Background In the meat meal production industry there are three types of byproducts: - sludge and wastewater, subject to treatment and transportation; - rejected production, representing entirely different types of waste and subject to separate treatment and transportation procedures and; - dry food waste, subject to yet another treatment and transportation procedure. Environmental problems associated with the byproducts of the meat industry include excessive consumption of fossil fuels, overproduction of meat products, odour and wastewater treatment. Sludge from the meat industry cannot be used as a fertilizer because of the toxic chemical content, bacteria and the problem of odour. Objectives The purpose of the project is to develop and demonstrate a wastewater and sludge treatment method for the meat industry. Instead of non-recyclable sludge, a product with high energy content for use in biogas plants and as clean drain water will be produced. In the process the waste material will be sanitised and suitable for other users such as composting plants. The project will demonstrate the first full-scale plant with application of the "CLEANTREAT" technology. The treatment system will be compact, free from odour emissions and will contribute to a reduction of the transportation volumes and the overproduction of meat meal. Furthermore, it will improve the subsequent wastewater treatment processes by producing effluents of a much more even quality. By application of the new method, a considerable reduction (more than 85%) of the COD/BOD (Chemical Oxygen Demand/Biological Oxygen Demand) should be achieved. 99% of the phosphorus content, 50% of the nitrogen and at least 50% of all the heavy metals will be removed simultaneously from the dehydrated end product. It is expected that the sludge will be reduced by 100% and the dehydrated end product will represent 20% of the former sludge volume, thus contributing to a decrease in the transportation volume. The project represents an innovative way of thinking and will go some way to solving the sludge problem in a European context. Results The project developed a combined wastewater and sludge treatment procedure for wastewater from a petfood factory. The waste, which previously had difficult characteristics for normal municipal treatment plant processing, has been turned into relatively pure water, which can be treated at the municipal wastewater treatment plant, and into dewatered sludge with high energy (fat) content. The key parts of the process are filtering, dewatering, thermal heating of the sludge flocculation and flotation. All phases of the process were designed and constructed taking the characteristics of the waste into consideration. The consumption of chemicals in the flotation and flocculation is necessary. The treatment method resulted in a reduction of the BOD and COD by up to 85 % and the fat by some 95 % compared to the original content of the incoming waste and waste water. The outgoing waste water has lower heavy metal contents than the incoming water. The dewatered sludge has a reduced volume, amounting to around 25-25 % of the original volume, which reduces the transportation and other after-treatment costs. The dewatered sludge with high energy content is especially suitable for bio-gasification, which the project has tested. The project has achieved its objectives as set out in the approved application. The sludge treatment method is applicable at larger scale in the food and pet food industries, but as one alternative of several available possibilities. The process is biologically simple and technically compact. The technical concept seemed to work well and difficulties experienced highlight the need for a dedicated and competent project management to keep things in order.