Engineered microbes could tackle climate change – if we ensure it’s done safely

As the climate crisis accelerates, there’s a desperate need to rapidly reduce carbon dioxide levels in the atmosphere, both by slashing emissions and by pulling carbon out of the air.

Synthetic biology has emerged as a particularly promising approach. Despite the name, synthetic biology isn’t about creating new life from scratch. Rather, it uses engineering principles to build new biological components for existing microorganisms such as bacteria, microbes and fungi to make them better at specific tasks.

By one recent estimate, synthetic biology could cut more carbon than emitted by all passenger cars ever made – up to 30 billion tonnes – through methods such as boosting crop yields, restoring agricultural land, cutting livestock methane emissions, reducing the need for fertiliser, producing biofuels and engineering microbes to store more carbon. According to some synthetic biologists, this could be a game-changer.

But will it prove to be? Technological efforts to “solve” the climate problem often verge on the improbably utopian. There’s a risk in seeing synthetic biology as a silver bullet for environmental problems. A more realistic approach suggests synthetic biology isn’t a magic fix, but does have real potential worth exploring further.

Engineering microorganisms is a controversial practice. To make the most of these technologies, researchers will have to ensure it’s done safely and ethically, as my research points out.

What potential does synthetic biology have?

Earth’s oceans, forests, soils and other natural processes soak up over half of all carbon emitted by burning fossil fuels.

Synthetic biology could make these natural sinks even more effective. Some researchers are exploring ways to modify natural enzymes to rapidly convert carbon dioxide gas into carbon in rocks.

Perhaps the best known example is the use of precision fermentation to cut methane emissions from livestock. Because methane is a much more potent greenhouse gas than carbon dioxide, these emissions account for roughly 12% of total warming potential from greenhouse emissions.

Bioengineered yeasts could absorb up to 98% of these emissions. After being eaten by cattle or other ruminants these yeasts block production of methane before it can be belched out.

Synthetic biology could even drastically reduce how much farmland the world needs by producing food more efficiently. Engineered soil microbes can boost crop yields at least by 10–20%, meaning more food from less land. Precision fermentation can be used to produce clean meat and clean milk with much lower emissions than traditional farming.

If farms produce more on less land, excess farmland can be returned to nature. Wetlands, forests and native grasslands can store much more carbon than farmland, helping tackle climate change.

Synthetic biology can be used to modify microbe and algae species to increase their natural ability to store carbon in wetlands and oceans. This approach is known as natural geoengineering.

Engineered crops and soil microbes can also lock away much more carbon in the roots of crops or by increasing soil storage capacity. They can also reduce methane emissions from organic matter and tackle pollutants such as fertiliser runoff and heavy metals.

Sounds great – what’s the problem?

As researchers have pointed out, using this approach will require a rollout at massive scale. At present, much work has been done at smaller scale. These engineered organisms need to be able to go from Petri dishes to industrial bioreactors and then safely into the environment. To scale, these approaches have to be economically viable, well regulated and socially acceptable.

That’s easier said than done.

First, engineering organisms comes with the serious risk of unintended consequences. If these customised microbes release their stored carbon all at once during a drought or bushfire, it could worsen climate change.

It would be very difficult to control these organisms if a problem emerges after their release, such as if an engineered microbe began outcompeting its rivals or if synthetic genes spread beyond the target species and do unintended damage to other species and ecosystems. It will be essential to tackle these issues head on with robust risk management and forward planning.

Second, synthetic biology approaches will likely become products. To make these organisms cheaply and gain market share, biotech companies will have an incentive to focus on immediate profits. This could lead companies to downplay actual risks to protect their profit margins. Regulation will be essential here.

Third, some worthwhile approaches may not appeal to companies seeking a return on investment. Instead, governments or public institutions may have to develop them to benefit plants, animals and natural habitats, given human existence rests on healthy ecosystems.

Which way forward?

These issues shouldn’t stop researchers from testing out these technologies. But these risks must be taken into account, as not all risks are equal.

Unchecked climate change would be much worse, as it could lead to societal collapse, large-scale climate migration and mass species extinction. Large scale removal of carbon dioxide from the atmosphere is now essential.

In the face of catastrophic risks, it can be ethically justifiable to take the smaller risk of unintended consequences from these organisms.

But it’s far less justifiable if these same risks are accepted to secure financial returns for private investors.

As time passes and the climate crisis intensifies, these technologies will look more and more appealing. Synthetic biology won’t be the silver bullet many imagine it to be, and it’s unlikely it will be the gold mine many hope for.

But the technology has undeniable promise. Used thoughtfully and ethically, it could help us make a healthier planet for all living species.