SUCCESS STORIES - City of San Luis Obispo

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1. Voluntary Activities that Merit the “Completing the Cycle Award”


The City of San Luis Obispo merits the “Completing the Cycle Award” for its commitment to recycling of their organic waste streams. In May 2001, the City Council of San Luis Obispo made a concentrated effort to compost the biosolids generated from the city’s wastewater treatment plant operations. Prior to 2001, this material was trucked to the Central Valley and land applied. Provided an option with the opening of the Engel & Gray Inc Regional Composting Facility, the council voted to begin composting this waste material. This decision to further process the material through composting was a profoundly environmental friendly decision. The process of composting these biosolids converts the material into a humus-based compost product that is created from the decomposition and recombination of various forms of organic waste material such as leaves, grass, wood, and agriculture waste. Organic matter is absolutely essential to the sustenance of soil fertility. Inherent in these decaying dead residues are the living microorganisms (bacteria and fungi) that decompose, or digest, them in the composting process. The result is humus. As humus is formed, nitrogen becomes an integral part of its structure. Since the nitrogen and other essential nutrient compounds in humus are resistant to decomposition, this is nature’s way of stabilizing these important resources in the soil. They are absorbed and digested slowly by soil organisms, rather than being rapidly dissolved and dissipated.


Once the compost is added to the soil, the humus acts as a source of nutrient absorption and exchange for plants in the soil. As plant roots grow through the soil in search of nutrients, they feed off the humus. The root actually "trades" with the humus, exchanging some of its positively charged hydrogen ions for positively charged nutrient ions adsorbed onto the surface of the humus. An active exchange takes place between humus and roots. The plants "choose" which nutrients they need to balance their own internal chemistry. The addition of the compost helps stabilize the nutrients existing in the soil, making them more readily available for exchange by plants.


2. Environmental Benefits of the Activities


The environmental benefits of this program are truly significant:

1. The use of compost is much more effective and efficient than the direct land application of the biosolids.

2. Biosolid land application without prior composting could lead to runoff pollution.

3. Composting kills the harmful pathogens, stabilizes the nutrients, and provides another layer of environmental control of the agricultural process. Once the material is composted the benefits are:

4. Substantial reduction in the use of synthetic fertilizers

5. Improved the water holding capacity of the soil, reducing leaching and therefore preventing the contamination of underground water and runoff water sources (often called “non-point” pollution).

6. By increasing soil fertility, water demand is reduced, which in turn reduces precious irrigation water consumption.

7. Long-term compost use can reduce soil-borne pests, thus reducing the use of pesticides.

8. The use of compost reduces soil erosion.

9. The composting process kills pathogens in the waste material.

10. Compost replenishes nutrients in the soil and increases soil fertility.


3. Benefits to the Goals of Recycling


The conversion of this former waste material to compost helps to “complete the cycle” by recycling. Recycling, as the word implies, is a cycle. It is comprised of three steps represented by the familiar “chasing arrows” symbol: collection, processing/composting, and purchasing. The city of San Luis Obispo has completed the cycle by participating in the collection of organic material for processing into compost, and in so doing, has demonstrated a true commitment to protecting and preserving the environment to the benefit of the entire Central Coast.


  AMERICA  RECYCLES  DAY,  NOVEMBER  15TH

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