Compost 101: What is Compost and Where to Start?

Composting is the science and art of turning once-living organic waste into a rich, nutritious soil supplement. This article focuses primarily on composting methods you can implement in your home.

Imagine that there is a way to reduce environmental damage and turn a waste product into a fertiliser that can create lasting benefits for your soil and plants. This process is called composting. So what is compost?

Composting is the science and art of turning once-living organic waste into a rich, nutritious soil supplement. This article focuses primarily on composting methods you can implement in your home.


What is Compost?

Composting and composting is a natural recycling process. Organic materials such as leaves and food waste decompose spontaneously in nature over time and become valuable fertilisers for the soil. 

This is where composting comes into play: By accelerating this process, we support the transformation of organic matter by bacteria, fungi and other living organisms.

The resulting material is called “compost”, which resembles fertile garden soil. This compost, known as “black gold” among farmers, contains plant nutrients. It can be used in gardening and agriculture.

Organic waste can be processed in various ways, from large industrial plants to small community-based composting systems.

Why Is Compost So Important?

  • Reduces Waste Amount

Composting is a great way to recycle the organic waste we produce at home. Food scraps and garden waste comprise more than 28% of our “rubbish”. (1)

Food waste is not only a huge burden on the environment but also costly to process. Home composting allows us to divert some of this waste from landfill and turn it into a practical and nutritious substance for our gardens.

  • Reduces Methane Emissions

If the food we waste were a country, it would be the world’s third-largest emitter of greenhouse gases after China and the United States. This alone is enough to show the seriousness of the situation, because the food we waste produces greenhouse gases equivalent to about 3.3 billion tonnes of carbon, and it does this by producing methane gas in the airless environment of a landfill.

Methane has an effect 86 times more powerful than carbon dioxide. This gas is responsible for more than 25 per cent of climate change. (2) But the good news is that reducing methane emissions is one of the most effective steps we can take to help slow the rate of global warming. This benefit of composting is too great to ignore.

  • Improves Soil Health 

Composting food waste and other organic materials instead of throwing them away can contribute to the creation of nutrient-rich soil. Compost can serve as a healthy alternative to chemical fertilisers. Like pesticides, chemical fertilisers are produced with fossil fuels. Producing them causes greenhouse gas emissions, which contribute to global warming.

Generally more effective than conventional fertilisers, compost contains nitrogen, phosphorus and potassium, the three essential nutrients for agriculture. In addition to these nutrients, which are essential to support healthy soil, compost is known to improve soil structure. 

In this way, the soil can better store nutrients and water and becomes more resistant to plant diseases. As a result, this helps support crops and achieve higher yields of vegetables, flowers, fruit and other crops.

  • Provides Water Saving

When the soil experiences a lack of water, agriculture and ecology can be adversely affected. Fortunately, better water retention is one of the other environmentally friendly benefits of compost. 

Compost not only supplements the nutrient content of soils but also increases their water-holding capacity. Compost can hold 20 times its weight in water, so adding just 1% organic matter to the garden can help the soil hold thousands of gallons of extra water. In an increasingly arid world, this is another composting benefit that is needed.

  • Prevents Erosion Hazard

Drier soils are more prone to erosion, where soil is washed away by wind or rain and washed away from the landscape. As a further benefit of compost, adding compost to the soil increases the amount of organic matter, which helps to reduce erosion. 

Controlling erosion can help reduce water pollution, promote healthy plants and provide many other environmental benefits.

According to the US Composting Council, the composting process reduces soil erosion in several ways. (3) It increases water absorption, allowing water to penetrate the soil instead of being rapidly removed. 

It therefore slows down the flow of surface water. Compost also holds the soil together, especially on sandy soils prone to erosion. You can think of fresh compost as a “glue” that can hold the soil together thanks to the humus produced during the decomposition process of organic matter.

How to Make Compost: Components of Compost

Organisms that break down waste organic matter need four essential elements to survive: nitrogen, carbon, air and water. All compostable materials contain carbon, but also varying amounts of nitrogen. 

Successful composting is about using the right combination of materials. It is necessary to achieve the best carbon-to-nitrogen ratio and to maintain the right amount of air and water. The ideal carbon-to-nitrogen ratio should be 25 to 30 parts carbon to 1 part nitrogen

If carbon is high, the disintegration time is prolonged. Too much nitrogen-containing material can create a slippery, wet and foul-smelling pile. These problems can be easily solved by adding carbon or nitrogen-containing material, as needed.

  • “Green” Ingredients for Nitrogen

Nitrogen is an essential element for the growth and reproduction of plants and animals. A higher nitrogen-to-carbon ratio is usually found in fresh organic materials. Some green household materials include waste grass, food scraps and coffee grounds.

  • “Brown” Ingredients for Carbon

Carbon is also vital and is found in brown plant material. Carbon is the food source for decomposers. Brown materials include dead leaves, twigs and paper.

  • Oxygen and Water

Decomposers, like other organisms, need oxygen and water. For fast composting, it is necessary to provide the right amount of air and water. Optimal air flow can be achieved by layering materials, dividing materials into small pieces and turning the piles regularly. The ideal pile should be wet like a squeezed sponge in terms of water.

  • Heat

Hot composting is a process in which green and brown materials, with a balance of air and water, create ideal conditions for the growth of aerobic organisms. Aerobic organisms (species that reproduce in oxygenated environments) reproduce by breaking down waste, with an optimum temperature between 54 and 60 degrees Celsius. 

  • Regular Ventilation

Aeration promotes an aerobic environment, which speeds up the composting process and reduces odours. It is recommended to aerate your pile once a week in summer and every three to four weeks in winter. You can increase the natural airflow by adding pipes or large rods.

  • Maintaining Humidity Level

Moisture is essential for composting – your pile should always have the texture of a squeezed sponge. A pile that is too dry can slow composting, while a pile that is too wet can create an anaerobic environment, cause bad odours and slow decomposition. If your pile is dry (or add more wet material), water it; if it is too wet, add carbon-heavy brown materials.

  • Size

The ideal size for a compost bin or heap is 0.9 cubic metres. To add food or garden waste to your bin or heap, first cut it into smaller pieces. The smaller the pieces, the faster the decomposition. The main rule is not to add anything thicker than a finger thick.

  • Location

The ideal compost location is a dry and shady area. If you live in a damp location, avoid placing your pile under gutters or in places with poor water drainage; otherwise, the pile can get too wet. If you live in a sunny location, find a shady spot so the compost does not dry out too quickly and you do not have to add water constantly.

  • Compost Start-up and Maintenance

To build your pile, add the green and brown materials alternately in thin layers and finish the last layer with brown. You can keep adding materials until you reach the best height of 0.9 metres. 

Add water to the pile as needed as you layer it. Then leave the pile for four days to allow initial decomposition. You can then ventilate it regularly and check the humidity level.

What Can You Compost? 

  • Waste grass
  • Withered leaves and small twigs
  • Wood chips and sawdust
  • Saman 
  • Fruit and vegetable waste
  • Coffee grounds, filters, tea bags
  • Cardboard rolls
  • Waste in the dryer and vacuum cleaner hopper
  • Fireplace ash
  • Waste from houseplants
  • Nuts in the shell
  • Shredded newspaper
  • Cotton and woollen cloths

What You Cannot Compost? 

  • Dairy products. May cause odour and attract harmful organisms.
  • Medicated garden residues. Chemicals can kill beneficial compost organisms.
  • Coal or barbecue ash. Both can contain substances that can be harmful to plants.
  • Plants that are diseased or infested with insects. 
  • Pet faeces. It may contain parasites, bacteria or microbes harmful to humans.
  • Meat scraps or fish bones. They can cause foul odours and attract harmful organisms.
  • Twigs or leaves of the black walnut tree. May release substances harmful to other plants.
  • Vegetable oil, animal fat or any type of used fat. It can cause foul odours and attract harmful organisms.