Introduction

Composting organic wastes is

an environmentally sound

means

of recycling raw organic

materials into valuable soil

amendments with many

uses .

What is composting?

Composting is the process of producing compost through aerobic decomposition

of biodegradable organic matter .

Compost produced at the end of the process can be used in farming and gardening to

improve soil quality.

Principles of Composting

Composting is the controlled decomposition of organic matter.

Rather than allowing nature to take its slow course, a composter provides an optimal environment in which decomposers can thrive. To encourage the most active microbes, a compost pile needs the correct mix of the following ingredients:

Carbon, Nitrogen (from composting materials)Oxygen (from the air)Water

Type of composting

•Active (hot) composting –~55oC –Higher temperature kill most pathogens–Regularly stirring ensure aeration–Faster (take weeks)

•Passive (cold) composting–~30oC–Much slower (may take months)–May develop anaerobic condition, releasing odor and

greenhouse gas (e.g. methane)

Carbon : Nitrogen ratio

High-carbon sources provide the cellulose needed by the composting bacteria for conversion to sugars and heat. (e.g. starch and cellulose)

High-nitrogen sources provide the most concentrated protein, which allow the compost bacteria to survive and multiply. (e.g. animal manures, fruit and vegetable trimmings, leaves)

The most rapid composting occurs with the ideal carbon:nitrogen ratio of 25~30: 1 by dry

chemical weight .

Why use compost?

• Composting is a method of stabilizing organic wastes by the action of microorganism

• Increasing soil organic matter 30t/ha compost provides ~ 6 t/ha of organic matter = long-term benefits for soil structure, fertility and water holding

• Slow release nutrients 30 t/ha compost is worth ~ £90/ha

• Increasing soil microbial population

• Stabilizing soil pH (fertilizers acidify soil) Better crop establishment & yields

The composting process

Collection of suitably balanced feedstock materials

Shredding

Composting

Maturation

Screening

Application of finished product

Distributed by: Information Packaging Centre Alberta Agriculture, Food and Rural Development 7000 - 113 Street, Edmonton, Alberta Canada T6H 5T6

Material flow for the conventional composting process.

How does composting work?

Types of composting

-Farmyard manure (FYM)

-Poultry Manure

-Cattle slurry

-Town refuse

-Sewage sludge

Characteristics of compostGeneral properties of green waste compost

8.6 pH

0.773 Electrical conductivity (dS cm-1)

59 Dry matter(%)

0.5 Density (kg L-1)

19 Organic matter(%)

Characteristics of compost

Nutrient contents

An example of the effects on crop yields

Yie

ld (

per

cen

t o

f co

ntr

ol)

Potatoes Onions Cabbages Carrots

Effects on soil structure

• Organic matter additions improve soil structure on both heavy and light land.

• This has beneficial effects on water holding capacity, drainage, erosion and root penetration.

• Cultivations are made easier.

Effects on soil biology

• Biological activity is stimulated by the addition of nutrients and by the improvement to soil structure

• Some evidence suggests that there can be inhibition of plant diseases

ConclusionsComposting can be an effective way of

managing organic wastes.On-farm composting is a useful technique for

dealing with farm generated wastes – bringing in material from elsewhere can be a good business in itself.

Application of compost adds to the organic matter in the soil

Compost is a good source of available P and K.

The nitrogen it contains is in a stable state and relatively unavailable in the short term.