Topsoil Reconstruction

Focus

Treating subsoil to turn into nutrient rich topsoil in five years

Potential

Speeding up reclamation of disturbed lands

Introduction

In any industrial activity, from building a new house in Calgary to extracting bitumen in the oil sands, nutrient-rich topsoil is the first thing removed when a site is cleared, leaving behind the nutrient-lean subsoil. In the oil and gas industry, that nutrient-rich topsoil has to be replaced 40 to 50 years later when the project is complete. Operating companies will reclaim the disturbed land and return it to a condition that enables it to be used for other productive purposes such as farm land or natural habitat. Quality topsoil is a key requirement to make this happen.

Subsoil takes hundreds of years to turn into topsoil through natural processes such as biodegradation. One of COSIA’s member companies has developed a technology to transform subsoil into topsoil in just five years.

Technology and Innovation

Fifteen years ago, Imperial’s researchers questioned whether it was possible to speed up Mother Nature’s topsoil creation process. The goal was to come up with another way to manage the issue of a shortage of topsoil for reclamation. The question was whether there was anything one could do to use subsoil as a starting point and then amend that subsoil to create productive topsoil. This project might sound simple enough, but it is much more involved than simply taking subsoil and adding compost or green manure. As any gardener knows, evidence of compost you add to your garden in the spring is long gone by August. Bacteria and other organisms break simple organic matter down in a matter of just a few weeks or months. Researchers in the past have tried to manufacture topsoil out of subsoil and compost, but an amendment like that won’t do the trick, and any successes have been limited to the very short term. The trick to creating a perfect topsoil recipe is to combine a highly specific mix of organic and inorganic soil amendments, including some organics that decompose over a reasonably short time frame and others that take years or decades to decompose. The important piece of the recipe is to include amendments that will provide soil structure over the long term.  

The research encompassed bench scale, greenhouse and field studies using biochar (charcoal) or humalite (a low grade weathered coal) as amendments that can provide the necessary carbon but not breakdown quickly, and mimics the portion of natural soil that encourages microbial life and nutrient retention. The successful results from these studies led to a field scale application of the technology in 2012 at two Imperial lease sites to test its viability on a larger scale. The results from these two sites are successful in that one of the two sites have been granted a reclamation certificate from the Alberta Energy Regulator (AER) while application for a reclamation certificate will be submitted to the AER in 2018. While the recognition of the technology by AER paves the way for a wider adoption of the technology by Imperial and other COSIA members, future sites that incorporate this method of reclamation must have pre-approval from the regulator for site specific application as part of the reclamation certificate process.   

Barley crop growing on topsoil reconstructed using wood charcoal

Barley crop growing on topsoil reconstructed using wood charcoal

Collaboration

This topsoil conversion project is a contributed technology from Imperial Oil to the COSIA companies.

Environmental benefits

Most current practices have the topsoil cleared from a site and stockpiled for later use in reclamation. This topsoil can sit for decades degrading, causing the nutrients to leach from the soil. Having a methodology to engineer synthetic topsoil that is sustainable and of equivalent quality as native topsoil in a relatively short time will significantly speed up and improve the quality of reclamation. Additionally, having the ability to speed up the creation of topsoil will be very helpful in the reclamation of older sites where topsoil salvaging was not a requirement at the time of clearing.