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Processes​​​​


The process flow diagram for the integrated dairy manure treatment system is shown below. The resources, process steps, products and flows are indicated on the diagram.

9-2-15 DAIRIEES_ProcessFlowDiagram (1).jpg
A brief overview of the process components is outlined below. More information about each can be obtained by clicking on the process title.

Fermen​ter
Raw manure is fed into the fermenter. The fermenter is a biological reactor that creates acids from the products in the raw manure. These acids are the crucial precursors to the chemicals used to make bioplastics. The acids are transferred to the PHA reactor, while most of the solids are then transferred to the anaerobic digester.

Anaerobic Digester
The solids from the fermenter are transferred to the anaerobic digester. This works the same as the AD in the conventional system described above. The manure is degraded by bacteria to methane, which can be used to produce electricity that is used by the farm or sold. Solid byproducts of this process can be used to for fertilizer (for the portion that is nutrient-rich) or for animal bedding.

PHA Reactor
The PHA reactor is another biological reactor. The bacteria inside use the acids as “food” to create a plastic precursor called PHA. In a subsequent reactor to enrich the PHA, a plastic called PHBV. PHBV is a plastic that, because of its properties, exhibits potential for packaging applications (Dai 2010). It also serves as a more long-term sink for carbon compared to fuel sources.

Algae Cultivation

The algal cultivation system takes some of the nutrient-rich liquid from the system and, supplemented with light and CO2, produces algae. The purpose of algae cultivation is to create ad​ditional biomass, which serves as another carbon sink. The algae is harvested on a regular basis, and the part that is high in nutrients (like nitrogen and phosphorus) can be used as a fertilizer. Most of the algae mass is redirected to the fermenter where it serves as an additional source of carbon to supplement the manure and contribute to the amount that can be produced by the AD and the PHA reactor.

Biomass Treatment​

​​The algal or PHA residual biomass is thermochemically treated by either hydrothermal liquefaction or pyrolysis.