After four years of extensive testing, the N.C. Department of Agriculture and Consumer Services is employing a new method for analyzing nitrogen in swine, dairy and poultry lagoon samples that will produce quicker more accurate results, reduce costs and increase safety for employees conducting tests.
The lab recently moved from Total Kjeldahl Nitrogen (TKN) testing to the Total Nitrogen by chemiluminescence (TNb) method for analyzing nitrogen in manure.
The TKN method has been widely used for over 100 years to analyze nitrogen in organic materials such as plants, food and wastewater. While TNb is a standard method used in the analysis of nitrogen in wastewater, petroleum and biological materials, it has never been used to measure nitrogen in manure.
The Agronomic Divisions' Waste and Compost Lab has been testing the TNb method to assess its accuracy, precision and equivalence to TKN, said Dr. Kristin Hicks, director of the Waste and Compost Lab.
“We found TNb produces the same results as TKN but it’s more precise, meaning that it produces more consistent results with much less variation,” Hicks said. “In addition, using the TNb method reduces the need to use hazardous chemicals such as concentrated sulfuric acid, which adds potential risk to laboratory staff.”
The TNb method does not require the use of hazardous chemicals, which is a major improvement to safety and eliminates costly hazardous waste disposal.
The new method has proven less costly in both staff time and input costs. A recent cost analysis showed that the lab testing materials for TNb are $0.76 per sample compared to TKN, which is $3.31 per sample. Additionally, the time required per sample for TNb is half that of TKN.
With the lab’s sample volume of 13,000 samples per year, this represents a major cost and labor savings to the Division.
“We are excited to make this important method change, which will produce more reliable results, be safer for the laboratory staff, eliminate hazardous waste disposal, save money on inputs and improve sample turnaround time for our clients here in North Carolina.” Hicks said.