[Faz]

According to DEFRA figures, in 2005 approx 66% (just under 1 million tonnes per year) of sewage sludge was used in agriculture. Admittedly, sewage sludge is not raw sewage but is the stuff left over after biological treatment in the sewage works.

I am not sure how much of a resource modern farmers think animal wastes are - I sort of guess there must be significant imbalances in where it could be usefully used to supplement crop growth with where it is produced, due to the intensive nature of modern agriculture. A more mixed approach to farming would be ultimately more sustainable I feel.

[Salmo]

Farmers use treated sewage. Sometimes it is available as an odourless semi solid material which is spread on the land. It is also available as a liquid sludge which is delivered to the field in a tanker and then pumped to a tractor pulling a machine with hollow tines which injects it underground. This avoids any smell. This used to be just spread but was a filthy job and needed ploughing in within about a day.

Adding to comments above about farmers spreading slurry from their livestock. This is now highly regulated by Defra. It is not allowed to be spread in the Winter months to avoid run off and leaching into watercourses.

[Oscar Too]

...and an untranslatable German joke based on the fact that the German word for "nut" (as in "nut-and-bolt") is Mutter - mother in English.

Little boy is crying by the side of the slurry tank.  Farmer asks what's wrong.  Boy says that his "Mutter" has fallen in the tank.  Farmer dives in and dives again and again, before saying he can't find her.  "Well, now the bolt is no use either" grumps the boy, and walks off.

It's funnier in German, honestly.

[elibump]

 

Over here there is loads of animal poo in the fields at regular intevals waiting to be spread.  Also it is not unusual to find that 'older' houses and inhabitants have an earth closet in the garden.  Being so rural many houses have septic tanks, which if you're a wiley bird you get the local farmer to empty when necessary rather than paying the 'septic tank emptying' companies who charge you a fortune to empty your tank then sell the contents to farmers to spread on the fields.  Basically its a shi**y job, but somebody has to do it.

[wafflycat]

Years ago when Brian had his landscaping business, he used to get sewage from the treatment plant that he would put underneath new lawns that he laid, but it was burnt or something.  He said it was very black and flaky and dry

But like Poultrygeist said, they use the stuff from composting toilets, although Dick Strawbridge did say that they only empty them every 6 months.  That's why they had 2.  You use one, then leave it for 6 months while you use the other one!

Back in the dim reccesses of the dawn of time, when I was at school... One of the early biology trips was to the local sewage treatment works. By heavens - the stuff flowing into the treatment works *stank* It was often highly coloured due to the neighbouring industrial estate, where one of the factories was a company using dyes. The colour of the sewage depended upon what colour dye was being used that day..

Anyhow.. went through the whole process of sewage treatment, which was fascinating. In the labs, towards the end of the visit, we were shown this dry, odourless, thick brown cardboard-looking stuff, which was the solid left after the treatment. We were told it made excellent fertiliser, and folk could come to collect as much as they needed, but this was rarely done as many folk were squeamish (this was back in the 1970s). The reason it sticks in my mind is that we were told the added bonus was free tomato plants.. as the tomato seeds passed through the human gut unchanged.  That stuff really was dry and odourless and if I could get it now I wouldn't hesitate to use it.

[wafflycat]

There was also a prog on the other day - can't remember which channel or name of programme (Mrs Useless is my nickname), and it was about a system of using marshes on the outskirts of the city to effectively clean the human waste from the city to create water and fertiliser for the farms on the outskirts to provide the veg for the city. It was great viewing and a great system.

[chrissie B]

i carnt think of any thing more revolting , i did know some one who put their dog poo on their heap till i pointed out they may get worms , they said their dogs didnt have such things and i pointed out dogs pick up all manner of stuff we dont even know they have , they did stop doing it if you could put dog poo on i would have a huge heap cos mine never stop and the little dogs the worst .
chrissie b

[Oscar Too]

i carnt think of any thing more revolting , i did know some one who put their dog poo on their heap till i pointed out they may get worms , they said their dogs didnt have such things and i pointed out dogs pick up all manner of stuff we dont even know they have , they did stop doing it if you could put dog poo on i would have a huge heap cos mine never stop and the little dogs the worst .
chrissie b

I would stay well away from asking any further, if I were you - it's likely to be happening not too far away...

[ex-cavator]

As a relative newbie, I thought I'd ask what people's views were on using sewage sludge on their lotties - but, having done a quick search and found this thread, I guess a general lack of understanding may be leaving many folk blinkered ...

First of all, on such a densely populated island as Great Britain, and since disposal at sea has not been an option since the late 1990s, where do you think the solid matter that is a by-product of sewage treatment (otherwise known as sewage sludge) goes to? Well, as previously mentioned, about two thirds of it goes to agricultural land (of the rest, most is incinerated). And that amounts to (fag packet calculation) about 120,000 tonnes/year of dry matter. Or about 600,000 tonnes/year as a wet cake at 20% dry solids, in which form it will most typically be applied.

But the popular misconception is clearly that it looks, and smells like .... well, sh*t. It doesn't. Clearly there has to be strictly enforced standards as to what can be spread upon our agricultural land, and in order to meet these standards, the sludge has to subjected to robust treatment processes in order to render it safe. Both the standards, and the processes, have in recent years been made even more rigorous in order to meet the demands of the British food industry and in turn, to answer the concerns of an increasingly more aware British buying public.

A number of processes may be used, resulting in either a liquid product (typically 3 - 6% dry solids - about the consistency of double cream) or a cake (typically 18 - 25% dry solids - and 'cake' pretty accurately describes the consistency, although at the lower end of the range, it's more like a sticky chocolate gateaux!).

The vast majority of sludge in the UK undergoes anaerobic digestion for several days at 30-35 degrees C, followed by cold digestion in open tanks, to kill pathogens and render it safe. The end product (the liquid sludge) is quite sweet smelling and certainly not offensive. Subject to passing rigorous tests it can now be disposed of, though in most cases it will pass through further processes to dewater it to a cake primarily to reduce the haulage cost.

Some cakes may then be composted with lime, further increasing the dry solids content but giving rise to a high pH (alkaline) product.

As for using on allotments - liquid sludges are not so readily available and perhaps not entirely practical. But cake, if you can get hold of it, is an ideal and perfectly safe soil conditioner, and in no way offensive in it's nature. I say, if you can get hold of it - because of the audit processes that have to be satisfied in order to prove to the regulatory authorities that the product is safe & has passed all the necessary tests, it is not so easy to encourage some to 'fall off the back of a lorry' these days. But if you can manage it, then you would be foolish not to do so. Just check that it is a digested product, or stabilised with lime for pathogen kill - and if lime stabilised, keep an eye on your pH levels  :happy:

[Ice]

ex-cavator, using anything that has "fallen off the back of a lorry" or has not been approved for use is not something we can condone on here.  Rules are rules and whether we agree or not is irrelevant.

[ex-cavator]

Ice - I am sorry - perhaps my turn of phrase was inappropriate - I was not trying to suggest we do anything untoward, but it may be that on occasion, forum members are given the opportunity to use treated sewage sludge. It is only fair, therefore, that I try to dispel some of the wildly inaccurate preconceptions voiced earlier in the thread, and to try and clarify the point that this product is not only safe for use on crops for human consumption, but also a valuable alternative to the many other products and by-products in more frequent use - it would be a shame to pass up such an opportunity should it arise.

[Aunt Sally]

It contains lots of viable tomato seeds though.  These are not killed in the digester. 

[mumofstig]

So very true Aunty

[Salmo]

Treated sewage is used by farmers. It used to be delivered after most of the liquid had been squeezed out of it. I think most of it is now delivered in tankers and pumped out either on to the land and then ploughed in, or injected into the soil via a long pipe attached to the tines of a cultivator.

The stuff that is pumped out stinks and the rules are that it is ploughed under within 24 hours.

[ex-cavator]

Treated sewage is used by farmers. It used to be delivered after most of the liquid had been squeezed out of it. I think most of it is now delivered in tankers and pumped out either on to the land and then ploughed in, or injected into the soil via a long pipe attached to the tines of a cultivator.

The stuff that is pumped out stinks and the rules are that it is ploughed under within 24 hours.

Liquid sludges can be surface applied or direct injected as you suggest, but if it stinks it is most likely a raw (undigested) product. As stated before, fully treated products suitable for food crops do not have any unpleasant odour, although there may be some smell released from lime stabilised cake when it is disturbed, since any residual ammonia is in gaseous form due to the high pH.  The disposal of undigested sludge is being phased out, if not already stopped, though I believe that, currently, some products that have failed to meet the required pathogen kill can still be disposed of to sacrificial, non-foodstuff crops (such as hemp grown for the manufacture of soundproofing material in cars, or some such use).