Anaerobic Digestion and Compostable Packaging

The Closed Loop Foundation, in partnership with the Danaher Foundation explores the efficacy of large-scale anaerobic digestion facilities’ ability to breakdown compostable packaging.

While we know certified, food-contact compostable packaging containing food scraps can be properly recovered in composting facilities, some U.S. municipalities rely on anaerobic digestion (AD) for organic waste management. This prompts a crucial question: can large-scale AD facilities in the U.S. also effectively handle compostable packaging? 

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To help answer this question, the Composting Consortium, managed by the Center for the Circular Economy at Closed Loop Partners, conducted a study published by the Closed Loop Foundation to assess the extent to which compostable packaging is currently processed within existing large-scale AD infrastructure in the U.S. The analysis, done in partnership with BioCycle and Target Renewables, LLC., was focused on those facilities that process hundreds to thousands of tons of organic waste per day.  

The findings of this study suggest that large-scale AD, in its current state in the U.S., may not be a suitable solution for processing food waste with compostable packaging. Given the nascency of industrial anaerobic digestion systems that process compostable packaging in the U.S., the Consortium connected industry learnings from the UK and European Union (EU) to the U.S. market. Markets like the European Union (EU) are leading the way in processing compostable packaging, particularly liner bags used in source-separated food waste collection. This success is attributed to their well-developed infrastructure for integrating anaerobic digestion (AD) and composting, allowing them to effectively manage the compostable packaging stream on a large scale. 

What Can We Learn from European AD Markets?

While AD might not currently be a standalone solution in the U.S., Europe offers valuable insights for future development.

  • Using Hybrid Anaerobic Digestion

    European markets are initiating hybrid models that co-digest food waste and compostable packaging. These models maximize biogas production and facilitate subsequent composting of the digestate, overcoming limitations of wet mesophilic AD systems. While these hybrid systems can have higher capital and operating costs, they demonstrate the potential for maximizing both the economic and environmental benefits of organic waste recycling.

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  • Creating Industry Collaborations

    Strong partnerships among AD operators, composters and manufacturers are crucial in Europe. This collaboration fosters innovation in packaging design and pretreatment methods that align compostable packaging with AD recovery, ensuring smooth material flow and improving the entire organics management ecosystem. Supportive policies, including feedstock quality regulations and financial incentives for hybrid facilities, further incentivize adoption of these approaches.

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  • Digestate Standards

    Unlike the U.S., the UK and the European Union have established standards for digestate produced via anaerobic digestion of food waste and other feedstocks. The standards benefit end market development, especially with regard to quality assurance. The UK’s PAS 110 digestate quality standard, for example, specifies that input materials (feedstock) shall be “source segregated biowastes and/or source segregated biodegradable materials.” By this definition, compostable packaging is an acceptable input to a PAS 110-certified process. However, if such materials remain visible in whole or in part in digestate after AD, or post-AD composting, they would be considered contaminants and likely cause the digestate to fail. A hybrid model with back-end composting facilitates complete disintegration and thus compliance with the standard.

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