Manure Composting: Opportunities and Challenges

Katherine Buckley, PhD PAg

Small Market Sustainability – Size Matters! Solid Waste Association of North America/Canadian Public

Works AssociationMay 11-14, 2009

Winnipeg, Manitoba

In some places manure is a point of pride

In others ….. Not so much

• odour from the storage

• transportation of nutrients

• nutrient application and accumulation issues

• flexibility in window for application

• public perception

• pathogens

Challenges to livestock production partially mitigated by composting:

Manure composting challenges:• Specifications/regulations for composting site (land

requirements)

• Hauling distance from feedlot to composting site

• Suitable equipment

• Climatic effects

• Nitrogen retention

• Product quality and consistency, plant response

• Composting of low-solids manure and layer manure

• Deriving an economic value for compost use• Acceptability for organic production (has to be

derived from organically managed livestock)• Behavior change in fertilizer use

Specifications/regulations for compost sites

• Lack of details for compost site construction– Every site is different – some have natural

slope and underlying impervious layer– Some sites may require runoff collection,

others might be better served by grassed strips that could be harvested to remove nutrients.

– Requirement for security

These specifications need to be consistently applied across the province

Clear guidelines are needed• Locational criteria:

– surface and ground water protection; distance from existing right–of-way; protection measures within a floodplain.

• Construction/Design Criteria: – Specify minimum requirements for pad surface;

identify need for collection, containment, and use of all waters within the site confines.

• Operational requirements– Methods of operations at the facility; analytical

data for leachate detection; manure (compost) management plan; control of public/animal access

Management of permanent cover to capture nutrients

Hauling distance from barn or feedlot

• To reduce cost and labour, transportation of the manure needs to be minimized.

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Suitable equipment

Small PTO-driven turner

Mid-sized PTO-driven turner

Self-propelled turner

Composting systems - In-vessel

Aerated agitated bed Rotating aerated drum

• High capital costs• Not suitable for large livestock operation

Climatic effects

• Hot, windy weather results in need for additional moisture– Can result in decrease in moisture below a

critical level for good compost activity– Difficult to rehydrate straw amended composts

• Extremely wet conditions result in need for frequent turning to restore porosity– Wet weather late in the composting process

can result in a soggy product– Inability to turn wet compost can increase

odour potential

• Cold, snowy conditions can hinder composting operation

Controlling climatic effects

Light weight woven polyester or breathable GoreTex fabrics

Controlling climatic effects

• Curing and finished compost should be covered to prevent rewetting

Factors affecting nitrogen loss:• total nitrogen content• carbon content• pH• moisture• temperature

Nitrogen retention

Product consistency

• Compost properties, can differ greatly in NPK values, physical characteristics, salt levels, density and porosity.

• Characteristics depend on species, bulking agent and process intensity.

Factors affecting consistency of plant responseThe decomposition and mineralization of compost

is dependent upon: • Carbon content - lower decomposition rate at a

high C:N ratio.• Soil temperature – slower at low temperatures.• Soil moisture – slower in dry soils.• Soil texture - faster mineralization rate on sandy

soils.• Soil nutrient status - inherent fertility, pH and

microbial diversity.

A better understanding of multiple crop response to compost over time would improve marketing opportunities

Benefits of Composting (cont’d)Manure Composting Opportunities

• Pathogen and weed seed destruction• Good source of phosphorus, potassium and

micro-nutrients• More predicable source of nutrients for crop

production than raw manure• Improved handling characteristics and

transportation• Improved soil quality• Control of soil-borne plant diseases• Improved economics of crop production

Improved Handling and Application

Improved Handling and Application

Physical changes during composting

Water content• Decreases from 70 to 30%

Dry matter• Mass loss of 20-30%

Bulk density • Increases 3-4 fold

Implications for transportation of product!

Improved Handling and Application

Apply the equivalent amount of manure as raw manure and as finished compost. (Larney et al., 1999)

Fresh Manure CompostWet wt: 22.3 t Wet wt: 7.9 tWet BD: 0.3 t/m3 Wet BD: 0.7 t/m3

1 (10 m3) Truck = 3.3 t 1 (10 m3)Truck = 7 t

# Truckloads = 7

# Truckloads = 1.1

Improved soil quality

Reduced wind erosion

Improved soil quality

Reduced water erosion and soil crusting

Control of plant disease

• USA – potting mixes with composted animal manure suppressed diseases caused by Pythium and Rhizoctonia.

• Spain – field trials with composted chicken litter reduced root-knot nematodes in tomato and pepper plants.

• Canada – early indications that cattle manure composts may suppress potato diseases.     

Control of plant disease

Mechanisms of action:

Competition for nutrients

Secretion of antibiotics for suppression of disease.

Parasitism of plant pathogens and consumption.

“Systemic acquired resistance” may occur, where plants grown in compost have a higher level of an enzyme associated with disease resistance.

Control of plant disease

• The composting process must be done properly to obtain a disease-suppressive product: a poorly composted product will actually increase the risk of disease, while an over-mature product has little microbial activity.

• Future research will provide guidelines on using composts for disease control.

• It is expected that “inoculated” composts will become commercially available to prevent specific diseases in specific crop situations.

Economic value of compost• Increase in soil aggregate (crumb) stability →

improved water absorbing capacity and permeability during heavy precipitation → higher moisture reserves during drought.

• Compaction protection, increase of soil resilience → improved traffic tolerance → decrease in draft weight and fuel.

• Enhanced soil biological activity → increased mineralization.

• The quantity of N, P, K, Zn, Cu and other trace elements.

Value of compost ~ $200/tonne

Acknowledgements

• Agriculture and Agri-Food Canada “GAPS” program

• Manitoba Conservation “WRAPP” program• Manitoba Rural Adaptation Council• Western Grains Research Council• Manitoba Agriculture Food and Rural

Initiatives “Green Cover” program