How to Think About Greenhouse Gas (GHG) Emissions in the End-of-Life (EOL) Phase for Products Made With Renewable Resources

Landfilling and composting biogenic materials (example: plants) can produce a variety of greenhouse gas emissions, namely carbon dioxide (CO2) and methane (CH4) emissions.^3,4

The CO2 emitted during this life-cycle phase is mostly biogenic carbon dioxide, with a small percentage (less than 1% in our models) coming from non-biogenic or anthropogenic carbon emissions.  

Biogenic carbon emitted as CO2 from landfills or during composting is not thought to have a net global warming effect. Biogenic carbon emissions are considered to be part of the natural carbon cycle, and the CO2 emissions that occur during the degradation process of biogenic materials returns carbon dioxide to the atmosphere that was originally removed by photosynthesis.^2,3,4,5

However, when carbon is converted to CH4 in either landfills or compost facilities it is no longer considered to be biogenic, and instead is considered to be anthropogenic. Anthropogenic CO2 and CH4 emissions are considered to have a net global warming effect, and are expected to be included in GHG Inventories. ^2,3,4,5

The graph below shows the breakdown of CO2 and CH4 emissions in the EOL phases for our products made with PLA and molded fiber. The majority of CO2e emissions in the EOL phases of our products are attributed to biogenic CO2. Of the CO2e value for this phase, 75% or more is attributed to biogenic carbon emissions.

Why GWP Should Not be the Only Environmental Consideration – Especially for Compost EOL

Global Warming Potential (GWP) with Carbon Uptake is a valuable LCA indicator used to understand carbon impacts of different products and processes. However, additional considerations should be applied when using this indicator as a decision-making tool across a variety of raw materials, especially as it relates to compost as an end-of-life scenario for plant-based raw materials.

What environmental impacts does GWP with CO2 Uptake not include?

• GHG emissions reduced due to the food scraps that are often sent to compost facilities along with compostable foodservice products. Food that is sent to compost facilities instead of landfills reduces GHG emissions associated with the disposal of food waste by more than 50%.⁶
• Climate benefits of producing compost from food and compostable products, ultimately harnessing embedded resources to create compost rather than ‘wasting’ them in a landfill.⁷ Benefits include⁷:
  • Improved soil health 
  • Water retention, assisting in stormwater management
  • Increased crop yields if compost is used in farming applications
  • Reduced need for chemical fertilizer production and application
  • Carbon sequestration, when finished compost is applied to land. An additional carbon reduction associated with composting that should be considered.

Emissions factors associated with composting are more meaningful in a broader context that includes keeping organic waste out of landfills, and the variety of benefits associated with applying finished compost to land.^1,2

Since many LCA studies do not include externalities outside of typical LCA indicators, it is critical to consider a variety of additional impacts associated with different raw materials and their end-of-life scenarios used for foodservice packaging.

We have spent more than two years revamping our PCF models and have identified substantial data gaps up and down the value chain for compostable products and materials.

As a result, some of the data generated by the tool we use to present PCF data are at odds with things we know to be true about our products and the materials they are made from. Check out some specific examples of data gap below.

We have made the decision to share this imperfect information publicly in an effort to bring awareness to the danger of using it as a standalone decision-making tool.

Every consultant, researcher, and impact professional we know has their own way of expressing the “grain of salt” factor that should be applied to reports like these. “It’s a compass, not a map”, is a phrase we’ve grown to like. Tools like ours provide directional information, but can’t get you home the same way a map can.