Can you use human feces as fertilizer?

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Can you use human feces as fertilizer?



Everyone knows that food consumed by any living form is ultimately expelled as an excrement and given that foods contain valuable nutrients, whatever is generated as a result of digestion must have a further nutrient value. This is known to be the case for excrement with output from herbivores. Here we consider human feces. Humans are different. Humans are omnivorous, our diet includes a broader spectrum of foods, the excrement from which needs careful consideration.

So, can you use human feces as fertilizer? Yes you can. It’s a very rich source of nutrients but there are worries about contaminants that are present in human sewage including those from pharmaceuticals and a variety of heavy metals. Anything to do with human feces must be managed with extreme caution.

Anyone thinking about adding human feces to their composting system needs to think very carefully. The best way to manage this, in the micro-form, is to use a specially designed composting toilet that processes this type of material away from your main compost system. We have a post that looks at how this can be done. Check out ‘Composting toilet’ to find out more. 

Those who promote the recycling of sewage waste want to present it as a natural product that can be processed in ways that will remove harmful bacteria and viruses. Having been treated, it can then be spread on farm-land for growing crops. This is by far the most convenient solution. The alternative is to dump it somewhere and where would this be? Out to sea? Landfill? An ongoing problem of this size can’t be just ‘wished’ away.

What else would you like to see?

Do US farmers use human waste as fertilizer?

Do farmers use human waste as fertilizer UK?

Can you use human feces for compost?

Can you put human urine in compost?

Can human feces be used as fuel?

To instill a little more dignity into the subject, sewage that has been processed for use as fertilizer is now being known as’ biosolids’. A simple, natural product being placed back into the ecosystem in a way that disposes of the problem at the same time as producing crops to feed the world.

While the level of bacteria and viral contamination appears to be largely under control in treated waste, there are serious concerns about other ingredients that modern-life has added to our sewage. Most of the problems appear to be generated by the pharmaceutical industry. It’s long been known that there are a range of metals that ride through the processing of sewage waste. The modern demands for new and improved, or luxury, products has given rise to a range of metals being used, consumed and then allowed to go down the drains into the sewers. One of these being silver. Although in very small quantities, metals can build up in agricultural soil over time if there are regular doses of treated sewage sludge applied to land.

Recent research has, worryingly, shown low levels of contaminants in animals that have fed on crops and plants that have been fertilized with sewage sludge. It’s being argued that the regulations need to be much tighter.

Sewage sludge has to be processed in two ways before it can be released for use as a plant-food fertilizer. The first is anaerobic digestion. This is done in an airtight vessel that excludes oxygen. When the digestion is complete we are left with methane, carbon dioxide, water and solids that have been broken down into fine particles.

The second part involves high-temperature heat sterilization. These two approaches aim to remove the pathogens that will be there from the outset.

The concern among some is that this process may not be enough to destroy all the bacteria that gather in sewage waste and that some of these bacteria may have antibiotic resistance.

No one knows the long term effect of applying sewage sludge on land as a fertilizer. The levels of worrisome contaminants are very low. The effect on the environment may never be noticed as the soil may have the ability to neutralise the problem enough to suppress it.

Farmers can apply for sewage sludge to be spread on land for cropping. This is a much cheaper fertilizer option compared to conventional synthetic pelleted fertilizers. The municipal, local government departments are in favour of off-loading the problem for payment as it eases landfill pressures and raises cash.

Organically managed land mustn’t have any sewage waste applied. Organic farming is strictly regulated. The use of sewage waste is seen as too much of a risk, with the judgement being that there are so many potentially harmful contaminants.

It’s clear that this is a subject that needs to be monitored closely. At this point in time the general view is that a level of contamination from the pharmaceutical industries is being acknowledged. We have the ability to measure down to very low levels to establish the presence of almost every known compound.

The question being played with here is, how much of this can nature absorb and disperse before it gathers up and revisits us as a much larger problem? Biosolids are manageable. We need to develop the ability to extract, isolate and or neutralize any potentially harmful compounds that are found in our modern-day sewage waste.

The prize is big. Just imagine if all the gathered sewage waste could be used to safely produce food all over the developed world. This would be a ‘utopia’ among recycling systems.



Do US farmers use human waste as fertilizer?

About 50% of the sewage waste generated in the US is used in by farmers in agriculture as a fertilizer. All of it has to be treated to a standard that satisfies the Environmental Protection Agency. This requires that all sewage waste has to be treated at least once before it can be applied to land for agricultural purposes. This involves anaerobic digestion which reduces the sewage waste to a watery mix of broken down organic sludge with methane gas having been released.

This stage will remove the familiar smells that are associated with human sewage waste. After this one treatment the remaining material is known as a class B biosolid. At this stage it can be used but there are restrictions on where it can be used and what it can be used for. This basic treatment will only reduce the concentration of pathogens, it can’t clear them completely.

Class A biosolids are achieved only after high-temperature treatment. This can then be used without restrictions as there are no pathogens that are detectable. There will, however, be an assortment of compounds that accumulate in human sewage waste that will ride through both processes.

Do farmers use human waste as fertilizer UK?

In the UK the whole process appears to be accepted without too many concerns. Some farmers are using just human waste as fertilizer rather than buying conventional chemical fertilizer. Human sewage waste has to be fully treated before it can be spread on the land. There are strict standards which have to be met allowing it to be used as fertilizer for producing crops for human consumption and animal feed.

It’s spread as a sludge on fields that grow maize, oats and other corn crops e.g. barley and wheat.

This hasn’t been favoured by some of the supermarkets. Some declare that they are selling products that have been grown using ‘biosolids’ while others have banned it completely amid controversies about potential health worries.

The government has confidence in the safety of using biosolids, for what that is worth, a practice that appears to be on the increase due to increasing demand. Spreading biosolid sludge on land for crop growing is a relatively new way of disposal. In the past it was dumped at sea, this is now banned. Incineration and sending to landfill sites have been the other options.

There hasn’t been much, if any, public resistance to the using of biosolids as a crop fertilizer, largely due to the fact that not many people know that it’s happening. The only people who complain are those who live in the immediate vicinity as there is a smell when spreading, although this doesn’t last long. The smell is much reduced due to the digestion treatment process. After spreading, the sludge will settle into the soil and any smell will quickly subside. Some farmers are using only biosolid sludge as it is much cheaper than conventional manufactured fertilizers.

The treatment process will remove most of the pathogens that give cause for concern but there still remains the issue of a range of heavy metals which can be found in sewage biosolids. Among these is Cadmium which tends to be found in most vegetables that are grown where sewage sludge is applied. The worry is that Cadmium is thought to be responsible for kidney malfunctions.

Government regulations require that sewage sludge is worked deep into the ground so that it is fully exposed to the natural actions of soil. There must be a period of no less than 10 months between being ploughed into the soil and the harvesting of any crops. For vegetables that will be eaten raw e.g. lettuce, the period between application and harvest is no less than 30 months. During this timeframe we can expect there to be sufficient rainfall to effectively rinse away much of the heavy metal impurities that we want to avoid.

Can you use human feces for compost?

There are environmental enthusiasts who want to take recycling to the absolute extreme and to the point where they knit their own toilet paper and recycle their own feces. There is no doubt that this can be done but is it a good idea?

If you talk to anyone who understands the chemistry and biology involved with this, they will tell you that making compost, or humanure, from  human feces is not a safe thing to do. No one is doubting that feces contains nutrients that plants would use if presented but there are worrying complications that come with it.

Feces contains a vibrant selection of bacteria and viruses that will easily survive the basic decomposition process that is ‘composting’. How many of us would feel comfortable about the roots of edible or fruiting plants, of any kind, being dangled in such material?

You need to be aware that any ‘home-made’ system for making humanure won’t have the advantages of a large-scale industrial process. Here there will be a precisely-planned procedure where the feces goes through a digester to break the material down as far as possible. It’s then subjected to high temperatures that remove potentially harmful bacteria and viruses. The whole process is fully regulated with samples being tested to ensure that the final product is compliant with all requirements.

There are specially designed composting toilets. They will be approved for the purpose as they contain the waste in a sealed compartment while it converts into compost. You can find out more about composting toilets here.

Can you put human urine in compost?

Adding human urine to a compost pile is effective. Urine is rich in nitrates which is just what we need for making compost. There doesn’t appear to be anything about human urine that’s harmful to the environment. The adding of such a rich source of nitrates to a compost heap will help enormously if we are trying to make compost from woody, carbon based material.

Here we include leaves, dried grass clippings, shredded hedge trimmings shredded paper and cardboard. The carbon in these components requires enough of a nitrate input to achieve a balance. If there is too much of either carbon or nitrogen then compost won’t be formed.

As a good source of nitrogen, urine can be diluted and applied directly to a cropping area. This has been done for thousands of years in a variety of countries around the world. Urine must be diluted before applying directly as a fertilizer plant-feed. In an undiluted form there is a risk that the nitrate concentration may be too much for the plant to handle. This could kill the plant rather than promote growth.

Can human feces be used as fuel?

Solid human feces will burn if dry. This may be done somewhere in the world but you are more likely to find dried cattle dung being used as a fuel. This happens in some of the hottest parts of the world e.g. India where it’s dried as cakes in the baking sun and used for cooking.

Human feces can generate gas when allowed to digest in a sealed compartment with some low heat applied. This is known as anaerobic digestion. The contents of the digester vessel must be liquid enough for the gas bubbles to be able to migrate to the top where it can be channeled for collection and storage.

A range of gasses will be generated. Some may be sulphurous. There will be carbon dioxide but the main gas will be methane, it’s this that will serve as a fuel. Everything except the methane is an impurity and will need to be separated by passing the gaseous mixture through a series of filters to clean it. The practicalities of doing this just for the gas yield is questionable. Methane production by this means is often a by-product of a digestion process used for converting human sewage into safe-to-use, biosolid fertilizer. After the gas has been removed, the remaining sludge can be spread on the land for growing crops.

Related Questions

What is night soil in agriculture?

Night soil is the term that has been used in the past when human excrement was collected from receptacles where it was collected, e.g. buckets or pits. This was almost always done at night, for good reasons. The ‘soil’ part of the description is believed to have come from the practice of earth-soil being used to cover the excrement for hygiene purposes.

What germs are in human feces

There is a whole range of infectious diseases that can be contracted from human feces. They are the scary bacterial ones which include cholera, diarrhea, or dysentery, E. coli and salmonella. Added to this we need to know about viral infections which include norovirus, rotavirus and hepatitis A and B.

Then there are the parasites. Among these you may find tapeworms, pinworms, cryptosporidium, ascariasis and giardia. Plenty of reasons for washing our hands and avoiding having anything to do with human feces after it’s been expelled.

Image source:

geograph.org.uk

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