Hot Composting - Increasing Throughput

 My current hot composting facilities comprise:

• an early version of the 200L HotBin bought from its inventor (Tony Callaghan) - at least 10 years old
• a current 200L Hotbin bought in last year's Black Friday sale and used for the first time in 2025
• two prototype Supercomposter Bins developed by Tony Callaghan after he sold his HotBin company in 2015
• 4 x 200L plastic maturation bins for storing and finishing the HotBin output
• a Bosch AXT Rapid 220 Garden Shredder

Photo 1: From l to r, Supercomposter, Current HotBin, Original HotBin, Maturation bins

In the busy gardening seasons (Spring, Summer & Autumn), I will have two (occasionally three) hot composters running. During Winter, I will just maintain one active HotBin. In addition to my own garden waste, I also accept waste from up to six other neighbours. Every autumn, I receive a large amount (about 2 cubic metres) of hedge cuttings from one particular neighbour. More generally, neighbours drop off their garden waste intermittently in quantities of two or three 60L bags (Photo 2).

Photo 2: Large & Small Bags of Garden Waste 

A few days ago, I took delivery of a large quantity of garden waste when the ivy/privet hedge belonging to a neighbour at the rear of our garden was heavily trimmed. The rear bag in Photo 2 is what remains of that delivery after I had shredded and fed some into my hot composters. A day later, the contractor who cut the hedge (Paul) popped round and asked if I was interested in taking more garden waste (lawn mowings and hedge trimmings in the main). I had, perhaps mistakenly, mentioned that I used hot composters to speed up the process. I agreed, on the basis that I could turn down future supplies if the amounts involved became too much, and immediately took delivery of another 400L of grass cutting and hedge trimmings (Photo 2, front bag). The next day, a further 200L of ivy cuttings arrived but I'm not expecting anything else for another week. Photo 3 is my current stock of garden waste but, at least, the 3 x 60L bags have been shredded and are composting away at 60 ℃.

Photo 3: Garden Waste Awaiting Shredding (18th May 2025)

With so much garden waste to process, I have had to change my modus operandi. In the past, my standard procedure was to half fill a hot composting bin with shredded waste/grass cuttings (50/50) using a minimum of 20L hot (50-60 ℃) partially-composted waste from an operating bin to kick start the process. Adding a couple of 2.5L bottles filled with hot water is an alternative way to kick start the composting process. As soon as the bin is up to temperature (50-60 ℃), usually the next day, continue to add shredded/kitchen/grass at the rate of 6-10L per day. At this rate it takes between 20-30 days to fill a bin.

To process the extra quantities of garden waste now available, I will be looking to fill the bins at a much faster rate as well as bringing my two Supercomposter bins back into action (Photo 4). The two Supercomposter bins are currently being used as (i) a store for shredded garden waste, and (ii) a maturation bin.

Photo 4: Supercomposter Bin in Use as a Maturation Bin

One of the Supercomposter bins is already in use and operating at over 60 ℃ after just 24 hours. So far, approximately 250L of shredded garden material is undergoing hot composting! I am also trialling  the use of heat reflective coverings laid on top of the compost to retain and re-use the heat generated by the composting process. Currently, I'm using extra wide (450 mm) catering aluminium foil which is working well. The covering should only loosely cover the compost to allow for ventilation and easy egress of water vapour/steam (Photo 5). Early indications are that the reflective shield increases the rate of initial warming, maintains a greater depth of warming, and reduces the rate of cooling towards the cool-warm (<40 ℃) composting phase.

Photo 5: Reflective Heat Shield (Aluminium Foil)

At a later date, I will report in more detail on the benefits or otherwise of using a heat-reflective covering when hot composting.

Living on the (H)edge

The kitchen garden backs onto a row of terraced houses. Along this southern boundary, there is a giant hedge (Photo 1). Ivy dominates the hedge which overhangs our boundary. Occasionally, I will trim the overhanging vegetation, shred it and put it through my hot composting system.

Photo 1: The Walled Kitchen Garden

House sparrows nest and roost in this giant hedge. A cacophony of sound often greets me when I visit my composting corner but soon changes to an eerie silence apart from the odd chirp from a young house sparrow.

I got a bit of a shock the other day on my way to tend to the hot compost bins. One side of the hedge was much reduced in height. I could hear noises on the other side of the wall so called out and received a reply.

Photo 2: The much-reduced Ivy Hedge

I almost said that it wasn't the best time of year to be cutting down hedges due to nesting birds but I would have been wasting my breadth as the job had already been finished. My neighbour would have happily hacked down all the hedge if he had been able to access it.

Photo 3: Close-up of the Much-Reduced Hedge

Being neighbourly, I offered to take all the cuttings for my hot compost bins. I probably should have checked how much stuff there was before making the offer because he started chucking it over the wall (I had agreed to this).

Photo 4: Hedge Cuttings Covering the Maturation Compost Bins

Photo 5: Side View of the Cuttings Pile

It took me about 6 - 8 hours to cut up the hedge trimmings into 3" to 4" pieces ready for shredding. In all, I ended up filling the equivalent of 11 x 80L bins (approx one cubic metre) before the kitchen garden returned to normal. You can see in Photo 6 how much the height of the hedge had been reduced.

Photo 6: All Tidied Up

There were a couple of house sparrow nests in the hedge debris ...

Photo 7: House Sparrow Nest

... and, fortunately, no eggs or young. There is still quite a lot of the original hedge still standing so hopefully the sparrows will continue to breed and raise their young here. For the moment they are still visiting our bird feeders in good numbers.

In an earlier blog, I made reference to man's urge (it is usually men!) to tidy up nature and this is another example. I suppose the neighbour's garden lets in a bit more light and I've gained lots of greenery for composting but that doesn't, in any way, make up for the fact that some house sparrows are now homeless. 

May Blossom

 You can guess what month Hawthorn flowers from its common moniker, May Blossom. This year's display of flowers has been spectacular, especially in hedgerows where hawthorn is a dominant species.

I took these pictures on my way home from a citizen science outing after testing the Yazor Brook adjacent to the Environmental Gauging Station mentioned at the start of this guided walk. This popular and well-used walking/cycling route has benefited from ongoing improvements to the area in the form of the Yazor Brooks Restoration Project.

Photo 1: May Blossom near Bulmers, Hereford (9th May 2025)

Cow parsley is also in full flower at this time of the year, often seen along the verges of country lanes.

Photo 2: Cow Parsley along the Cycle Path 

Along this particular route, however, there are fields of it covering the floodplain of the Yazor Brook ...

Photo 3: Fields of Cow Parsley on the Yazor Brook Floodplain

It has been allowed to spread in an urban environment as the floodplain is unsuitable for building. No doubt its existence will be threatened someday by the inexorable desire of humankind to tidy up nature. 

Photo 4: Pathway to Cow Parsley Heaven?

On a perfect Spring day, nature has crafted a beautiful urban landscape ...

Photo 5: Hawthorn and Cow Parsley, Yazor Brook, Hereford (9th May 2025)

Only a couple of hundred metres away from this nature idyll is the sprawling industrial complex that includes Avara Foods and Heineken (formerly Bulmers Cider). Avara Foods (purveyors of chicken, turkey and duck products to supermarkets/restaurants) are considered one of the 'bad guys' with regards to the pollution of the River Wye and one of the reasons we need citizen scientists to monitor river quality. Unfortunately, Avara is part of the Cargill US conglomerate and they do not have a good record of environmental protection in their home country. There is no getting away from the fact that Avara is a major employer in Herefordshire and that it produces cheap protein-rich food (an important consideration in a cost-of-living crisis). The main issue is with the intensive poultry farms and how they dispose of the high phosphorus waste. Avara have stated that none of their poultry waste will be spread on land in Herefordshire which is a good start. Unfortunately, their preferred disposal route is via anaerobic digestion and there are environmental issues with this process.

View from the Rear Window - December 2024

December - the tenth (decum) month of the Roman calendar which became the twelfth and final month of the year in the Julian and Gregorian calendars. This month's photo was taken on Christmas Day (25th) when the winter-flowering cherry was in bloom, the heady fragrance of the sarcococca bush was divine and the Christmas tree was adorned with baubles.

Photo 1: The Back Garden on Christmas Day 2024 

The daily photos for December 2024 are collated in Video 1 ...

Video 1: Daily Photos of the Rear Garden in December 2024

December 2024 was mild, windy and relatively dry though lacking in sunshine. December's weather stats, collected by our garden-based Davis Weather Station, are presented in the table below:

December 2024
Weather Parameter	Value	Dates
Average Monthly Temperature	7 oC
Maximum Monthly Temperature	15 oC	1st & 5th
Minimum Monthly Temperature	1 oC	28th
Number of Air Frost Days	0
Number of Hot Days (> 25 oC)	0
Monthly Precipitation	52.0 mm
Greatest 24 h Precipitation	22.8 mm	18th - 19th
Number of Dry Days	11
Monthly Sunshine Hours (estimated)	41
Highest Wind Speed	61 km/h	7th
Heating Degree Days	337.4
Cooling Degree Days	0

The minimum and maximum daily temperatures for December 2024 are shown in Figure 1. With no frosts and moderate day and night-time temperatures, December 2024 felt unseasonably warm. 

Figure 1: Min/Max Daily Temperatures for December 2024

Cloudy skies were the main reason for the absence of frosts and the relatively uniform daily temperatures -in other words, the sun remained hidden on most days (see Figure 2).

Figure 2: Daily Rainfall & Sunshine Data for December 2024

Figure 3 shows the highest daily wind speeds recorded by our weather station in December 2024. The highest wind speed of 61 km/h was recorded during Storm Darragh (5th to 7th December). Consistently strong winds throughout the UK, meant that wind power generated 39% of all the UK's electricity - more than any other source.

Figure 3: Highest Daily Wins Speeds Recorded in our Rear Garden (December 2024)

We now have weather data for December covering the period 2019 - 2024 which I have summarised in Figures 4 & 5. Over this period, the maximum December temperature has been creeping upwards (Figure 4) although it is still possible to get cold Decembers (2022, 2023; Figure 4). Rainfall is trending downwards, though not because it is sunny, while maximum wind speeds are on the up (Figure 5) - overall, good for wind power generation but not for solar PV.

Figure 4: December Temperature Data for the 2019 - 2024 Period

Figure 5: Rain, Wind & Sunshine Trends in December for the 2019 - 2024 Period

The next three figures are taken form the UK Met Office's monthly report for December 2024. All of the UK experienced a mild December including our little corner of Hereford (Figure 6).

Figure 6: UK Mean Temperature Anomalies for December 2024

There was heavy rain in the northernmost parts of Scotland, but the rest of the UK had average to low rainfall (Figure 7). The Met Office's weather station at nearby Credenhill gives an average December rainfall of 72.67 mm (1991-2020 data), so the 52 mm (Table above) recorded in our Hereford garden is 25-30 % lower than normal.

Figure 7: UK Rainfall (relative) for December 2024

Despite the low precipitation, sunshine levels were also much lower than expected in Hereford and also the whole of the UK (Figure 8).

Figure 8: UK Sunshine Hours (relative) for December 2024

Jobs in the Garden

• Harvesting potatoes, beetroot, parsnip, spinach and Swiss chard
• The final few of this year's tomato crop were eaten

Photo 2: The Last Tomatoes of the 2024 Crop (23rd December 2024)

• Still a few pears left from the 2024 crop

Photo 3: The Final Five Pears from This Season (30th December 2024)

Flora & Fauna (seen in the Garden)

• Blackbird (x1)
• Blue Tit (x3)
• Collared Dove (x1)
• Crow (x2)
• Dunnock (x1)
• House Sparrow (x6)
• Magpie (x2)
• Robin (x1)
• Starling (x10)
• Wood Pigeon (x2)
• Wren (x1)

Not many photos from the garden which is quiet at this time of the year ...

Photo 4: White Hellebore/Christmas Rose (2nd December 2024)

Photo 5: What's Left of a Wood Pigeon in the Kitchen Garden (predator unknown)

Photo 6: HotBin Nice & Cosy at 50 ℃ (30th December 2024)

Photo 7: Xmas Baubles on the Acer Tree (23rd December 2024)

Wall of Strawberries

 Never had much luck growing strawberries - most of the produce being eaten by birds, slugs, snails and rodents. I often find woodlice in and around damaged fruits but I suspect they are just scavenging on damaged berries.

Past failures are not, however, going to stop me trying again (note to myself: a fool is someone who keeps repeating his mistakes while expecting a different outcome). This time I'm going to create a wall of strawberry plants hoping the height above ground will deter at least some of the slugs and snails. I will need to add some protection against birds, probably netting of some sort. The other issue is irrigation to encourage juicy plump fruit. I will address this issue later.

My first job was to screw some tanalised timber battens to the south-east facing wall. Here I am using Worth Wall Planters bought quite a few years ago. They seem to be very similar, if not identical, to the current version. Other wall planters are available. It is possible to fix these planters to the wall using fewer battens (e.g. see here), but this arrangement is stronger and stabler.

Photo 1: Almost Finished Fixing Wall Planters to Battens

Photo 2: Installation Complete

The strawberry plants arrived a few weeks ago from D.T. Brown. They were immediately potted up in Fertile Fibre Potting Compost and hardened off in the polytunnel. There are 32 strawberry plants in this wall: 12 x Malling Champion, 10 x Summer Breeze (Snow), and 10 x Summer Breeze (Rose)

Photo 3: The Wall of Strawberry Plants (3rd May 2025)

Work still to do: (i) attach net and support to deter birds, and (ii) fix up some form of automatic irrigation system.

Historical Note: We found the W. Earp & Son enamelled sign in the cellar. It is not a reference to Wyatt Earp (of OK Corral Fame) but to the lesser known Willam Earp, a nurseryman, seedsman and florist who business was in the adjoining street.