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Glossary of Terms

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AERATION - bringing about the contact of the compost with air through turning, or ventilating to allow microbial aerobic metabolism.

AEROBIC - occurring in the presence of oxygen. For successful composting, sufficient oxygen should be provided to keep the system aerobic. This ensures that the composting proceeds rapidly and with minimal odour.

AMBIENT TEMPERATURE - temperature outside the compost pile.

ANAEROBIC - occurring in the absence of oxygen. Anaerobic composting proceeds slowly and is odiferous.

BIODEGRADABILITY - the potential of an organic substance to be broken down into simpler compounds or molecules through the action of microorganisms.

BULKING AGENT - material, such as wood chips, added to compost primarily to help create good pore structure for air flow. Often provides part of the carbon source as well.

BULK DENSITY - the mass of a unit volume of soil, generally expressed in gm/cm3. The volume includes both solids and pores. Thus soils that are light and porous will have low bulk densities, while heavy or compact soils will have high bulk densities.

CATION EXCHANGE CAPACITY - a measure of the negative charge on soils (primarily on clays and organic matter). It is expressed as the quantity of cations (positive ions) that can be adsorbed by the soil and is expressed in centimoles of charge/kg of soil (6x1023 charged particles are contained in one mole of charge).

CONTAMINANT - unwanted material. Physical contaminants of compost include glass, plastic, and stones, and chemical contaminants include trace heavy metals and toxic compounds.

DECOMPOSITION - the breakdown of organic matter through microbial action.

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HEAVY METALS, TRACE METALS - trace elements whose concentrations are regulated because of the potential for toxicity to humans, animals, or plants. Examples include chromium, copper, nickel, cadmium, lead, mercury, and zinc.

HUMUS - a complex aggregate made during the decomposition of plant and animal residues; mainly derivatives of lignin, proteins, and cellulose combined with inorganic soil parts.

INORGANIC - substances in which carbon-to-carbon bonds are absent. Mineral matter.

LEACHATE - liquid that drains from the mix of fresh organic matter.

MACRONUTRIENTS - Nutrients that plants require in substantial doses. They include nitrogen, phosphorus, potassium, calcium, sulfur and magnesium.

MACROORGANISM - Living organisms in the soil which are large enough to be seen with the naked eye. Includes mite, millipede centipede, snail, slug, spider, ant, beetle, cut worm, earthworm, rodent. (See herbivores, detritivores, and carnivores)

MESOPHYLLIC BACTERIA - This group of bacteria species work to break down organic matter under "warm" conditions of 40 degrees up to 110 degrees. The ideal temperature of their environment is 70 to 90 degrees.

MICROORGANISM - These are microscopic plants and animals. They exist in soil for the purpose of breaking down organic matter into basic mineral elements. (See mineralization) They include bacteria, fungi, actinomycetes, algae, protozoa, yeast, germs, ground pearls, and nematodes.

MOISTURE CONTENT - weight of water in material divided by weight of solids in material.

MULCH - Covering for soil. Mulch should not generally be mixed into the soil, it is not a fertilizer or soil amendment. There are many types of mulch, including partially decomposed compost, bark, wood chips, hay, nut shells, pine needles, and others. The point is to cover bare ground so that top soil is not washed away, soil temperature is buffered, and weeds are reduced from lack of light. A good organic mulch will also supply nutrients to the earth as it decomposes.

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NPK - an abbreviation for nitrogen (N), phosphorus (P), and potassium (K). In the chemical philosophy, these three elements are considered important to force crop production (as opposed to the organic philosophy goal of improving the biodiversity of the soil). U.S. law requires that the ratio of these three elements be specified on every bag of commercially-available fertilizer. A ratio of 3-1-2 or 4-1-2 is considered good.

ORGANIC - Literally refers to something derived from plant or animal matter. Includes anything that is or was living, made from something living, excreted from something living. The term "organic" is used to describe a philosophy of working within the laws and systems existing in nature to achieve a healthy environment that is bountiful long-term. Healthy soil is the foundation of this philosophy, therefore, the term comes up frequently in discussions of home composting.

PATHOGEN - an organism including viruses, bacteria, fungi and protozoa capable of producing an infection or disease in a susceptible host.

PERMEABILITY - A measure of the rate at which water can percolate through soil.

pH - For our purposes, pH is a scale from 1 to 14 which expresses the relative acidity or alkalinity of the water in soil. A pH of 7 is neutral, i.e., neither more alkaline or more acidic. Values below 7 are acidic, increasingly acidic toward 1. Values above 7 are alkaline, increasingly alkaline as the values increase toward 14. pH is the standard abbreviation for "potential hydrogen" which denotes the hydrogen ion concentration of a solution

PHYTOTOXIN - an element or compound that injures plants.

PSYCHROPHILIC BACTERIA - This group of bacteria species work to break down organic matter under "cold" conditions of 0 degrees up to over 55 degrees. They generate low levels of heat.

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SOURCE SEPARATION - the practice of separating waste generated within each household or commercial operation into separate fractions such as newspapers, glass etc., and placing them in separate containers for recycling, composting, and disposal.

STABILITY - the degree to which the composted material can be stored or used without giving rise to nuisances, or can be applied to the soil without causing problems due to incomplete degradation of readily biodegradable materials.

THERMOPHILIC - relating to organisms growing at high temperatures. A stage in composting.

THERMOPHILIC BACTERIA - This relates to a group of bacteria that works to break down organic matter under "hot" conditions (40°C-60°C). This type of bacteria can perform the greatest decomposition in the shortest amount of time.

TOXINS - substances that cause a reduction of viability or functionality in living things.

VCU - Vertical Composting Units (VCU) operates at extra high temperatures , is odourless and is safe to operate in residential areas.

WINDROW SYSTEM - composting mixture is placed in elongated piles called windrows. These windrows are aerated naturally through the chimney effect, or by mechanically turning the piles with a machine or by forced aeration.

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