Compost Magazine

Composting tips, advice and science.

Wood chips in compost.

Researchers Unveil Secrets to Effective Home Composting

30th March, 2023

Bulking agents key to effective composting – scientists identify the best ones to use

As global warming and waste management continue to dominate headlines, a team of Greek researchers has identified some of the keys to efficiently transforming food-waste into quality compost within just 21 days. 

The research highlights the urgent need to reduce the amount of food-waste ending up in landfills, where it contributes to the greenhouse effect and threatens water supplies.

Home composting is already an effective way to deal with organic waste, say the researchers, especially in areas where municipal composting does not exist. 

It creates high quality compost and diverts waste away from landfills – a factor especially important in developing regions.

At the same time it leads to improvement in local soil quality. 

However, the researchers did identify several potential problems with home composting. 

The final product can vary in quality, while the potential for smell can put people off. 

What’s more, the researchers argued that people need more training on including bulking agents in compost. 

To resolve this, the researchers set out to identify optimal but low cost bulking agents for use in compost to increase speed and aeration. 

What are bulking agents?

Bulking agents are dry, high carbon materials that are mixed in with other compost materials.

They create spaces in the compost which allows air to flow through the compost.

Read more…

Four different materials were tested:

  •  Zeolite
  • Vermiculite
  • Perlite
  • Wood chips

The researchers used a bioreactor (a closed compost vessel) to simulate home composting. 

The scientists noted that zeolite was promising for its ability to remove heavy metals from compost. 

Perlite and vermiculite increase the air pockets in the compost heap, which leads to increased temperatures. 

The study found that using bulking agents in home composting could produce compost within 21 days. However, the compost would still require further maturing before use.

Which were the best best bulking agents?

Zeolite and perlite performed the best in terms of improving nutrients and balancing the Carbon: Nitrogen ratio.

Woodchips worked well when combined with the Zeolite and Perlite, but didn’t work well on their own. 

It’s worth noting that results may be different in actual home composting. 

The researchers added a lot of material over a short time, which may not be feasible for most gardeners, and many composters don’t have access to a bioreactor.

Many composters use sawdust as a bulking agent, and this wasn’t tested in the research. Sawdust should break down more quickly than woodchips due to its smaller size.

However, the study is valuable for identifying good, cheap bulking agents to use, as well as highlighting their importance for home composting.


Margaritis et al, 2023, An Experimental Investigation of the Composting Process in an Innovative Home Composting System: The Influence of Additives

Further reading

Bulking Agents: The Key to Successful Composting?
Optimizing Oxygen: Understanding the Role of Air in Making Compost