Composting or Anaerobic Digestion?

By Ben Parry, CEO

In a recent article in The Spinoff, Kate Walmsley, a community composter in New Zealand, wrote an article headlined “Why industrial anaerobic digestion is not the answer to food waste.”   In the article, she provides a number of arguments to support her case that composting is a vastly superior solution for disposing of food scraps.

I am not a “silver-bullet” thinker.  I believe we need different technologies at different scales working together to solve the environmental problems facing our planet today.  Composting and anaerobic digestion both have important roles to play.

However, Kate’s article points out an important distinction that we must keep in mind when comparing the two processes.  The primary goal of composting is to recover organic resources to restore soil fertility.  Anaerobic digestion’s primary goal is to break down the organic waste to satisfy demand for electricity and fuel. 

Our world today faces many challenges.  Degrading soil is one we don’t often think about, but may be the most important of all.  As articulated by Michael Gove, the UK’s environment secretary, in this article from the Guardian:

“We have encouraged a type of farming which has damaged the earth,” Gove told the parliamentary launch of the Sustainable Soils Alliance (SSA). “Countries can withstand coups d’état, wars and conflict, even leaving the EU, but no country can withstand the loss of its soil and fertility.

“If you have heavy machines churning the soil and impacting it, if you drench it in chemicals that improve yields but in the long term undercut the future fertility of that soil, you can increase yields year on year but ultimately you really are cutting the ground away from beneath your own feet. Farmers know that.”

At Compost Crew, we promote aerobic composting because not only does it keep food scraps out of the landfill, it prepares these feedstocks to return critical nutrients that will help restore the health of our local soil.