- Acid
- – pH below 7 on scale of 0 to 14; normal product of decomposition characterized by hydrogen ions.
- Actinomycete
- – A group of microorganisms, between the bacteria and the true fungi, that usually produce characteristic branched mycelium. These organisms are responsible for the earthy smell of compost.
- Aerated static pile composting
- – See Static pile composting.
- Aeration
- – The process by which the oxygen-deficient air in compost is replaced by air from the atmosphere-Aeration can be enhanced by turning compost.
- Aerator
- – A tool used to create new passages for air and moisture in a compost pile.
- Aerobic
- – Characterized by the presence of oxygen.
- Aerobic composting
- – Decomposition of organic materials by microorganisms in the presence of oxygen. See Composting.
- Alkaline
- – pH above 7 on a scale of O to 14; containing bases (hydroxides, carbonates) that neutralize acids to form salts.
- Ambient air temperature
- – The temperature of the air in the vicinity of the compost pile.
- Amino acids
- – An organic compound that is essential as a building block of proteins.
- Anaerobic
- – Characterized by the absence of oxygen.
- Anaerobic fermentation
- – Decomposition of organic materials in the absence of oxygen.
- Bacteria
- – A group of microorganisms having single-celled or noncellular bodies. Some bacteria provide a gummy substance (a mucus) that binds soil particles together.
- Berm
- – A barrier adjacent to a facility to intercept and deflect water and noise; can also provide visual screening.
- Bin
- – A structure for holding compost.
- Biodegradation
- – The transformation by microorganisms of organic materials, such as fallen leaves, into stable humus. See decomposition.
- Bulking agent
- – Relatively large sized particle materials, such as wood chips, brush, and bark which creates air space within compost.
- Carbohydrate
- – Any compound containing only carbon, hydrogen, and oxygen (such as sugars, starches, and cellulose).
- Carbon-to-nitrogen ratio
- – (expressed as C:N) -The ratio of the weight of organic carbon (C) to that of total nitrogen (N) in an organic material.
- Catalyst
- – Substance which facilitates a chemical reaction.
- Cation exchange capacity
- – The ability of clay and high organic matter (humus) soils, which contain negatively charged particles, to attract and exchange positively charged ions called cations. These cations, such as calcium, potassium, magnesium and ammonia, are thus held in the soil and are not lost due to leaching.
- Cellulose
- – A long chain of tightly bound sugar molecules that constitutes the chief part of the cell walls of plants.
- Chemical persistence
- – The time a chemical remains essentially unchanged in the environment.
- Chipper/Shredder
- – A machine used to reduce volume of yard debris by chipping or splitting the refuse into smaller pieces.
- Compaction
- – Compressing wastes to reduce their volume. Compaction allows for more efficient transport, but may reduce aeration.
- Compost
- – Decomposed, humus-like organic matter produced through composting. Depending on the waste source, compost may have some nutrient value and generally improves soil characteristics.
- Compost pile
- – A stack of mixed organic materials prepared for decomposition.
- Composting
- – The biological degradation or breakdown of organic matter by a managed process.
- Composting facility
- – A facility which produces compost from the organic part of the waste stream.
- Cooperative Extension Service
- – The county-based office of the state land grant university, providing education in youth development, family and consumer sciences, and commercial and home agriculture.
- County agent
- – The local professional educator employed by the Cooperative Extension Service and the state land grant university.
- Cubic yard
- – A unit of measure equivalent to 27 cubic feet or 22 bushels. A box that is 1 yard wide, 1 yard long, and 1 yard high has a volume of 1 cubic yard. For compacted leaves, one cubic yard is roughly equivalent to 500 pounds or 1/4 ton, assuming an average rate of compaction and moisture content.
- Curing
- – The final holding stage of composting, after much of the readily metabolized material has been decomposed, which provides additional biological stabilization. Damping off disease – The wilting and early death of young seedlings caused by a variety of pathogens.
- Decomposers
- – The microorganisms and invertebrates that cause the normal degradation of natural organic materials.
- Decomposition
- – The breaking down of organic material, such as fallen leaves, by microorganisms. This process turns small biologically active molecules, such as starches, into large, very complex and stable molecules that make up humus.
- Dripline
- – A line on the ground defined by the outer edge of a plant’s branches.
- Ecology
- – The study of the relationships of living things.
- Enzymes
- – Any of numerous complex proteins that are produced by living cells to catalyze specific biochemical reactions.
- Evaporative cooling
- – The cooling that occurs when heat from the air or compost pile material is used to evaporate water.
- Fast composting
- – An intensive composting method that produces finished compost in two months, more or less. This method requires an ideal mixture of materials and frequent turning to maximize aeration. When temperatures of 140°F (60°C) are achieved, a “thermal kill” of pathogens, or “partial sterilization,” occurs.
- Fermentation
- – Anaerobic decomposition involving only organic compounds.
- Flail
- – A metal flange or tine attached to a rotating shaft for moving, mixing and aerating leaves.
- Fungi
- – A group of simple plants that lack a photosynthetic pigment. The individual cells have a nucleus surrounded by a membrane, and they may be linked together in long filaments called hyphae. The individual hyphae can grow together to form a visible body.
- Green manure
- – Plant material that while still green is incorporated into the soil, to improve the soil.
- Groundwater
- – Water in a zone of saturation below the ground surface.
- Heavy metals
- – Metallic elements with high molecular weights. Some elements present human health risks at certain concentrations; some may be phytotoxic to plants, and others may adversely affect livestock. While high concentrations can be harmful, low concentrations of some heavy metals such as copper and zinc are essential trace (or micro-nutrient) elements for life processes.
- Herbicides
- – The agents used to inhibit plant growth or kill specific plant types.
- Humic acids
- – The chemical or biological compounds composed of dark organic substances that are precipitated upon acidification of a basic extract from soil.
- Humus
- – That more or less stable organic remnant of soil matter remaining after the major portion of plant and animal residues have decomposed. Usually it is dark in color.
- Hydrogen sulfide
- – A gas, H2S, with the characteristic odor of rotten eggs, produced by anaerobic decomposition.
- Inoculant
- – The dried or inactive microorganisms that become active when added to the compost pile. Inoculants are not required for composting.
- Inorganic
- – Containing no carbon-to-carbon bonds; examples of inorganic substances include ammonia, carbon, hydrogen, oxygen, ni
trogen, phosphorus, potassium, calcium, magnesium, and sulfur as well as chlorine, boron, iron, sodium, copper, sulfur, manganese, molybdenum, zinc. - In-vessel composting
- – A system of composting organic matter involving mechanical agitation, and/or forced aeration, normally enclosed within a building.
- Landfill
- – Georgia law refers to landfill facilities as “municipal solid waste landfills,” which may be operated by either municipalities, counties, or private firms.
- Landfill capacity
- – The predicted life span of a given facility, based on a stated loading rate.
- Landfill site
- – Location for present or projected facility.
- Leachate
- – Liquid that results when ground or surface water comes in contact with solid waste, and extracts material, either dissolved or suspended, from the solid waste.
- Leaching
- – The washing out of soluble substances by a solvent. Usually used in connection with soil and rain.
- Leafate
- – Liquid resulting from composting leaves and brush. It consist of tannic acid and is dark in color.
- Leaf mold
- – Compost composed entirely of leaves, sometimes only partially decomposed.
- Leaf pile
- – A passive method of composting, where leaves are placed in large piles until a usable product is developed, a minimum of 2-3 years.
- Legume
- – Plants belonging to the clover or pea family. They have the characteristic of being able to utilize atmospheric nitrogen, by the aid of certain bacteria in their root zone.
- Lignin
- – A substance that, together with cellulose, forms the woody cell walls of plants and the connecting material between them. Lignin is resistant to decomposition.
- Limb chipper
- – A machine pulled behind a truck to chip tree limbs and brush; used by tree trimming companies.
- LULUs
- – “Locally undesirable land use.” An acronym employed to describe a local development which members of the public oppose.
- Mesophilic
- – Favoring an environment of moderate temperature between 40°-110°F (4°-43°C). Mesophilic microorganisms are most common at the beginning and later stages of the compost process.
- Metabolism
- – Chemical processes necessary for life.
- Microbe
- – See microorganism
- Microorganism
- – Microscopic plants or animals that they can be seen only with a microscope.
- MSW
- – See Municipal solid waste.
- Mulch
- – Material put between rows or around the bases of plants to conserve moisture and to discourage the growth of weeds. Wood chips and fallen leaves make excellent mulches.
- Municipal solid waste
- – Garbage, refuse, trash and other solid waste from residential, commercial, and industrial activities.
- Mycelium
- – The collective term for fungus filaments or hyphae.
- NIMBY
- – “Not in my back yard.” An acronym employed to describe the position of those opposed to some type of development, such as solid waste sites.
- Nitrogen
- – The element that comprises four-fifths of the earth’s atmosphere. The essential element for energy for the microbes in composting.
- N:P:K Ratio
- – The ratio of nitrogen to phosphorus to potassium in a compost product; indicates fertilizer value.
- Non-compostable
- – Incapable of decomposing naturally or of yielding safe, non-toxic end products. Non-compostable materials include glass, batteries, cans, etc.
- Noxious weeds
- – A group of weeds that harm cultivated plants by crowding them out.
- Nutrient-holding capacity
- – The ability to absorband retain nutrients so they will be available to the roots of plants.
- Nutrients
- – Minerals and organic compounds that provide substance for organisms.
- Organic
- – Containing carbon-to-carbon bonds.
- Organic matter
- – The matter derived from living or once-living organisms that gradually can be broken down to yield important plant nutrients composed of materials which contain carbon-to-carbon bonds and are biodegradable; includes paper, wood, food scraps, yard trimmings and leaves. Organic matter content is said to be the single most important indicator of a soil’s fertility.
- Oxidize
- – To combine chemically with oxygen.
- Oxygen demand
- – The requirement for oxygen exerted in aerobic decomposition by microbial respiration.
- Pathogen
- – Any organism capable of producing disease or infection. High temperatures (above 131°F or 55°C) over a consecutive period (3 days) have been shown to effectively kill pathogens.
- Peat
- – The unconsolidated soil material consisting largely of undecomposed, or only slightly decomposed, organic matter accumulated under conditions of excessive moisture.
- Percolation
- – Downward movement of water through the pores or spaces in rock or soil.
- pH
- – An indicator number showing how acidic (pH less than 7) or basic (pH above 7) a material is. A pH of 7 is considered neutral. It is a measure of the concentration of hydrogen ions in a solution. Material that has a pH of 8 has ten times fewer hydrogen ions than something with a pH of 7. The lower the pH, the more hydrogen ions present and the more acidic the material is. The higher the pH, the fewer hydrogen ions present and the more basic it is. Compost decomposes fastest with a pH of around 6.5 (slightly acidic).
- Photosynthesis
- – The ability of a plant, with the aid of sunlight, carbon dioxide and water to form sugars.
- Phytotoxic
- – An adjective describing a substance that has a toxic effect on plants. Immature or anaerobic compost may contain acids or alcohols that can harm seedlings or sensitive plants.
- Porosity
- – The volume of pores divided by the total volume.
- Pre-cycling
- – Waste prevention considerations prior to the purchase of the item such as extra packaging.
- Putrescible
- – With a tendency to become putrid. Some organic materials are prone to degrade rapidly, giving rise to putrid odors.
- Recycling
- – An integrated, comprehensive approach to solid waste management; involves separation of materials from the waste stream which can be reused to manufacture the same or different materials and products.
- Red worms [Eiseniafetidae]
- – These worms, deep maroon in color, thrive only in manure compost or garbage and are rarely found in ordinary soils.
- Resource recovery
- – A term used to describe the extraction of economically useful materials and/or energy from solid waste. See “Waste to energy.”
- Respiration
- – Metabolic function consuming oxygen.
- Runoff
- – Any liquid originating from any part of a composting facility that drains over the land surface.
- Screening
- – The process of passing compost through a screen or sieve to remove large organic or inorganic materials and improve the consistency and quality of the end-product.
- Self-heating
- – Spontaneous increase intemperature of organic masses resulting from microbial action.
- Shredder
- – A mechanical device used to break up materials into smaller pieces, usually in the form of irregularly shaped strips. Shredding devices include tub grinders, hammermills, shears, drum pulverizers, wet pulpers, and rasp mills.
- Slow composting
- – A minimal effort composting method that produces finished compost in a year or more. Slow composting requires little maintenance.
- Soil amendment/Soil conditioner
- – A substance such as lime, sulfur, gypsum, or sawdust, which stabilizes the soil, improves its resistance to erosion, increases its permeability to air and water, improves its texture and the resistance of its surface to crusting, makes it easier to cultivate, or otherwise improves its quality. Fertilizers are one type of soil amendment. However, many soil amendments or conditioners do not have significant fertilizer value.
- Soil profile
- – An indicator showing how characteristics of the soil change with depth. Coloration and other features can be used to determine soil types, texture, and seasonally high water table.
- Soil structure
- – The combination or arrangement of primary soil particles into secondary particles, units, or peds. Compost helps bind primary particles to improve the structure of soil.
- Soil texture
- – A characterization of soil type, based on the relative proportions of sand, silt, and clay in a particular soil.
- Solid waste
- – Any unwanted or discarded solid materials discarded by the community that goes to the landfill.
- Solid waste stream
- – The total amount of municipal solid waste generated by a given community.
- Stabilization
- – The decomposition of compost to the point where it neither reheats when wetted nor gives off offensive odors.
- Static pile composting
- – A method of composting in which oxygen and temperature levels are mechanically controlled by blowing air through a large stationary pile.
- Swale
- – A slight depression, often for drainage, in the midst of generally level land.
- Thatch
- – Dead grass plant parts (such as roots, stems, and shoots) that have accumulated above the soil surface of a lawn.
- Thermophilic
- – Favoring higher temperatures ranging from 113°-155°F (45°-68°C). Thermophilic microorganisms thrive when the compost pile heats up.
- Topdressing
- – Applying a layer of compost, or other material, to the surface of soil.
- Trimmings
- – Plant pieces clipped from trees or shrubs.
- Turning unit
- – A system used to compost large amounts of yard and kitchen scraps in two months, more or less. Ingredients are stored until enough are available to fill an entire bin. Materials are then chopped, moistened, and layered to ensure a hot compost. Piles are turned regularly (weekly) to enhance aeration.
- Vector
- – Any organism capable of transmitting a pathogen to another organism, such as mosquitoes, or rats.
- Vermicomposting
- – The process by which worms convert organic matter into worm castings.
- Volume reduction
- – The processing of materials to decrease the amount of space they occupy. Compaction, shredding, composting and burning are all methods of volume reduction.
- Waste stream
- – The total flow of solid waste from homes, businesses, institutions, and manufacturing plants that must be recycled ordisposed of in landfills.
- Waster to energy
- – Refers to the burning of waste for energy.
- Wet ton
- – Two thousand pounds of material “as is”. It is the sum of the dry weight of the material plus its moisture content. Yard wastes weighed on truck scales would typically be reported this way.
- Windrow composting
- – A method of composting leaves in long piles. The piles or “windrows” are turned periodically to aerate and mix the leaves, speeding up the decomposition process and reducing odors.
- Worm castings
- – The dark, fertile, granular excrement of a worm. Granules are rich in plant nutrients.
- Yard trimmings (waste)
- – Leaves, grass clippings, yard residue, brush, and other organic garden debris.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas AgriLife Extension Service is implied.
Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.
Publication Revised February 2009
