Some will remember my letter re alternatives to road salt for gritting our roads - see here.
Well it seems hard to find anything that doesn't have a downside. Certainly there is a growing concern about the use of salt on our roads: it can have a significant impact on local biodiversity (especially in sensitive areas) and on local water courses and indeed water supplies. Furthermore in addition to the public health and environmental problems associated with chloride deicers, the corrosivity of salt impacts on vehicles and infrastructure.
So bearing all that in mind I asked what consideration has Gloucestershire given to alternatives to salt like Calcium Magnesium Acetate and Potassium Acetate? I also noted that some Councils like York have switched to a product called 'Safecote' which is a combination of salt and sugar based food industry residue. Apparently the sugar coating makes it stick so that it is washed away more slowly and means that frequency can be reduced and the level of salt content is also reduced.
Glos County trial Safecote
In reply I learnt that Highways have already carried out a trial on Safecote from the Cannop Depot, and found that it had it's own problems. It seems the County found that the claimed reduction in spread rates do not recoup the extra costs of the material. Furthermore the material must be kept a lot drier than conventional rock salt, which requires extra storage buildings. The claims on reduced vehicle corrosion is based on not needing to wash out the Gritters after every run. This is however, conditional on them being stored inside in the dry, so not only would we need extra buildings for salt, we would need more for gritter storage as well.
The theoretical reduced spread rates are fine in theory, but by reducing the rate of spread to fine margins, the risk of a slight blockage (very common) could reduce the coverage to dangerously low rates. Other problems found relate to an unpleasant aroma from stock-piles, and that the taste/smell was attracting animals such as deer to the roads in the Forest of Dean.
So there are problems - but it cuts the salt. Is it worth the extra costs or are other options better?
It seems many of the solutions sound fine in theory, and if dealing with mass/known controlled areas such as runways or motorways then they can produce recognisable savings. However in Gloucestershire with hilly, narrow roads, the theory doesn't always relate to reality. The County does not have a single specification for Gritters, due to the diverse needs, whereas the Highways Agency for example has hundreds of identical vehicles purely built for motorways.
The County have also tried in the past pre-wetting salt, which can also reduce spread rates, but they experienced problems with mixing brine in sufficient quantities, the vehicles needed brine tanks as well as salt which increased their payloads resulting in greater fuel costs, road and vehicle damage etc.
In response to my other possible alternatives here is what came back:
Calcium Magnesium Acetate is more suited to de-icing concrete or grass surfaces, apparently not so good on tarmac, which is what most of our network consists of. It's also much slower acting, 15-30 times longer than conventional rock salt and I suspect such delays would be unacceptable. I see this as great for runways for example where usage can be controlled but not on the public network.
Potassium Acetate is apparently quite corrosive, so apart from the potential damage to equipment, using it in the public domain may be an issue, but apparently it is used quite widespread in the States.
Both of these products are 'manufactured' and as far as we are aware, not available in sufficient quantities in this Country, whereas rock salt is a natural resource and is mainly sourced from Cheshire or Northern Ireland. I welcome that the County is giving consideration to alternatives - it seems much more work is needed to work out what the impacts are - and I have asked that they liaise with wildlife/biodiversity groups re sensitive sites. I have also asked that consideration be given to sites like Humphreys End where the barrel grit bin keeps getting tipped over and leading to salt in the local brook there. I am seeking additional funds for a better design at those sites.
I see Iowa have used garlic salt - see here. Apparently the US use 8 to 12 million tons of salt every year on roads! See a good article here where the alternatives are discussed.