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May 19, 2018

No Shit! Facts About Manure Composting

Oh Shit! Facts About Composting Manure

If you’re corprophobic (irrational fear of poop 💩) you better skip this post- this one is where the brown stuff hits the fan!

I’ve been around composting (and manure) for a good part of my life. It amazes me how much people DON’T know about poo or particularly about composting it.

Let’s begin by examining the problems associated with manure in modern society.

Lake overgrown by algae

Environmental Impact

In nature animals just do their business on the ground, herds of bison as far as the eye can see all just dropping their waste. This has a net positive effect on soil because as nature intended it is added to the top of soil and broken down when the animals migrate to new feeding grounds. Spread out like this over thousands of hectares of soil it is quickly devoured by everything from bacteria to earthworms and dung beetles. The negative impacts of manures comes with the flaws of modern farming. Huge herds of animals are grazed in limited space or worse placed in buildings where manure accumulates and is removed into piles. In these conditions, manures are able to accumulate in much larger quantities than nature is equipped to handle. In large piles where more manure is frequently added (but oxygen isn’t) microbes and other detritivores just can’t keep up; the pile ferments in an anaerobic state. Anaerobic piles of manure off gas ammonium, hydrogen sulphide and methane. Methane is considered by scientists to be a more potent greenhouse gas than carbon dioxide, so manure piles contribute to climate change.The result of rain or snow seeping through these piles is a leaching of plant nutrients and potentially pathogens into groundwater. Such an occurrence combined with a series of blunders resulted in over 2000 illnesses and 6 deaths in the small, rural town of Walkerton, Ontario in Canada in the year 2000. Flies will lay their eggs in manure and can potentially carry pathogenic bacteria and viruses into homes and onto food supplies. Manure piles can result in outbreaks of illness. When manure is composted following best practices (we will get into best practices a little later) pathogens are easily brought to levels low enough to avoid infection.

When plant nutrients from manure are leached into wetlands, ponds, lakes or streams it can cause algae blooms and seaweed growth that rob aquatic life of precious oxygen. Manure results in fish die offs and damages ecosystems.

Long term, excessive applications of raw manure result in accumulations of salts that damage the microbiology of soil by stealing water through osmosis. Long term manure use DECREASES soil fertility.

Financial Impact

Dissolved nutrients promote seaweed growth that hinders recreational as well as commercial boat traffic. Manure negatively affects tourism and trade.Dredging seaweed diverts tax dollars that could go to roads or schools, un-composted, raw manure is a financial burden to communities.

What About Solutions?

It would seem that manure issues will continue to be with us well into the future. Even if all the world turned vegan today, setting free the quantity of existing livestock isn’t feasible and would result in undesirable encounters with humans. Domesticated animals just aren’t equipped to find their own food and lack the fear of humans that wild animals instinctively have. A massive slaughter would be wasteful and unacceptable to most of us (and particularly so with vegan principles and belief systems). So finding solutions to the problems associated with manures is crucial.

There are a few solutions for turning farmyard manures into valuable products. Three well researched solutions are:

  • Anaerobic digestion
  • Aerobic composting
  • Vermicomposting

Any of these solutions results in a large decrease in volume of manure, meaning more can be stored in the same space if necessary. Composted manure can be added directly to fields or gardens to increase yields, plant health and help deter pests and disease; without dangers of pathogens reaching water supplies.

Anaerobic digestion involves placing manure into large airtight receptacles with water and allowing it to ferment. As mentioned earlier this produces methane and hydrogen sulphide gasses. The difference here is that the gases are captured and diverted for heating or cooking fuel. This reduces the usage of hydrocarbon fuels, a non renewable energy source. After the digestion process the remaining solids are similar in texture and appearance to sphagnum peat moss. These solids can be incorporated into soil or potting mixes.

Aerobic Composting- this is perhaps the easiest and most cost effective method of dealing with large quantities of manure and other waste products. In this process manures can be mixed with other municipal waste and aerated to create a valuable soil amendment. Ideally composting can even occur on-site right on the farm as an additional source of farm revenue. In many cases manure and bedding can simply have temperature monitored and be turned and aerated at the appropriate times. The high temperatures of composting destroys pathogens, sterilizes weed seeds and locks up many nutrients into a form that is much less harmful when leached into groundwater or wetlands, streams etc.

Composting has a greatly reduced off gassing of greenhouse emissions and stabilizes nitrogen into plant usable forms rather than ammonium gas.

Vermicomposting is similar to composting but is done at lower temperatures and uses worms to enhance the rotting process. Manure can be aerobically composted prior to feeding worms or can be directly added to worm beds in layers thin enough to allow heat that would accumulate in an aerobic compost pile to dissipate quickly.

Advantages of vermicomposting is compost that’s finished without a curing period, and worm casts are considered a “premium” compost for gardening and farming. The worms themselves can also be used as protein for livestock or sold for additional farm revenue.

The one disadvantage of vermicomposting if you’re using manure directly is that, without the heating of aerobic composting; weed seeds can and do survive the gut of an animal and aren’t sterilized by worms either. Vermicomposting large quantities of manure also requires specialized equipment to separate worms from compost.

Best Practices

Anaerobic Digestion

When using anaerobic digestion to cope with manures, best practices mainly involve preventing oxygen from entering the vessels and preventing resulting gasses from venting into the atmosphere. Anaerobic microbes eventually create sufficient quantities of volatile waste products to almost sterilize the remaining solids. Much like in wine or beer making you cannot brew to over around 11-12% alcohol before yeasts die and distillation is required to further raise alcohol concentration so too anaerobic digestion ceases when concentrations of waste reach a critical point.

Aerobic composting

Safety standards for composting are well documented and in the USA are recognized by the Food and Drug Agency (FDA), the United States Department of Agriculture (USDA) and the Centre for Disease Control (CDC). Similar standards are mirrored by government agencies in many other nations.

The requirements are for ALL material being composted to reach 131 degrees Fahrenheit or 55 Celsius for a period of at least 3 consecutive days. This means to follow these standards, temperature needs to be closely monitored and recorded and cooler parts on the outer portion of the pile must reach the centre of the pile and be reheated. The high temperatures sterilize stray weed seeds and neutralize pathogens.


Actual standards for vermicomposting manures are (at the time of posting) are still under review inside the USA. Research seems to indicate that vermicomposting can bring pathogens below safe levels within 14 days. The FDA however is/was leaning toward the more conservative suggestions in the book Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management.

Those standards are as follows: Materials of animal origin (manure) should be processed for a minimum of

  • 45-60 days in a continuous flow through reactor.
  • 120 days in a batch system (like a plastic tote or where you dump it and harvest).
  • 120 days in a wedge windrow (walking windrow)
  • 365 days in a static windrow.

BioFiltro, a company in Santiago, Chile has designed a wastewater treatment system based on worms and microbes to clean and filter water contaminated with manure from dairy farms. Similar filtration systems have been used for recycling black water (toilet water) India.

What About DE-Worming Meds And Worms?

I’ve long suspected that the hub-bub about worm medications was far overblown. I have an online friend who works in a veterinarian’s office who has tested almoist every worm med they have- including those used for dogs and cats as well as heart worm medications.  She’s tested them from the bottle at full strength and also fed the poop from treated animals to worms without ill effect. I haven’t asked for permission to use her name or quote her here yet so I will not.

George Mingen- owner of  Kookaburra Worm Farms Australia’s largest commercial worm grower had this to say: “We use a lot of horse poo to feed our worms. The horse worming medications do not appear to affect earthworms. They are frpom a completely different animal family! (from parasitic helminth) We have done trials with several common horse worming medications and none of them have harmed the compost worms. 

 If in doubt, try a small of poo first and if the worms are into it and all ok after a week or so thenit is safe to use. Wet horse poo down thoroughly first.” 

Soldier Fly Composting

Similar to vermicomposting but using the maggot of the black soldier fly (Hermetia illucnens)  in the place of worms. Soldier fly composting has a somewhat lower value compost but has a high value protein source for fish, fowl and livestock. Soldier fly also process a larger amount of waste into biomass and reduce waste by a larger percentage. Soldier fly maggots however cannot handle animal bedding like straw whereas worms can.

Soldier fly larvae in combination with vermicomposting, farming or gardening and aquaculture or aquaponics is a potential closed loop system of handling manure.

Hazards Of Manure Handling

There are risks in any activity, the risks of composting manure are fairly low and relatively easy to minimize.  Raw, uncomposted manure should be handled using a pitchfork or shovel when possible. If you must handlke it with your hands then wear gloves and practice proper hygiene methods. Wash hands thoroughly with soap and water and scrub your fingernails after handling manure and eating, drinking, rubbing your eyes or any other activity where pathogens could enter your body.

What About Antibiotic Resistant Pathogens?

The chance of contracting antibiotic resistant strains of pathogens is very low from handling manure. Most pathogens do not compete well with other microbes and in that way manure may actually be safer than a public restroo, visiting a loved one in the hospital or even riding the bus or a taxi. Places that are cleaned regularly leave little competition for pathogens and become a breeding ground.

In Conclusion

The negative environmental and financial impacts of not properly handling manure far outweigh the minimal risks of properly composting manure. For the farmer composting manure could provide additional revenue for the farm, greatly reduce or eliminate chemical fertilizer costs, reduce irrigation and the costs associated with it.  Anaerobic composting requires a large initial investment but could be a move toward self sufficiency. Vermicomposting and/or soldier fly composting has the additional income stream from selling worms or maggots to others for their own composting or as  high protein animal or fish feed.

For the small scale composter or vermicomposter there’s a satisfaction in knowing you’re part of a larger solution.

Now go gather up some manure and help the planet.

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