See my post #70!
Will add that at least one big compost-producer ("Wipptal Biogas," located in the Italian province of South Tyrol) that processes chiefly animal dung (in large tanks) always captures the resultant CO2 and boasts that it is used to make carbonated drinks.
"By processing solid livestock waste and liquid manure, associated greenhouse gas emissions (e.g., methane and CO2) can be significantly lowered beginning right at the level of animal husbandry. The deposition of the fermented material onto meadows and fields reduces nitrate contamination and ammonia emissions. [...] Thanks to the use of the latest technologies, the highly purified liquefied carbon dioxide derived from the biogas fulfills the quality standards of international beverage and food manufacturers. The possible applications of highly purified, liquefied CO2 range from the production of carbonated soft drinks, the enrichment of the air in greenhouses to accelerate photosynthesis, all the way up to the production of dry ice."
Regards,
YUCK, OMG!! That is enough to turn anyone off of soda!!!