Co-Composting Material

Co-composting material is referred to any material added to the composting pile to aid in the composting process. Mortalities are high in nitrogen; therefore, co-composting materials high in carbon such as sawdust, straw, and woodchips should be used when composting deadstock. Particle size should also be taken into consideration. The co-compost material should be large enough to allow air flow into the pile, but small enough not to cool the pile. Particle size ranging from 0.25 - 2 inches should be targeted.

The amount of carcass:co-compost material required on a volume basis shown below has proven to be effective for mortality composting. For all other carcass:co-compost ratios, please contact your local GO Office.

Co-compost Carcass:Co-compost ratio
Sawdust 1:12
Straw 1:3-5
Woodchips 1:4-6

Note:  If manure is used as a co-compost material a Manure Management Plan (MMP) must be filed with Manitoba Conservation for operations with 300 or more animal units.

Type Advantages Disadvantages
  • Fine particle size
  • Retains head
  • Sheds rain water
  • Absorbent
  • High carbon content
  • Allows for air infiltration
  • Availability may be limited
  • Less straw required than sawdust
  • Readily available
  • Core temperature may not be as high as with sawdust
  • Requires water control management
  • More susceptible to leaching then sawdust
  • May form air pockets
  • Provides excellent surface contact
  • Easy to work with
  • Helps mask odours
  • Availability may be limited

Other materials can be used as bulking agents (see table below) such as old silage, manure/litter, finished compost (not exceeding 50%) and bedding.

Origin C:N Ratio, nutrients Structure, porosity Moisture - as is Degradability Treatment required Cautions
Agricultural Residuals
Poultry manure (fresh, no litter) 10 Poor Moist Good Bulking material Odour
Poultry manure (with litter) 13-30 Medium Low-dry Medium - Odour
Slurry (urine) liquid 2-3 Poor Liquid Good Mix with dry matter Odour
Manure (cattle) liquid 8-13 Poor Liquid Good Mix with dry matter Odour
Manure (pig) 5-7 Poor High Good - Odour, moisture
Cattle manure 20 Medium Medium High - -
Manure with straw 25-30 Good Good Medium - -
Horse manure 25 Good Good Medium - -
Vegetable wastes 13 Poor Moist High - Low pH, Odour
 - Oat/Rye 60 Good Dry Medium Rough chopping -
 - Wheat 100 Good Dry Medium Rough chopping -
 - Barley/Pulses 40-50 Good Dry High - -
Wood and Lumber Industry Materials
Bark 100-300; Low P, Ca; Low pH Very Good Medium; Good Very Good Pre-grind -
Paper sludge 100-110 Medium to Poor Very Moist Medium Presscake Dioxins
Cotton sludge 20-40; N-rich; Low P, K Poor Very Moist Very Good Pressed -
Beech ~100 Very Good ≤ 50% good Excellent Already ground -
Fir ~230 Very Good ≤ 50% good Medium Already ground -
Aged <100 Very Good ≤ 50% good Poor Already ground -
Garden / Landscape Materials
Wood chips 40-100 Good Too Dry Low Grinding Coarseness
Garden wastes 20-60 Good Medium Medium Grinding -
Green foliage 30-60 Medium to Good Good/Dry Good - -
Leaves - Good - - - Matting
Grass clippings 12-25 Poor Moist High Bulking material, pre-drying Odour