Comprehensive Integrated Strategies For Food Waste Valorization: From Livestock Feed Conversion To Biotechnological Energy Generation

Food waste currently stands as one of the paramount challenges of our time, situated at the nexus of food security, resource sustainability, and climate change. In developed economies, the largest waste stream occurs at the consumption stage at the end of the food chain (restaurants, households). Traditional management via landfilling not only squanders land and water resources but also generates greenhouse gases and toxic leachate [1,2].

Amidst depleting fossil reserves and fluctuating oil prices, these two studies propose a paradigm shift from "waste disposal" to "waste valorization". This strategy integrates two primary pathways: (1) ReFeed—recycling waste into animal feed to substitute grains, and (2) Biotechnology—utilizing enzymes and microorganisms to transform waste into clean energy and industrial chemicals.

Extraction and (bio) conversion of food wastes into value-added materials

• The ReFeed Strategy: Turning Waste into Livestock Protein [2]

  Dou et al. (2018) assert that food waste is not refuse but an untapped nutrient reservoir.

• Nutritional Profile: Pooled analyses from multiple trials indicate that consumption-stage food waste is highly nutritious: Mean Crude Protein is 19.2% (nearly double that of maize grain), Lipids 21.5%, and Carbohydrates 38.6%. Theoretically, one ton of dry food waste could replace an equivalent amount of maize in pig diets without detrimental effects on meat quality.
• Safety Technologies: To overcome biosecurity barriers (such as bacteria and viruses), modern treatment technologies have been developed.

  + Wet-based: Heat sterilization (e.g. 100^oC for 4 hours) eliminates pathogens, creating liquid feed suitable for nearby farms.

  + Dry-based: Combines sterilization with dehydration (e.g. fluidized bed or drum drying) to produce low-moisture feed (80-95% dry matter), which is easy to transport over long distances and store for extended periods.

  + Ensiling/Fermentation: Uses lactic acid bacteria and yeast to ferment waste, stabilizing nutrients and extending shelf life up to 30 days.

  In South Korea, landfilling of food waste was banned in 2005; instead, 45% of the waste is converted into animal feed through strictly controlled centralized processing facilities, and no disease outbreaks associated with this practice have been recorded since its implementation.

• The Biotechnological Strategy: Energy and Bio-based Chemicals [1]

Sufficiency et al. (2022) expand the scope to advanced biotechnological methods, particularly suitable for waste streams unfit for animal feed.

• Anaerobic Digestion (Biogas): This process involves the microbial decomposition of organic matter in the absence of oxygen to produce biogas (principally methane and CO₂). Biogas is a renewable energy source used for electricity generation, heating, or engine fuel, while the digestate becomes a nutrient-rich biofertilizer. Co-digestion of food waste with other organic wastes enhances gas production efficiency.
• The Role of Enzymes and Immobilization: Enzymes are crucial biocatalysts for converting carbohydrates, lipids, and proteins in waste into valuable commodities. However, free enzymes are often unstable. The study highlights "enzyme immobilization" technology on support materials (such as porous silica, hydrogels, biopolymers). This technique enables enzymes to withstand harsh conditions (pH, temperature) and facilitates recovery and reuse, thereby reducing industrial production costs.
• Through fermentation and enzymatic catalysis, starch- and sugar-rich waste (like fruit peels, processing residuals) can be converted into ethanol, biohydrogen, bioplastics, and organic acids (e.g., succinic acid, lactic acid)^42424242. This forms the foundation of future biorefineries.

  Integrating these two strategies offers superior benefits compared to traditional methods:

• Carbon Footprint Reduction: Converting food waste to animal feed (dry-based) emits approximately 200 kg CO₂-eq/ton, significantly lower than the 1,010 kg CO₂-eq/ton associated with landfilling [1].
• Upstream Resource Savings: The greatest benefit of ReFeed is the "sparing" effect. When waste replaces corn/soybeans, we save the land, irrigation water, and fertilizers required to grow those crops. For instance, recycling food waste for pigs in Europe could reduce cropland demand by 1.8 million hectares [2].
• Transforming waste reduces disposal costs (e.g., landfill fees) and generates revenue from new products (feed, energy). Simultaneously, the waste processing industry creates new jobs in transportation, plant operation, and equipment maintenance [1,2].

• ðIn conclusion, food waste must be recognized as a sustainable raw material resource rather than an environmental burden. A flexible combination of recycling into animal feed (for safe, nutrient-rich waste) and biotechnological treatment (for mixed waste to recover energy) is the optimal direction. Realizing this requires a shift in management policies, investment in advanced enzymatic technologies, and the establishment of rigorous safety control protocols.

References

1. Sufficiency, E., Qamar, S. A., Ferreira, L. F. R., Franco, M., Iqbal, H. M., & Bilal, M. (2022). Emerging biotechnological strategies for food waste management: A green leap towards achieving high-value products and environmental abatement. Energy Nexus, 6, 100077.

2. Dou, Z., Toth, J. D., & Westendorf, M. L. (2018). Food waste for livestock feeding: Feasibility, safety, and sustainability implications. Global food security, 17, 154-161.