Separation and cleaning for reuse
Closing loops, reusing more material in a high-quality manner, without wastage of any raw materials; reuse and recycling are necessary in order to keep the earth liveable. Gulden Yilmaz of Wageningen Food & Biobased Research is happy to explain how she and her colleagues can use their expertise help make this possible.
Separating and cleaning are two central themes in her story. Yilmaz and her colleagues work with complex mixtures of waste water, manure, sediment, pulp, organic kitchen and garden waste and crop remnants, but they can also process grains and grasses in such a way that they gain a broader range of possible applications. They develop and combine techniques for the extraction of potentially valuable components and the removal of disruptive substances from the biomass in the most efficient and economical way possible – in other words: top-level recycling. “If consumers and the industry want us to, we can quickly start producing in a much more sustainable way.”
These mixtures can be seen as structures made from many different building blocks. In some cases, you will only want to use the blue blocks, and in other cases you would prefer the large white and green blocks.
“If consumers and the industry want us to, we can quickly start producing in a much more sustainable way.”
Waste water treatment
In the Netherlands, attention has been devoted to waste water since the 1960s. Over the course of the twentieth century, the pollution of surface water took on serious proportions. Fish died and disappeared from rivers; foam floated on the surface of the water and the rivers sometimes stank. From 1970 onwards, waste water treatment boards and sewage treatment plants were set up, and the discharge of many substances was restricted.
Undesirable substances found in mixtures such as waste water and biomass that render the product unusable (a residual flow) include contaminants such as medicine residues and pesticides. Water treatment is important for the greenhouse horticulture sector, for example. To this end, researchers are working on a kind of tea bag that can pick up and remove certain pesticides through adsorption. It can be suspended in the middle of a drainage pipe and remove the substances from it as the water flows through.
Another example is the removal of pathogenic bacteria from the water that is used to irrigate vegetable crops. Together with a large number of businesses, including farmers, vegetable processors and suppliers of water technology and irrigation equipment, WUR researchers are developing solutions to enable the safe use of ditchwater for the irrigation of fresh vegetables such as lettuce.
The ‘disruptive substances’ that are removed can also be salts or sugars. For instance, salt can be removed from seawater to make drinking water; salt can be extracted from industrial waste water so the water can be reused; and excess salt or sugar can be removed from foodstuffs to make them healthier.
The recovery of valuable substances has also become possible, such as minerals (including phosphates), proteins, carbohydrates (sugars and starch), fibre, vitamins, dyes or colourings, ammonia and clean water. ‘This results in the creation of new raw materials,’ says Yilmaz, programme manager for biorefinery. In addition, clean water and sustainable production and consumption are Sustainable Development Goals (SDGs).
A win-win situation
‘We are also looking for win-win situations,’ says Yilmaz. ‘For instance, we improved an agricultural residual flow that could be used as animal feed by removing sugars from it. This gave the feed a higher protein content and the cattle benefited from the quality improvement. The sugars could then be used for other purposes. In this way, you can use raw materials efficiently for maximum value creation.’
The same applies to the recovery of ammonia from waste water. Ammonia is harmful to the environment, but it forms the basis for agricultural fertiliser production. Wageningen-based researchers are working on closing the loop by reclaiming this waste ammonia by means of membrane technology so that it can be used directly for the production of artificial fertiliser.
Technically speaking, it is not always possible to completely close the loop. However, because WUR is working on new techniques, the possibilities and applications are increasing in number. The crux often still lies in the costs. At present, processing techniques only break through if they are proven to be profitable due to the value of what you extract from them (such as sugars) or of what is left behind (good feed, clean water, etc.). ‘At present, it is the costs that often prevent application,’ says Yilmaz, ‘and this hinders the transition to a circular economy in which we use raw materials as efficiently as possible.’
In the case of some substances, recovery should already be considered an urgent matter. Take phosphate, for example. Phosphate is essential for all living organisms, whether plant, animal or human. ‘Although we still have a phosphate surplus in the Netherlands, there is a shortage of phosphate in other parts of the world, and the impact of that is being felt there,’ says Yilmaz. It’s a mineral that we have to use economically. The phosphate mines will one day be empty. In addition, phosphate is now polluting our surface water and groundwater, and damaging biodiversity.
To come back to the example of building blocks, there are two other questions to be answered. What if reused building blocks turn out to be a little more expensive than new ones? Would you still want to buy the product that has been made with the reused blocks, even though it is a little more expensive? And does it matter to you where the building blocks came from? If consumers and the industry want use to, we can quickly start producing in a much more sustainable way,’ says Yilmaz.