Cornwall Sustainable Waste Network
There is not one definitive solution. So many things will effect how waste is dealt with in the future. Hopefully, people will see the need to save the planet and cut down on their need packaging, and increase the use of materials that can easily be recycled.
It should also be noted that in the current economic climate the value of recyclable items has diminished, and the cost of transport has risen. This is why one important feature should be to market or process the recyclate as near to the waste treatment plant as possible.
As a result of these factors any system needs to be as flexible as possible.
Anaerobic Digestion - With front end Autoclave and Autosort
All MSW, Food Waste and Commercial and Industrial Waste is delivered directly into the autoclave. Larger items are stripped and shredded first. Agricultural Waste is pumped into the "Agri-line" Digestion tank. The Autoclave steam sterilises the waste to kill germs, prevent dust and smells and deters rodents.
Two autoclaves operate in tandem so that the steam can be swapped between one and the other to prevent wastage. The "cooking" cleans the glass and tins of their labels, and shrivels and cleans the plastic., The process also pulps paper, card and small pieces of wood reducing it to ligno-cellulosic fibre. Food waste is also pulped.
The power and heat for the autoclave is derived from some of the energy produced by the process (parasitic load). The Auto-sorter separates the main recovery lines via a trommel system. Infrared and laser then further sort the items, with metals separated by magnets and eddy current devices. This produces hoppers full of different coloured glass cullet, PET and HDPE plastic, mixed plastic, aluminium, and ferrous metals.
The ligno-cellulosic fibres can be filtered out or added to the food waste. The food waste passes into the "MSW-line" Digestion Tank. If Kerb-side separated recyclate is treated, it can be cleaned by the autoclave. There is also the possibility of sterilising whole bottles and jars and returning them to be refilled. Any separated food waste is fed into a "Food-line" Digestion tank. In the three AD line tanks, the digestate is mixed with water and seeded with bacteria. These multiply and digest the waste producing heat (which is exported), and biogas, which is a mixture of methane and carbon dioxide. The biogas is used to run gas engines fixed to generators that produce electricity. Heat from the heat shields round the engines is circulated to reheat the steam for the Autoclave. The exhaust heat is used to warm up the AD tanks.
Carbon dioxide is scrubbed out of the exhaust and used to split apart the cellular structure of the biomass under pressure, to produce a higher gas yield. The reason for separate AD lines is because of the purity of the spent digestate. The residue of the Agri-line can be spread directly back onto the fields, (it has no smell).
The Food Waste line produces very high quality compost that can be bagged and sold to Garden Centres. The MSW-line residue is screened and checked for hazardous content. In most cases it is clean and can be used for non-agricultural purposes such as Motorway embankments and other Civil Engineering infill.
This whole process takes place in an industrial unit similar to those found on most Industrial Estates around Cornwall. The AD Tanks are outside, about the size of a small grain silo and are green in colour. There is no chimney and no pollution.
As for the fate of the recyclate, the PET and HDPE plastic are shredded and keyed and can be repressed into food grade bottles. The mixed plastic can be shredded and keyed and pressed into a variety of items such as toolboxes and garden furniture. The clear glass culllet can be re-annealed into whole glass while the coloured cullet is ground up and used as aggregate. The metals are smelted into ingots. The ligno-cellulosic fibres can be made into cardboard, hardboard, MDF or insulation boards. There is a very small residue such as stones, very hard bones and pieces of leather. These can be ground up and used as inert infill for potholes.
Some items cannot be treated on site and may have to be removed elsewhere for further treatment. These are dry-cell batteries and textiles. Otherwise this system deals effectively with all items likely to be found in the four main waste streams.
Latest News:
Petition against Incinerator
Good people of Cornwall this maybe your last chance to get to grips with what SITA is trying to do to this Duchy. A 120 Metre waste incinerator chimney at St Dennis will contaminate the land, water and air within Cornwall with dioxins.
The farming and food industries within this Duchy are one of the most important businesses that we have here and MUST BE PROTECTED at all costs.
Read more here....
SITA appeal incinerator decision
Controversial plans to build an incinerator in Cornwall which were turned down by Cornwall Council are being sent to appeal, the waste company behind the application has confirmed today.
SITA Cornwall confirmed it has submitted an appeal, which they claim is in line with the company’s contract and follows instruction from Cornwall Council to institute proceedings.
Read more here....
Incinerator protest balloon 'shocks'
THE chimney height of the proposed incinerator may be seen from across the county, after a balloon launched last week hovered high above the manmade landscape of Clay Country.
On a clear day the 120-metre stack, part of the planned energy from waste plant to deal with Cornwall's household waste, is likely to be seen from Goonhilly, Carn Brea and Newquay.