Smarter Manure Management: New Tools to Save Nitrogen and Protect the Environment

By Sarah Zeiler

Manure is a valuable resource for farmers. It provides crop nutrients, adds organic matter to the soil and contributes to the soil foodweb. If not managed carefully, too much nitrogen can harm the environment. Nitrogen can volatilize into ammonia and escape into the air or be converted into nitrate and leach into surface and groundwater. Ammonia and nitrate are forms of nitrogen unavailable for plant uptake.

Manure is a valuable resource for farmers. It provides crop nutrients, adds organic matter to the soil and contributes to the soil foodweb. If not managed carefully, too much nitrogen can harm the environment. Nitrogen can volatilize into ammonia and escape into the air or be converted into nitrate and leach into surface and groundwater. Ammonia and nitrate are forms of nitrogen unavailable for plant uptake.

Two recent studies from UW-Madison are testing ways to keep more nitrogen in the soil, where crops can use it, while cutting down on pollution.

Study 1: Using electricity to recover nitrogen from manure

One team of researchers tested a new technology called a bioelectrochemical system (BES). This system uses crores and electricity to break down manure and collect nitrogen into a form that plants can use.

The system has two chambers separated by a membrane. The manure goes into one chamber, where microbes break it down. Electricity helps move nitrogen across the membrane into the second chamber, where it turns into ammonia fertilizer.

They tested the system with both lab-created (synthetic) manure and real dairy manure. Here's what they found:

• The system removed over 90% of organic matter from synthetic manure.
• It removed up to 60% of nitrogen when running on electricity.
• Real dairy manure also showed about 60% nitrogen removal, but it worked a little less efficiently due to extra materials in the manure.