Category: Green Mantle

compost making at The Oak Tree and sensor network design

Laverstoke Park Tea Brewer

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 bucket
Air stone in bucket
Air stone running
Air 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The kits came with some microbes in a tube, but the tube seemed to be out of date.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 heap 160901 , or heap 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!

Outer wrapping restored about 13:00 to maintain temp

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.

Temperature against time and date of this compost heap.

Good points and bad points of this heap:

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.

Second compost turn at 70C

After the drama of needing to turn this heap very early on a Sunday morning (we had obviously overdone the chicken manure slurry) it  heated up over the day so we turned again at about 19:30 Sunday evening.

Before the turn.
Heap uncovered
Heap uncovered
close up
close 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.

First compost heap turn at 74C

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 6am
overheating compost heap, turned in the morning at about 6am
heap contents
heap contents
Heap 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 outside
Close up of outside
Showing inner core. It really was hot!
Showing inner core. It really was hot!
detail of photo above.
detail of photo above.
Turning the heap
Turning the heap

 

 

New compost heap 160910 with chicken manure

New heap declared, using about a third of a 20kg bag of pelleted chicken manure dissolved in water to a liquid/slurry, to see if raising the N will help with the fade problem that affected heap 160901

We used only about 3/4 of one wheelie bin of wood chip so mental note to only prepare one next time for the black plastic composting container!

Allocated transmitter AT with fresh batteries today (for monitoring temperature).

all the materials collected with the team
all the materials collected with the team
10kg of pelleted chicken manure dissolved in water, about 7 kg used
10kg of pelleted chicken manure dissolved in water, about 7 kg used

Other materials:

Some sweetcorn and mostly french beans - 4 wheelbarrow loads
Some sweetcorn and mostly french beans – 4 wheelbarrow loads
Nettles and comfrey: 1 wheelbarrow load
Nettles and comfrey: 1 wheelbarrow load
Grass and clover with some nettles: 1 wheelbarrow load
Grass and clover with some nettles: 1 wheelbarrow load
Shredded evergreen leaves from Joanne’s old allotment neighbour, Rob’s, clippings: 1.5 wheelbarrow loads used
Crew: Josh, Glennis, Richard and Joanne chopped beans & sweetcorn laboriously using spades and shears!
Deployment of the chicken crap, which was then lightly mixed in with a garden fork

The whole heap was pressed down and then insulated with two lengths of black plastic above heap, and another length wrapped round fairly loosely to allow airflow. Used mist sprayer to wet all except pre-soaked woodchip and the chicken shit slurry.

Joanne and Glennis by the finished heap
Joanne and Glennis by the finished heap

Composition Data processing for 160910

Material WLB loads density Nitrogen Green Woody Norm N Norm G Norm W notes
Sweetcorn & French beans 4 0.8 0.3 0.7 0.96 2.24 0 estimate
Nettles and Comfrey 1 0.6 0.5 0.5 0.3 0.3 0
Grass and clover w some nettles 1 0.8 0.3 0.7 0.24 0.56 0
shredded evergreen leaves 1.5 1 0.2 0.8 0.3 1.2 0
woodchip 2.25 1 1 0 0 2.25 one wheelie bin is three wheelbarrows
Chicken shit 0.25 1 1 0.25 0 0 estimate, was 7kg
totals 2.05 4.3 2.25 checksum
Normalised proportions 24% 50% 26% 100%

Second compost heap turn and move to the small container

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 turn
We 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.

New 50:50 compost heap 160901

New heap instigated, roughly:

  • 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?

Composition Data processing for 160901

Heap ID 160901
container large black plastic
volume (init)
Material WLB loads density Nitrogen Green Woody Norm N Norm G Norm W checksum notes
Grass, clover, nettles, comfrey 1 0.8 0.5 0.5 0.4 0.4 0 1
shredded evergreen leaves 2 1 0 1 0 2 0 1
woodchip 3 1 1 0 0 3 1 one wheelie bin is three wheelbarrows
totals 0.4 2.4 3
Normalised proportions 7% 41% 52% 100%