Biosolids, aka domestic wastewater (sewage) treatment solids, is pretty interesting stuff, to me anyway. From a soil scientist's perspective it is chock full of good stuff: Essential plant nutrients and humic substances (humic acid, fulvic acid) beneficial to soil quality. Biosolids is superior to chemical fertilizers from both a crop production perspective and an environmental protection perspective.
This is not raw sewage solids or raw septic tank solids. This is the microbial biomass solids produced during the time the sewage is being treated, usually a 20-30 day process, prior to the treated liquid being discharged to a surface water body. These solids have about the same ratio of N:P:K:S present in soil microbial biomass.
Since the 1972 Clean Water Act, USEPA has been encouraging treatment facilities to give preferential consideration to recycling the soil property enhancing constituents in biosolids. These constituents were originally derived from crops grown on agricultural land and federal legislative intent is to see these materials recycled and put to beneficial use at their source. At the basis of this intent is a conviction that the overall benefits of beneficial use exceeds the added economic and regulatory burden placed upon the local and regional taxpayer and the wastewater treatment ratepayer.
Because of costs to transport material beyond the reach of urban sprawl, it would be cheaper to dispose of it in the ocean, or, for interior cities, in a landfill.
The constituents within biosolids are derived from nonrenewable resources and energy intensive processes and, being a regulated material under the authority of the federal government, cannot responsibly be allowed to be simply discarded when the opportunity for beneficial use is available. This policy makes more sense with each passing year.
Critics and skeptics of beneficial reuse on farm land abound, but fears of environmental degradation have yet to be borne out by events.
Once I had the opportunity in the 1980's to ask the then-President of the Washington State Farm Bureau why the American Farm Bureau Federation had a policy in opposition to land application of biosolids on farmland. He was a respected, retired soil scientist, and I asked for a science-based explanation. Instead, he explained that the national Farm Bureau was using their opposition to biosolids to persuade legislators to address burdensome regulation of farmers related to wetlands and surface water quality. They correctly recognized that Farm Bureau support was valuable and wanted a quid-pro-quo accommodation or to at least be able to make a statement.
You have to respect this point of view. It may not be science-based but its not off base either. That Farm Bureau fellow was just staying in character.
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A German soil science research center reports that Precision Agriculture has not delivered on promised benefits, stating: