Put a compost pile inside your greenhouse and you get warmth and CO2 for your plants: https://www.lowtechmagazine.com/2015/12/reinventing-the-gree...

This is of no use in the developed world for a normal house. Try getting your home owners insurance to pay off a claim against an accident involving this. Also, according to its specs you can get 2hrs of cooking per day if you supply 5 gallons of animal manure. That's a tiny amount of energy compared to modern energy needs.

For most people this would be a novelty, maybe you could run an outdoor grill off of it.

I'm sure most families can gather 5 gallons of organic waste per week, which would provide them enough gas to have a BBQ once a week.