Is it possible to co-finance a personal grant in Europe if it doesn't meet salary conditions of the country? If one obtains a personal postdoc grant to cover a couple years of research as a full-time employee, but the value of the grant is only 60% of the union-stipulated wages in the country in which you wish to tenure it (and additionally does not include social benefits), what alternatives are available?

I can only fathom three choices, none of which seem appealing/feasible:


Decline the grant in favour of working on an existing project that covers full wages. (That seems wasteful and to forego an opportunity to further one's career opportunities as a researcher who attracts external funding.)
Convince the department to co-finance the remaining 40% of the wage as an "income supplement" out of their operational budget (That doesn't seem very likely.)
To obtain another grant from some other funding agency, on short notice, to co-finance the grant. (I'm not even sure that such actions exist, particularly at this time of year.)
As usual, rules on this sort of thing will vary from country to country and from grant agency to agency.

However, all three options that you mention sound plausible to me. To go over them:


  Decline the grant (...)


Sure. Nobody can fault you for declining a grant that pays so much below standard salaries. Honestly, unless I had no other options, this is likely what I would do. I am not sure I would call it "wasteful" to decline a grant that, honestly, sounds like a terrible option to begin with.


  Convince the department to co-finance (...)


This is indeed not unheard of. Of course, whether you will be able to convince the department to do so largely depends on how much they want you to be there, what their regulations are, and if they have money to spare. I have seen this sort of co-financing mostly in cases where the department and the applicant were already in longer contact, and the public grant was mostly acquired as a way to make a move that was happening anyway cheaper for the department (that is, it was planned that the candidate joins them anyway, but now a part is paid via an external grant). If the department had no intentions to hire you without the grant it becomes substantially less likely that they will be willing or able to chip in.


  (...) obtain another grant (...)


This sounds like another plausible option, but check the regulations of both grant agencies. In many cases, full-time personal grants are exclusive - that is, you can have only one at a time, even if the stipend is very low. However, it may still be an option to apply not for a second personal grant, but for a regular research project that allows you to pay a salary supplement for yourself. Whether this is possible again depends on the grant agency. For instance, the SNF in Switzerland as a rule never allows to pay any money to yourself as part of a regular research project. The FWF in Austria, on the other hand, is perfectly fine with this as long as the rules of the host institution (regarding, for instance, maximum employment), are followed. That being said, with this option you should probably expect to live off the 60% stipend for a while, as the application procedure for grants tends to take a while.