Whole farm assessment of nutrient extraction from dairy manure

Authors: Rotz, Clarence - Al; Reiner, Michael; Fishel, Sarah - Sarah K Marshall; Church, Clinton

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/28/2022
Publication Date: 4/20/2022
Citation: Rotz, C.A., Reiner, M.R., Fishel, S.K., Church, C. 2022. Whole farm assessment of nutrient extraction from dairy manure. Waste to Worth Conference. Oregon, Ohio. April 18-22, 2022. https://lpelc.org/whole-farm-assessment-of-nutrient-extraction-from-dairy-manure/

Interpretive Summary: No Interpretive Summary is required for this Proceeding. JLB.

Technical Abstract: Animal manure contains nutrients and organic material that are beneficial for crop production, but the concentrations of those nutrients are too low to allow economically viable transportation of bulk manures over long distances. Therefore, dairy manure tends to be applied to soils near where it is generated, leading to excess P in the soil and increased risk of surface water eutrophication. A possible solution to the P overloading is to remove some of the P from manure before it is applied using a decanter centrifuge. A farm in Pennsylvania with distant cropland was simulated with the Integrated Farm System Model to evaluate the feasibility of extracting P to reduce transport requirements on farm or to produce a concentrated P product for off-farm use. On a large dairy farm of 2000 cows and 3450 acres of land, where manure must be transported to distant cropland to obtain uniform distribution, centrifuge extraction provided a better ratio of nitrogen and P contents in manure used on nearby cropland and reduced transport costs for nutrients applied to more distant cropland. Centrifuge extraction was found to be more practical and economical when used with manure scraped from the barn floor than with flushed manure. When barn floors were scraped, the volume of material processed was reduced, which improved extraction efficiency and reduced electricity consumption providing more economical P extraction. To avoid long-term accumulation of soil P on the farm with less land (2000 cows and 2720 acres) where concentrate feed (27% of total feed) was imported, centrifuge extraction provided a material with a high P concentration that could be exported from the farm for other uses. Extracting the P in excess of crop needs cost about $1.14/lb P. This was generally greater than the price of phosphate fertilizer, but the extract also included other nutrients and micronutrients of value to crops. A centrifuge provides a useful tool for extracting and concentrating manure P, but the economic benefit to the producer depends upon the value of the full array of nutrients contained, other manure handling practices used on the farm, and the end use of the extracted material.