Breakthrough for bioreactor

Jan Erik Kaarø

When oil tanks are cleaned out, the oil companies are left with oil-sludge that is difficult to get rid of. Esso Norge A/S has carried out successful tests at Vaa Biomiljø A/S in Telemark, in which oily sludge has been composted. SINTEF has monitored the tests and has determined that most environmentally harmful compounds in the oil are degraded."We cannot obtain total cleaning, but this type of treatment is better than just dumping the sludge, says Ove Bergersen, a microbiologist.

Composting is currently being tried out as a means of dealing with many different types of waste, and the technique is on the verge of a breakthrough... It started with the treatment of sewage sludge from purification plants, in a bioreactor run by the inventor Arne Vaa in 1989. SINTEF Oslo has helped to further develop the technique, and Vaa Biomiljø is currently operating two bioreactors with capacities of 25 and 40 cubic metres respectively. Several local authorities, particularly in Southern Norway and the County of Rogaland, are interesting in starting similar facilities. The principle is simple; sludge and bark are filled into a rotating tank. By controlling the temperature, ventilation and humidity, the mass is converted in the course of 14 days to a steaming heap of compost with a temperature of 60 - 70o C. After stowing for a month, the sewage sludge has turned into an attractive, odourless soil improvement agent.

Ove Bergersen sees a great deal of potential for this technology in the future. For example, the bioreactor can be used to deal with waste from the fishing, meat-packing and food industries, as well as manure and sorted domestic waste. Local trials of composting domestic waste have already been started in many parts of the country.