All subjects
Biogas

Novel biogas plant feasts on culinary cultivar

Novel biogas plant feasts on culinary cultivar
Endives, a culinary cultivar, and spent chicory roots.

While Belgian endives may have been discovered by accident, the biogas plant at endive grower Joluwa N.V. is purpose-built. Commissioned in September 2010 the fully automated plant uses spent chicory roots as feedstock. It is the first commercial installation of a novel high yield digester technology developed by another Belgian firm GreenWatt SA.

An error occurred

You are logged in as subsbriber at Bioenergy International, but something is wrong.

On your profile you can see what subscriptions you have access to and more information.

Is some of the information wrong – please contact our customer service.

Please reload the page

We could not ascertain if you are logged in or not. Please reload this page.
Bioenergy International premium

Do you want to read the whole article?

Only logged in payed subscribers can read all contents on bioenergyinternational.com
As an subscriber you get:
  • Six editions per year
  • Full access to all digital content
  • The E-magazine Bioenergy international
  • And more ...

In the culinary world, the term “Endive” denotes a lettuce-like leaf vegetable, Cichorium endivia, from the chicory genus. Often used in salads they are especially popular in France, Belgium, and the Netherlands.

Somewhat confusing Belgian endives or Witloof is a cultivated variety of the common chicory, Cichorium intybus, whereby the blanched, tight heads known as Chicons are produced by forcing mature chicory roots to grow in darkness.

Once the Chicon is harvested the root is discarded.

Residual endive leaves and chicory roots
Residual endive leaves and chicory roots from the production line.

Located in the countryside just outside the town of Nivelles, is the Witloof grower and producer Joluwa N.V. The company currently produces around 4 000 tonnes of forced chicory roots per year at its growing, harvesting, and packing facility.

According to Joost Depaepe from Joluwa the company needed an environmentally suitable, cost-effective, and long-term solution for the growing volume of residue from spent chicory roots.

The expanding business was having issues with odour and leaching from storage piles of rotting roots. Disposal costs at external processing facilities were increasing and the company had heat and power needs but had no particular desire to run a biogas plant.

It is important for us to be independent and cost-efficient in our waste and energy management but biogas in itself is not our business or interest. We wanted to address these issues with a turnkey solution that was easy to manage and not time-consuming, said Joost Depaepe from Joluwa.

Novel technology

A project to utilize the energy potential of the chicory roots was set up in 2009 with GreenWatt SA, a Belgian company that specializes in the design and installation of on-site biogas plants for farms and agribusinesses.

View of the Joluwa biogas plant. To the left the red receiving bin with the hydrolysis tank, the HYFAD unit is inside the shed. In the foreground the feedstock chicory roots and endive leaves alongside the solid digestate discharge. Further to the right, out of view, is the CHP unit and the post digester.
View of the Joluwa biogas plant. To the left is the red receiving bin with the hydrolysis tank, and the HYFAD unit is inside the shed. In the foreground, the feedstock chicory roots and endive leaves alongside the solid digestate discharge. Further to the right, out of view, are the CHP unit and the post digester.

A research spin-off from the Catholic University of Louvain, GreenWatt developed a novel high yield flushing anaerobic digestion (HYFAD) reactor and the Joluwa project is the first commercial installation of this patented technology.

We specialize in designing biogas plants based on fruit and vegetable waste as substrate. Each project is tailored to fit the residue generated, said Baptiste Genin, an R&D engineer at GreenWatt.

The different stages of the anaerobic digestion process have conflicting operating parameters which need strict regulation management.

A change in the composition or volume of the feedstock input in a conventional biogas plant risks destabilizing the process through acidification damaging the methane-producing bacteria.

We have removed this risk entirely. The methane production is stable and consistent regardless of feedstock quantity variations. Our multi-stage technology process is based on the separation and specialization of these phases into two or three stages to controlling the operating parameters of these different reactions independently of one another, Genin said.

Two-stage AD plant

The Joluwa facility is a two-stage anaerobic digestion (AD) biogas plant with three main process steps: a hydrolysis tank, the HYFAD reactor, and a post-digester.

Baptiste Genin, R&D Engineer at GreenWatt
Baptiste Genin, R&D Engineer at GreenWatt.

On average the plant produces 850 m3 biogas a day 75 percent of which is produced in the reactor and the rest in the post-digester. The solid digestate is used as fertilizer and the fluid is discharged into the public wastewater system after decantation.

The biogas has an average methane content of 54 percent and is used to fuel an on-site combined heat and power genset with 104 kW power rating. All the electricity and around 65 percent of the heat are used by Joluwa for the chicory processing plant and self-consumption of the biogas plant.

An additional 30 percent of the heat is supplied via a small network to a printing company located about 1 km from the biogas plant.

The overall heat loss is only 5 percent which is very low for a biogas plant, Genin pointed out.

In the first step, hydrolysis, and acidogenesis, the chicory roots along with other vegetable matter are loaded into the receiving hopper using a front loader.

An X-ripper grinder pump is used to get the material into the hydrolysis tank where it is converted into a liquid loaded with volatile fatty acids. In the second step, methanogenesis, this acid liquor is fed into the HYFAD fixed bed reactor to produce biogas.

View of the two well insulated HYFAD tanks
The HYFAD reactor consists of two well-insulated 25 m3 vessels keeping a temperature of 38 oC and neutral pH. It produces 75 percent of the biogas.

The HYFAD reactor consists of two 25 m3 vessels that are side by side and connected to each other. The vessels are packed with vertical honeycomb columns which function as the fixed bed media.

The honeycomb structure provides a very large surface area in relation to the reactor volume. This leads to a high concentration of bacteria attached to the bed as biofilm enabling a high methane yield.

Organic loading rates (chemical oxygen demand) of up to 35 kg COD/m3 per day have been achieved with this reactor. The reactor has an anti-clogging system that cleans the columns and recovers the biofilm.

Stable temperature and pH

The temperature in the HYFAD phase is kept at 38 oC and the pH is always kept neutral and remains stable even if the liquefier is overfed.

The post-digester in the final step allows the digestion of organic material that had not been fully processed in the hydrolysis tank. The global hydraulic retention time (HRT) for the plant is 45 days.

This project was about EUR 1 million EUR including the 1 km heating circuit to the printers. Payback is within four years, Genin said.

The plant uses on average 11 tonnes of chicory roots per day but can handle up to a 30 tonnes per day peak.

According to Genin, chicory roots yield about 38 m3 methane per tonne.

This is quite low compared to other feedstocks and is due to the high water content, around 85 percent, said Baptiste Genin.

Facts

About Joluwa

Start-up: September 2010

Technical: Two-stage anaerobic digestion (AD) plant: hydrolysis tank, High Yield Flushing Digester (HYFAD) reactor & post digester. Combined heat and power (CHP) unit with 104 kWe power rating

Feedstock: 4 000 tonnes/year of forced chicory roots and vegetable waste

CH4 potential: 38 m3 per tonne (chicory roots)

Peak input

Hydrolysis tank: 30 tonnes/day, 165 tonnes/week, 500 tonnes/month

HYFAB: Up to 35 kg COD/m3 per day

Annual production

Biogas: 280 000 m3 at 54% methane content

Electricity: 500 MWh

Heat: 760 MWh

This article was first published in Bioenergy International no. 1-2014 (70). Note that as a magazine subscriber you get access to the e-magazine and articles like this before the print edition reaches your desk!

Most read on Bioenergy International

Get the latest news about Bioenergy

Subscribe for free to our newsletter
Sending request
I accept that Bioenergy International stores and handles my information.
Read more about our integritypolicy here