a compost heap tracked all the way from start to thermal equilibrium. The sensr for the green trace was reallocated to ambient about 1/4 way through
I recently tracked a compost heap from start to reaching thermal equilibrium. Partway through we started another one, and one of the sensors was allocated to tracking ambient. While a single data point isn’t conclusive, it was interesting to see the week 37 (12-18 Sept 2016) second breath of this heap after the second turn coincided with a week of particularly warm weather. This points to a potential ambient sensitivity and it being worth tracking ambient in future and perhaps insulating the heap more in the later stages.
I will keep the technology of remote temperature sensing here, because I’d imagine horticulturalists aren’t that into electronics š
Both of our current compost heaps, 160901 and 160910 have now reached stable equilibrium. The two graphs below show the complete “heap lifetime” temperature against time. The tail of each chart is now reasonably steady, suggesting they are now “mature”. It’s between five and six weeks since we first built these heaps.
The complete ālifetimeā temperature profile of compost heap 160901 started on the 1st September 2016. The second probe was first at a different level within the heap, and then reallocated to monitoring outside temp at the start of week 37Temperature profile of the heap using chicken manure slurry, heap number 160910, showing the much faster burn initially
In both of these there seems to be a reasonable evenness through the pile when both temperature probes are active, the temperature recording tips of the probes were set in the centre of the pile horizontally, and at about 1/3 and 2/3 from the top of the compost heap material.
We had a quick look at 160901 compost under the microscope a little while back and it was very exciting!
Fungal hypha in heap 160901Bacteria and protozoa, magnification 400x in heap number 160901Another fungal hypha
The best GPS for a Brit searching for prehistoric stones is a GPS which has OS maps built in.
GPS with OS maps
The trouble with these is the sticker shock, you’re looking at about Ā£300-400, which is still a bit stiff. If you start with nothing, it’s probably still the best way, and you will undoubtedly get a better moving map experience, particularly with a GPS including an electronic compass, which will orient the map correctly for you.
I had a smartphone and Viewranger. I’d bought the Landranger 1:50k set of OS maps on viewranger for about Ā£70 – once you buy digital mapping you’re locked into that provider unless you want to pay up again.
Smartphone GPS is awful and power-hungry
The big problem with a smartphone is that GPS performance is dreadful. Quite how dreadful I hadn’t realised until I got out on Dartmoor and tried to use Viewranger, which made no attempt made to track current position.Well, pretty much until I was on my way back to the start point. I had a paper map anyway, although the smartphone version was easier to control in the wind!
A-GPS doesn’t help you here
The problem with a smartphone GPS is that by design it will fail you when you need it most, on a featureless moor with no signal. It is new-born each time you start it up. Rather than maintaining the ephemeris (knowing where to look for the satellites) when the phone is off, smartphones use A-GPS – getting the rough location from the network connection and using this to simulate the ephemeris.
Which is OK in towns, and no good to man nor beast in rural areas, because there’s no network connection. So you get to do a cold start of the GPS which can take over half an hour. No fun at all when you are out on Dartmoor. Even in towns the performance of smartphone GPS is dire, compared to a handheld GPS, as I found out looking for birds. Plus it’s power-hungry – running about 43mA @ 5V with continuous GPS on, compared to 25mA with a BT GPS.
Go for a separate Bluetooth GPS
A secondhand CoPilot BTGPS3, 2003 vintage The default Bluetooth code for one of these is 0183 (from NMEA 0183 protocol, I guess)
and use an app to get the location signal into the phone, something like Bluetooth GPS to set this as a mock location provider. Then shut off the internal GPS to save power. Start the hardware, then start the app before starting Viewranger, and everything will work better than before. The CoPilot battery is good for six hours, ebay has many more modern equivalents which probably have better battery life. You can save more smartphone power in the sticks by putting the phone into flight mode and specifically re-enabling Bluetooth, this shuts down the power-hungry wifi and phone data systems. Plus it stops Google knowing where you are in real time š
I still hanker after a Garmin GPSMAP64 because while this sorts out the poor GPS performance, it is hard to see the smartphone display outdoors, even under a wide overcast sky, and impossible with sunlight falling on it. Nevertheless, the smartphone app is a lot more practical now.
Laverstoke Park Farm is a UK site with specialised knowledge of Elaine Ingham’s methods. Sadly their farm shop has closed, we dropped by on route back from holiday last week in the hope of buying a bag of their compost (to inoculate our soil and compost heaps), but no joy, so we’ll email them in the hope of being able to buy a bag or two, or maybe even visit (it looks fantastic!)
We had invested recently in a small compost tea brewer which Laverstoke Park developed, to learn more about how it is done, before we try this on a bigger scale. We have used compost extract rather than compost tea to date as it is easier and safer.
The kit is basically a 3W aquarium pump, an air stone and bucket
Air stone in bucketAir stone running
The kits came with some microbes in a tube, but the tube seemed to be out of date. Sadly our first attempt with this mix failed as the pump fell from its perch (no harm done, fortunately) and this, admittedly early aborted, brew didn’t appear to contain much exciting under the microscope.
We are now going to wait until we have some promising Oak Tree compost (from heapĀ 160901 , or heapĀ 160910 if either look good under the microscope) or have some Laverstoke Park compost before we try using the brewer again. We’ll keep you posted!
The heap is now dropping below the 66 deg C temperature mark so the outer wrapping was replaced around 1pm. Today is a hot day, the highest September recorded for many years, so the heap has ambient temp on its side.
This heap heated up far more successfully than any of our previous heaps! and we look forward to putting some of the matured compost (when it has dropped ambient temperature) under the microscope. We put this sucess down to the pelleted chicken manure pellets mixed into a slurry with water which raised the temperature dramatically!
Outstanding issues:
It is possible the fast high burn rate of the early stages has exhausted the material, or that some was pasteurised at 74C?
The temperature profile isn’t 100% perfect, but it is certainly very promising.
After the drama of needing to turn this heap very early on a Sunday morning (we had obviously overdone the chicken manure slurry) itĀ heated up over the day so we turned again at about 19:30 Sunday evening.
Before the turn.Heap uncoveredclose up
This time we left off the insulation around the outside of the container, though retained the insulation in the top made of bundled up mypex woven black weed control fabric.
This graph shows the temperature against time/date of a new heap that included a slurry of pelleted chicken manure, as explained in this earlier post. There is a gap in the data near the top of the graph – Richard had an upper limit of 70C on the data logger which he swiftly raised as a result!! You may notice that the rapid rise of temperature to danger point happened at approximately 5.30 am on a Sunday morning. Yes, this meant that Joanne woke Richard at this time to tell him, “the heap is going anerobic!!!” (very worrying and could cause a fire!) so we rushed up to the farm to turn it…!
overheating compost heap, turned in the morning at about 6amheap contentsHeap had gone down about a third (it wasn’t loaded to the top before, down to about the first set of holes probably)Close up of outsideShowing inner core. It really was hot!detail of photo above.Turning the heap
Although the temperature profile wasn’t up to scratch this heap has rotted down well, so it was turned into the small container to free up the big container for the next heap. Temperature sensors were reallocated to heap 160910 but box AS retained and long probe inserted, second probe is set to monitor ambient.
The end result of this turn: we moved the heap to our smallest compost bin as it had shrunk down so much.Before this second turnWe carefully took out the middle to ensure that a part of the heap that had not been fully heated in the centre had its turn.We wrapped the heap up in mypex woven weed control plastic to insulate it, ensure plenty of space for air flow.
This heap turned Tuesday afternoon. Used fine mist on the spray to rewet some of it
Composting bin removedDetail after top layer removedSeparating the different sections of the heap to ensure all parts get heated in the centre at some point.Detail of above.
50% grass and clover with some nettles and comfrey
50% wood chippings.
Approx 15% N but estimated from the grass clover mix at about 50% grass, roughly equal mix that and green leafy (including relatively high nitrogen comfrey and nettles) and woodchip.
This was seeded with (very small!) soil samples from Staverton Thicks, Rendlesham forest and Captain’s Wood, all old, well established woodlands. We did this in the hope of introducing a wide soil food web to our heap, and subsequently to the soil. When we looked at these soil sample from the woodlands under the microscope they were certainly far richer in soil life than the soil at The Oak Tree at the time!
shredded evergreen shrub leaves
So the heap was made up of :
30% green leafy shredded conifer leaves
30% grass, clover nettles & comfrey
40% woodchip
Shredded conifer foreground and grass and clover background
Good initial progress but this was not sustained. Perhaps this should have been turned on the first Monday, rather than the Tuesday
Compost heap temperature profile: both probes were in the centre of the heap.
Review of what went wrong with this heap…
What happened – did well in reaching temperature, so sufficient N to get there, but no staying power. Possible causes:
Exhausting N by turning a day late?
Poor mix with insufficient N in the first place due to a lower clover to grass ratio than assumed?
possibly there is something too woody in the evergreen leaves?
possibly would have benefited from additional insulation to be able to turn earlier to avoid exhausting nitrogen?
