Revision as of 10:09, 6 February 2013

Introduction to Composting

Composting, is the partial decomposition of organic materials by aerobic microbes. This has the effect of "stabilising" the nutrients, sanititising pathogens in the organic material and producing a useful soil amendment.

Purpose of composting

There are two main purposes of composting:

reduction in the volume of "waste" (plant matter, feces). It is thus useful as a "waste management technique"
creation of stable compost from the plant matter, which is a very useful compound in farming. It is useful for this as
- it improves soil structure, improves aeration, water-retention, erosion problems, and makes the soil easier to work.
- it adds nutrients to the soil, but arguably more importantly adds organic matter to the soil. As a sponge holds water, so organic matter helps to retain nutrient ions in the soil that the plants need to grow. These nutrients may not have originated in the compost - so soils with higher levels of organic matter can be said to be more fertile than those with much lower levels.

In addition, composts can be used as mulches to reduce water losses from the soil surface and slow growth of competitive weeds between rows and around plants. See Mulching for further details.

Composting process

Composts need:

Air & moisture: whilst composts can be too dry, they are more of a problem when too wet, as the water displaces oxygen within the matrix, which may prevent efficient aerobic microbial activity.
Food: organic matter containing carbon and nitrogen
Warmth: all microbes have optimal temperatures to survive, and 'friendly' compost microbes multiply at higher temperatures.

When conditions are not optimal, the process may be slowed, may not happen at all, or may not destory harmful microbial pathogens. Care should be taken as it is possible to have areas of poor conditions within a compost heap that is performing well. High or low levels of moisture may also have a big effect length of time it takes for the compost to stabilise. Stabilised compost is dark in colour (exact colour will depend on the materials used), consistent (in the sense that it is hard to identify what was used to make it), is fairly fine and does not contain many contaminents (such as pieces of plastic, large pieces of wood etc). In most places with good management, stable compost can be produced within 8 weeks. However systems which are not ideal (sometimes known as 'cold composting') may take a lot longer. Composting toilets should be left to mature for at least a year after use and may still not be fully stable.

Composting is the cumulative digestion effect of many different kinds of organism and may involve several different steps and various types of organism, which may include worms, microbes and other biota. The Building compost guide gives additional general information about simple composting systems.

C/N ratio

It is important to understand the Carbon:Nitrogen ratio as this will have a dramatic effect on the success of a composting system.

Sludges, animal wastes and fresh green materials are high in nitrogen. Straws, browned plants and woody materials are high in carbon. If using woody materials, chopping will be necessary as the microbes require a high surface area to get to the carbon in the wood, which is often stored in a way that is difficult for them to access. On the other hand, having larger pieces of material within the compost may assist the process as it will aid air circulation. It may be necessary to remove these towards the end of the process.

Successful composting requires a mix of organic materials as large amounts of high N (nitrogen) material will lead to high losses of N and other undesirable processes. As a rule of thumb, a target ratio of carbon: nitrogen should ideally be 30:1 or lower. Materials which are high in N, such as animal manures, human sewage sludge, food wastes etc should therefore be mixed with large amounts of materials which are high in carbon, such as straw, wood, sawdust etc. Compostable materials is an introduction to different types of materials that can be effectively composted.

Hot composting

In ideal conditions, the rapid respiration of microbes within the compost will lead to high temperatures and so this is sometimes refered to as 'hot composting'. Higher temperatures are highly desirable as it will denature pathogenic microbes (who are usually most active at around body temperature) and seeds of many species of weed.

Cold composting

Cold composting is composting in sub optimal conditions. Materials may be left in heaps without attention, mixing or protection from rain. Composting may be slow, may not take place at all or the conditions may even encourage undesirable processes to occur. Cold composting should therefore be avoided and the products may need additional processing or composting to be safely used.

Composting at different scales

Many different types of composting are conducted in different places around the world and at different scales. These range from bin composting at a household scale all the way to full industrial scale windrow composting.

Pile or bin composting

In fairly small scale composting, bins, piles and heaps are used. Bins may be produced from various different kinds of materials and can help to produce good compost if they assist with the flow of air through the heap. The disadvantage of bins is that the compost can be more difficult to turn and aerate. A heap on the ground can be seen as an easier option, however care may be needed to prevent the material from speading and to ensure it is adequately aerated. This page has more detail about home composting.

Regarding the types of bin, plastic bins such as the geobin system have been used to produce compost of reasonable quality, but bins made of wood or other locally available materials can be used just as effectively. Sometimes bins have been designed with special equipment to aggitate and aerate the compost, which can also be a good way to ensure that the compost is properly aired without the user having to manhandle the compost.

See this technical brief about manufacturing bins.

Industrial scale composting

Windrows are large compost heaps which can be hundreds of metres long. They are usually this shape because specialist turning equipment is used to move along the whole length to turn and mix the compost. Arcata Marsh is an example of a large industrial scale composting plant.

Farm waste composting

In many farm systems, animal extreta from animal houses is mixed with urine and bedding and stored in bays beneath the buildings, to be excavated and removed at a later date. The effectiveness of this as a composting system will depend on the animals and the bedding materials used, but farmyard manure can often be used as a valuable soil amendment. In many areas it makes more sense to remove and store the waste away from the animal houses due to problems with dust and odors. Care should be taken when removing animal wastes from underground storage pits as there may be hazards from airborne pathogens and the material may not be adequately sanitized.

Troubleshooting

Regularly turning compost to encourage the movement of air is always a good idea
Increase surface area of materials by chopping them up.
If your compost is smelly it is not getting enough oxygen (going anaerobic).
If space is an issue (ie if you are living in a house or apartment with not much of a yard), you could try vermiculture (i.e. using a worm bin).
Animals (ie bears, raccoons, rats, and other animals) may become a problem if there is something in a compost pile they would like to eat. Access to compost must be restricted (ie by using a high, fully closed bin); avoiding the scraps that attract them too can help, especially meat, fish.

External links

Composting, vegan permaculture, native plants - a podcast by Paul Wheaton and Helen Atthowe (very informative on composting)
Territorial Seed

@@ Line 1: / Line 1: @@
 {{topic header| default.png |Composting}}
 {{TOCright}}
+=Introduction to Composting=
-'''Composting''',  is the partial decomposition of organic materials by aerobic microbes. This has the effect of "stabilising" the nutrients, sanititising pathogens in the organic material and producing a useful soil amendment.  This can be considered to have a long term fertilising effect on the soil, but may also be considered to have other useful properties - for example as mulches, composts added to the soil surface may prevent weed growth.
+'''Composting''',  is the partial decomposition of organic materials by aerobic microbes. This has the effect of "stabilising" the nutrients, sanititising pathogens in the organic material and producing a useful soil amendment.
-Successful composting requires a mix of organic materials as large amounts of high N (nitrogen) material will lead to high losses of N and other undesirable processes.  As a rule of thumb, a target ratio of carbon: nitrogen [[Composting#C/N ratio|should be 30:1]] or lower.  Materials which are high in N, such as animal manures, human sewage sludge, food wastes etc should therefore be mixed with large amounts of materials which are high in carbon, such as straw, wood, sawdust etc.
-Due to the amorphous nature of composting, the mix of air within a heap may be poor.  This may mean that there are parts of the compost which are actually anaerobic, and pathogenic microbes are more likely to survive in anaerobic conditions.  Frequent mixing and turning of compost is therefore essential.
-High or low levels of moisture may also have a big effect length of time it takes for the compost to stabilise.
-Around the world, there are many examples of different ways of composting, however the most effective systems are usually fairly large, as larger compost heaps (sometimes called windrows) retain heat from microbial activity for longer, which is an important consideration when using composting for treatment of sludges which may contain pathogens.  Smaller scale sites are easier to establish, but require careful attention and management to ensure the C:N ratio is maintained, the materials do not get too wet (or dry) and that the materials are regularly turned to ensure aeration.  There are a range of designs of small bins and containers which mix materials and aerate or aggitate them.
-Stabilised compost is dark in colour (exact colour will depend on the materials used), consistent (in the sense that it is hard to identify what was used to make it), is fairly fine and does not contain many contaminents (such as pieces of plastic, large pieces of wood etc).  In most places with good management, stable compost can be produced within 8 weeks.  '''However''' systems which are not ideal (sometimes known as [[Composting#Cold composting|'cold composting']]) may take a lot longer.  Composting toilets should be left to mature for at least a year after use and may still not be fully stable.
-Like all organic matter additions, compost can add valuable plant nutrients to the soil to help plants grow and stay healthy.  One advantage of composts are that they are often more stable than sludges and other materials, so may be less of a threat to water courses.  In addition, the nutrients in compost may be in a form which is more appropriate for agriculture, however care must be taken when applying to soil as the compost may not be able to supply nutrients to the crop at the time or in the amount required.  As a consequence, composts should be carefully considered as a part of a sustainable soil management system with other amendments.
 ==Purpose of composting ==
-The purpose of composting is two-fold:
+There are two main purposes of composting:
 * reduction in the volume of "waste" (plant matter, feces). It is thus useful as a "waste management technique"
 * creation of stable compost from the plant matter, which is a very useful compound in [[farming]]. It is useful for this as
 ** it improves soil structure, improves aeration, water-retention, erosion problems, and makes the soil easier to work.
 ** it adds nutrients to the soil, but arguably more importantly adds organic matter to the soil.  As a sponge holds water, so organic matter helps to retain nutrient ions in the soil that the plants need to grow.  These nutrients may not have originated in the compost - so soils with higher levels of organic matter can be said to be more fertile than those with much lower levels.
+In addition, composts can be used as mulches to reduce water losses from the soil surface and slow growth of competitive weeds between rows and around plants.  See [[Mulching]] for further details.
 == Composting process ==
@@ Line 27: / Line 18: @@
 *Air & moisture: whilst composts can be too dry, they are more of a problem when too wet, as the water displaces oxygen within the matrix, which may prevent efficient aerobic microbial activity.
 *Food: organic matter containing carbon and nitrogen
-*Warmth: all microbes have optimal temperatures to survive, and generally speaking warmer composts are better for most 'friendly' compost microbes.
+*Warmth: all microbes have optimal temperatures to survive, and 'friendly' compost microbes multiply at higher temperatures.
-Composting is the cumulative digestion effect of many different kinds of organism and may involve several different steps and various types of organism.
+When conditions are not optimal, the process may be slowed, may not happen at all, or may not destory harmful microbial pathogens.  Care should be taken as it is possible to have areas of poor conditions within a compost heap that is performing well. High or low levels of moisture may also have a big effect length of time it takes for the compost to stabilise. Stabilised compost is dark in colour (exact colour will depend on the materials used), consistent (in the sense that it is hard to identify what was used to make it), is fairly fine and does not contain many contaminents (such as pieces of plastic, large pieces of wood etc).  In most places with good management, stable compost can be produced within 8 weeks.  '''However''' systems which are not ideal (sometimes known as [[Composting#Cold composting|'cold composting']]) may take a lot longer.  Composting toilets should be left to mature for at least a year after use and may still not be fully stable.
-=== C/N ratio===
+Composting is the cumulative digestion effect of many different kinds of organism and may involve several different steps and various types of organism, which may include worms, microbes and other biota.  The [[Building_compost_guide|Building compost guide]] gives additional general information about simple composting systems.
-{{Main|In-depth explanation of bin composting}}
-Compost piles and windrows are made according to a specific ratio of carbon materials to nitrogen. This ratio should generally be 30:1, C:N. The carbon/nitrogen ratios of different materials are explained in [[In-depth explanation of bin composting]].
+== C/N ratio==
+It is important to understand the Carbon:Nitrogen ratio as this will have a dramatic effect on the success of a composting system.
 Sludges, animal wastes and fresh green materials are high in nitrogen.  Straws, browned plants and woody materials are high in carbon.  If using woody materials, chopping will be necessary as the microbes require a high surface area to get to the carbon in the wood, which is often stored in a way that is difficult for them to access.  On the other hand, having larger pieces of material within the compost may assist the process as it will aid air circulation.   It may be necessary to remove these towards the end of the process.
-====Hot composting====
+Successful composting requires a mix of organic materials as large amounts of high N (nitrogen) material will lead to high losses of N and other undesirable processes.  As a rule of thumb, a target ratio of carbon: nitrogen should ideally be 30:1 or lower.  Materials which are high in N, such as animal manures, human sewage sludge, food wastes etc should therefore be mixed with large amounts of materials which are high in carbon, such as straw, wood, sawdust etc.   [[Compostable_materials|Compostable materials]] is an introduction to different types of materials that can be effectively composted.
+==Hot composting==
 In ideal conditions, the rapid respiration of microbes within the compost will lead to high temperatures and so this is sometimes refered to as 'hot composting'. Higher temperatures are highly desirable as it will denature pathogenic microbes (who are usually most active at around body temperature) and seeds of many species of weed.
-There are several international standards regarding the times needed at particular temperatures for effective pathogen destruction.  It has been proved that the best composting systems are able to elevate temperatures to these standards, however care should be taken as there may be variations within composting heaps (for example the edges of a heap are usually colder than the top middle).  Several mixes may therefore be needed to ensure that all of the materials have reached the required temperatures.  Unless temperatures have been regularly measured, and ideally microbial pathogens have been analysed, it should never be assumed that a particular compost mix has been able to kill off all pathogens, so composts including animal and human wastes should always be handled and used with caution.
+==Cold composting==
-====Cold composting====
 Cold composting is composting in sub optimal conditions.  Materials may be left in heaps without attention, mixing or protection from rain.  Composting may be slow, may not take place at all or the conditions may even encourage undesirable processes to occur.  Cold composting should therefore be avoided and the products may need additional processing or composting to be safely used.
-==Types of compost==
+==Composting at different scales==
-===Pile or bin composting===
-{{Main|In-depth explanation of bin composting}}
-In fairly small scale composting, bins, piles and heaps are used.  Bins may be produced from various different kinds of materials and can help to produce good compost if they assist with the flow of air through the heap.  The disadvantage of bins is that the compost can be more difficult to turn and aerate.   A heap on the ground can be seen as an easier option, however care may be needed to prevent the material from speading and to ensure it is adequately aerated.
-Often people making compost use a recipe, often arrived at by trial-and-error, which is known to produce good compost in their situation.
+Many different types of composting are conducted in different places around the world and at different scales. These range from bin composting at a household scale all the way to full industrial scale windrow composting.
-This is one recipe using a layering technique:
+===Pile or bin composting===
+In fairly small scale composting, bins, piles and heaps are used.  Bins may be produced from various different kinds of materials and can help to produce good compost if they assist with the flow of air through the heap.  The disadvantage of bins is that the compost can be more difficult to turn and aerate.   A heap on the ground can be seen as an easier option, however care may be needed to prevent the material from speading and to ensure it is adequately aerated.  [[Home_composting_(Practical_Action_Brief)|This page has more detail about home composting]].
-:Layer the pile by alternating the previously mentioned "brown" and "green" layers. The ideal way to layer materials is by first loosening the ground on which the pile will be located to allow for drainage.  The first layer should be a stalky material to allow for air flow and drainage, sunflower stalks, corn stalks, small branches or twigs work well for this.  Then add a significant amount of dry vegetation or carbon such as leaves or straw.  After that comes the nitrogen layer, which is green waste or kitchen scraps topped with a thin sheet of soil.  The process is then repeated leaving out the stalky layer.  If there is enough material, it is best to make the whole pile at once.  For really cold climates a pile should be 4x4x4 feet to insulate it, but in a mild climate 3x3x3 feet is sufficient.  A pile will shrink to about a fourth of the size and usually takes 3-6 months to fully break down.  You will know that a pile is done when it is rich in color, falls apart easily in your hand, and you can not discern any of the original contents.
-Whilst strictly speaking there is no need to layer the materials in a compost heap, a recipe such as this ensures that there is a good mix of different kinds of organic materials in the compost.  Even with a recipe such as this, the compost should be examined regularly and changes made wherever necessary.
-It is also often advisable to use several bins if there is a reasonable amount of organic material to be composted as it is easier to turn and mix compost from one bin to another.  'Turning' is the process of mixing the composts and allowing air to circulate around.  Turned composts are usually better than those which have not been turned.
 Regarding the types of bin, plastic bins such as the geobin system have been used to produce compost of reasonable quality, but bins made of wood or other locally available materials can be used just as effectively.   Sometimes bins have been designed with special equipment to aggitate and aerate the compost, which can also be a good way to ensure that the compost is properly aired without the user having to manhandle the compost.
@@ Line 65: / Line 49: @@
 See [[Compost_bin_manufacture_(Practical_Action_Technical_Brief)|this technical brief]] about manufacturing bins.
-===Windrow composting===
+===Industrial scale composting===
-Windrows are large compost heaps which can be hundreds of metres long.  They are usually this shape because specialist turning equipment is used to move along the whole length to turn and mix the compost.  Sometimes is also makes sense to compost in windrows even if there is to be mixing and turning by hand.
+Windrows are large compost heaps which can be hundreds of metres long.  They are usually this shape because specialist turning equipment is used to move along the whole length to turn and mix the compost.  [[Arcata_Marsh_compost|Arcata Marsh]] is an example of a large industrial scale composting plant.
 ===Farm waste composting===
 In many farm systems, animal extreta from animal houses is mixed with urine and bedding and stored in bays beneath the buildings, to be excavated and removed at a later date.  The effectiveness of this as a composting system will depend on the animals and the bedding materials used, but farmyard manure can often be used as a valuable soil amendment.  In many areas it makes more sense to remove and store the waste away from the animal houses due to problems with dust and odors.  Care should be taken when removing animal wastes from underground storage pits as there may be hazards from airborne pathogens and the material may not be adequately sanitized.
-=== Green manures and mulches ===
+==Troubleshooting==
-Green manures and mulches are sometimes thought of as composts, although they may not be.
+* Regularly turning compost to encourage the movement of air is always a good idea
-[[Green manure|'Green manure']] is the process of growing a specific crop with a view to turning it into the soil, where it will break down.  In some climates, it is often advisable to grow green cover crops in the Winter to prevent leaching and erosion of bare soil, which are then turned into the soil in the Spring.  Sometimes uncomposted green organic material is spread onto the soil surface and ploughed in.  As suggested above, this may not be ideal and a better option might have been to properly compost the material instead.
-[[Mulching_and_using_cover_crops|Mulching]] is a technique where a thick layer of material is placed on the soil surface to prevent regrowth of weeds between rows or around plants.  Although slow release materials are often used as mulches - such as leaves and wood chippings - it can often make sense to use composts as a mulch.
-Materials that are not organic in origin, such as old carpets, have sometimes been attempted as simple mulches.  Their use is not advised because even carpet made of natural fibres can take a very long time to break down in the soil and removal can be a time consuming and annoying process.
-==Troubleshooting a pile==
-* Make sure you increase the amount of air regularly by turning it over.
 * Increase surface area of materials by chopping them up.
 * If your compost is smelly it is not getting enough oxygen (going anaerobic).
 * If space is an issue (ie if you are living in a house or apartment with not much of a yard), you could try [[vermiculture]] (i.e. using a worm bin).
-* Animals (ie bears, raccoons, rats, and other animals) may become a problem if there is something in a compost pile they would like to eat. Access to compost must be restricted (ie by using a high, fully closed bin); avoiding the scraps that attract them too can help, especially meat, fish, ... scraps. As you still need to discard these somehow, you can opt to compost them anaerobically (using a biogas digester).
+* Animals (ie bears, raccoons, rats, and other animals) may become a problem if there is something in a compost pile they would like to eat. Access to compost must be restricted (ie by using a high, fully closed bin); avoiding the scraps that attract them too can help, especially meat, fish.
 ==See also==
 * [[Composting human feces]]
-* [[Biogas|Dry anaerobic digestion: a bit similar to composting]]
+* [[Biogas|Dry anaerobic digestion]]
 * [[Vermicomposting]]
@@ Line 96: / Line 70: @@
 * [http://www.richsoil.com/permaculture/160-podcast-015-compost-vegan-permaculture-native-plants/ Composting, vegan permaculture, native plants] - a podcast by Paul Wheaton and Helen Atthowe (very informative on composting)
 * [http://www.territorialseed.com/product/7190/20 Territorial Seed]
-* [http://www.groworganic.com/item_GCO350_Geobin_Home__Garden_Compost_Bin.html Grow Organic]
 [[Category:Agriculture]]

Composting: Difference between revisions