Which condition is a result of using an anaerobic digester?
a. increase in the road quality by coating with material from the anaerobic digester
b. increase in land fertility due to the addition of the nitrogen and phosphorous byproduct
c. increase in pulmonary diseases due to poor air quality from gases produced in cooking and heating
d. increase in the number of cattle supported by a given area of land

b. increase in land fertility due to the addition of the nitrogen and phosphorous byproduct

Anaerobic digestion is a process by which microorganisms breaks down complex biodegradable materials into simpler products, in the absence of oxygen. The anaerobic digesters hold the manure or any another form of organic matter which needs to be decomposed off in the absence of oxygen allows the extensive growth of microbes in it. The partially digested biodegradable waste in the form of slurry can be distributed over an agricultural land which can be useful in adding up the organic matter in the form of organic nitrogen and organic phosphorus produced as byproducts. The organic nitrogen and organic phosphorus are important elements are important for plant growth and development. Hence, the waste will increase the fertility of the land.  

c is the correct answer hope this !