Ryland Grace got me researching what a UNESCO conference even does and why he would be invited to speak at one. Most of the org's website seems to be problem-solving and application-oriented so I'm not sure if his paper (which we don't know anything about except it's on the topic of non-water-based lifeforms) would even apply in an organization like that.
Googling microbiology on their website doesn't seem to include speaking events. It's mostly news on their microbiology prize, but that requires a lengthy nomination process, so I don't think that's what he was there for because it means the rest of the field would have to know and agree with what he's presenting, which we know they did not.
When you broaden the search to just biology, you get more articles on scientists and their stories eradicating diseases and providing resources/education to smaller, underdeveloped regions. But that's not really what his research was geared towards, since he was focused on extraterrestrial life.
After browsing their website a bit, it seems the most likely option is along these lines:
The webinar will begin with brief opening remarks from the organizing partners, followed by short presentations from invited speakers representing different areas of expertise across environmental health, exposomics, and cellular biology. The event will conclude with a moderated panel discussion bringing together the speakers and additional experts to reflect on future directions for interdisciplinary collaboration.
Format
Opening remarks from UNESCO, the Human Cell Atlas, and the Global Exposome Forum
Four talks (10 minutes each)
Moderated panel discussion with speakers and experts
Audience Q&A
^ thats from an event announcement on microplastics. It seems likely that Grace was employed at some lab (maybe private or academic), then sent to represent them. It explains why he could present his case despite people disagreeing with him, and why he got fired for being rude because it reflects badly on the institution since they sent him specifically to represent them for collaborative purposes. I also assume the guy he called a staggering waste of carbon would be one of those "organizing partners" mentioned, but he could also be some other expert brought on by the assembly.
From a writing perspective, it's interesting how UNESCO is geared towards helping the world (you can argue about its effectiveness but that's still the organization's goal), and Grace agreed to attend and present there, but it was also his disastrous behavior that ran him out of academia for years until he was chosen for the Astrophage crisis. Not sure how intentional that is from Andy Weir, but you can find thematic relevance there. Call it foreshadowing or parallelism, but the point is that Grace wanted to help people but his personal issues (be it his foul attitude or cowardice in the face of his field's scrutiny) prevented him from doing so.