20% of all food produced in the EU is currently wasted. 70% of this waste stems from households and processing. Although actions are primarily needed to reduce food waste, existing waste can be recycled in several ways to capture valuable nutrients .
When selecting recycling solutions for food waste, the food waste hierarchy can be used as an indicator as to which solution to give preference (see visual) . Reuse for consumption and high-value products, followed by recycling of nutrients, should be preferred, where possible, over incineration for energy recovery only.
Figure 1 Food waste hierarchy 
Several solutions exist to recycle food and nutrients:
Using waste products and leftovers from food production to create new products
Waste products, especially stemming from processing or unsold production can be used as input for new products instead of being thrown away. For instance, old bread from bakeries can be used for beer production, spent grain from whiskey and beer manufacturing for flour production (AGRAIN), whey in cheese production for protein powder, and fruit pits for protein powders and cosmetic products (KERN TEC). More examples for circular food products can be found in EIT Food’s Rising Food Star Association, WaysTUP and Greenovate!Europe.
Figure 2 VALUEWASTE biowaste valorisation [VALUEWASTE]
Extracting nutrients from consumer food waste
When biowaste consists of different products mixed together, it becomes more challenging to reuse it. Extraction from household biowaste requires first the collection of the waste, and then the technologies to extract nutrients or other valuable parts of the waste.
DECISIVE uses micro-scale anaerobic digestion (AD) and solid state fermentation (SSF) to create a circular metabolism for biowaste in cities. Nutrients and energy from biowaste are returned to urban farms in the city [DECISIVE].
Companies in the SCALIBUR project treat household and production food waste in cities. They extract sugars, create biopesticides and bioplastics from household waste through enzymatic hydrolysis and fermentation. Black soldier fly larvae are used to digest food waste from restaurants and turn it into biomass from which protein, fats and chitin can be extracted and used for many industrial applications and the organic residues can be used to improve the quality of soil [SCALIBUR].
WaysTUP explores different product value chains for biowaste, including coffee oil production from spent coffee grains, insect proteins from insect feeding on biowaste as well as extraction of flavours, carotenoids, gelatines and other products [WaysTUP].
The HOOP project will offer more insights on circular bioeconomies for cities [SCALIBUR].
Figure 3 WaysTUP Transforming Urban Biowaste into new products [WaysTUP]
Maturity levels vary strongly depending on the selected solutions. For several solutions, maturity levels are high and solutions are already implementable (such as anaerobic digestion, fermentation, production of new products from leftovers). Innovative processes and business ideas are needed to create new products from current waste streams. While technology is available, business ideas and room for testing and for implementation is still needed.
Production of sugar
SCALIBUR partner companies use enzymatic hydrolysis to create sugars from biowaste. The process requires enzymes, water and moderate temperature to break down the polymers into simple sugar molecules, such as glucose and fructose. The technology is at demonstration scale (using 3000l batches) and at a TRL 6/7. [SCALIBUR]
Production of biopesticides and solid state fermentation (SSF)
In a further step in the Scalibur project, the extracted sugar hydrolysate can be converted into a microbial biopesticide using Bacillus thuringensis. The biopesticide works with toxic proteins that are taken up by the target insect larvae. The technology is expected to reach TRL 6/7 at the end of 2022 with a demonstration batch of 1000l [SCALIBUR].
In a similar case, production of biopesticides through solid-state fermentation and the use of the same bacteria was tested at bench scale [DECISIVE].
Protein production through insects WaysTUP and VALUEWASTE
Fly larvae or other insects can be used to feed on the organic waste and be sold as protein used as animal fodder [WaysTUP]. TRL ranges from research to market availability and there are already companies in the market providing fly larvae as solution.  VALUEWASTE’s insect production, for instance is at demonstration/TRL7 level [VALUEWASTE].
Chemical and Biodegradable Plastic Production
Horizon 2020’s WaysTUP contains a broad portfolio of technologies to process biowaste. One technology (HYDAL) transforming cooking oil into biomaterial polymer is already at industrial scale and TRL 9 [WaysTUP].
Biofertilizer and energy through (micro) anaerobic digestion (AD)
Anaerobic digestion (AD) units are available on the market and at TRL 9 and can be purchased in different sizes for use by local communities or for larger-scale applications.
WaysTUP’s portfolio contains many technologies that are still under development and have not reached market implementation yet, but many demonstration cases are available.
Figure 4 Closing the biowaste loop in cities [DECISIVE].