HOTBIN is diverting food waste
Waldringfield Community Composting scheme is successfully diverting food waste from landfill.
Last weekend we visited our friends at Waldringfield Community Composting to look at the results of the first 3 months of the HOTBIN use.
Everyone was keen to learn how much food waste the 12 households had actually diverted from landfill. The results are in and the weighing scales revealed: 5 Kg/week per household. (It was much higher in the B&B – but they have guests each week which accounted for the 10Kg/week.)
What a marvellous community composting effort.
How does this compare to other customers and the national picture?
Nationally the WRAP figures indicate that 5 Kgs per household per week is the average – I’m sure they will be happy to learn they are normal!
Our own HOTBIN customers survey is less rigorous in terms of weighing exact amounts, but it also indicates HOTBIN users divert around 3-6 Kg of food waste per week from landfill The main difference is between users who choose to really get stuck into what you can hot compost such as cooked food waste and chicken carcass etc. versus those that choose to only compost vegetable peelings.
What does all this mean? Does it make a difference?
If we take all the HOTBIN customers across the UK, the total diversion is still not that huge but as they say from little acorns….
There are 30 million households in the UK, if just 3% actively composted all food waste at home, that would remove 250,000 mt of waste from landfill. That also happens to be about the same amount of waste 10 major anaerobic digestion facilities to be built would process.
Clearly it works in our favour if more people have a HOTBIN but the figures speak for themselves!
What does this mean in terms of garden compost?
Each household is also composting garden waste. A total of 250-500 Kgs of starting material will give 75-150 Kgs of compost which is 5-10 bags of compost a year. That’s saving around £25-50 (maybe £10 more if we include car petrol) over buying from the garden centre.
Are there other benefits?
Yes. There are two huge, almost hidden, benefits of composting:
- More food waste results in more compost. More compost results in more humeric substances. More humeric substances means more fertile soil which means stronger plants and vegetables which in turn means more and better food.
- Humeric substances are ‘recalcitrant forms of carbon’ – they are resistant to further decay so they store carbon in the soil. Adding stable humeric substances to the soil results in carbon sequestration which off-sets the impact of global warming due to CO2.
What could be simpler, compost more!
HOTBIN composting on an allotment
The HOTBIN was developed to compost all food, garden and grass in the home and garden.
We want to know how it works on an allotment; so this week we’ve enlisted the help of Gil and Steve at their Jesmond West Allotment, and Karin at the Morpeth East Green Allotment to help us test the HotBin.
HOTBIN composting on an allotment
Tony went out to set them up with the volunteers this week. Before we started we checked the temperatures of the heaps around the allotments. They were ‘cold’ (very), with ambient (5C) in two, and 8C in centre of a big full 1m3 heap. There were plenty of compostable materials around in existing dalex/plastic cones and wooden bins on the allotments so both HotBins were filled to the three-quarter level. Some of the materials added were mushy wet fruit and vegetables (bits were anaerobic smelly), lots of stalks (cabbage/broccoli) and stems from raspberries etc. Also some shredded paper (Karin) and cardboard (Gil).
We basically just ‘hoofed it all in’, and in this instance, we did not cut or chop things up – we wanted to compare current composting taking typically 12-34 months with the same waste in a HOTBIN. We used the ‘winter heater’ in one HOTBIN and not in the other. We’ll report back on temperatures each week or so.
What are the allotment users composting objectives and requirements
- Compost – humus for helping soil fertility, reducing fertiliser, increasing water holding
- Clear up waste – very few allotments get a ‘waste collection’ so there is a need to reduce and remove plant waste
What’s different in an allotment over the house/garden?
- Volume of waste – allotments tend to produce a lot, and on a highly seasonal basis – ie spring & autumn clear ups.
- Additions to the heap tend to be ‘once a while’
- Not necessarily the time (or inclination) to chop or shred waste, on the whole just want to dump it on the heap.
- There is either a lot of turning (active) or none at all (digging out after 12 months and restarting new heaps after scrapping out).
- More weeds such a couch grass and dandelion
- Some (but not all) will take caddies of vegetable peelings etc down depending on the location etc
Possible HOTBIN advantages / disadvantages?
Space – One observation is that each plot (approx 250m2) has between 2 and 4 heaps taking an area of 2m2 per plot. On a site of 50 plots, that’s 150 compost bins, and a whole plot used for composting. If we can arrange a ‘communal system’ and keep all HotBins composting at 60C, then this could reduce to 8 HotBins.
Economics – Many allotment owners enjoy growing their own food, but we can’t avoid that it is also a ‘low cost’ activity with average rents being £50/year. Costs including compost bins need to be kept under control. There could be a communal saving – 150 standard bin @ £20 each= £3K v 8 x Hotbins @ £138 each = £1K.
Ease of use – Allotment owners are used to hard work, but our gut feeling is they would rather be growing and using compost than turning heaps.
It looks like the Hot will be put through its paces on the allotments and it will interesting to hear back how the HotBin and the users get along!
How does composting benefit my garden
Rich compost in 90 days
Most gardeners just ‘know’ compost is good – they use it and they see the benefits in terms of plant growth etc.
Perhaps less well known is that humus (see definition below) is absolutely critical to soil structure, tilth, fertility, etc. It is hard to grasp just how many aspects of life on earth are linked to humus – agriculture, sustainable agriculture, reduction in inorganic fertilisers, peat., carbon sequestration, biochar, desertification, land rehabilitation, the list goes on.
So just an opinion – humus is hugely important.
We have not re-listed the huge long list of beneficial properties of humus; (they are available in all good soil chemistry books and well reviewed on Wiki etc. However we do think it is helpful to clarify that humus as defined in soil science has a different meaning to the more colloquial gardening use of the term where it often used as another name for compost. In soil science, humus is a distinct fraction of the soil organic matter (SOM).
- Dark (almost black), mushy, sticky and watery
- Is a colloidal mass, ie it holds many times its own weight in water – squeeze humus and water will come out.
- The water in humus dissolves and holds the critical plant nutrients (NO3- nitrate ion, ammonium ion (NH4-), Sulphate ion (SO4-). As soluble ions, roots easily absorb them. The ions are not easily washed out (leached out). In humus, both water and the soluble ions are retained but are ‘plant available’, ie absorbed via plant roots
- Humus has the capacity to hold and exchange cations (e.g. metal ions such as so sodium, calcium, aluminium, iron). Soil cation exchange capacity “CEC” affects fertility – CEC increases as you move from poor soils (e.g. heavy clay) to good (e.g. rich loam). Adding humus increases soil CEC, i.e., soil fertility.
- Humus is highly resistant to further mineralisation (decomposition). It is routinely carbon-14 dated at 200-500 years old
- Humus is made of large polymeric chains. However, when extracted for chemical analysis, it has the following constituents: humeric acid, fulvic acid and humin. This family of ‘aromatic ring compounds’ are used as ‘building blocks’ linked in many different ways to create a complex polymeric substance.
‘Mature compost’ is not ‘humus’, although it will contain humus. The more humus in your compost the better for your plants, soil and the environment. There is an awful lot of soil fertility and soil science that indicates humus is one of the most important items in soil fertility. Nutrients from decay end up in the soil at some stage. These nutrients are retained and made available for plants via humus.
It is a sad and growing fact that nitrates and other nutrients added to soils tend to leach very quickly from soils with low humus content.
Want to know more about humus?
Wiki has some good info and you can browse J Stevenson – Humus chemistry at Amazon
Other names for Humus:
There are numerous names to describe humus and commercially available humic materials. These include: humates, humic acid, leonardite, brown coal, lignite, slack lignite, oxidized lignite, weathered lignite, humalite, fulvic acid, fulvates, ulmic acid, humic shale, carbonaceous shale, colloidal minerals, humin, concentrated humus, soil organic matter, peat, humus acid, humus coal.