INTERNATIONAL CLEANER PRODUCTION INFORMATION CLEARINGHOUSE

CASE STUDY #5 1. Headline: Recovery of protein from potato starch effluent 2. Background: The Avebe Foxhol site produces starch from potatoes. Potato starch production involves washing and grinding potatoes to produce a pulpy liquor of potato fruit water, starch and fibers. The starch is extracted and refined by hydrocyclones, and the fibers are then separated from the liquor by centrifuge. The residual potato fruit water contains protein, sugars and minerals at a concentration previously too dilute to recover. The Foxhol site alone produces 2.2million cubic meters per year of this potato water, which was originally disposed of without treatment into the North Sea and into Holland's canals. The effect was a major contamination of the waterways, the contaminants giving rise to strong odors and killing water life. This caused a public outcry. Avebe is the largest potato starch producer in the world. Founded in 1919, Avebe is now an international cooperative with four starch production plants in Holland, the largest being at Foxhol. The company also have plants in Germany, France, Sweden, Thailand and the USA. PCI Membrane Systems Ltd is a specialist in membrane filtration equipment with 25 years experience in solving a wide range of effluent and processing problems. The company has a UK manufacturing base, and up to 90% of its business is exports. 3. Cleaner Production Principle: Internal recycling 4. Description of Cleaner Production Application: In the late 1970's and early 1980's, Avebe made a major effort to clean up its production. After several years of test work, internal recycling has become possible by installing a reverse osmosis plant to concentrate the potato fruit water to a level at which the protein could be recovered economically by coagulation. The process installed at Avebe utilizes open-channel tubular membranes which can handle high levels of suspended solids without clogging, and which are easy to clean. Since the concentration process is non-thermal and does not involve a change of phase, it is energy- efficient and does not change the nature of the proteins. The system which is designed for continuous operation, compromises six parallel process lines. Following concentration of the potato water, protein is extracted from the concentrated stream by steam coagulation and dried. The product is a high grade protein concentrate used in animal feeds for small animals, such as piglets, poultry, furred animals including dogs, cats and minks. The residual potato water is evaporated and used for the enrichment of the potato fibers and incorporated in a cattle feed. The process thus produces two saleable products. Due partly to the reverse osmosis process and partly to a counter-current extraction process installed at the same time, the volume of process water intake was reduced from 7 m3/ton of potatoes to 0.6 m3/ton, saving 17million m3 of water per annum. The process also recovers 1.1million cubic meters per year of water (the filtrate from the reverse osmosis process) which is recycled within the factory to further reduce process water intake. Effluent emissions are thus greatly reduced. Reverse osmosis is a process which separates water from dissolved and suspended solids using a membrane made of organic material. A pressure of 40-50 Bar is applied to force water through the membrane while dissolved substances are retained. The process thus produces two streams: a concentrated liquor and clean water. The equipment is in the form of robust, open-channel membranes with the features of high retention and low-fouling. 5. Economics: An effluent treatment problem is solved and wastewater disposal costs are avoided. Water consumption is also reduced with further savings. Two by-products are produced, both of which generate revenue. The overall cost to Avebe of concentrating the liquor with reverse osmosis et the time of installation was approx. US$0.54/m3 of potato water treated. The economic benefits depend upon the market value for the by-products as well as water and wastewater charges. 6. Advantages: Major reduction in the volume of process water consumed through the recycling of wastewater. The reduction in the quantity of water handled enables the heat coagulation and evaporation plant to be half the size, so giving capital and energy cost savings. Production of two by-products from the effluent. 7. Constraints: N/A 8. Contacts:Mr Wijnholds Avebe Foxhol Avebeweg 1 9607 PT Foxhol The Netherlands Tel: +31 5980 42136 Fax: +31 5980 90093 Miss N J Randles Business Development Manager PCI Membrane Systems Ltd Laverstoke Mill Whitechurch Hampshire RG28 7NR United Kingdom Tel: +44 256 896966 Fax: +44 256 893835 9. Keywords:UK, United Kingdom, the Netherlands, food processing, potato, starch, recycling, process modification, water saving, filtration, reverse osmosis, agriculture 10. Reviewer comments: This case study was originally published in the UNEP IE document "Cleaner Production Worldwide". In the process of preparing the document the case study underwent a technical review.