Have you talked to your boss about it?

Do you have to use Facebook or Instagram? What about LinkedIn?

It is very stressful when a company requires you to write content for marketing/advertisement/promotion of the company in your own social media accounts like Facebook and Instagram - How can they require you to do this? What country is this?

Well, at least you have an excuse if your boss catches you on Facebook during work hours.... ;-)

You say your employer's goal is to recruit volunteers. Is recruiting volunteers a central part of your role at the org? If so, then I would set about demonstrating to your employer that you're able to bring in the necessary number of volunteers without involving your personal media. If not, then a frank discussion about the boundaries between your personal and professional life is probably in order.

If they are looking for volunteers then don't volunteer if you don't want to.

@DJClayworth unless you're being "voluntold" - it's voluntary but with very heavy pressure to do it.

Non-profit corporation sounds so wrong.

“creating new Instagram/Facebook account..and fake it like it's your actual accounts you use everyday” — I believe the kids call it Finstagram.

By "writing content" do you mean your personal authorship?

Asking volunteers to do so is one thing, requiring workers to do it is a very different thing. I do not think you are under any obligation to comply (but check your contract and the applicable laws) but I think the best way of solving the problem is running away from such employer as soon as possible.

Related: workplace.stackexchange.com/q/50368/325

Possible duplicate of Is creating a professional Facebook account considered suspicious?

@TomášZato Non-profit corporations are common in the US.

@TomášZato In the U.S., many, if not most not-for-profit organizations are set up as corporations. 'Corporation' has to do with how it's managed and its legal status (i.e. it can sue or be sued and the members have a significant degree of protection from being personally sued for the organization's actions) rather than its profit motive or lack thereof.

What happened when you said "no" to your employer?

Facebook and Instagram require a personal account before it can "manage" a company account. This is all the OP is referring to. Ya, its a dumb practice by Facebook et al, but it's the way it is. I... simply made a fake account and use that to manage the company profiles. Easy.

What do you not understand in word 'personal'?

@DanubianSailor there's no such thing as not a "personal" account on Facebook. There's accounts, and some can be setup to "Manage" company "Pages". It's just a login that identifies a user. There's no rule saying it has to be a real Facebook account... just make a new one that you don't use for anything else!