Read on
A trial section of bioasphalt lies in front of the H4A office in Sas van Gent, the Netherlands. There is huge attention from the media, and interest from the infrastructure sector is likewise enormous. That is not so strange, says manager Martijn Verschuren of the contractor in Zeeland. ‘Making asphalt more sustainable is a hot topic in our sector. Half of the bitumen in our innovative asphalt mix is replaced by lignin; the environment benefits substantially from this.’
Edwin van Gastel

Project partners including Wageningen UR, the Dutch Asphalt Knowledge Center (AKC), Zeeland Seaports, Cargill and H4A joined forces two years ago on the initiative of Impuls Zeeland. The aim was to develop a bioasphalt in which some of the bitumen is replaced by lignin, a residual substance released in various industrial processes and essentially widely available.

Speeding up

‘There are many different kinds of lignin, however,’ explains Verschuren. ‘You can’t simply substitute the bitumen in asphalt with lignin without consequences for the final product. We had to go to the laboratory. Researchers at the University of Wageningen and the AKC worked for more than one-and-a-half years on a method for processing it into a good substitute and on finding the optimal proportions. What you do is make pavement tile-size pieces of asphalt which are then tested for all kinds of properties. The asphalt must not crumble, not become mouldy, you name it. It is a lengthy process, definitely when you leave it in the hands of scientists. After all, there is always space for improvement. However, the commitment of H4A as contractor, Zeeland Seaports as road authority and Cargill as potential supplier of lignin ensured the necessary speed. It is our nature to seek the market, and we want to put it into practice fast.’

Road salt

A 70-metre trial section, 3.5 metres wide, was laid at the start of July 2015. The bioasphalt is used in the top layer, about 3.5 cm thick. There is a good reason for laying the trial section in front of the H4A company grounds. The road is used intensively by heavy trucks which drive to and from the asphalt plant. How the asphalt reacts to frost and road salt will be examined next winter. This will be followed by an assessment of how well it handles the weather conditions in spring and summer. Verschuren is not worried, however.

‘It underwent exhaustive testing in the lab, and thus far it has held up perfectly. And if it works well here, it will work well at every conceivable location. All the parties involved in this product believe very strongly in it, all the more because it is so enormously beneficial for the environment. We have succeeded in replacing half of the bitumen by lignin. All around the world substantial investment is being made in the development of sustainable asphalt, such as reducing the addition of new raw materials and working with low temperatures. As far as we know, our solution is totally unique. That is emphasised by the huge number of calls we receive, from the Netherlands, but also from places such as England, Germany and Sweden. There is enormous interest.’

Critical questions

Putting an innovative, sustainable product on the market does not automatically guarantee success. Verschuren knows that, but he also feels positive about it. ‘Many governments are following our project closely and they are enthusiastic. Potential buyers will always ask critical questions. Actually there are two questions. What is its life cycle like and how much does it cost? Asphalt on roads has to last at least 12 years; so does ours. And everyone wants bio, but not at extra expense. If you can’t supply at prices in line with the market, then you have a problem. But we are convinced that our bioasphalt can make it on the market on both fronts in the near future. We are investing in further developments at the same time. It is a continuous process and highly challenging. One thing we are currently working on is pushing down the production price of the lignin we use. And perhaps we can go up to sixty percent lignin, or eighty, or even one hundred percent. We don’t know what the future will bring, but we believe for a fact that it will be sunny.’