we have quite a lot of it here in Germany. Most wastewater treatment facilities collect the sludge and let it ferment in order to produce gas. As a side effect the fermentation also gives off a lot if heat which is used to heat both the facility and any nearby houses, hospitals, schools etc.
In an asparagus farming area in my region they even give some asparagus beds a floor heating, resulting in an earlier harvest. In my opinion his practice is rather irresponsible as long as there are humans who can hardly afford proper heating. I therefore boycot this unnaturally grown asparagus and rather wait 4 weeks longer for the real thing (which is tastier anyway)