Benefits of composting all food waste – is it worth it?
Why compost food waste?
An estimated 7.2 million tonnes of food waste is collected by UK Local Authorities and sent to landfill. This is approximately 150-250 Kg per household per year (ref. WRAP, 2011). Around 7m UK homes already home compost, but they compost as little as 35% of their total food waste – typically adding vegetable peelings and tea bags. The other 65% of food waste (plate scrapping, meat, fish, cooked food, rice, pasta, leftover bread, cakes, etc) is on the “do not add” to your compost bin list. This advice is well founded when cold composting food waste as it often results in odour, vermin, yuck and mess (ref Defra funded, Brook-Lyndhurst 2008).
Successful home composting of all food waste has environmental benefits as it reduces fuel used to collect and transport waste to landfill, prevents methane release in landfill, [methane is a potent greenhouse gas] and reduces the number of new industrial composting / anaerobic digestion plants required in the UK.
WHAT SAVIINGS does this TRANSLATE into?
A quick estimate is 250Kg/house x 65% x 7m households upgrading to hot composting = 1.12 million mt of food waste diverted from landfill. This equates to roughly 50 large scale AD/IVC central plants. Whilst costs vary, this is around £500 million of capital costs and 10 years of planning and building.
We clearly have a vested interest, but it would appear to be a good environmental case to subsidise the more expensive “all food waste compost bins” for those households that want them. If the government exempted the compost bin from VAT (£25) and matched 3 years of food waste collection cost (£20/yr/hh for FW), then that would get to around a £75-85 subsidy!
(No VAT? – Within the overall UK energy & environmental programme there are a number of energy saving devices classified as zero rated VAT goods. So if we lobby politicians along the lines of “what’s the difference between energy saving and saving the environmental impact of transport/landfill/building AD processing facilities)
We need to get a couple of council officers thinking £75 subsidy. At a price point of £75 per HOTBIN we know people would buy on mass. From here it is a virtuous circle – high volume production reduces costs, which means lower prices which equates to more volume. We are miles away from this – but our goal has to be large scale diversion!
It’s a big lobbying task, but the rewards could be large.
Just for clarity – we are not anti the WRAP/government strategy to build anaerobic digestion (AD) plants to extract energy from food waste. Technically sound and matches the council’s need to build solutions that cater for most of the population. Composting is not going to work for all (flats, no gardens etc come to mind). At best composting is relevant for 20-30% of households, but this 20% can make an immediate and large impact winning time for the planning consents and large AD facilities to handle the other 80%.
My Council Collects food waste in Kerbside containers –
Is it still worth composting?
Some Local Authorities collect and transport food waste to either a large composting or anaerobic digestion processing plant – well done your council. To meet UK commitments on landfill diversion, we estimate 300 new reprocessing plants will be needed across the UK. Each will cost many millions to build and take many years to fully commission.
Processing at home can start immediately; it saves labour, transport costs and the need to build as many reprocessing plants. If you have very little waste (less than 2.5Kg, or a small 5 litre kitchen caddy per week), or have no garden to use compost, then using a kerbside collection makes sense.
My Council Offers cheap/free dalex/plastic compost bins –
Is it worth using a HOTBIN?
We believe so. The key issue we see is this – almost all compost advice sites (government, user, expert) will state: “do not add cooked food, meat, dairy, fish, bone etc to a traditional cold dalex type composter – the food is likely to decay anerobically and generate odour which in turn will attract rats and flies”.
1) This means around 65% of food waste items are not added to a coldcomposting bin
2) You only get significant diversion if home composting can handle all food waste
3) You need a special food waste compost bin to handle all food waste
In our opinion, as soon as you establish an objective like ‘compost all food waste with low odour, without attracting rats or flies’ or ‘compost using an easy recipe; ‘compost faster’; ‘compost all year round’ then you need to look at ‘hot composting’.
You can find a full list of the benefits of hot composting and how to evaluate a specialist HOTBIN over a traditional heap at our post on choosing the right compost bin.
Things to consider unclude;
- Do you want to make a more positive contribution to the environment?
- Recycling all your food waste so your local council no longer has to collect and transport it to landfill or a central AD/IVC reprocessing plant?
- Are you just fed up with allocating more and more of your flower or vegetable patch to overflowing compost bins that never seem to do anything?
- Do you only have seasonal waste, or do you also have regular weekly amounts of food waste all year round
You will find a full list of the benefits of hot composting over cold composting at this post
My Council Collects Green waste –
Is it still worth composting?
Many councils charge for green garden waste collection (e.g. £20-30 per year) and these charges are likely to increase. Many green bins are collected near empty (wasting time and fuel). Most of the time they are filled with mainly grass – grass is really easy to compost!
If you are a keen gardener, more than likely you will buy fertiliser, peat and/or compost to maintain the quality of your garden. Why not make your own compost and fertiliser. It takes no more effort and you could save you money.
Why is COMPOST & Composting Important?
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.
Soil chemistry books are 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). Humus is:
- 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.
So if you are keen to get hot composting take a look through this blog or visit our website which also has a substantial composting FAQ