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What does ‘Source-Separation’ Imply in Regenerative Resource Recovery?

Source-separation of food waste from non-organic materials is crucial in bokashi processing and opens up many regenerative food waste application options compared to industrial approaches.

The quality of organic resources recovered in hospitality kitchens stands or falls by the integrity of its source-separation. Source-separated organics (SSO) is an approach whereby generators of foodwaste segregate compostable from uncompostable materials at the very source for eliminating contamination. For regenerative agricultural purposes, source-separation implies the strict sorting out of all non-biodegradable materials before collection. For industrial food waste management, source-separation is much less stringent and tolerates up to 20% non-biodegradables making it unfit for regenerable applications.

In the SoilFeeders project, source-separation of food trimmings is aimed at organic-grade, regenerative food production. Organic certification requires to eliminate any sources of Genetically Modified Organisms (GMO). To achieve this, Soil Trust (泥玩) not only avoids GMO-prone produce like papaya, corn, soy, potatoes or zucchini but also processed foods like meat, seafood, bread, pastries, fats, dairy, bones and ornamental plants because of their processes additives. Most importantly, non-food inputs like ubiquitous fruit stickers, cling wraps, cooking foils, tea bags/labels, tissues, straws, charcoal and ash ought to be removed. What goes into the SoilFeeders collection bin are the hotel’s self-grown kitchen herbs, fruit peels (citrus, melons, pineapples), spent tea leaves, coffee grounds, eggshells, nutshells and Chinese medicine residues (pre-consumer, GMO-free inputs).

Industrial source-separation of food waste (image on left) permits up to 20% of non-biodegradable packaging material to be processed while regenerative food-separation (image on right) depends on uncontaminated organic resource collection.

In contrast, regenerative kitchens and farmers not bound to organic certification standards can also accept cooked and processed foods in their bokashi operation as long as all non-biodegradable materials are removed. Regenerative bokashi compost with GMOs and processed foods can have a valid place in conventional agriculture, flower cultivation, landscaping, or as feedstock in vemiculture, insect breeding, poultry or pig farming. Indeed, bokashi fermentation is very conducive to processing post-comsumer food waste including cooked meals, processed foods, oily residues, meat, fish and small bones—as long as the material is drained and balanced with an equal amount of non-greasy organic matter like veggie trimmings, fruit peels, coffee grounds or spent tea leaves.

In any case, regenerative source-sepatation highlights the importance of packaging-free collection of freshly generated food waste. This differs from industrial source-separation that permits food waste to contain a certain percentage of ‘inert’, non-food materials such as plastic wraps & bags, foamed polystryrene, plastic straws and utensils, metal cans, aluminum foils, glass bottles, ropes and threads, toothpicks, tissue papers, and teabags. In industrial waste management it is deemed impractical to remove all packaging at the point of waste generation. For example, Hong Kong’s municipal biodigester facility (O-PARK1) accepts up to 20% of inert non-food material by weight. The challenge here is that post-collection removal of ‘inert’ non-biodegradables is costly, insufficient and thus unable to stop accumulative, environmental contamination since the associated biodigestion processes emit atmospheric gases and solid residues burdened with the non-organic load.

Keyword: Inert contamination; biodegradables; lax source-separation; output quality.

Related links:

Code of Practice on Separating, Collecting and Transporting Food Waste to Organic Resources Recovery Centre Phase 1 (Environmental Protection Department, The Hong Kong Special Administrative Region Government, May 2018):


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