The Knowledge: How to Rebuild Our World From Scratch (9 page)

As long as you can grow grain for yourself, along with some other fruits and vegetables for the sake of nutritional balance and a more interesting diet, you’ll never starve to death. You could, of course, always hunt for meat, but keeping livestock, and sacrificing some of your arable capacity to support them, actually contributes a critical function for keeping your fields productive. As we’ve seen, without chemical fertilizers farmland would deteriorate in fertility, but animal manure allows you to return nutrients to the soil. Furthermore, there is a particular class of crops that will naturally boost soil nitrogen levels for you, the
incorporation of which was a crucial step in the agricultural revolution in the seventeenth century. In the immediate post-apocalyptic world, the husbandry of plants and of animals will once again become inseparable, mutually supporting endeavors.

Throughout the Middle Ages, European farmers followed an agricultural convention of routinely leaving plots fallow—a woefully inefficient practice, as at any one time up to half of your fields would be growing no crops at all. Medieval agriculturalists recognized that their land became tired and its productivity plummeted if cereals were grown on it season after season, but they didn’t understand what caused this and could only attempt a solution by resting the ground for a year. We now understand that this drop in fertility is due to the loss of plant nutrients, which is why modern agriculture is so dependent on the liberal smearing of artificial fertilizers. This solution will be closed to you for the immediate aftermath, and you’ll need to revert to an older solution to the problem.

The key is that while most crops plunder nitrogen from the ground, some plants inject this vital nutrient back into the soil as they grow. This family of astounding plants is the legumes, which includes peas, beans, clover, alfalfa, lentils, soy, and peanuts. By plowing a crop of legumes back into the soil at the end of the season, or feeding them to livestock and using their manure to fertilize the land, vital nitrogen is captured and restored to the land. The incorporation of this fertility-pumping capability of legumes transformed agriculture and set Britain on course for the Industrial Revolution.

Varying between legumes and other crops on a plot of land will therefore maintain the productivity of the soil. But rather than simply swapping back and forth between two—from clover to wheat, say—a far better option is a crop rotation with several stages, as it also breaks the cycle of diseases and pests. These are often very specific to the plant they can attack, and so annually shifting, and not growing the
same crop on a plot for several years, means that you can exert natural control without pesticides.

The Norfolk four-course rotation is the most successful of these historical systems and became widespread only in the eighteenth century, spearheading the British agricultural revolution. In the Norfolk system, succession of crops through each plot follows the order: legumes, wheat, root crops, barley.

As we have seen, growing legumes is intended to build up the soil’s fertility for the rest of the cycle. Clover and alfalfa grow well in the British climate, but in other regions you might be better off with soy or peanuts. At the end of the season, if you’re not harvesting any part of the plant for human consumption, the entire crop can be grazed by livestock or simply plowed back into the ground as green manure. The year after the legume course you want to plant a crop of wheat to capitalize on the soil fertility and produce your staple cereal for human consumption.

Don’t leave the field fallow the following year, but plant a crop of a root vegetable such as turnip, rutabaga, or mangold wurzel (field beet). One of the main purposes for leaving a field fallow in the Middle Ages—to plow and harrow it in spring but leave it unplanted for a year—was to kill off weeds in preparation for the next season. But with a root vegetable, you can plant a crop and still be able to rip out weeds between the rows. This course will yield you another crop, but rather than intending all of it for your own consumption—unless the crop is potatoes—you can use it to feed the animals. Your livestock will fatten up more quickly and will also produce more manure that you can spread back onto the field to preserve its fertility. By feeding your livestock a purpose-grown fodder, rather than simply letting them forage and browse grass for themselves, you also free up pastureland, which can now be used to cultivate even more crops.

Indeed, the adoption of the humble turnip and other root crops for
fodder heralded a revolution in medieval agriculture. Not only are these more effective than grazing for fattening up livestock over the summer, but they also provide a reliable energy-rich feed throughout the winter. Before their introduction, every late autumn medieval Europe witnessed the mass slaughter of livestock, as there was simply insufficient food to keep the animals from starving before spring. Turnip, as well as other fodder crops like rutabaga, kale, and kohlrabi, are biennial plants, which means they can be left in the ground over winter and plucked out to feed cattle when needed. Used to supplement the energy-poor roughage of hays and silage (fermented grass), these nutritious fodder crops support large herds of livestock through winter, continuing not only the supply of fresh meat, but also providing fresh milk and other dairy products. These are a vital source of vitamin D over the dark winter months when your skin cannot synthesize it from sunlight.

The last phase in the rotation is the planting of barley, which you can again use to feed your livestock—but remember to keep back a portion for brewing beer (as we’ll cover in the next chapter). After the barley course, the rotation loops back to the beginning with the cultivation of legumes to restore the fertility of the soil and make it ready for the nitrogen-hungry cereal crop. So the rotation system is a harmonic coupling of the requirements and products of both plants and animals, it naturally combats pests and pathogens, and it allows the recycling of nutrients back into the soil. This particular system of crops won’t work universally, and you’ll need to find a set suited to your local soils and climate.
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But the two key principles of the rotation system will ensure that you can reliably feed yourself and maintain soil productivity without exogenous chemical fertilizers after the apocalypse:
alternate legumes with cereals, and grow root crops not for your own consumption, but specifically for your livestock. Reverting to small-scale methods, five acres of land will be enough to support a group of up to ten people: wheat for bread, barley for beer, a diverse range of fruits and veggies, as well as cattle, pigs, sheep, and chickens for meat, milk, eggs, and other products.

Spreading animal manure helps fertilize the fields, but could you exploit human waste in the same way for post-apocalyptic farming? The challenge of agriculture without modern artificial fertilizers is how to turn feces back into food (crap into crop) as efficiently as possible, and ideally you would be able to close the loop on human consumption and ensure that precious nitrogen is not lost.

At the time when the open gutters in the streets of European cities were overflowing, Chinese cities were diligently collecting their waste, not with underground sewage pipes but with buckets and carts, and spreading it on surrounding fields. Each of us produces roughly 100 pounds of feces, and around ten times as much urine, every year—waste that contains enough nitrogen, phosphorus, and potassium to fertilize crops to yield around 450 pounds of cereals.

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.

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.
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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.