I want to know the answer to the following question:
How are these gases formed?
All the background I'm provided with is that "Some such organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form H2 gas by specialized hydrogenases in the chloroplast.". Is that enough to answer the question?
Answer: yes