Upvote:3
Just because you're not getting paid doesn't make you a volunteer. This is why there are usually different visa schemes for genuine volunteering for a charity and non-paid work (e.g. unpaid internships or au-pair), and each of these will have different requirements. For Denmark:
Many people in your situation presume that if you don't get money, it's not "work", but work of a set number of hours a day for a non-charitable entity (farm, hostel, etc.) in return for non-monetary payment (i.e. room and board) is work under the law in many countries, including Denmark, no matter how much travellers would like it to count as "volunteering", or how many people tell you they did it and didn't have any problems.
Your risks:
There are some grey areas, of course. Things to consider:
For example, if as part of your travels you spent a couple days on a farm where you helped gather the vegetables that would be used to cook dinner, then helped cook dinner for you and the family you're staying with, that might arguably be part of some sort of cultural experience learning about farm life and local cuisine.
If you plan to spend your entire holiday on a farm working 4-5 hours a day harvesting vegetables in return for your accommodation, that will be considered work.
Probably your best bet is to find some sort of homestay scheme where you pay for a room in a house, living and eating with a family. This can often be much cheaper than a hotel particularly where food is included. If you just want to experience staying on a farm, the Danish word you're looking for is "bondegΓ₯rdsferie"-- a paid experience, but again could work out cheaper than hotel plus you may get to pet a cow. You can certainly help out with incidental chores in a homestay or farmstay situation e.g. helping to feed the horses or doing a few dishes.