Advantages and Disadvantages of In-vessel Composting Food Waste
The in-vessel composting of food waste is being carried our increasingly, particularly in the
United Kingdom, with the prime purpose being to divert this waste from landfill, in order to comply with the
EU requirements for the reduction in organic materials being placed in landfills. In this discussion, the
advantages of in-vessel composting will be compared with the alternatives of windrow composting and anaerobic
digestion (which produces biogas/energy in addition to a liquid fertilizer and a fibrous soil improver).
Advantages: Factors in support of the in-vessel composting food waste are:
1. The high control ability of in-vessel system ensures that the food waste, which may be seasonal in its quality
will always be composted to high quality standards, and produce a consistently high quality compost with excellent
properties when applied to the ground both in the release of nutrients and as a soil structure improver.
|In-vessel Composting Plant
showing ventialtion fans. (Image courtesy: Hytech-Water
Of course, every one of these options is better than sending these wastes to landfill, as was being done in the
past. In a landfill it would produce landfill gas and ammoniacal nitrogen (to name just a few) and stay in the
landfill for a very long time, as a result the organic nutrients in the waste are a threat to the environment
should they escape in an uncontrolled way to the groundwater, or surface water streams.
2. Some food wastes are potentially a risk to livestock from vectors infectious diseases they
might contain. For example, it is thought to have been sausages discarded by passengers from a flight into a
UK airport which were included in pigs swill which infected the first UK farms with Foot and Mouth Disease in
the 1990s. As a result, pig swill and other livestock feeding methods using animal by-products, are no longer
Another good reason for the in-vessel composting of food waste is the enhanced capability of in-vessel composting
to be certain that the temperature is elevated sufficiently and for long enough, through the whole body of the
compost material, to comply with the UK Regulations for Animal By-products, which contain strict requirements for
the pasteurisation of potentially infectious food wastes.
|Aeration pipes used in commercial in-vessel composting carry substantial air-flows, requiring
This contains the extra benefit of adding confidence to all those who will buy and
use the compost, that there is as far as is possible, no risk of infection from it. That will protect against
making the error of producing a compost product which farmers and horticulturists won't use due to fear of
biological contamination being passed to their plants or livestock through use of the compost product.
3. It is easiest also to obtain PAS100 certification for high quality, highly marketable and sought after compost
using in-vessel composting techniques
Then there's the speed of the composting process which is increased by using and in-vessel rather than a windrow
composting method. That is certainly very important because it can easily take three or more months to windrow
compost in cold winter climates, and in some cases composting plants then require very large windrow areas and may
even run out of space by the end of the winter. After you take that under consideration, then it makes sense to use
in-vessel composting of food waste.
That is the good side of the advantages and disadvantages of in-vessel composting food waste. There's a bad side as
well. Let me examine some of the downsides.
Downsides: Reasons Against the in-vessel composting of food waste
1. Capital and running costs are much higher than carrying out composting entirely by a windrow slab method.
If you ever consider the cost effectiveness of in-vessel composting food waste versus windrow you will likely see
that in-vessel methods are substantially more expensive, that might produce the effect of pricing the compost
product out of the market if competing with sellers of compost who are carrying out composting entirely by a
windrow slab method. There is no way that could be a good thing. In fact, it may well be a good enough reason to
avoid it completely.
2. In-vessel composting requires the use of aeration and fans to pump air through the compost pile while it is in
the composting vessel. The source of the power is usually the local electricity grid and therefore the power is
from non-sustainable (mostly fossil fuel based sources). Therefore, in-vessel composting is not very
The sustainability of a process is becoming more and more important these days.
3. Aerobic composting whether by windrow or accomplished in a vessel, bears a disadvantage over Anaerobic Digestion
(AD) in that it does not produce any energy (power) in the way that AD plant does.
One more cause to avoid the in-vessel composting of food waste is that it will become more expensive over time, as
the cost of energy rises and experts in energy supply say that power costs will continue to rise even above current
prices, over time. Everyone ought to consider this point with great care, considering the fact that it can result
in a big financial impact a few years from now.
So, if you want to carry out the in-vessel composting of food waste it is still better
than windrowing and you could add an AD Plant later, anyway.
So that is it. We have now looked at the pluses and minuses of in-vessel composting food waste.