Definition of composting:

Composting is a process in which microorganisms break organic material down into smaller parts.

What is composting?

Composting is a subset of biodegradability; it refers to materials that biodegrade under certain conditions and within a specific time period. Many materials are biodegradable, though this process can sometimes take centuries. For a material to be compostable, it must break down under certain conditions (e.g. temperature, humidity, aeration) and do so in less than 12 weeks (though this can be slightly longer for certain types of industrial composting).

 The most common type of composting is done at home, in the garden. This involves placing organic matter into soil, where it then decomposes. Industrial composters are also widely used: these can process large quantities of materials under tightly controlled conditions.

Why is composting important?

The world generates over 2 billion tonnes of waste every year, and more than 33% of this is not processed in an environmentally safe way. Developing a circular economy, in which materials are reused or safely reabsorbed into the Earth, is therefore a major priority for governments, organizations, and individuals all over the world.
Composting food and other organic materials leads to significant reductions in methane emissions. The compost produced also has numerous benefits: it increases crop yields, improves water retention in the soil, and sequesters carbon.

How does composting work?

In the composting process, microorganisms eat organic waste and break it down into smaller parts. As the organic matter decomposes, nutrients like nitrogen are released back into the soil. Once everything has biodegraded, we are left with something known as “humus compost”.
When it comes to industrial composting, there are three main types:

  • Windrow composting: an open-air process in which compost is placed in long piles known as “windrows”

  • In-vessel composting: where organic materials are placed into a large drum, silo, or similar container. These interior conditions allow for careful control of temperature, moisture, and aeration

  • Aerated static pile composting: this process involves organic waste being placed in a large outdoor pile. Bulking agents are then added to the mix to improve airflow, and the piles are placed over a network of pipes that blow air in and out of the pile

What are the challenges associated with composting?

Whether composting at home or in an industrial setting, people face the same essential challenge: keeping conditions at the right levels. The ratio of carbon and nitrogen must remain in balance: too much nitrogen starts to rot the compost, and too much carbon means that composting can’t take place. Temperature, water levels, pH levels, and sufficient aeration are other important considerations.

What is the future of composting?

The coming decades will see huge progress towards our goal of a circular economy. This will involve the production of new items that are fully compostable, such as shoes made from organic material. Items like this are already on the market, but we expect this trend to continue – and for consumer costs to decrease – in the coming years.

Find out more about Stahl’s contribution to the circular economy here.

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