1. How many biogas systems were in operation in the U. S. in 2017?

2,200 operational biogas systems

Biogas systems turn organic material into soil amendments and gaseous fuel by using anaerobic digestion, a natural, biological process in a sealed tank. There are more than 2,200 operational biogas systems in the U.S. today with the potential for over 13,500 new systems to be built

Explanation:

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As of August 2017, AgSTAR estimates, 250 manure anaerobic digester biogas recovery systems were in operation at commercial livestock facilities in the United States. The full potential to provide renewable energy is much greater: an estimated 8,100 U.S. dairy and swine operations could support biogas recovery systems.

Explanation:

the glands which are associated with each description is given below:

answer denitrification;