On-Farm Composting: the story so far…

| Compost, Nutrient Cycling | comments | Author :

On-farm composting is a big part of our farm’s nutrient cycling, and an essential technique for ensuring nutrient density for our veggies and tree crops. Over the past couple of years we’ve tried and trialled various methods of hot-composting, with varied success.

As our composting needs have grown alongside our vegetable outputs, we’ve had to figure out how to scale-up our composting operations so that we can one day soon be self-sufficient in compost needs for Milkwood Farm. One hand-turned pile just doesn’t cut it any more!

How we started making compost at Milkwood Farm in 2007:

We started off with Berkley Method style hot compost, which (in theory) takes 18-21 days to turn a 1.5m cube of varied organic matter into 1m cubed of lush compost, with frequent turning that is defined by the pile’s temperature.

We’ve made many, many piles with this method now, and they do yield good compost for us, but the big caveat is that they take a lot of time and people power. Which is fine if you have a lot of time and people power, but for us, turning a pile or three by hand every other day was a lot of energy input for a not really significant quantity.

Considering we needed to turn a pile every 1-3 days, which takes 1-3 people about 20 minutes per turn, that is a lot of labor spent for 1m cubed of compost.

Hot ‘Berkley Style’ compost made by the lasagne method, as we made it from 2009-2012, using a ring to contain the pile (much easier for turning)
Which quickly becomes a pile of steam (if made in early Spring)

We turned piles in Spring, in Summer and Autumn. We turned them next to the kitchen garden…
.. and we turned them next to the market garden too (yay, PDC students!)

And eventually, each pile would turn into a nice big brown cake of compost.

As you can appreciate, compost is not, it cannot be, the center of our daily routine at Milkwood Farm. There’s just too much else to do. So we started looking for other composting strategies that would yield good compost in a reasonable time frame, with our available resources.

We looked at windrow compost, but we have very little flat land to make it on and to be honest we didn’t want to be driving a tractor or bobcat up and down our creekflat every other day, burning large amounts of oil for the sake of  compost. Hmm.

We also realised that in order to make compost on a large scale takes A LOT of ingredients. Primarily carbon. We could ship it onto the farm, in the form of hay or straw, but again, that would defeat the purpose. We’re trying to figure out nutrient cycling strategies, not nutrient input stream strategies.

Interestingly, at Milkwood Farm, it’s fulfilling the carbon needs of our compost piles that is the hardest. We have plenty of high-nitrogen materials (manures, food waste, urine, green grass etc) but not a great stock of dry carbon materials (hay, straw, woodchips, dry leaves etc). And that’s what takes the time for our piles – gathering the carbon.

In short, we haven’t decided on our long term plan for our goal of farm-scale composting at Milkwood Farm, so we designed a stop-gap system in the Autumn to make the most of our creekflat’s pasture grass and the glut of various other organic materials at harvest time.

So now we’re essentially making Berkley-with-a-Bobcat compost. In quantity.

Fast forward to Autumn 2012. Massive piles of scythed pasture hay from our creek flat await our new composting regime

The mega-pile, composting nicely and due for a turn (there’s only that much steam because the air temp at this point is about 8 degrees)

And into the next bay. And so on, with less and less frequent turns as the pile progresses. By Spring we will have a serious amount of organic compost.

Our temporary composting system is 2 bays made from concrete blocks (the blocks are waste concrete from the local depot). We made a gigantic compost pile in one bay, layering high carbon materials with high nitrogen materials at about 5:1 and making sure the whole pile was kept moist as we went.

We made this pile using a bobcat from next door, in order to get it done. We covered the pile with a tarp, and once it got hot, we moved it to the next bay using the bobcat (and someone on hose patrol to ensure adequate moisture). When it got hot again, we moved it back to the first bay.

This system is working better than anything else we’ve tried on the farm. It’s probably a combination of factors: the sheer size of the pile ensures a degree of thermal mass, as well as a sizable population of micro-organisms to get on with the job. The concrete bays protect the pile from drying out, and provide further thermal mass.

The bobcat part I’m ok with. If we weren’t doing it this way, it’s unlikely we could produce enough good quality compost by Spring for our spring planting in the market garden. Which would mean that we’d have to buy in compost. Which would definitely be made with a big, oil-guzzling machine.

This way, we have providence over the compost’s ingredients, and all the micro-organisms as well. And the nutrient cycling of the farm can continue. Our future, perfect on-farm composting system will ideally not involve machinery, but we’ll let you know when we get there!

Long term, we would like to replace the Berkeley method piles (ie active turning) with a series of big slow cool compost that didn’t need turning..  because that would be truly low energy input. We have some good leads on techniques for this, it’s just a case of getting far enough in front of ‘the compost needs curve’ to get such piles rolling.

All in all, it’s far cry from how my first compost pile turned out:

Hmm. And here was I thinking back then that we’d only ever need enough compost for a veggie patch for two. Funny where life takes you, eh?

>> more posts about composting and nutrient cycling at Milkwood Farm

Many thanks to all the family, interns, woofers, students and friends who’ve helped turn compost piles at Milkwood over the years. Our on-farm fertility thanks you all!

See the comments

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13 responses to “On-Farm Composting: the story so far…

  1. Yes, composting in bulk without lots of fossil fuel guzzling machinery and without too many WWOOFer hernias … I think you must be right that cool composting is ultimately the way to go.

    I’ve been having fun with hot composting since the PDC in Feb. Your method with the fencing ring worked well for me, though I immediately caught an eye infection because I forgot Nick’s advice about wearing glasses! When I say ‘immediately’ I mean within 5 minutes of turning the first pile.

    Aside from stupidity, my main problem has been time. It was all going swimmingly until my publishers reminded me that they do like to see the odd book from me, from time to time and preferably NOW. Without turning, the piles (I had two on the go) rapidly cooled down and became the Williams Slightly Warm Composting Method.

    Hopefully I’ll find time for a couple more hot composts to produce about 4 m2 of compost come the spring.

  2. I have seen a video of a guy with a compost turner which is a recycled cement truck, that way it can be filled and turned an a few min with minimal effort.He was said to have the best compost, he also used to compost cane toads in there.

    1. Yep, we’d love that to be a part of future composting strategies. The polyface version involves a heap of sawdust and hay (again, carbon inputs we don’t yet have available on-farm), a heap of pigs, and a heap of corn (neither of which we have in quantity at this point). In future years, pigaerators will definitely be used tho, if our systems lead in a direction that supports their integrated addition!

  3. Thanks for sharing that Kirsten, it certainly gets trickier getting into the larger scale. The large compost operations here don’t turn they just inject air into the bottom of the piles through in place pipes. Not that it’s much use for you guys. 🙂

  4. Great story and i think one that highlights the need to design mulch plants into a farm through forest gardens. Way more than a food forest a forest garden can be designed with woody and non-woody plants to generate a mix of mulch when they are cut to add into composts. These can stack function into windbreaks aswell. Further, well designed coppice systems can generate carbon too and you can stack it once more by using the coppice wood to heat your dinner and create biochar with a world stove and then add that to the compost. O the things you can think.

    Also my experiance wih forest gardens has been that slow woody composts generate better soil for trees. My fast composts never ate sticks or had much mycelium but my slow stacks were teaming with mycilium and the sticks were mostly gone. Perhaps we can slow compost the old shitake logs?

  5. thanks for your ideas on larger scale composting Kirsten. after doing the organic market garden course at milkwood last sept, making enough compost has kept me fitter than is sensible. However a part solution appeared today. A man and his digger came to do several jobs including to enlargen the hand dug drain above my market garden to help with the wet winter/spring here in tassie, that leaves the garden saturated til late november and the paths like skating rinks on hills. in the past, the paths have been kept usable in the wet with loads of sawdust from the mill down the road. The paths also serve as a duck highway for the children’s big mob of beloved ducks. Today when the paths were scraped back to double as a really big drain, we moved over 2 feet over lucious compost from the paths!!!!!! I got altitude sickness looking at the pile! Lesson for today: sawdust + duck poo = compost abundance = :o)

    I’ve done similar on a smaller scale in the veg garden with sawdust paths & pulling paths up onto beds periodically. I still add other compost with a more diverse range on ingredients though.

  6. We made some bio-dynamic composts on our far which worked pretty well. We made 2 and they were 2m high and 5m long. We made a core of straw to let the air in and piled layers of chicken poo and hay..with a tractor….watering all the way.
    After we dug holes with a crowbar and put in the bio-dynamic compost preps.
    The beauty of it for me is that we didn’t have to turn them.
    We made them in summer when they break down faster and I had enough to top up all the beds in our half acre market garden for 8 months….They took 4 months to be ready but the timing was that this was when i needed them after the first crops were harvested and i wanted to re plant.
    Bio-dynamics Rocks !

  7. What if you put the matter to be composted in huge round irrigation tanks, drilled with air holes, and put the tanks on rollers. There’d still be some labor to turning them, but less.

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