Farm-scale nutrient and energy recovery technique wins fifth Ivan Tolpe Award

Flemish Green Service has won the Ivan Tolpe Prize 2023 with a new concept for nutrient and energy recovery at farm scale.

Four nominees were accepted. EMA depuració (Spain) with the concept 'Solar drying of manure and digestate', GlasPort Bio (Ireland) with 'GasAbate manure additive', Biolectric (Belgium) with 'Mono manure digester, manure separator and nitrogen stripper combination' and Green Service (Belgium) with 'Nutrient and energy recovery at farm scale'.

The awards ceremony took place at Agrotopia on 24 May and VCM members selected Green Service as the winner through a live vote.

Green Service

Green Service (www.greenserviceeurope.eu) has been supplying small-scale biogas plants since 2017.

Using a new concept with (a combination of) different techniques, Green Service Belgium wants to contribute to circular agriculture in which nutrients, water and energy can be recovered from manure. Specifically, manure is converted by a digestion plant into digestate with additional formation of biogas that is converted into electricity and heat in a cogeneration plant. By thermophilic digestion of the manure (temperature between 50 and 55°C), the digestate can be immediately hygienised provided the right treatment time is applied. For recognition that there is sufficient hygienisation at relevant time-temperature combination (> 1 hour, 50-55°C), an application file must be submitted to the local authorities.

The digestate or manure is then separated by conventional methods into a solid and liquid fraction, with the liquid fraction being further removed of suspended solids using a dissolved-air-flotation unit. The resulting watery fraction is filtered through reverse osmosis technology into reusable/dischargeable water and a concentrate.

The reverse osmosis technology used is distinguished by its unique membrane technology and was designed by Rochem Technical Services which is involved as a partner in this innovation. The highly turbulent water flow along the membrane and the construction of a larger feed channel ensure that (1) deposits are less likely to occur on the inside of the membrane module; (2) chemicals are given better access to carry out more efficient cleaning and (3) water flows with SDI up to 5 (instead of SDImax = 3 in classic reverse osmosis membranes) can be processed. This allows simple sand filters and other filtration systems to be used and does not require complex and expensive pre-filtration.

The system for converting manure into water and nutrient-rich concentrate has already been demonstrated, proven in several pilot plants and is currently being marketed. Recovery of nitrogen and other valuable nutrients through the above-described technique(s) enables farmers to produce their own nitrogen supply.

Schematic overview of the Green Service concept

4 nominees

The three other nominees for the fifth edition of the Ivan Tolpe Award were EMA depuració, GlasPort Bio and Biolectric.

The Spanish entry from EMA depuració (edepura.com), proposed a solar-powered combination of drying and stripping-scrubbing to recover nutrients from manure and digestate. By recovering ammonium salts and reducing the water content, it is possible to obtain a dried product that remains stable for a long time.

Biolectric's Flemish submission (biolectric.be) showed a small-scale company-owned manure refinery. It is a combination of a mono manure digester, a manure separator and a nitrogen stripper. There is an integration of an extraction of ammonia from the hygienised solid fraction to the nitrogen stripper. Heat from the digester is also used to heat up the liquid fraction to the nitrogen stripper. These techniques can be applied to a combination of pig and cattle manure.

Glasport Bio's Irish submission (glasportbio.com) described an innovative manure additive 'GasAbate'. By using GasAbate, it temporarily inhibits gas-producing microbes and reduces gaseous emissions, reduces bad odours and provides increased nutrient retention.

Nominees will also have the chance to present their realisations to an international audience during ManuREsource 2024 (see www.manuresource.org).