How pigs can compost manure on a farm scale, saving you fuel and money

Rebecca Hosking
Friday, 6th May 2011

Farmer, Rebecca Hosking, takes a trip to a biodynamic farm in Cornwall to find out how they use Joel Salatin's method of composting with pigs, rather than diesel, to turn their cow manure into fertiliser. These are pioneering farming techniques in the UK

I'm sure many are familiar with this scenario: you're driving along in the countryside and you're suddenly hit with the overwhelming stench of manure from a farm. A dilemma ensues do you A) wind up your window to stop any more of the smell entering the car thus trapping the low level smell that's already made it in; or do you B) keep the window down, taking on the full brunt in the hope the smell will quickly pass and fresh air will blow the rest of it away.

When this happens to us (we're windows open people) we usually comment – 'That farm is wasting money'.

What we're all actually smelling is a combination of Ammonia (NH3), Sulfur Dioxide (SO2), Hydrogen Sulfide (H2S) Nitric oxide (NO) and numerous volatile organic compounds (VOCs). Mixed in with those pungent gases are their odorless greenhouse bedfellows, nitrogen dioxide (NO2), Carbon dioxide (CO2) and methane (CH4).

Whether the smell from the farm is emanating from a yard dung heap, a slurry pit, a shed full of manure from over-wintered cattle or the muck spreader spattering its way across the field... it is the aroma of valuable nutrients fizzing off into the atmosphere where they do considerably more damage than good. Nearly all of these smells are the result of anaerobic decomposition – or as it's known to the gardener, poor composting.

Now not all farmers are die hard environmentalists and some may even doubt the science behind global warming. All of them, however, are concerned with making ends meet and, as such, the escape of these gasses (particularly the nitrogenous ones) from the farm, where they will fertilize nothing but the nostrils of passers-by, must be a concern. If half the nitrogen in your farmyard manure wafts off over the M5 corridor and beyond then you have to pay good money to replace it to keep the farm productive. And with synthetic nitrogen fertilizer currently trading around £350/tonne, the cost soon adds up.

Gardeners have long known the best way to lock down nitrogen in manure is to compost it; and the best way to do that is to physically turn the material to aerate it. Many studies have trialed alternative methods but as yet nothing beats brute intervention. In all fairness, on a garden scale even we've found this is relatively easy to achieve, all you need is a sturdy fork, a bit of elbow grease, cups of tea and biccies.

However if I walk into one of our cattle sheds where the stock has been wintered for three months, the volume of dung to turn and aerate becomes an overwhelming challenge. Could it be possible with human labour? Well, nobody in their right mind would willingly volunteer for this job, no farmer could afford to pay for the necessary workforce and we abolished slavery in England back in 1772 (thankfully), no, it's not an option.











Instead immediate thoughts turn to diesel powered machinery, much work with a front-end loader and investing in a trailer-operated compost turner. This is farmer speak for a lot of money, time, effort and fuel; making it an expensive exercise to even contemplate.

But what if there is another way, which is fraction of the price, requires no manual labor, no fossil fuel and no new farm machinery?

Enter Pigs; Stage Right

I first became aware about using pigs for this job back in 2007 while reading about holistic farmer – and a bit of a visionary – Joel Salatin. I'm sure many of you will already be aware of his work.

Joel and his family run Polyface Farm in West Virginia. He openly admits they stumbled backwards into pig rearing. Initially they purchased just a few pigs to use as a cost saving device to aerate the farm's cattle dung into compost. Polyface's 'pigaerator pork' as the Salatins named it is now one of their most popular products.

Since then I've heard a lot about the theory of pigaeration and we've longed to trial it here, but the older generation on this farm, namely my father and uncle, don't like change – I think I may have mentioned this before in previous posts! Anyway, in addition they have an irrational dislike of pigs so it's not going to happen here anytime soon. However, luckily this year our friends decided to test it out on their farm so finally I got to witness it in action.

Laura and Jim Wallwork manage Tregillis, an organic, biodynamic farm at South Petherwin in Cornwall. As I've often joked with Laura, I'm happy keeping an open mind but still struggle with cow horns acting as cosmic antennae but, when it come to soil health, we could all learn an awful lot from the biodynamicists. At Tregillis, soil health and condition is a priority, hence their interest in composting dung on a large scale. Last week I popped down to see them and their pigs at work and Laura kindly walked me through what had been happening.

Laura has used Salatin's approach as a template but has adapted the materials and ingredients to suit the particulars of her own farm. For the composting to be successful and the pigs to be agreeable, the preparation began right back at the beginning of December as the cattle first entered the shed.

Each day while bedding up the stock with fresh oat straw, Laura liberally sprinkled their own grown polycrop of peas, triticale and oats in amongst the bedding.

This differs slightly from Salatin's original ingredients of woodchip as bedding and corn (maize) as feed. However, whether you use peas or maize, the results are the same. The dry food gets stomped into the bedding by the cattle, where it ferments in the compacted anaerobic dung and urine. The result at the end of winter is thousands of little, sweet, mildly alcoholic piggy treats tantalizingly hidden in a barn full of manure.

With the arrival of Spring, the cattle go back out onto the pasture and the pigs are let in to commence their own version of a giant Easter egg hunt.

By the time I'd arrived the pigs had been at it for a week and had made short work of turning and ploughing the dung back and forth whilst snuffling through the deep litter. It was a joy to see such happy pigs – stimulated, entertained and getting plenty of exercise – a far cry from any intensive pig system.

The next sense that struck me was the agreeable smell. Gone was the all too familiar aroma of cow urea that catches the back of your throat; instead a far milder, sweeter fragrance. Not quite forest floor but closer to that than the smell of raw slurry.

Finally I noticed the texture of the litter was completely different to what I'd expect to see in a used cattle barn. It was far drier with more noticeable brittle and broken up straw. As a comparison, a clod of dung of the same age from one of our barns could knock someone unconscious at twenty yards whereas the stuff from Tregillis would scatter in the spring breeze before it even reached its target.

Adding Seaweed

Laura has come up with her own addition of heartily broadcasting dried seaweed across the bedding; if this works then it's a smart move. UK soils, owing to thousands of years of agricultural pounding, are mineral poor. Livestock farmers heavily rely on bought in mineral/salt licks to supplement their animals' dietary needs and cattle get through these licks like...well...a dose of salts.

The licks are expensive and completely unsustainable so by adding the dried seaweed to the bedding Laura hopes to boost her pasture's mineral content when applying this rich compost later in the year.

In a further Tregillis enhancement, Laura has also been adding a biodynamic herbal preparation to improve the composting process and final result. Like many things biodynamic, I don't think anyone really knows exactly how it works but it does. As the late ecologist, Frank Egler, said "Nature is not more complicated than we think; nature is more complicated than we can think" and that certainly applies to compost. The trillions upon trillions of births, deaths, rebirths, predations, consumptions, emissions, absorptions, assimilations and reactions that occur to create healthy nourishing compost really is beyond comprehension

So were Laura and Jim happy with the results? ...yes and no.

Laura pointed to parts of the bedding that were still wet and to the very bottom layer of dung that the pigs had not touched but she knew exactly where they'd gone wrong. By not spreading the food evenly and not putting a thick layer down first at the beginning of December before bedding up with straw had meant the pigs were not interested in those areas. Pigs are very much led by their snouts so no food means no aerating but it's something they can easily correct next winter.

Over all though Laura is pleased with the pigs' efforts. The compost/dung will next be taken out of the shed, covered and left to cure for a good few months before being spread on Tregillis pastures.

As for the pigs, well to paraphrase Joel Salatin, "They are farm machinery that never needs an oil change, they appreciate over time; and when you're done with them, you can either breed from them, sell them, or eat them." This year, Laura and Jim have a load of lovely sausages in the freezer.

Rebecca Hosking and Tim Green made the BBC2 film, 'A Farm For a Future' which explored peak oil and climate change in relation to farming. Whilst researching, they discovered permaculture and decided to return to the small mixed farm that Rebecca grew up on in Devon, help with day to day tasks and experiment with some cutting edge ideas and techniques. They regularly report the results for Permaculture online.

Useful resources

How to build a pig enclosure from pallets

Joel Salatin's pattern for carbon farming at Polyface Farm

Heating a greenhouse with compost and manure

Want to find out more? SUBSCRIBE to Permaculture magazine and get a quarterly dose of practical inspiration. Or download a FREE sample issue and try before you buy. Also available as a digital subscription (for just £10) and Apple and Android devices. 

More from Rebecca and Tim

'A Farm for the Future' - the full length film on peak oil, farming and permaculture

'Earth' - so important they named a planet after it ( and how to build hugel beds)

Fossil fuel fertilizers vs compost teas on the farm

Farming for the future - despite what the neighbours think

How to design more resilient, food producing systems (without money and fossil fuels)

Lauenna |
Sat, 14/05/2011 - 14:31
Very interesting. This happened quite by accident one year on a farm I was working on, a litter of greedy pigs turned the deep litter over beautifully. Not being a big pig fan myself I thought, now this is useful. However the following spring the pigs just wouldn't do it. I would go around with a crowbar leaving depositing pig nuts in little holes to encourage them but they were not interested. This system makes a lot of sense. I wonder did Laura have to spread the feed everyday over winter or could you just do it once a week?
Schroederek |
Thu, 30/01/2014 - 16:30
I love the management strategy you are using on your farm and it looks like and inspiring system. I work on the Deck Family Farm in Junction City, Oregon and we are doing some pretty neat stuff as well, and will no doubt be following suit with pig aeration come spring when our animals can return to pasture. We keep a blog about the goings on at the farm. Check it out!
compostturner |
Mon, 05/09/2016 - 09:11
this is really great method. pig manure is an excellent fertilizer containing nitrogen, phosphorus, potassium and other nutrients. It also adds organic matter to the soil which may improve soil structure, aeration, soil moisture-holding capacity, and water infiltration.I have read an article about pig manure organic fertilizer manufacturing technology: I think this article will also help those guys who are planning to effectively manage your waste!
compostturner |
Mon, 05/09/2016 - 09:16
this is really great method. pig manure is an excellent fertilizer containing nitrogen, phosphorus, potassium and other nutrients. It also adds organic matter to the soil which may improve soil structure, aeration, soil moisture-holding capacity, and water infiltration.I have read an article about pig manure organic fertilizer manufacturing technology: <a href="">swine manure organic fertilizer production technology</a> I think this article will also help those guys who are planning to effectively manage your waste!