Once the Landfill Directive came into force in 2001, the way in which hazardous waste was disposed of changed forever. The burying of hazardous and non-hazardous waste together was banned, sites were reclassified and, inevitably, landfill tax increased. Until this point, landfill disposal accounted for almost 40% of hazardous waste.

Other directives coming out of Brussels, such as the Waste Electrical and Electronic Equipment (WEEE) Directive (yet to be implemented in the UK) and the Waste Acceptance Criteria (WAC) Directive are further restricting the options for hazardous waste management. There is no question about it: a serious problem has been posed for business and the waste management industry in general.

Dangerous material

Of course, there are companies out there that will continue to pay the price for disposing of their dangerous material – both economically and environmentally. Landfill tax has become astronomical and, according to waste experts, is likely to rise exponentially over the coming years. And from a green perspective, we simply can’t keep dumping our rubbish underground; it isn’t a sustainable option and for forward-thinking businesses, just isn’t best practice.

But this isn’t a problem that is likely to go away any time soon. Consigned hazardous waste has more than doubled in the past ten years; in 2004, more than 5.6 million tonnes was produced. Meanwhile, nearly 100,000 businesses produced some special waste in 2003, and more than 1,000 waste management companies were involved in dealing with its treatment or disposal.

Joining forces

One such waste management company that has been making tracks in the right direction in a bid to ease the situation is Veolia Environmental Services. The French company, which employs more than 6,000 people in the UK, has joined forces with a salt mining company in Cheshire. Sounds strange, doesn’t it? That’s because what has been created isn’t your everyday waste-management project.

Salt has been mined from the Winsford rock salt mine for the past 160 years and has become a very profitable operation for the owners, Salt Union (part of the Compass Minerals Group). It’s huge cavities 170m below ground, which stretch 3.5km in one direction and 5.5km in the other, have been serving the needs of highways maintenance teams up and down the country. In fact, if you’ve had your road gritted over this winter, there’s a good chance the salt that was used came from Salt Union – the third largest salt company in the world.

However, the directors of the company wanted to look at alternative streams of revenue that could be generated by the salt mine to supplement the leaner summer months. And so, Minosus was created in 1997 – a 50-50 joint venture with Veolia – with the aim of evaluating and developing waste management options in “worked-out” areas of the mine.

The belief was that the deposition of hazardous wastes in the dry, stable and secure cocoon afforded by the void space within a 200 million-year-old bed of salt was a more environmentally responsible option than hazardous waste-only surface landfill. So, in April 1999, a planning application was handed to Cheshire County Council.

Held-up proceedings

Resistance from one local resident in particular held up proceedings, and it wasn’t until six years later, in August last year, that the mine began to accept waste for the first time.

Managing Director of Salt Union, David Goadby, lives locally, so he knew he had to make the right decision on allowing the age-old mine to shift its attention to waste management. “We expected to see pickets at the gates but when I met a local environmental campaigner and explained what we were doing, he said: ‘It seems like a good idea.'” And so, work began on the surface in January 2005.

The IPPC permit, issued by the Environment Agency (EA) in 2004, allows the site to receive 42 individual hazardous waste categories, with a further 24 that can be accepted subject to specific EA agreement. The waste types are predominately those from the thermal process industries and essentially comprise fly ashes, slags and drosses.

The underground storage facility (which also looks after important documents for

various clients) is exempt from meeting the Waste Acceptance Criteria legislation governing leachate limits. But Minosus does have its own criteria to ensure its activities pose neither a threat to human health nor the integrity of the mine. All waste received must therefore be dry, in solid, granular or powder form and must be non-volatile, non-combustible, non-flammable and non-reactive. The first type of waste to arrive at the site was Air Pollution Control (APC) residue – the fine powder material that results from the cleaning of the stack emissions at waste-to-energy plants.

The Minosus planning permission (so heartily struggled for by the team involved) allows for 100,000 tonnes of waste to be received each year. The permitted void space underground occupies 2 million cubic metres – less than 10% of the whole mine – and is expected to take between 15 and 20 years to fill. Once it has been filled, bulkheads will be installed that will seal off the disposal area from the remainder of the mine. After the designated area has been filled – who knows? The mine has the salt capacity to be excavated for the next 80 years, so the future of waste storage suggests longevity.

The key to the success of the Minosus storage facility thus far is the slick operation by which waste is accepted, handled and stored deep underground. Acceptable waste is transported to the facility packaged in either flexible, intermediate bulk containers or in steel and plastic drums on returnable pallets.

Final resting place

The waste is sampled and analysed for compliance at the on-site laboratory. If approved, it is loaded on to transit capsules (purpose-built steel containers) that are used to take the waste from the surface to the underground disposal location. Every step of the process is manually logged.

At the bottom of the shaft, six workers ensure the hazardous material makes a safe 2.5km journey along the mine shaft to its final resting place. A tractor unit, capable of pulling 90 tonnes, tows up to six capsules on three self-steer trailers. The disposal area itself is divided into a number of rooms so different types of waste can be segregated.

On arrival, the transit capsules are opened and the containers or flexible bags are lifted into their ultimate disposal position.

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