What can you do with green waste apart from composting or fermenting it? Is it possible to process local green waste in such a way that it can serve as raw material for the industry? In order to find an answer to that question, Pro Natura started an exploratory research project in cooperation with Renewi , Studio Transitio, UGent and HOGent at the beginning of 2018. This research project consisted of several phases. In a first phase, we looked for the right fractions of green waste, based on what kind of biobased raw materials certain producers in the industry were already using. In a second phase, we focused on the processing and conversion of those materials, with an eye on possible applications. Then, in cooperation with interested companies, we conducted small-scale practical tests on the different types of applications. The results were promising, so in a next step we investigated how these different applications could be brought together into a totalconcept. We also used interviews and workshops to bring together different actors who were interested in this conversion process. Finally, we also paid the necessary attention to the dissemination of our results.
We were able to draw up an extensive list of promising applications for the fibre fractions obtained from the processed green waste: design of furniture boards, synthetic floors, insulation material, natural plaster, etc.
We also found several possible applications for the juices that are released in the processing of the green waste, such as herbicides and other (phyto)pharmaceuticals.
We have shown that we can directly use natural fibres for various applications. It is therefore not necessary to break down biomass into its smallest building blocks (sugars, proteins, etc.) in a very energy-consumingand unsustainable process in order to subsequently reconstitute them into materials and products, as is the case in petroleum refining.
If, in the long term, we can develop this process into a truly circular industry, it will certainly create more local jobs for low-skilled people, especially in the selective collection and separation of streams, such as jobs at container parks and green waste processors.
MOST IMPORTANT LESSONS LEARNED
The valorisation of green waste, in which all components, both juices and fibres, are reused, offers interesting perspectives as a sustainable and profitable raw material for the (small-scale) circular bio-based manufacturing industry.
The homogenisation of residual flows from green waste, which are very heterogeneous by nature, remains a major challenge. No matter how pure we try to be, we still come across variations. For example, in the case of roadside cuttings: due to the location of the roadside, the mowing method or mowing head used, the time of mowing, etc.
Besides valorising certain niche streams from green waste, fermentation and composting will still have a place in a truly circular bio-industry.
The good cooperation between the various sectors and stakeholders in this project means a great added value in terms of innovation. Also, the use of employment care and social economy gives room for creative designs and working methods that would not be possible in a traditional way.