Nothing to do with heating, but

So we are catching up with the third world.
About 42 years ago I lived in India for 6 months.
There was something referred to as "Gobar? Gas Plants" (digester).
Simply take a 8' diameter open tank and bury or berm it into the ground. Then take a 7.5' domed tank, turn it upside down and stick it into the 8' tank. With a trapped opening under the water line you throw in all the cow dung you can collect. Add a little water. Plus put the family toilet above it, (squatter floor opening), so all night soil and urine ends up in the tank. Top tank was painted black for solar gain. Eventually methane was produced and captured in the upper dome of top tank. The methane gas would be pressurized and attempt to raise the upper dome. A 1/2" pipe tap on that and the gas could be used for cooking or lighting.

This may sound like an insignificant issue. But it had several purposes.
1: It produced cooking gas, without this the women and children had to walk miles to collect firewood (we would call kindling here) to cook meals. They had to travel farther every day as the fuel became scarce, leading to more deforestation of a country that was once partly forested.
2: Also the digester produced sludge that was richer fertilizer than raw manure.
3: Manure was no longer being burned for cooking, (imparts a unique flavor to your chapattis and dal (lentils).
The smoke put off by burning dried dung caused a severe eye irritation leading to blindness in some cases, let alone simple air pollution.

Cow dung was a coveted commodity in that part of the world.
In New Delhi you could buy yogurt in a dish made of leaves. As you walked down the street eating it with your own traveler spoon a cow was following you. When done you dropped the leaves on the ground and the cow quickly ate these up, as with any organic item that hit the ground. Banana peels etc. The lower caste "collectors" followed the cow waiting for the deposit on the pavement. This was quickly gathered up barehanded and put into a basket. At the end of their day the soft dung was made into patties (again by hand) about 10-12 inches in diameter and stacked for drying to be sold as fuel. There would be cone shaped stacks going up to 10' high for drying.

Then there was the "night soil people" possibly the lowest caste. They were not usually seen during the day. Hotels and houses in the city had the toilet on the top floor. Just some form of catch basin for your use. Early morning, before sunrise, the night soil people would come and collect it to be taken away and never seen again.

And those Sacred Cows we in the west can not understand, they would return to their barn looking for real food/feed at night and get milked and again in the morning before they were set out to the streets to wander unmolested. A native friend told me that after the cows no longer produce milk or calves they are sold to the Muslims, who appreciate beef. This is not an advertised transaction or widely know to the locals.

Well after this trip thru many countries, one understands why we have plumbing and sanitation codes. I painfully gained immunities to many "bugs" and seldom suffer any aliments that might put others down.
We here take so much for granted.....but think about the fact that you can go to 98% of this country, drink the water and not get deathly ill.......far from it in many parts of the world.
We push a lever and our "night soil" goes away and hopefully never shows up to plague us again.
We don't know how good we have it.

I better go before starting another chapter..