Alternative Waste Management: Composting

General and Special Uses

Dr. Lynne Carpenter-Boggs

BIOAg Coordinator

WSU CSANR

Sustainable

BIOAgBIOAg

Organic Biologically-

Intensive

Sustainable

BIOAgBIOAg

Organic

Biologically-

Intensive

BIOAg = Organic and/or bio-intensive, if it’s sustainable.

Organic agriculture: A legally defined and regulated practice that focuses on use of natural materials & non-use of synthetic pesticides, fertilizers, etc.

Biologically Intensive: using renewable biological materials & processes.

Sustainable: Producing high quantity and quality food & fiber with long-term economic, environmental, & social viability.

CompostingAdvantages

• Reduces odors• Volume reduction• Nutrient concentration• May result in a marketable product• Potential income by incorporating other waste

streams• Reduced pathogens• Relatively simple

Disadvantages• Requires two handling systems – liquid and solid• Does NOT address excess nutrient problem• May not have an available market for product

What is composting?• Decomposition en masse

The transformation process is similar to that

which occurs in every topsoil

• Transformation of raw materials biologically chemically physically

• Bacterial and fungal activity thermophilic = heat-loving organisms Microaerobic = not fully aerobic, not anaerobic

Raw materials

•Organic matter

•Oxygen

•Water

•Microbes

Heat CO2

Finished compost with humic matter

Composting is a biological process wherein organic raw materials or “feedstocks” are transformed by organism activities into a stabilized soil-like material called compost.

Compost Temperature Tem

pera

ture

Time

active phase

130 F

Tremendous microbial activity produces heat.

At ~130 F, most plant and animal pathogens and weed seeds die.

Thermophiles

curing phase

Good compost builds rich topsoil•Complex humic acids (humus) form. •Composted material is darker, particles are smaller and softer, texture is fine like good topsoil.

•Good compost is often unrecognizably different from its feedstocks.

•No unpleasant odor, no undecomposed material, and stable in long-term storage.

•Approx. ½ of C, volume, and mass have been lost but most nutrients were retained.

Create a Composting Environment

Factor OK range Optimum

C:N 20:1 – 50:1 25-30:1

Moisture 40 – 65% 50 – 60%

Oxygen >5% >>5%

pH 5.5 – 9.0 6.5 – 8

Particle size1/8 – ½” varies

Animal carcass 5:1Narrow or low C:N

Soil humus 10:1  

Young grasses 20 - 40:1 

Manure 20 - 50:1  

 

Wheat straw 80:1 

Tree leaves 60 - 100:1 

 

Material C:N ratio 

Wood 400:1 Wide or high C:N

Energy materials

Balanced materials

Bulking materials

Passive composting pile

• Temperature will rise, stabilize, slowly drop.

• Minimal management

• Inconsistent results.

Aerated Windrow Composting

NRCS National Engineering Handbook Part 637 -Chapter 2 Composting

BlowerPerforated pipe

Compost Temperature –Passive or static system

Tem

pera

ture

Time

active phase

130 F

curing phase

Turned composting

• Heavy equipment used to mix compost every 1 - 14 days

Compost Temperature – Turned System

Tem

pera

ture

Time

curing

active

turn turnturn

130 F

•When compost no longer reheats after turning, curing begins.

Decomposition continues to slow, but never really ends.

Composting Bins

4-bin composter - Iowa

Compost quality determines its best use

• 3 primary uses for compost: 1. potting soil (best quality required)2. soil amendment, turf topdressing3. mulch (esp. for compost with C:N>25)

• The closer the plant contact (in space and time), the greater the quality and maturity must be. Lower quality composts may be used as mulch, or less mature compost may be incorporated in soil several months prior to planting.

Special-use compost: livestock bedding

• Starting and ending materials have higher C:N

• Some “high energy” feedstock necessary for producing high temperature

• Larger particle sizes ok

• Final product drier (25-40% moisture)

• Compost as bedding may reduce mastitis

Specialized composting: livestock carcass disposal

• Not rocket science, but must be done right

• Some high carbon feedstock necessary for collecting moisture, odor, balancing the high-N carcass

• Composting saves money and nutrients

Mortality is a Waste Management Issue

• A carcass is a concentrated source of organic matter it is a source of odors it is a source of undesirable critters it is a potential source of pathogens it is a source of nutrients

• Thus, the mortality problems are similar to manure problems

Planning for the Impossible...

• Natural disasters can and do happen Flooding (IA, 1993 & NC, 2000) Heat Waves (CA, 2005) Snow (Blizzard of 1993)

• millions of broilers and chicks lost to building collapse and loss of power for heating

Whole herds may be destroyed

Responding to tragedy

Place the carcass on >24” high-carbon base to absorb moisture & allow airflow

Passive Piles or Windrows

Cover the Carcass, Build the Pile

Minimum 24” co-composting material around the carcass to help decompose, discourage critters, and allow airflow

WAIT -- Composting takes time

• With carcasses, wait ~2-6 months before disturbing the pile

• An active pile stays hot. This pile was 135-152 F through December.

Typically only large bones are left identifiable

after 2-6 months.Re-compost these

quickly.

Allow 1-2 more composting periods

• Temperature will rise again, but not as hot.

Special-use compost: organic agriculture

• Moderate-to-high quality compost• Must follow special NOP regs: Feedstock mix C:N must be 15 – 60:1 Temperature must reach 131 F at least 3 days Turn or ensure that all parts of pile reach temp

• Test for E. coli, Salmonella• Use a turned or aerated system, not passive• No biosolids, no prohibited materials used• If requirements not met, use as if it’s manure

Composting – It’s hot!