By: Mary H. Dyer, Credentialed Garden Writer
In this era of environmental consciousness and sustainable living, it may seem that composting human waste, sometimes known as humanure, makes sense. However, others believe that human waste composting can be effective, but only when it is done according to accepted protocols and strict safety guidelines. Let’s learn more about human waste composting.
In the home garden, composted human waste is considered to be unsafe for use around vegetables, berries, fruit trees or other edible plants. Although human waste is rich in plant-healthy nutrients, it also contains viruses, bacteria, and other pathogens that are not effectively removed by standard home composting processes.
Although managing human waste at home is generally not sensible or responsible, large-scale composting facilities have the technology to process the waste at extremely high temperatures for extended lengths of time. The resulting product is heavily regulated and frequently tested by the Environmental Protection Agency (EPA) to ensure bacteria and pathogens are below detectable levels.
The highly processed sewage sludge, generally known as biosolid waste, is often used for agricultural applications, where it improves soil quality and reduces dependence on chemical fertilizers. However, stringent record-keeping and reporting are required. In spite of the high-tech, closely monitored process, some environmental groups are concerned that the material may contaminate soil and crops.
Proponents of using humanure in gardens often use composting toilets, which are designed to contain human waste safely while the material is converted to usable compost. A composting toilet may be an expensive commercial device or a homemade toilet in which waste is collected in buckets. The waste is transferred to compost piles or bins where it is mixed with sawdust, grass clippings, kitchen waste, newspaper, and other compostable material.
Composting human waste is risky business and requires a compost system that produces a high temperature and maintains the temperature long enough to kill bacteria and pathogens. Although some commercial composting toilets are approved by local sanitation authorities, homemade humanure systems are rarely approved.
This article was last updated on
Read more about Compost Ingredients
There is always a risk when you use manure or manure tea in your garden, but there are some precautions you can take to stay safe.
Aside from contamination risk, the fresher the manure, the more of a chance it will be high in nitrogen and ammonia, which can burn plant roots and even inhibit seed germination. If the manure is from a plant-eating animal, it is probably also full of weed seeds, which will not be inhibited from sprouting.
If you still want to make use of fresh manure, don't apply it after your garden has been planted. The U.S. Department of Agriculture recommends an application window of 120 days prior to harvesting and eating any vegetable where the edible part comes in contact with the ground. That includes anything grown below the ground (beets, carrots, potatoes, radishes, etc.) as well as anything sitting on the ground, like lettuce, spinach, and even vining crops like cucumbers and squash. You can apply fresh manure up to 90 days prior to harvest for vegetables that are far enough away from the soil that nothing will splash up on them but err on the side of caution.
Instead of using manure as a fertilizer, use it as a soil conditioner. Add fresh manure in the fall for spring planting. It will have time to work into the soil and compost. Wait until all vegetables have been harvested before adding it to the soil.
Another option is to side-dress with composted manure during the growing season. Manure that is composted lessens the risk of contamination, especially if the pile heats up to 140 degrees or more. You can purchase composted manure or, if you have a source of fresh manure, compost it yourself. According to Stephen Reiners, Cornell University horticulturist, hot summer temperatures will usually kill E. coli.
If you are buying packaged manure, the bag should state whether it is pathogen-free. Don't assume that just because it is sold as fertilizer that it is fully composted. If you are getting your manure locally, inquire at the farm if their animals have had any health problems.
Thoroughly wash your hands and nails before and after harvesting produce grown with manure. Since root crops (beets, carrots, radishes) and leafy vegetables (chard, lettuce, spinach) are the most susceptible to contamination, wash these vegetables well and possibly peel them before eating. Cooking will also kill pathogens.
If you have been susceptible to foodborne illness in the past, avoid eating any uncooked vegetables fertilized with manure. Children, pregnant women, people with weakened immune systems, and those with chronic diseases should also avoid eating these vegetables.
Truth be told, even if your pee isn’t the fine wine of pee, it’s probably still safe to use in the garden. First of all, if it comes out in your urine, then guess what? It’s already going into your body in the first place. Putting it back in your garden isn’t going to significantly increase your risks.
Also, when you put it on your garden, the soil will process some of that toxicity in the way your kidneys do. Soil is naturally a pretty good biofilter. That’s why it is frequently is used in many applications to clean water, air, and eliminate odors.
Also, according to the EPA, there’s no reason to believe that plants will uptake any of the toxic man-made chemicals that might be in urine. The EPA is so certain that this is not a risk, they even allow farmers to apply minimally processed sewage materials (called Class B Biosolids) to fields that grow food. These biosolids contain urine from everyone who flushes in cities, along with poop, medical waste from hospitals, run-off from agricultural applications, over-fertilized lawns, road pollution, and more.
Now, I personally have reservations about Class B Biosolids because what enters the sewers isn’t just urine or manure from healthy homesteaders. But, still, the fact that city-scale stuff is considered safe to use in large amounts for large scale farming, make me feel like using my own urine might not be that big of a deal.
According to United Sludge-Free Alliance, legal loopholes supported by the Environmental Protection Agency, state environmental protection agencies, the United States Department of Agriculture and the Centers for Disease Control and Prevention helped catapult the sewage sludge industry to become big business. After all, there’s a lot of waste to deal with…it has to go somewhere.
This human sludge used to be dumped at sea but was causing major problem and was banned in the 1990s. Instead, federal, state and local entities decided to market this harmful sludge as “biosolids” and “organic fertilizer” or “compost” to get rid of it in a cheap way.
The real issue is we need to clean up our nation’s chemical laws so toxic chemicals don’t wind up in wastewater treatment plants that can’t handle them in the first place. But until then, I can’t recommend you using compost or other fertilizers containing human sewage sludge in your garden or anywhere else. And get this: Arizona State University researchers are now turning to human sewage sludge to track the harmful chemicals inside of humans. Knowing this, it’s pretty clear our sludge is in no way safe to use in our gardens, farm fields or beyond. (2)
Here are important dangers of human sewage sludge in compost and fertilizing products:
Milorganite, a sludge-based product marketed as organic-based nitrogen fertilizer, comes from the Milwaukee Metropolitan Sewerage District. According to Darree Sicher of United Sludge-Free Alliance, some Milorganite human sewage sludge in compost/fertilizer products contain a warning label that reads: “WARNING this product contains detectable quantities of chemicals known to cause cancer, birth defects, or other reproductive harm. This notice in no way implies that we have any evidence or experience to indicate that any genuine hazard of cancer, birth defects, or reproductive harm results from the normal, proper handling described on our label and related literature.”
Milorganite’s also been under fire for high levels of PCB contamination. (PCBs are linked to several types of cancer.) According to a Milwaukee Sentinel report, the Milwaukee Metropolitan Sewerage District faced toxic sewer conditions that led to tons of Milorganite fertilizer contamination. Thousands of pounds were distributed before routine testing uncovered the contamination. Thirty recreational fields using the “organic” compost were closed until the hazardous topsoil could be removed. The contamination in this case came from leaking storage tanks and hydraulic lines that were oozing into city sewers. (3)
Heavy metals, including nanoparticle silver, have been detected in human sewage sludge. (4, 5) If you continuously apply sewage sludge contaminated with heavy metals in your garden, be building up dangerous metals in your soil and food.
As Sicher notes, even the EPA, USDA and the U.S. Food and Drug Administration recognize that heavy metals “translocate” into edible tissue of plants and animals. She says many sludges contain substances that could contaminate certain crops, making them unfit for human consumption. The contaminants of greatest concern are heavy metals, toxic organic compounds and pathogenic microorganisms.
The EPA federal policy recognizes the following edible plants by gauging their metal uptake:
Flame Retardants & Personal Care Chemicals
Arizona State University scientists found that 10 of the 11 chemicals found in greatest abundance in treated municipal sludge or biosolids included high-production volume chemicals: flame-retardants, antimicrobials and surfactants. (Surfactants often can be found in detergents, emulsifiers and foaming agents and dispersants found in everything from the fracking industry to shampoos and soaps.) The treated sludge also tested positive for abundant levels of pharmaceutical and personal care products. Also detected? Brominated flame retardants commonly found in plastics, textiles, electronics and couch foam. (6)
In fact, phthalates, hormone-disrupting chemicals found in fragrances used in shampoos, sunscreen, lotion and soaps, are now detected in tomatoes grown in human sewage sludge. (7)
Possible Sewage Sludge Symptoms
Sewage sludge exposure has reportedly caused everything headaches, nausea and vomiting to breathing problems, asthma attacks, skin infections, joint pain, diarrhea and even death. (8, 9)
Compost is certainly important for home gardens and if properly sources, is much safer than harsh chemical-based products that can sterilize beneficial microorganisms in the soil. Here are a few tips to make sure you’re avoiding human sewage sludge in compost:
According to United Sludge-Free Alliance, here are some (but likely not all) products containing human sewage sludge:
Final Thoughts on Human Sewage Sludge in Compost