Upgrading residues to high value materials that have a sufficient market
A circular approach implies that residues are not considered as a waste stream, but as raw materials with an intrinsic value that can be transformed into useful products. One of the consequences is the need for further separation of waste streams in order to maintain their intrinsic value. New technologies are needed to achieve the transformation of certain residue types into high-value products. The final product that can (possibly) be obtained from the residues needs to be leading in the design of the circular approach. So the approach is not anymore about finding the cheapest disposal techniques for residues, but about maintaining the intrinsic value of the residues and about upgrading them to high value materials that have a sufficient market.
Biogenic residue flows have big volumes and high recycling potential
Today, many techniques for conversion of current waste streams into valuable materials for new products are available and under development, and thus may facilitate the transition to a circular economy. Biogenic flows represent the largest volume for cities. This volume consists mainly of the relatively wet waste stream of GFT-residues. Half of this stream is collected separately, while the other half is mixed through the domestic residual waste. The second largest waste stream is waste paper and cardboard. Besides solid waste there is also the liquid waste stream that is leaving the households through the sewer.
The most promising technologies for the various biogenic residues are (italic indicates the current processing method):
- vegetable & fruit waste (GF) – composting, anaerobic digestion, production of organic acids & fatty acids and production of PHA
- fine garden residues (T) – composting
- coarse garden residues – combustion, gasification and pyrolysis
- waste paper & board – combustion, recycling, gasification, pyrolysis, production of fermentable sugars and production of furans & bio aromatics
- textile residues – combustion, recycling, gasification and pyrolysis
- beverage cartons – combustion, recycling and gasification
- wood residues – combustion, recycling, gasification and pyrolysis
- sewer drain – anaerobic digestion, aerobic purification, production of PHA
For the non-biogenic residues plastic and glass, the standard technique of recycling remains the most suitable. In the future 3D printing may offer new opportunities for these residues. Ashes from solid household waste can be used in construction materials. New washing processes can improve the potentials for these.
Download the full ACC report on “Circular Solutions Part 4 – From waste to resource” here