Phase 3 Renewables

Phase 3 Renewables

Nutrient Management System Provider


In addition to converting your manure, agricultural wastes and other organics to energy, our biomass energy systems often provide new options for nutrient management. Phase 3 Renewables will work with you to look at different equipment and processes that could save you money and potentially provide new sources of income.

One of the most common options for anaerobic digestion plants is to process the digestate using a screw or roller press to mechanically separate the remaining lignocellulosic fibers from the digested liquid. The fibers can then be used for animal bedding, compost, soil amendments, or for making compressed wood plastic composites. Due to both chemical and physical bonding, most of the phosphorus will remain with the separated biofibers, while most of the nitrogen will be in the liquid.

The amount of biofibers your system will generate depends on the:

  • amount of silage, haylage or other roughage in animal feed
  • amount of partially digested roughage in manure
  • type of animal bedding used (straw, biofibers, shavings, or sand)
  • amount of solids destruction in the digester (time, temperature will have an impact, as will other biochemical factors)
  • type of fiber separation equipment used (screen size or belt type)

Nearly every dairy that separates biofibers after digestion is able to fully replace other bedding materials, and normally has an equal amount of excess biofibers for other uses. The separated liquid can then be pumped and applied using center pivot irrigation systems.

For some farms, manure application is severely limited due to elevated phosphorus and nitrogen levels in the soil. In these situations, the liquid digestate can undergo additional treatment in order to reduce the nutrient levels and allow the remaining liquid to be used for irrigation. There are three process options to choose from:

  • Chemical treatment: a combination of polymers and coagulants are used to form a sludge layer containing most of the nutrients.
  • Struvite precipitation: phosphorus is crystallized into a salt, and then separated from the liquid.
  • Aeration and clarification: the liquid is aerated in separate tanks, producing a sludge that is separated in a clarifying tank.

The value of these additional processes depends on your current situation and your future plans. We can provide equipment and operational cost estimates to help you make the decision.

If your farm has excess nutrients and has the ability to reach other markets, it is also possible to minimally treat the liquid digestate so that it is suitable as a liquid organic fertilizer. Using waste heat from your energy conversion system, the liquid digestate is heated to >140 degrees for a short period of time to limit further biological activity. This makes it stable for storage and packaging.

More and more homes and businesses are looking for natural, local fertilizers. Talk to your neighbors, homeowners associations, horticultural companies and your county extension agent to see who might be interested in a uniform supply of liquid organic fertilizer.

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