[Joerg]

That is a complex question and difficult to address.

Different places in the world lead to different answers. For example, thermal (in most cases incineration) treatment of MSW is commonly applied in many countries in the EU and also North America. Is it the best/preferred approach?

In the US the most common approach is landfilling -with or w/o prior recovery of recyclables- and possible extraction of the generated LFG for beneficial use. Is that the best/most desired approach?

Other places apply a mechanical biological treatment (MBT) process to recover recyclables and organics for AD/composting -biogas generation and stabilization- prior to landfilling provided that the to be landfilled material has a very low biological residual potential = is close to being considered inert/does not show a notable potential for landfill gas -and toxic leachate formation. Is that the best approach?

(Europe prohibits land application of organics extracted from a mixed MSW stream per EU directive. In the US, there is no such law = land application of organics extracted from an MSW is allowed in principle, as long as it meets certain requirements, e.g., compost standards.)

Others want to chime in here?

[Graham]

I agree with Joerg… Here in the US we see landfills dominating together with recycling and composting. To my mind, probably due to the fact that there is a robust existing infrastructure in place for this already, which helps make it cost effective.

[Peter]

Comparing landfills and anaerobic digestion of a mechanical separated organic fraction, anaerobic digestion captures much more of the potential methane emissions, conserves limited landfill space, and in some cases can recover soil nutrients.

Landfills only capture methane after cells have been closed. When a new cell is being filled the food waste is degrading (some aerobically, some anaerobically) releasing emissions to the atmosphere. At the same time landfill space is limited and permitting new landfills can take a long time due to the environmental risks. That being said, landfills aren’t going anywhere and will remain an important part of MSW management and the biogas landscape even if 100% of organics could be diverted.

While digestion of MSW is not always the best available option, there are several pretreatment and digestion technologies that have been used effectively. The anaerobic digester technology that will be most effective at treating a mechanically separated organic fraction will depend on the characteristics of the local MSW waste stream. Characteristics will be substantially different if there are organics diversion, paper recycling, or glass recycling programs in place. The design decisions will also be influenced by local prices for disposal of residuals, water, and energy.

If you are interested in MSW digestion and feedstock characterization you can reach me at peter.quosai@azuraassociates.com.