De-icing
Why use salt for de-icing?
Salt, i.e. Sodium chloride is the most widely used de-icing agent in Europe and throughout the world due to its huge advantages over the alternatives.
It is the ideal de-icing material because:
- It prevents or melts ice and snow quickly
- It is widely-occurring and readily available
- It is the least expensive de-icer
- It is highly efficient, needing only a relatively low rate of application
- It is easy to store and handle
- It is easy to spread
- It is non-toxic and harmless to skin and clothing
- It has low environmental impact in production and when used and stored properly
How it works
When salt is applied to ice and snow it creates a brine that has a lower freezing temperature than the surrounding ice or snow. It is also most efficient as a de-icer when spread before ice has formed. Whilst in theory salt can work to lower temperatures, it usually used at temperatures down to -15°C.
Safety
Highways professionals work hard throughout the winter period to keep the roads free of snow and ice and safe for the travelling public. Each country has its own policies which state which organisations are responsible for winter maintenance and which roads they have to maintain, this can vary depending upon the type of road.
For example, in the UK, the Highways Agency (a central government body) has responsibility for winter maintenance for the motorways and major trunk roads and local authorities (regional local government) maintain the other roads within their geographical area. Throughout Europe, winter maintenance operations are often contracted out by the responsible body to private operators, with clear performance standards set out in the contract.
Whatever the individual country differences however, the primary aim remains the same: to keep the travelling public and industry safe and on the move during winter.
Environment
Of all de-icing agents, salt has probably the lowest environmental impact in production, as it is a naturally occurring chemical which requires no chemical transformation. Little waste is generated from any form of production, and the very wide abundance of salt means that effectively salt use is sustainable. According to the German Institute for Applied Ecology, alternative de-icing formates are six to eight times more expensive than salt.
De-icing salt has a very low environmental impact when used responsibly. By following codes of good practice winter maintenance professionals ensure salt is used sensibly and selectively. Good training for winter maintenance professionals is vital but there are also a growing number of sophisticated support tools to help highway engineers ensure they are spreading just the right amount of salt. These include detailed road weather information, GPS tracking systems that confirm the correct routes and highly sensitive spreading vehicles that can be finely calibrated to alter the spread rate according to a variety of factors.
Ultimately the environmental implications of de-icing salt vary enormously depending upon local conditions. The design of the road, local weather conditions, traffic volume and the geographical make up of the area are just some of the variables which will influence the degree to which de-icing salt will affect the local environment. It is for this reason that it is not practical to develop a Europe wide code of practice for how de-icing salt should be spread.
Logistics
The weather is notoriously unpredictable and across Europe there are huge regional and local variations. In any single country the weather can be markedly different from region to region and from year to year. This presents a major challenge for winter service providers.
For example, over the last 10 years, January de-icing salt despatches in France have varied from 30kt to 700 kt. Annual sales in Germany have shown extremes from <300kt to >2.700 kt. Daily winter salt despatches from one UK producer have ranged from 0 to 17000t.
However it is possible to manage the unpredictable and every winter European countries do just that. Effective winter maintenance requires a good and reliable salt supply, adequate transport and effective communications between salt manufacturers and winter maintenance professionals.
Availability
European salt producers have access to extensive resources which means they are generally able to respond to any unexpected increases in demand. In periods of particularly cold weather in winter, salt producers often work a 24 hour shift pattern, seven days a week.
Stocks
Well managed stocks are necessary to manage the unpredictable. Only established salt producers are able to guarantee ongoing supply during hard winter conditions. By working together, salt producers and highways professionals ensure adequate stock piles are built up during the summer months so that they are well prepared when bad weather arrives.
Supply Chain
The wide distribution of salt deposits throughout Europe means that there is usually a salt source quite close to the users, thus minimising transport costs and the associated environmental impact. However, transport remains a challenge in the supply of salt. Being able to supply quickly (usually within 48 hours of order) depends on the available transport capacity and the regional infrastructure including the accessibility of roads, waterways and railways. Salt producers have installed innovative logistic management systems that help customers to closely monitor their stock levels so they can request more salt before it becomes urgent. Everyone involved in winter maintenance knows that efficient communication between suppliers and customers is also vital, to ensure salt is always available whenever and wherever it’s needed.
Codes of practice
It is clear that climate, road types, traffic densities and budgets vary so much throughout Europe that each country must take its own approach to winter maintenance and most regions have developed specific codes of practice. Whatever the individual differences however, the primary aim of all of these codes remains the same: to keep the travelling public and industry on the move during winter.