Livestock manure is a nutrient-packed resource that should not be categorized, classified or regulated in the same way as human waste, according to Dr. Pius Ndegwa, Washington State University Biological Systems Engineering School associate professor and livestock manure specialist.
He explained that the main difference between human waste and livestock manure is that human waste contains pathogenic organisms and heavy metals such as arsenic, cadmium, chromium, lead, selenium and mercury in sewage sludge. These potentially dangerous substances are not found in livestock manure, he said.
The Environmental Protection Agency "makes clear scientific distinctions between livestock manure and human waste, where a significant number and variety of harmful pathogenic organisms and disease-causing agents can be found," Ndegwa said. "For anyone who understands the nature of the two waste streams, there is no scientific basis for classifying livestock manure nutrients the same as sewage sludge as the latter pose significantly higher potential threats to the environment and human health.
"Large dairy farm operations in Yakima County (Wash.) may leave the incorrect perception that they cause high nitrate levels in ground water, but it would be disingenuous to single out dairy farm operations as the cause of high nitrate levels in lower Yakima Valley ground water when there is so much farming activity there — many using chemical or synthetic fertilizers," he continued.
"Application of dairy manure may also be incorrectly perceived as causing high groundwater nitrate levels," Ndegwa said, "because nutrients are more dispersed in manure than in conventional fertilizers, and typically larger volumes of manure are utilized compared to that of synthetic or chemical fertilizer. Nitrogen contained in the manure, however, is taken up by the crops in much higher rates than that of synthetic or chemical fertilizer. Further, manure nitrogen is mostly in ammonium and organic forms, which are not as easily leached to groundwater as the nitrate forms in most synthetic fertilizers."
According to a recent newsletter from the law firm Shook, Hardy & Bacon, several large dairies in Yakima County are embroiled in a dispute with EPA (over its release of confidential documents) and environmental organizations that claim that the dairies are responsible for pollution in the lower Yakima River.
Ndegwa conducts research with emphasis on sustainable livestock manure management systems, air and water quality control engineering, bio-energy or biofuels and livestock odor emission control technologies.