Compost Magazine

Composting tips, advice and science.

Plants growing in a raised bed enriched with biochar.

Scientists Find Biochar Improves Compost Speed and Quality

1st Feb 2023

Have you ever wished your compost would break down faster?

A recent study might have the answer for you! A study by Wang et al has found that adding biochar combined with bacteria to compost can speed up the process.

That’s not all! They also found it reduced emissions and improved the quality of the finished compost.

What the study tried to solve

Composting has long been an effective way to dispose of organic waste in a sustainable manner while also benefiting the soil.

However, Wang et al argued that it also has some drawbacks – namely, low compost quality and greenhouse gas emissions.

(The argument that compost is low quality could be a bit broad reaching! Low quality compost could be down to poor composting techniques which are common, rather than the composting process itself. This includes allowing the heat to rise too high in the thermophilic phase or not allowing the compost to mature for long enough.)

The study pointed out that we already know biochar has a number of benefits for composting. These include:

  • Reducing gas emissions
  • Improve the environmental conditions of the heap
  • Reducing emissions
  • Increasing nutrient retention, moisture content and total organic carbon content in the mature compost
  • Reducing nitrogen loss and increases organic matter degradation

The study aimed to look at whether it can be improved further with the addition of microorganisms.

What is biochar?

Biochar is a carbon-rich material that is produced by pyrolysis (heating in the absence of oxygen). It has a high surface area, which makes it ideal for adsorbing nutrients and water.

Adding biochar to compost can help increase its porosity, aeration, and water retention. In turn, this can improve both the speed and quality of composting.

What did the study do?

This study compared the effects of adding three additives to sheep manure and composting it for 28 days.

The compounds were:

  • a compound microbial agent
  • biochar
  • biochar with a microbial agent supplement

Researchers evaluated the effects on nitrogen transformation, greenhouse gas, ammonia emissions and bacterial communities.

What were the results?

The study found that adding biochar with a microbial agent had a number of benefits. These included

  • Prolonging the thermophilic (hot) stage of composting
  • Increasing the ability of organic material to break down
  • Improving the physical properties of the compost by preventing large clumps
  • Promoting compost maturity
  • Reducing emissions by between 42 and 67%.

What does other research say?

A 2019 study by Awasthi et al also found that biochar combined with bacteria had a number of benefits. These included reducing emissions, preserving nutrients and improving the amount of carbon and nitrogen in the finished compost.

Wrapping up

This study is new, and it would be good to see further research into this area. In the meantime, composters can still benefit from biochar by adding it to their compost to speed it up.

Read more:

Biochar in Compost
16 Easy Ways To Speed Up Your Compost