Cleaning up mine sites with carbon-negative bioremediation

By Moji Karimi, Co-founder and CEO of Cemvita Factory

For a long time, the remediation of closed mine sites has been a passive afterthought for mining companies, and emissions due to the remediation itself have been even less of a concern.

However, that is starting to change as more companies pledge to become carbon-neutral in the next few decades.

As we take steps towards building a cleaner world, bioremediation is proving to hold immense promise. On one hand as an effective solution to reduce or eliminate waste that is damaging to the environment, and on the other, as an opportunity to take carbon out of the atmosphere.

We should be excited about the prospects of carbon-negative bioremediation and its potential use cases. But first, what exactly is bioremediation, and how does it work?

What is bioremediation?

Bioremediation uses living organisms to treat contaminated sites. Processes typically involve the use of microorganisms for the purpose of eliminating or reducing the concentration of waste which can be hazardous to the environment.

In this process, microorganisms which are naturally occurring or, sometimes, genetically engineered for specific purposes, are introduced into the contaminated site in a controlled fashion. A range of different microorganisms can be used in bioremediation and each has the capacity to improve or restore specific environmental conditions.

For example, certain bacteria, algae, and fungi can alter the chemical composition of heavy metals. These can be used to treat acid mine drainage (AMD) as the microorganisms can degrade heavy metals and increase the PH of the waste material, eliminating the need for lime and its associated logistics.

The idea for bioremediation isn’t new, but it’s only been with the recent advancements in synthetic biology that we can apply it economically and on a large-scale.

How is CO2 utilisation changing bioremediation?

If coupled with CO2 utilisation technology, bioremediation can be carbon-neutral or even carbon-negative. This is done by engineering microorganisms to consume CO2 as feedstock and produce chemicals that are used in the bioremediation process.

CO2 can be captured through direct air capture (DAC) or separated from the flue gas of nearby industrial emission points and fed into bioreactors containing bacteria which consume CO2 and release other useful compounds. An example of such arrangements is BHP via its investment in the CO2 DAC company, Carbon Engineering.

To provide a sense of scale; Occidental Petroleum is building a DAC system with Carbon Engineering that can capture one million metric tonnes of CO2 per year (offsetting the CO2 emitted by more than 200,000 cars) for use in its CO2 enhanced oil recovery operations.

The same captured CO2 can be used in the bioremediation process (as our company Cemvita Factory does. More on that below).

At the heart of biologically inspired CO2 utilisation sits photosynthesis. Photosynthesis is a process by which plants absorb the energy from sunlight, CO2, and water to produce biomass.

The figure below illustrates the structure of CO2-consuming photosynthetic bacteria, cyanobacteria, which are being used in bioremediation after the appropriate bioengineering has taken place.

Think of this as the opposite process to a harmful algal bloom (HAB) where the algae causes negative impacts to other organisms via the production of natural toxins, mechanical damage or by other means.

Here the microorganisms (not limited to algae) are specifically programmed to consume lots of CO2 and degrade heavy metals and other toxins found in mine tailings ponds.

This is a sustainable step towards solving the problem in-situ instead of having to introduce more chemicals into the environment. Microorganisms engineered to consume waste chemicals could be an integral part of us moving towards a greener future.

Where does Cemvita Factory come in?

While mining has significantly contributed to the advancement of human development, the negative environmental impacts of mining are well published. Utilising biological mechanisms, we can reduce the impact of the mining process and decrease the time taken to return environments to their original state.

Cemvita Factory’s technology uses synthetic biology, or biomimicry, to improve the metabolic capacity of environmentally friendly (and sometimes photosynthetic) microorganisms for CO2 utilisation.

These microorganisms may be used for different purposes, including the treatment of heavy metal or acidic contamination, utilising and sequestering carbon dioxide in the process.

Cemvita Factory also has a portfolio of extremophile microorganisms that are further optimised to survive in harsh environments and are engineered specifically for bioremediation.

The company recently received investment from BHP whose chief geoscientist, Laura Tyler, expressed that: “Biomimetics have the potential to convert CO2 into useful downstream products such as chemicals and polymers, and it also holds promise for the remediation of mine sites.”

How will this impact the future of mining?

We are already witness to a number of examples of bioremediation in mining and should expect to see countless more as the benefits become more widely known and adoption increases.

More and more companies are using microbes and other methods to remove metals and other contaminants from mine wastewater, including hydrotalcite, sulphate and nitrate. After this, the water can be safely returned to the environment or recycled and reused in mine production.

With bioremediation technologies, not only can mine waste be cleaned, but CO2 is also used in the process, resulting in a carbon-negative practice, providing both a solution and an added benefit of CO2 utilisation.

This enables mining companies to have a proactive approach towards solving the problem of closed mine-site contamination instead of passively treating their tailings (with lime etc.)

Early techno-economic assessments show the possibility to treat one billion gallons of contaminated water over the course of just a few months.

The commercial uses of carbon-negative bioremediation to reduce mining waste are still in their infancy, but the future holds huge promise.

By being able to deliver from both a waste elimination and carbon reduction standpoint, Cemvita Factory hopes to stand at the forefront of this movement towards cleaner mining processes and a greener future.

Read more about biomimicry and Cemvita Factory’s work here