Solving the bottleneck in biogas production

September 23, 2013
Solving the bottleneck in biogas production
Credit: Shutterstock

Agro-biogas plants produce renewable energy, extracting gas produced in the anaerobic fermentation of animal manures mixed with organic wastes from the food sector. One by-product of this fermentation process is a thick liquid waste called 'digestate', which is difficult to manage but rich in organic matter and minerals.

The EU project WAVALUE ('High added value eco-fertilisers from anaerobic digestion effluent wastes') will demonstrate a cost-effective industrial process for producing a new range of sustainable fertilisers, with digestate as their main component.

"The volume and of digestate produced in the biogas extraction process are very similar to the original waste treated," says Aritz Lekuona of project coordinator EKONEK Innovacion en Valorizacion de Subproductos.

"Today, despite existing regulation, this material is often spread as fertiliser in near the biogas plants where it is produced but this is not always the optimal strategy as its high causes soil and , namely eutrophication. It is also relatively costly - the material is more than 90 percent water, and moving it any distance using trucks is expensive. So figuring out what to do with digestate waste is a serious limiting factor for new biogas projects, especially when is not available nearby for spreading."

With the EU promoting , the use of biogas should be increasing rapidly. But the digestate problem is actually slowing the development of biogas plants in many EU countries. Lekuona says, WAVALUE researchers understood that digestate could be used to produce valuable fertilisers.

"Our approach will be to develop fertilisers in a granular form," he says, "similar in appearance to small green beans. The process will involve mixing the digestate with to get a tailored formula, and then drying the mixture to get small, round, regular-sized granules, with slow-release nutrients that can go into the special fertilisers market."

The WAVALUE pilot plant will be the first of its kind in Europe, producing high-value from digestate and making biogas plants more profitable. Moreover, the system for fertiliser production from digestate will be easy to incorporate into new or existing agro-biogas plants.

"There are about 6000 biogas plants in Europe today," says Lekuona, "but with the available organic waste, there is a huge potential to multiply this number several times. This project provides a new digestate management solution that will increase the feasibility of new biogas plants, while enhancing the added-value of digestate generated in existing biogas plants.

"From an environmental and social point of view, digestate utilisation as the basis of a high-value product would close the nutrients cycle, reducing greenhouse gas emissions, improving economic performance of agro-biogas plants and solving an environmental issue."

The consortium aims at treating about 900 tonnes of sludge per year in its pilot plant. After the project, two full-sized plants will treat 57 000 tonnes per year. Altogether, the system will save an estimated 11 tonnes of CO2 emissions per year during the project.

Lekuona adds: "Digestate granulation plants can deliver a reasonable return on investment, based on the sales of the final fertiliser product. This is a relatively new activity that also has the potential to generate new jobs at agro-."

WAVALUE received over EUR 900 000 in EU funding under the Eco-Innovation Programme and will run through 2014.

Explore further: Biogas from animal waste in need of maturity

More information: www.wavalueproject.eu/

Related Stories

Biogas from animal waste in need of maturity

May 7, 2013

Biogas-based energy could solve both the environmental concern of agricultural waste and reduce dependency of fossil fuels, particularly in Eastern Europe, albeit at a steep production cost.

From food waste to bus fuel and biofertilizer

March 19, 2012

Banana peel, coffee grounds and other food waste will be transformed into green fuel for Oslo’s city buses starting next year. The Norwegian capital’s new biogas plant will also supply nutrient-rich biofertilizer ...

Electricity from straw

February 3, 2009

Researchers have developed the first-ever biogas plant to run purely on waste instead of edible raw materials -- transforming waste into valuable material. The plant generates 30 percent more biogas than its predecessors. ...

Energy efficient sewage plants

August 13, 2009

High-rate digestion with microfiltration is state-of-the-art in large sewage plants. It effectively removes accumulated sludge and produces biogas to generate energy. A study now reveals that even small plants can benefit ...

Big pig poo problem solved

May 20, 2013

An Australian led-project to turn 1.4 million tonnes of Chinese pig poo into alternative energy and fertiliser has been hailed in a national science award.

Regions could use food waste for fuel

March 21, 2013

Murdoch University researchers are touting biogas from small-scale food waste digesters as a source of renewable energy for rural and regional communities.

Recommended for you

A not-quite-random walk demystifies the algorithm

December 15, 2017

The algorithm is having a cultural moment. Originally a math and computer science term, algorithms are now used to account for everything from military drone strikes and financial market forecasts to Google search results.

US faces moment of truth on 'net neutrality'

December 14, 2017

The acrimonious battle over "net neutrality" in America comes to a head Thursday with a US agency set to vote to roll back rules enacted two years earlier aimed at preventing a "two-speed" internet.

FCC votes along party lines to end 'net neutrality' (Update)

December 14, 2017

The Federal Communications Commission repealed the Obama-era "net neutrality" rules Thursday, giving internet service providers like Verizon, Comcast and AT&T a free hand to slow or block websites and apps as they see fit ...

The wet road to fast and stable batteries

December 14, 2017

An international team of scientists—including several researchers from the U.S. Department of Energy's (DOE) Argonne National Laboratory—has discovered an anode battery material with superfast charging and stable operation ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.