THE HUMAN NUTRIENT CYCLE

“For the living, three things are inevitable: death, taxes, and shit.”
Dan Sabbath and Mandel Hall in End Product

When crops are produced from soil, it is imperative that the organic residues resulting from those crops, including animal excrements, are returned to the soil from which the crops originated. This recycling of all organic residues for agricultural purposes should be axiomatic to sustainable agriculture. Yet, spokespersons for sustainable agriculture movements remain silent about using humanure for agricultural purposes. Why?

Perhaps because there is currently a profound lack of knowledge and understanding about what is referred to as the “human nutrient cycle” and the need to keep the cycle intact. The human nutrient cycle goes like this: a) grow food, b) eat it, c) collect and process the organic residues (feces, urine, food scraps, and agricultural materials), and d) return the processed organic material back to the soil, thereby enriching the soil and enabling more food to be grown. The cycle is repeated, endlessly. This is a sustainable process that mimics the natural cycles of nature and enhances our ability to survive on this planet. When our food refuse is instead discarded as waste, the natural human nutrient cycle is broken, creating problems such as pollution, loss of soil fertility, and abuse of our water resources.

We in the United States each waste about a thousand pounds of humanure every year, which is discarded into sewers and septic systems throughout the land. Much of the discarded humanure finds its final resting place in a landfill, along with the other solid waste we Americans discard, which, coincidentally, also amounts to about a thousand pounds per person per year. For a population of 250 million people, that adds up to nearly 250 million tons of solid waste personally discarded by us every year, at least half of which is valuable as an agricultural resource.

The practice we humans have frequently employed for waste disposal has been quite primitive — we dump our garbage into holes in the ground, then bury it. That’s called a landfill, and for many years they were that simple. Today’s new “sanitary” landfills are lined with waterproof synthetic materials to prevent the leaching of garbage juice into groundwater supplies. Yet, only about one third of the active dumps in the US have these liners.⁴ Interestingly, the lined landfills bear an uncanny resemblance to gigantic disposable diapers. They are gargantuan plastic lined receptacles where we lay our crap to rest, the layers being carefully folded over and the end products of our wasteful lifestyles buried as if they were in garbage mausoleums intended to preserve our sludge and kitchen trash for posterity. We conveniently flush our toilets and the resultant sewage sludge is transported to these landfills, tucked into these huge disposable diapers, and buried.

This is not to suggest that sewage should instead be used to produce food crops. In my opinion, it should not. Sewage consists of humanure collected with hazardous materials such as industrial, medical, and chemical wastes, all carried in a common waterborne waste stream. Or in the words of Gary Gardner (State of the World 1998), “Tens of thousands of toxic substances and chemical compounds used in industrial economies, including PCBs, pesticides, dioxins, heavy metals, asbestos, petroleum products, and industrial solvents, are potentially part of sewage flows.” Not to mention pathogenic organisms. When raw sewage was used in Berlin in 1949, for example, it was blamed for the spread of worm-related diseases. In the 1980s, it was said to be the cause of typhoid fever in Santiago, and in 1970 and 1991, it was blamed for cholera outbreaks in Jerusalem and South America, respectively.⁵

Humanure, on the other hand, when kept out of the sewers, collected as a resource material, and properly processed (composted), makes a fine agricultural resource suitable for food crops. When we combine our manure with other organic materials such as our food discards, we can achieve a blend that is irresistible to certain very beneficial microorganisms.

The US EPA estimates that nearly 22 million tons of food waste are produced in American cities every year. Throughout the United States, food losses at the retail, consumer, and food services levels are estimated to have been 48 million tons in 1995.⁶ That would make great organic material for composting with humanure. Instead, only 2.4% of our discarded food was being composted in the US in 1994; the remaining 97.6% was apparently incinerated or buried in landfills.⁷

In 1998, industrial countries were only reusing 11% of their organic garbage.⁸ The Organization for Economic Cooperation and Development, a group made up primarily of western industrial countries, estimates that 36% of the waste in their member states is organic food and garden materials. If paper is also considered, the organic share of the waste stream is boosted to nearly an incredible two thirds! In developing countries, organic material typically makes up one-half to two-thirds of the waste stream.⁹ According to the EPA, almost 80% of the net discarded solid waste in the US is composed of organic material (see Figure 2.1).

It is becoming more and more obvious that it is unwise to rely on landfills to dispose of recyclable materials. Landfills fill up, and new ones need to be built to replace them. The estimated cost of building and maintaining an EPA approved landfill is now nearly $125 million and rising. The 8,000 operating landfills we had in the United States in 1988 had dwindled to 5,812 by the end of 1991. By 1996, only 3,091 remained.¹⁰

In fact, we may be lucky that landfills are closing so rapidly. They are notorious polluters of water, soil, and air. Of the ten thousand landfills that have closed since 1982, 20% are now listed as hazardously contaminated Superfund sites. A 1996 report from the state of Florida revealed that groundwater contamination plumes from older, unlined landfills can be longer than 3.4 miles, and that 523 public water supplies in Florida are located within one mile of these closed landfills, while 2,700 lie within three miles of one.¹¹ No doubt similar situations exist throughout the United States.

Organic material disposed of in landfills also creates large quantities of methane, a major global-warming gas. US landfills are “among the single greatest contributors of global methane emissions,” according to the Natural Resources Defense Council. According to the EPA, methane is 20 to 30 times more potent than CO2 as a greenhouse (global warming) gas on a molecule to molecule basis.¹²

Tipping fees (the fee one pays to dump waste) at landfills in every region of the US have been increasing at more than twice the rate of inflation since 1986. In fact, since then, they have increased 300% and are expected to continue rising at this rate.¹³

In developing countries, the landfill picture is also bleak. In Brazil, for example, virtually all (99%) of the solid waste is dumped into landfills, and three-fourths of the 90,000 tons per day ends up in open dumps.¹⁴ Slowly we’re catching on to the fact that this throw-away trend has to be turned around. We can’t continue to throw “away” usable resources in a wasteful fashion by burying them in disappearing, polluting, increasingly expensive, landfills.

As a result, recycling is now becoming more widespread in the US. Between 1989 and 1992, recycling increased from 9 to 14%, and the amount of US municipal solid waste sent to landfills decreased by 8%.¹⁵ The national average for the recycling of all materials in US cities had jumped to 27% by 1998.¹⁶ Composting is also beginning to catch on in a big way in some areas of the world. In the United States, the 700 composting facilities in 1989 grew to more than 3,200 by 1996. Although this is a welcomed trend, it doesn’t adequately address a subject still sorely in need of attention: what to do with humanure, which is rarely being recycled anywhere in the western world.

If we had scraped up all the human excrement in the world and piled it on the world’s tillable land in 1950, we’d have applied nearly 200 metric tons per square mile at that time (roughly 690 pounds per acre). In the year 2000, we’ll be collecting significantly more than double that amount because the global population is increasing, but the global land mass isn’t. In fact, the global area of agricultural land is steadily decreasing as the world loses, for farming and grazing, an area the size of Kansas each year.¹⁷ The world’s burgeoning human population is producing a ballooning amount of organic refuse which will eventually have to be dealt with responsibly and constructively. It’s not too soon to begin to understand human organic refuse materials as valuable resource materials begging to be recycled.

In 1950, the dollar value of the agricultural nutrients in the world’s gargantuan pile of humanure was 6.93 billion dollars. In 2000, it will be worth 18.67 billion dollars (calculated in 1975 prices).¹⁸ This is money currently being flushed out somewhere into the environment where it shows up as pollution and landfill material. Every pipeline has an outlet somewhere; everything thrown “away” just moves from one place to another. Humanure and other organic refuse materials are no exception. Not only are we flushing “money” away, we’re paying through the nose to do so. The cost is not only economic, it’s environmental.