Back when I was in grade 6, in the late 80s, we had a unit on China. One of the films we watched (we watched actual film reels back then) showed the lifestyle in a small, Chinese, rural home, about 200 square feet, with an attached pig pen. At the top of the pen was a metal, inverted funnel which had metal piping leading to a storage tank. The film claimed that the methane was collected throughout the year and used for special occasions, such as lunar New year. The reason why I remember it was because I was fascinated by complex systems as a kid and thought the whole thing was clever. Think of the 11 year old who takes apart cameras and puts them back together. It was neat.

As to your comment about racism, you don't know me and that's quite a leap to make when I'm mentioning a piece of educational material from my childhood. My mother in law grew up in rural Bosnia, without electricity and without running water, raising animals and working a small plot of land with family, so to say that people didn't live with livestock 30-40 years ago is kind of ignorant, in and of itself. It's still how some rural areas are today, around the world.

I have close family members who went from rural, low-mechanization subsistence farming to technology driven, 21st century urban living. The contrast between the two lifestyles is crazy. Mind blowing.