Biosolids are inefficient pollutants, reader says

Published 8:31 am Friday, March 6, 2009

To the Editor:

On Feb. 21, The Tidewater News reported, “The reason a farmer would be interested (in biosolids) is that it’s basically a free fertilizer.” (“Biosolids may return to SoCo farms,” Feb. 22) That is true, but it is also the most inefficient fertilizer in common use.

If a corn crop is fertilized with chemical nitrogen fertilizer, the grain harvested from the field contains about 100 pounds of nitrogen, so about 20 pounds of nitrogen are released to the environment, mostly pollution.

In the case of sewage sludge, Nutrient Management Plans are written on the basis that only 30 percent of the nitrogen is plant-available the first year. This is unavoidable, because it takes time for microbes to decompose the organic material in the sewage sludge (or poultry litter) and make the nitrogen and phosphorous available for plant growth. Therefore, to supply enough nitrogen for plant growth, 400 pounds (120/0.3) of nitrogen are applied. This means that 300 pounds of nitrogen are released to the environment. Although some of the nutrients will be consumed by crops in subsequent years, the pollution is tremendously increased over responsible chemical fertilization. Nutrient Management Plans are “nitrogen-based” and so phosphorus is massively over-applied, especially if poultry litter is used.

The economics of cheap disposal of an unwanted waste and the mantra of “free fertilizer” currently trump water quality concerns by either Virginia or Environmental Protection Agency. Agricultural fertilization practices are the largest source of nitrogen and phosphorus pollution of Chesapeake Bay, an undisputed fact that has been known for decades.

Unless the efficiency of agricultural fertilization is considerably improved, it is impossible for water quality to improve. Banning the land application of animal wastes is an easy, cheap first step, which would affect only a few percent of Virginia farmers. Animal wastes are better used as biofuels.

Lynton Land