Why does daily spread have a lower footprint than an anaerobic lagoon?

The boundary of the ‘manure’ section of FARM ES is storage and handling. The emissions factor for manure management therefore does not cover emissions after the manure is applied. Because daily spread does not involve manure storage, it has a lower manure emissions factor. Emissions after land application (including daily spread) are incorporated in the feed production emissions category.

The feed production emissions category, which includes an estimate of emissions from land application, is based on LCA research using USDA and other datasets. It is not specific to the farm’s individual field practices.

For additional context, see the following straightforward explanation of the emissions tradeoffs between daily spread and other manure storage. There are many considerations that go into manure management decisions beyond GHGs (e.g. water quality, soil health, etc.). UW Extension has fact sheets on the topic of GHGs and manure.