. Energy News .

Using wastewater as fertilizer
by Staff Writers
Stuttgart, Germany (SPX) Aug 08, 2012

Struvite fertilizer recovered from wastewater is a high-quality product that slowly releases nutrients into the soil. Image courtesy Fraunhofer IGB.

Sewage sludge, wastewater and liquid manure are valuable sources of fertilizer for food production. Fraunhofer researchers have now developed a chemical-free, eco-friendly process that enables the recovered salts to be converted directly into organic food for crop plants.

Phosphorus is a vital element not only for plants but also for all living organisms. In recent times, however, farmers have been faced with a growing shortage of this essential mineral, and the price of phosphate-based fertilizers has been steadily increasing. It is therefore high time to start looking for alternatives.

This is not an easy task, because phosphorus cannot be replaced by any other substance. But researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have found a solution that makes use of locally available resources which, as unlikely as it might seem, are to be found in plentiful supply in the wastewater from sewage treatment plants and in the fermentation residues from biogas plants: a perfect example of the old saying "from muck to riches".

The new process was developed by a team of scientists led by Jennifer Bilbao, who manages the nutrient management research group at the IGB. "Our process precipitates out the nutrients in a form that enables them to be directly applied as fertilizer," she explains.

Mobile pilot plant for field tests
The main feature of the patented process, which is currently being tested in a mobile pilot plant, is an electrochemical process that precipitates magnesium-ammonium phosphate - also known as struvite - by means of electrolysis from a solution containing nitrogen and phosphorus. Struvite is precipitated from the process water in the form of tiny crystals that can be used directly as fertilizer, without any further processing.

The innovative aspect of this method is that, unlike conventional processes, it does not require the addition of synthetic salts or bases. Bilbao: "It is an entirely chemical-free process."

The 2-meter-high electrolytic cell that forms the centerpiece of the test installation and through which the wastewater is directed contains a sacrificial magnesium anode and a metallic cathode. The electrolytic process splits the water molecules into negatively charged hydroxyl ions at the cathode. At the anode an oxidation takes place: the magnesium ions migrate through the water and react with the phosphate and ammonium molecules in the solution to form struvite.

Energy-saving, chemical-free process
Because the magnesium ions in the process water are highly reactive, this method requires very little energy. The electrochemical process therefore consumes less electricity than conventional methods. For all types of wastewater tested so far, the necessary power never exceeded the extremely low value of 70 watt-hours per cubic meter.

Moreover, long-duration tests conducted by the IGB researchers demonstrated that the concentration of phosphorus in the pilot plant's reactor was reduced by 99.7 percent to less than 2 milligrams per liter. This is lower than the maximum concentration permitted by the German Waste Water Ordinance (AbwV) for treatment plants serving communities of up to 100,000 inhabitants.

"This means that operators of such plants could generate additional revenue from the production of fertilizer as a sideline to the treatment of wastewater," says Bilbao, citing this as a decisive advantage.

Struvite is an attractive product for farmers, because it is valued as a high-quality, slow-release fertilizer. Experiments conducted by the Fraunhofer researchers have confirmed its effectiveness in this respect: crop yields and the uptake of nutrients by the growing plants were up to four times higher with struvite than with commercially available mineral fertilizers.

The scientists intend to spend the next few months testing the mobile pilot plant at a variety of wastewater treatment plants before starting to commercialize the process in collaboration with industrial partners early next year. "Our process is also suitable for wastewaters from the food-industry and from the production of biogas from agricultural wastes," adds Bilbao. The only prerequisite is that the process water should be rich in ammonium and phosphates.

Related Links
Fraunhofer Institute for Interfacial Engineering and Biotechnology
Farming Today - Suppliers and Technology

Get Our Free Newsletters Via Email
Buy Advertising Editorial Enquiries


. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

New Zealand court backs farm sale to Chinese group
Wellington (AFP) Aug 8, 2012
New Zealand's Court of Appeal on Wednesday rejected a bid to stop a Chinese company from buying a bankrupt dairy farm group, in a case that has stirred heated debate about foreign land ownership. The court refused an application from a rival bidder to overturn government approval for China's Shanghai Pengxin Group to buy the 16-property Crafar Farms in a deal reportedly worth NZ$210 million ... read more

Test flight over Peru ruins could revolutionize archaeological mapping

Interview With Scott Braun About NASA's Upcoming Hurricane Campaign

France orders Google to hand over Street View data

Space Technologies Tackle Human and Environmental Security Problems

Raytheon completes GPS OCX iteration 1.4 Critical Design Review

Mission accomplished, GIOVE-B heads into deserved retirement

Boeing Ships 3rd GPS IIF Satellite to Cape Canaveral for Launch

GPS Can Now Measure Ice Melt, Change In Greenland Over Months Rather Than Years

Birds do better in 'agroforests' than on farms

WSU researcher sees how forests thrive after fires and volcanoes

New Hampshire leads U.S. in tree cover

Turkmenistan to plant huge forest in Aral Sea region

AREVA invests in bio-coal

German National Academy of Sciences issues a critical statement on the use of bioenergy

U.S, Australian navies focus on new fuels

Strategies to improve renewable energy feedstocks

SolarCraft Brings Solar to Altamont Apartments

Walmart Unveils 100th Solar Installation in California

Tecta Solar Completes Solar Photovoltaic Installation at Augustine Casino

REC rolls out its industry-leading certification program for solar installers in the US

Mexico goes ahead with wind power project

Clegg: Gov't 'committed' to renewables

Wales wind power line plans draw protests

Offshore use of vertical-axis wind turbines gets closer look

53 rescued from China coal mine: state media

Huge Australian coal mine wins conditional approval

Russia expands presence on Spitsbergen

Australia scraps coal port expansion

Tibetan sets himself alight in China: group

Workshop blast in east China kills 13

China's passion for fashion catapults blogger to stardom

China accuses US of prejudice on religious issues

Memory Foam Mattress Review

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement