysm.
Not only does all life on Earth require liquid water to grow and reproduce; organisms can also tolerate only a particular range of physical or chemical conditions. More specifically, the enzymes in a cell—the molecular machinery that drives the reactions of biochemistry and coordinates the processes of life—are active only over particular ranges of temperature, salinity, and pH (how acidic or alkaline a fluid is). Preservation can be achieved by pushing any of these three factors away from the optimum for microbial growth.
The easiest method of preserving food is simply to desiccate it. Without much available water, microbes struggle to grow (this is why it’s also critical to dry your harvested grain before storing it in silos). The traditional technique is air- or sun-drying, suitable for fruit such as tomatoes as well as meat to make biltong or beef jerky, but it is a slow process and not suitable for large bulks of food.
Without being commonly considered as desiccated, many other foodstuffs are also preserved by low water availability. Large amounts of dissolved compounds like sugars make a solution very concentrated, which acts to draw water out of microbial cells and stop all but the hardiest strains from growing. This is exactly the principle behind jams: the saccharine fruitiness tastes great on toast in the morning, but the very reason for the creation of preserves in the first place is to protect fruit by the antimicrobial action of the concentrated sugar solution. Sugar can be extracted from tropical sugar cane or the root of the temperate-growing sugar beet by trickling water through the crushed plant to dissolve the sugar and then recovering the crystals of it by drying. Honey is extremely long-lasting for the same reason.
Salt is needed in small amounts for the healthy functioning of the human body—which is why our palate craves it—but a far greater quantity is used for preservation. Salted foods are protected in the same manner as preserves: concentrated briny fluids draw water out of cells and hamper growth. Fresh meat can be effectively preserved by packing it in dry salt for several days, or keeping it submerged in a heavy brine solution—about 180 grams of salt dissolved into every liter of water creates a brine solution roughly five times more concentrated than seawater. Salting has been a crucial preservation technique throughout history, so it is worth looking at in more detail.
In principle, producing salt is childishly simple, provided you’re anywhere near the coast. Seawater contains about 3.5 percent dissolved solids, the vast majority of which is common salt (sodium chloride), which can be extracted by evaporating off the water solvent. If you live in sunny climes, you can simply allow seawater to flood shallow pans and evaporate in the heat of the day to leave a crust of salt precipitated behind. In very cold temperatures, you can allow shallow ponds of seawater to freeze, leaving a concentrated brine solution at the bottom. But temperate conditions, as are prevalent across much of Europe or North America over the year, require burning fuel to heat cauldrons of saline to drive off the water. In the case of salt, then, the availability of a valuable commodity is not due to the rarity of the substance itself—three-quarters of the Earth’s face is sloshing with saline solution—but to the energetic costs of extracting it in large amounts, or of finding and exploiting minable deposits.*
Salting is often used in combination with another preservation technique, whereby naturally toxic antimicrobial compounds are generated and infused into the produce, often meat or fish: the process of smoking. As we’ll see in Chapter 5, the incomplete combustion of wood releases a broad suite of compounds, one class of which, creosote, is responsible for the distinctive flavor and decay-inhibiting effect of smoked food. You can jury-rig a small-scale post-apocalyptic smokehouse very easily. Dig a pit for a small fire, with a metal cover, and a shallow trough leading a yard or two to the side, also covered on top with board and then soil, to channel the smoke. At the open end of the c
overed channel, where the smoke escapes, place a defunct fridge with a hole cut in the bottom. Stock the wire frame shelves with gutted fish, slices of meat, cheese, and so on, and smoke it for several hours.
Acidity is another great ally in resisting the hordes of invading microbes. Vinegar is a weak solution of acetic acid (which we’ll come back to later in this chapter) and is very effective as a preservative in pickling. The opposite approach, preserving food with alkalinity, is much less prevalent because it saponifies the fats—see soap-making in Chapter 5—and so grossly changes the flavor and texture of the food.*
Rather than adding acid from elsewhere to preserve by pickling, food can also be protected by encouraging the growth of particular bacteria that excrete acidic waste products—allowing food to generate its own preservative. Sauerkraut, Japanese miso, and Korean kimchi are all produced by first using salt to draw out moisture from the vegetables and then allowing fermentation by salt-tolerant bacteria to increase the acidity naturally, transforming the food into an extreme environment and so blocking colonization by other microbes that may cause spoilage or food poisoning.
Yogurt is produced in a similar way, by allowing a culture of lactic acid–releasing bacteria to sour the milk (in general, acids are perceived by the tongue as sour-tasting) in a controllable way. This again creates an internal environment with enhanced acidity that resists colonization by other microbes and so prolongs the consumability of the nutrients by several days. With milk being such a useful source of key nutrients, its preservation is key for survivors of the apocalypse.
Vitamin D is essential for preventing the bone-degradation disease rickets, since it aids the absorption of calcium from food. This vitamin is manufactured by the body when skin is exposed to sunlight, but at northern latitudes, with long, dark winters when people have had to wrap up against the cold, rickets plagued humanity for centuries. Milk is a wonderful source of both vitamin D and calcium, and so being able to reliably preserve the nutrients in milk will be crucial for the healthy inhabitation of the north.*
The Knowledge: How to Rebuild Our World From Scratch Page 8