The U.S. Environmental Protection Agency (EPA), Water Environment Federation (WEF) and Association of Metropolitan Sewerage Agencies all promote biosolids recycling as an environmentally safe and cost-effective solution for managing wastewater residuals. When conducted in accordance with strict state and federal regulations, the practice benefits communities and supports environmental protection efforts with an excellent source of safe, organic nutrients.
The benefits of responsible and safe biosolids recycling are many. EPA supports biosolids recycling and encourages composting of biosolids, including advanced alkaline-stabilized, heat-treated, and pelletized biosolids, as well as less highly processed liquid biosolids and biosolids cake. Among their benefits, the use of biosolids can:
- Improve crop production
- Reduce soil erosion and protect water quality
- Provide topsoil for recreational uses
- Reclaim strip-mined lands
- Enrich forestland
- Conserve landfill space
- Provide economic incentives
Improve crop production
Composting of biosolids that meet strict quality criteria and application rates is a beneficial use. It helps improve, replenish and maintain healthy soil by adding important nutrients, boosting soil water-holding capacity and reducing topsoil runoff, all of which serve to increase crop yields. According to EPA, about half of the biosolids generated in the United States is beneficially recycled. Biosolids provide farmers with about $100 per acre worth of organic fertilizer that includes many essential nutrients not typically found in chemical fertilizers. Farmers use biosolids primarily to reduce their dependency on chemical fertilizers.
Rich in nitrogen and phosphorus, two elements essential for crop growth, biosolids also contain micronutrients such as copper, boron, molybdenum, zinc and iron. Lime-amended biosolids supply valuable lime to the fields. Replenishing farm topsoil with biosolids promotes long-term productivity.
The largest component of biosolids is organic matter. It works as a soil conditioner to promote necessary bacterial activity, loosening clay and improving the consistency of sandy soils. The improved texture of these treated soils promotes dense, healthy root growth, allowing plants to take up nutrients better. This leads, in turn, to higher crop productivity than is possible with equivalent amounts of chemical fertilizers.
Reducing Erosion, Protecting Water Quality
According to EPA, biosolid composting can reduce soil erosion and improve water quality. The organic matter in biosolids assists with binding soil particles. The result is improved soil properties, including texture and water-holding capacity, which enhances root growth and increases the drought resistance of vegetation.
Adding biosolids to soil also supplies organic nutrients that are released slowly to growing plants. These organic forms of nutrients are less water-soluble and, therefore, less likely to leach into groundwater or be carried away by streams and other surface waters. Surface-applied biosolids are less likely to pollute than are animal manures or chemical fertilizers.
Providing Topsoil for Recreational Uses
As organic fertilizer, biosolids that meet EPA’s Part 503 requirements also provide nutrient-rich materials for use on golf courses, sports fields, public parks and other recreational areas. Biosolids composted with wood chips, sawdust or yard clippings provide slow-release nitrogen and phosphorus and abundant organic matter. Biosolids compost is commonly used by landscape designers, nurseries and soil blenders for building lawns and turf, mulching plant beds, establishing new vegetation and general gardening.
Biosolids have been used successfully to help reclaim disturbed land such as coal strip mines, gravel pits, quarries, construction sites and landfills. Heavy equipment can strip away topsoil and compact underlying soils. These and other industrial activities can leave rock and subsoil exposed, contributing to runoff and water pollution. Once soil is robbed of nutrients and organic matter, plant life cannot be supported.
Using biosolids replaces lost topsoil and improves soil fertility and stability, decreasing erosion. Land reclamation projects typically use one-time or infrequent applications of large quantities of biosolids to spur plant growth and provide a long-term supply of nutrients.
Because biosolids provide a balance of quick- and slow-release nutrients and organic matter, they are preferable to chemical fertilizers for establishing vegetation. Quick-release nutrients assure rapid, reliable seedling establishment. Slow-release nutrients sustain vigorous plant growth that leads to a permanent plant community. The organic matter helps to retain soil moisture, increase soil porosity and replace lost or compacted soil.
Biosolids can increase forest productivity for certain tree species, promoting, for example, the growth of hybrid poplars and enhancing the aesthetic value of Christmas trees. Biosolids used on forestland can shorten pulpwood and lumber production cycles, particularly in marginally productive soils. Because biosolids enhance vegetation growth, wildlife populations benefit from more abundant under story vegetation that give rise to more nutritious food supplies.
Conserving Landfill Space
According to EPA, recycling biosolids can help to conserve landfill space, freeing up disposal capacity for a community’s solid wastes. Regulations adopted a decade ago have increased the cost of developing and operating solid waste landfills and have resulted in larger and more expensive regional facilities. This and often-frequent community opposition based on land-use concerns have made siting new landfills a more difficult process. Many communities prohibit the disposal of yard wastes to conserve space. As an alternative, regulatory agencies encourage the beneficial use of biosolids.
EPA estimates that beneficial use of biosolids will increase from 60 percent in 1998 to 66 percent in 2005 and 70 percent in 2010. Of the biosolids sent for disposal in 1998, 17 percent went to surface disposal/landfills. EPA expects that percentage to decrease to 13 percent in 2005 and 10 percent in 2010, with corresponding increases in composting, advanced treatment and other beneficial uses.
The recycling of biosolids through composting and other methods offers an environmentally sound alternative to disposal and can conserve landfill space. In communities where disposal costs have risen because of diminishing landfill capacity, biosolids recycling can lower a community’s waste disposal costs. These savings can be passed on to communities in reduced taxes and lower utility bills. Some communities also generate revenue from the sale of biosolids-derived compost, fertilizers and other products.