Nutrient separation, solid–liquid separation, and manure drying systems are getting more attention across livestock systems, but when do they actually make economic sense? These technologies are often discussed as solutions to manure management challenges. Sometimes they are. Other times, they’re expensive ways to solve problems that don’t really exist, or problems that would be cheaper to address another way.
This article is not meant to be comprehensive, nor is it
intended to answer every question about separation and drying systems. Instead,
the goal is to provide a realistic look at what actually drives value in these
systems by walking through a few example scenarios and comparing manure
management before and after treatment. If you’ve wondered whether these systems
are a smart investment, or a shiny distraction, this one’s for you.
Why Are These Systems Being Considered in the First
Place?
At their core, manure treatment systems are an attempt to
solve a logistics problem, not a nutrient problem.
Most manure management challenges come down to some
combination of:
·
Too much water relative to nutrients
·
Nutrients concentrated in the wrong place
·
Limited land base near the livestock facility
·
Imbalances between nitrogen and phosphorus needs
·
Increasing hauling distances and application
costs
·
Tight application windows and labor constraints
Separation and drying systems don’t create nutrients, and
they don’t make regulations go away. What they do is change where nutrients go,
how concentrated they are, and how expensive they are to move. Interest in
these systems has grown as farms have gotten larger, hauling distances have
increased, and nutrient management has become more constrained. In some cases,
water reuse or off-farm nutrient export becomes the primary driver rather than
fertilizer value alone.
What Do Separation and Drying Systems Actually Do?
Rather than focusing on equipment types, it’s more useful to
think about these systems based on outcomes.
Broadly speaking:
·
Solid–liquid separation shifts nutrients
unevenly between a liquid fraction and a solid fraction.
·
Nutrient separation systems intentionally
concentrate certain nutrients (often phosphorus) into a smaller volume.
·
Drying systems reduce mass and volume by
removing water, dramatically changing transport economics.
What matters isn’t the technology, it’s what changes after
treatment:
·
Total volume that must be hauled
·
Nutrient concentration of each fraction
·
Where each fraction can be applied
·
Application method and timing flexibility
·
Labor, energy, and management requirements
Nearly every system creates tradeoffs. Liquids may become
easier to apply nearby, while solids require new handling, storage, or markets.
The value only appears if those tradeoffs align with real constraints on the
farm.
How Do We Evaluate Whether a System Pays?
Before talking about treatment, we need a baseline.
Step 1: Understand the Untreated Manure System
For any farm, the starting point is:
·
Annual manure volume
·
Typical nutrient content (N, P, K)
·
Average hauling distance
·
Application cost per gallon or ton
·
Effective nutrient value captured by the crop
This baseline represents the true cost and value of manure
without additional technology. If untreated manure is already inexpensive to
apply to nearby acres with good nutrient utilization, there may be very little
economic upside to separation.
Step 2: Compare the Post-Treatment System
After treatment, we look at:
·
New volumes and hauling distances
·
Changes in nutrient distribution
·
New application or storage costs
·
Operating costs of the system itself
·
Any new revenue or avoided cost
The key question isn’t “does it reduce volume,” it’s whether
the reduction saves enough money, or creates enough flexibility, to justify the
added cost and complexity.
Case Studies: Where the Economics Come From (or Don’t)
The following examples are simplified and illustrative.
Assumptions are intentionally transparent, and numbers can be refined. The goal
is to highlight drivers, not produce a universal answer.
Case Study 1: Dairy with a Centrifuge Solid–Liquid
Separation System
Baseline system:
A 1000-head dairy applies liquid manure to nearby cropland
using conventional dragline systems. Hauling distances are moderate, but the
farm isn’t making use of phosphorus at field levels have built up.
This farm produces 6.5 million gallons per year and at land application
time we’ll have around 81,000 lb N and 70,000 lb P2O5. Manure application will
cost about $0.013 per gallon for an annual expense of $86,000 a year. Based on
the problem, only the nitrogen is providing fertilizer value, which at $0.54 a
pound gives $43,000 in value. This system would be a net negative of around $42,500
per year for the farm.
After separation:
A centrifuge system separates manure into a liquid fraction
and a solid fraction. The solid product is phosphorus rich, while nitrogen
remains largely in the liquid. Liquids are applied to nearby acres similar to
before, while solids are hauled farther to access additional land or
sold/transferred off-farm. The total gallons hauled locally decline, but solids
require new storage and handling facilities.
This farm still produces 6.5 million gallons per year but
because of separation we end up with around 5.4 million gallons per year to
land apply and at land application time we’ll have around 77,000 lb N and 24,000
lb P2O5. Manure application will cost about $0.013 per gallon for an annual
expense of $73,000 a year. Based on the problem, only the nitrogen is providing
fertilizer value, which at $0.54 a pound gives $41,000 in value. However, now
we also have a solid manure product that can be hauled to fields where the P is
needed. We’d generated about 4600 tons of solid manure that cost about $6.20 a
ton to apply for a cost of $29,000 per year, but given its N and P it supplies
fertilizer value of $23,000. This system
would be a net negative of around $38,000 for the farm, or save around $5000
per year.
Case Study 2: Dairy with a Livestock Water Recycling
System
Baseline system:
A 1000-head dairy just like in the first farm, so we don’t’ need
to redo any numbers.
After treatment:
In this case, let’s assume the solid-liquid separation works
just like it did before, but the liquid stream is now going to get processed through
a membrane system that takes the nitrogen and concentrates it up to 100 lb
N/1000 gallons and the remaining liquid water is of discharge quality.
This farm still produces 6.5 million gallons per year but
because of separation we end up with around 5.4 million gallons that get run
through the membrane system. After treatment in the membrane, we are down to
around 1.6 million gallons to land apply and at land application time we’ll have
around 157,000 lb N (it is higher because I assumed I’d do something to reduce
N loss during storage and it will be 100% available) and 24,000 lb P2O5. Manure
application will cost about $0.026 per gallon for an annual expense of $41,000
a year. Based on the problem, only the nitrogen is providing fertilizer value,
which at $0.54 a pound gives $84,000 in value. However, now we also have a solid
manure product that can be hauled to fields where the P is needed. We’d
generated about 4600 tons of solid manure that cost about $6.20 a ton to apply
for a cost of $29,000 per year, but given its N and P it supplies fertilizer value
of $23,000. This system would be a net positive
of around $40,000 for the farm, or save around $80000 per year. Of course, this
would need to pay capital expenses on the equipment, labor and operation
expenses to run it, and handle doing something to reduce losses of N from the stored
fertilizer product.
Case Study 3: Dairy Farm with a Sedron Technologies Manure Drying
System
Baseline system:
A 1000-head dairy just like in the first farm, so we don’t’ need
to redo any numbers.
After treatment:
This is a drying system, so rather than wet solids, they’ll
be dry. Also, they are doing a different treatment system that should get the
nitrogen fraction up to around 7% N content. I’m not going to cover the details
this time, hopefully in the future.
This farm still produces 6.5 million gallons that get run
through the drying system. After the drying system we’ll be down to about 0.25
million gallons of liquid N fertilizer to land apply and at land application time
we’ll have around 157,000 lb N (it is higher because I assumed I’d do something
to reduce N loss during storage and it will be 100% available). Liquid
fertilizer application will cost about $0.041 per gallon for an annual expense
of $11,000 a year. The nitrogen is providing fertilizer value, which at $0.54 a
pound gives $84,000 in value. We also have our dried fertilizer product. We’d
generated about 2300 tons of solid manure that cost about $7.70 a ton to apply
for a cost of $18,000 per year, but given its N and P it supplies fertilizer value
of $29,000. This system would be a net positive
of around $80,000 for the farm, or save around $120,000 in manure handling
expenses and created value.
The Big Picture
These examples are far from complete, but they do illustrate
why we continue to look towards innovative manure treatment systems. Because
the dream of turning manure to gold is out there, and this analysis illustrates
if we can make the systems cost effective and work there is value to be had.
However, doing so will make sure we bring system costs down towards what we are
gaining in fertilizer value and potential land application expenses, because
while $120,000 sounds like a lot of money if I want this technology to pay
back, it means I’ll need to spend less than $1 million dollars on it in start
up expenses.
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