My, my, my how quickly people are to throw out the constitutional rights of others. This is a litmus test of how people are willing to stomach civil rights. Not saying this is how I would handle it, but does say something about how quickly society is to abandon things when it doesn't suit their tastes.
Also, just being an approved business does not mean Carte Blanc do as you see fit. Residential and business areas next to each other have to coincide. If people are complaining of smells (odors), that is a nuisance and likely against land use regulations (ie, a citable violation). It does not need to exceed an air quality limit to be a violation either....
Growing up in farm country, this kind of protest is MILD
Averial, here is my advice:
1. Make sure at least on of your signs has a political message such as "Screwed by Town of Meredith", etc. If the Town is dumb enough to question your tactics, immediately contact the NH ACLU. The town would quickly find out they have no leg to stand on.
2. Make sure you file all complaints with the town. File an appeal with the ZBA and do it quickly as there are time limits.
3. If anyone is on your property, do not confront them and just call the police.
4. The next time during daylight hours call in when you smell what you believe to be the odor. Document, document, document. Fill out the paperwork at town hall.
5. If the Town plays silent on this, get a lawyer. If the smell is leaving that property you can seek damages.
You'll probably be labled a troublemaker, etc but stand your ground. Long live the "little guy"!!