Solid Waste & Recycling

Feature

In Digestion (January 01, 1999)

Traditional methods for treating biodegradable wastes cannot effectively process such wastes when they contain high contaminant levels. However, a Canadian company has devised a system that successful...


Traditional methods for treating biodegradable wastes cannot effectively process such wastes when they contain high contaminant levels. However, a Canadian company has devised a system that successfully processes biodegradable wastes that contain as much as 20 per cent non-biodegradable materials into a commercially-viable organic fertilizer–one that’s free of pathogens.

International Bio-Recovery Corporation (IBR)–formed in 1993 in North Vancouver, British Columbia–developed the treatment, which is formally described as “autogenous thermophilic aerobic digestion.” The company claims that the technology uses thermophilic (heat responsive) microbes to process organic waste over a 72-hour period with no harmful environmental discharges. The digested waste is converted into organic fertilizer products with high market value in both liquid and dry pellet form.

The plant

The North Vancouver plant processes 50 tonnes per day of municipal biodegradable waste containing up to 20 per cent non-biodegradable materials. (This material would normally be landfilled.) Biodegradables, from vegetables and leafy plants, are converted in approximately 36 to 45 hours. Biodegradables from woody sources (including paper waste) are processed over a period of 48 to 100 hours.

The plant has a well-equipped laboratory and a two-tonne pilot plant that are used for ongoing research. Much of this research is sponsored by Canada’s National Research Council and potential customers. The research includes: product development in form and packaging; extension of the range of raw materials processed; process optimization (including beneficial use of heat generated during digesting, isolation, and cultivation of specific desirable bacteria); and, new product and by-product development. The plant uses 20-, 30-, and 60-tonne digesters. The plant currently processes 50 tonnes of waste per day. Plans include scaling up to 130 tonnes per day.

Process overview

Preparation of the raw materials–A mixture of raw materials of variable digestibility is made wherein hard-to-digest material is separated for extended treatment. Non-biodegradables such as metals, glass, sand, and plastics are segregated by a unique in-feed system or are removed by cleaning and screening during the liquid phase of the process. The cardboard content can be varied in order to alter the balances between the liquid and solid product.

Digestion–The resulting slurry is aerated. Aeration equipment for the digesters was developed and patented by IBR specifically for this application. The submerged aeration device saturates the slurry in the digester with oxygen and optimizes the process.

Refinement of finished product–The slurry is cleaned and dewatered. The solid fertilizer end products are then further refined by drying and pelletizing. In the case of liquid fertilizer, the material is processed by clarification and concentration.

Odour & end product

No significant emissions of either harmful gases or odours occur during the processing. The complete elimination of odours is achieved via biological method of cleaning the air. Also, the entire plant is operated under negative air pressure; this ensures no offsite migration of noxious odours and allows such plants to be located in sensitive urban areas on as little as three acres of land. The close proximity to sources of biodegradable waste materials is advantageous. Also, shorter hauling distances mean fewer trucks, lower waste handling costs, and lower vehicle emissions. The fertilizer is retailed as “Seasons” lawn fertilizer. Studies have shown that it can effectively increase the microbial activity in soil by 200 to 600 per cent, reducing a plant or flower’s need for nutrient concentrations by up to 50 per cent. Also, through trials by BC Research Inc. (an independent research facility), the fertilizer has been shown to be 30 per cent more effective in total plant growth than other leading commercial chemical fertilizers on the market.

Written by Dale Fehr, the project and development manager with International Bio-Recovery Corporation in North Vancouver, British Columbia.


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