Lessons learned from a Waste-to-Reuse-and-Energy Project at a Dairy Facility in Texas.Conference Paper
Environmentally sound and sustainable manure management is a challenge faced by dairymen, as well as other producers, in Texas and elsewhere. In a typical dairy operation, manure along with bedding material and unused feed material is flushed out of the barn using water at a rate of 100 to 200 gallons per day per cow. Large quantities of flushed water must be treated before discharge or reuse for flushing to prevent pollution or contamination problems. Lagoon treatment is the most commonly used treatment system by Texas dairymen. However, lagoon effluent requires a large area for land application that is a limitation for most dairymen for adequate disposal. The quality of the lagoon effluent is not always appropriate for reuse as flush water. The Southwest Regional Dairy Center (SWRDC) is an important part of the research infrastructure at Tarleton State University within the Texas A&M University Systems. Two years ago, a team of researchers and engineers started an ambitious project at SWRDC to demonstrate two complementary technologies for improving solid separation, quality of reuse water, and energy production from dried solids at the farm level. The first technology was for wastewater treatment that involved the use of advanced oxidation technology, sound waves and plant-based polymers for solid separation. The second technology was for energy production that collected the solid material that was separated from wastewater and used it to produce gas as fuel. The gas produced from waste solids was captured and utilized as fuel for electric generators. It was estimated that production of electric energy would surpass the needs of the dairy farm and offer the possibility of selling the excess energy back to the grid. The wastewater treatment technology was able to achieve more than 90% reduction in Phosphorus, more than 50% reduction in Nitrogen, and more than 99% reduction in Fecal Coliform, thus producing high quality reuse water. However, sand used for the bedding material was the biggest obstacle for operation of the advanced oxidation wastewater treatment technology using sound waves, and sand particles carried over into the dried solids reduced its energy content. This paper will present details on the challenges faced during this field scale demonstration project, discuss results of effluent quality achieved with different process schemes, and will focus on the lessons learned related to competitive nature of waste-to-energy projects for dairy operations in Texas.