Organic Materials in Landfills — Still Not a Good Idea

I’ve heard it all. Someone once told me that landfills need food scraps because it helps with the breakdown process. As if a banana peel is just what plastic cutlery need in order to break down. A more common view is that organic materials break down in a landfill without consequence or lost opportunity. Now, in light of our energy crisis, some are advocating for organics to go into landfills in the spirit of renewable energy production.

About half of states have a ban on yard waste in landfills. Recently, the Florida legislature voted to lift a decades long ban on landfilling yard waste. The goal was to divert the organic waste to landfills where methane gas would be produced from the fraction of organics that do break down. Some of this methane gas can be captured and used as an energy source. Governor Charlie Crist vetoed the bill in the spirit of Florida’s recycling goals. We are likely to see more of this kind of debate.

The timely May 2010 BioCycle magazine cover article, Putting The Landfill Energy Myth To Rest, explains why we should avoid organics in landfills. In short, the author Sally Brown, states “Landfills are best suited as a place to throw stuff away rather than to optimize the carbon, energy and nutrient values of organics”.

If you want to revisit some chemistry explained in clear and sometimes humorous ways, download the pdf of this article (BioCycle is making this available to non-subscribers for free). If not, read on. I’ll do my best to give some summary points.

Brown clearly explores the three potential uses for [no longer wanted] organic materials. The first is energy production, which is sparking this debate in the first place. Organics placed in landfills produce some methane, but not all organics are breaking down and not all of the energy from decomposing organics is captured. On the other hand, anaerobic digesters, which are designed for energy capture, are more efficient. Sorry folks, but straight up composting, although sometimes hot, is typically not an energy source for anything external to the pile.

The second potential function for organics is carbon sequestration, meaning keeping carbon in living things like trees or adding it to the soil rather than letting it go into the atmosphere as carbon dioxide. Depositing organics that don’t decompose well in landfills (e.g., wood) is another form of carbon sequestration, although not wise from a resource management perspective. In contrast, the resulting product from digesters and composting can be added to soil. This not only sequesters carbon in the soil in the form of organic matter, but also supports plant growth which removes carbon dioxide from the atmosphere. That’s bonus!

Last, there are the nutrients contained in organic materials. The nutrients tossed in landfills in the form of organic matter are lost for good, never to recycle as a plant or animal again. Digesters and composting, on the other hand, preserve and concentrate nutrients such that the end product can be used to fertilize plants. Again, more plants and less carbon dioxide!

To sum it up, landfills are a good place to put stuff we don’t want and can’t be used for something else. Unlike landfills, composting and anaerobic digestion both conserve the majority of the nutrients and a portion of the carbon from the original material, which in turn improves soil conditions and increases plant yield. Anaerobic digestion has the added benefit of energy production.

As resources become limited and harder to access, our focus needs to turn away from throwing stuff away and move towards wisely managing our resources for the long haul. This means less dumping and more digesting and composting.

Tags: carbon, landfills, methane, nutrients, organics, renewable energy, yard waste

This entry was posted on Friday, June 25th, 2010 at 12:02 pm and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.