Nutrient recovery

Animals on some livestock farms produce more nutrients that can be used by the crops grown. In such a scenario, land-applying all of the manure leads to phosphorus accumulation in the soil over time, increasing risks to water quality. In some but not all cases, excess nitrogen is also produced, increasing risks to the environment as well. Nutrient recovery refers to the manure treatment technologies and methods that allow farmers to reduce the farm’s nutrient surplus.

Comparison with solid/liquid separation

While solid/liquid separation systems will redistribute some of the nitrogen and phosphorus between the solid and liquid fractions, not all of these systems effectively recover nutrients. Typically, nutrient recovery technologies will produce a nutrient-dense solid and a-nutrient depleted liquid. To be effective, the nutrient recovery helps reduce the farm’s nutrient surplus if:

• it allows the farmer to replace purchases or imports of nutrients (commercial fertilizers) with recovered nutrients, or
• it helps the farmers export the recovered nutrients off-farm, particularly as beneficial products for other users or farmers.

To consider which nutrient recovery technologies may be appropriate for a given dairy farm, evaluations of how current and innovative technologies may work on B.C. farms. Read about these evaluations in the reports below.

Nutrient recovery reports

The following report evaluates some of the mechanical, chemical and biological nutrient recovery technologies available to farmers in B.C. The report highlights the capital and operational costs, as well as nutrient recovery efficiencies for each technology. Technologies reviewed include but are not limited to centrifuges, membranes, and flocculation.

• Evaluation of Nutrient Recovery Technologies for Dairy Manure and Digestate (PDF, 1.23 MB) (2016)

To better understand how centrifuges can help with phosphorus recovery, a centrifuge was trialed at seven different dairy farms in the Fraser Valley region. It was found that a centrifuge can recover as much as 40 - 60% of the phosphorus from dairy manure; phosphorus recovery was typically higher on farms with scrape collection versus farms with flush collection. To read more about phosphorus recovery with a centrifuge, click on the link below.

• Assessment of Phosphorus Extraction from Manure Using a Centrifuge (PDF, 1.41 MB) (2017)