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The N-Viro process is a patented biosolids stabilisation technology licensed to Bio-Recycle within Australia, New Zealand and Singapore.

The process produces a valuable and versatile soil-like material which is widely used within agricultural, landscaping and land rehabilitation markets.

Worldwide, more than 40 facilities in the U.S., Canada, the United Kingdom, Australia and Belgium produce over 1,000,000 tonnes of N-Viro Soil™ each year.

The N-Viro process is approved by the NSW EPA as a Grade A biosolids stabilisation process. It utilises a high pH, high temperature, high solids process to pasteurise, rather than sterilise, the biosolids. Within the process, alkaline and mineral reagents are combined to induce a number of ‘stresses’ within the biosolids. Specifically, the N-Viro process utilises dry by-products such as cement kiln dust (CKD), quick lime, agricultural lime, power station fly ash, lime kiln dust (LKD) and evenwood ash and spent lime from water treatment to induce the chemical and physical changes within the biosolids. The great surface area of the combined alkaline reagents is also able to deodorise the biosolids material.

Following the addition of these alkaline reagents to either digested or undigested biosolids, a number of changes rapidly occur. The pH of the biosolids is raised to 12 or greater, and remains at that level for 72 hours. During at least 12 hours of this initial 72 hour period, the temperature within the biosolids is raised to between 52†C and 62†C by the exothermic conversion of CaO or MgO to their hydroxides. After 72 hours, the combined solids content of the mix will have risen to 50% or greater. A second variation to the process raises the pH of the biosolids mix to 12 or greater for 7 days, or until the solids content of the mix reaches 60%. The mix should then be air-dried for at least 30 days to further raise the solids to at least 65%. N-Viro Soil is now ready to be applied to the soil.

The combined effect of the chemical and physical changes induced within the biosolids alters the biological nature of the biosolids. As a result, desirable species of bacteria are preserved as an aid against future re-infection. Once produced, N-Viro Soil may be stored in the open without threat of biological re-invasion.

N-Viro Soil offers many benefits to the market place. These include:

  • Improvement of soil structure and hence drainage and water retention.

  • Neutralisation of acid soils.

  • Supply of both macro (N, P, K, S, Ca) and micro nutrients to the soil.

  • Soil-like physical, chemical and biological properties.

N-Viro Soil has been utilised within many land application projects. In addition to having a lower concentration of harmful hydroxides than other alkaline biosolids products, when N-Viro Soil is allowed to age in the open, the hydroxides of Ca and Mg carbonate, thereby lowering the pH of the material to much nearer neutral. In this aged state, N-Viro Soil has been used as a complete topsoil replacement material in situations including rehabilitation of open-cut mines and disturbed lands (such as embankments and closed landfills, playing fields and parks and gardens). In its fresh state, N-Viro Soil has been used extensively in both agriculture and green waste management (N-Viro BioBlend™). Within waste management, fresh N-Viro Soil accelerates the composting process when mixed with a combination of leaf mulch, green or wood waste. N-Viro Soil usually contains around 45% of the liming value of agricultural lime, and is sold as a liming agent with added organic matter and slow release nutrients within NSW and QLD.

Some agricultural applications of N-Viro Soil have included cotton, wheat, barley, canola, sorghum, millet, sugar cane, peanut, oat, pasture, lucerne, apple, nectarine, vineyard, macadamia, avocado, banana, watermelon, rockmelon, tomato, eggplant, squash, broccoli and cabbage production.

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