You also have to consider the risk, however small, that mirror bacteria released in the wild survive just long enough to naturally evolve to consume the common chiral form of whatever molecule. We've observed that bacteria can evolve rapidly to changing environments, so it's not out of the question.

Seems like some kind of achiral algae would actually be the most dangerous.

People forget that blue-green algae caused a global climate apocalypse, polluted the oceans and atmosphere with deadly oxygen, caused all exposed iron to rust massively changing ocean chemistry, and threw the entire globe into an ice-age that lasted 300 million years.

I wonder how we would stop something like that. It'd be like the algae bloom from hell. Plankton likely wouldn't be very successful in attempting to eat it.

The report goes into a green goo scenario, a photosynthetic mirror bacterium eating the bottom of the oceanic food web and sending stuff up the chain extinct. One scenario that they deem less likely is it sucking enough co2 out of the atmosphere to doom us to an ice age, though they couldn't rule it out.

Besides the achiral glycerol mentioned in the article, some bacteria subsist on methane. That is also non-chiral and in large quantity in petroleum and under the sea.