From value chain to value loop with biogas and mushrooms

Waste is only waste if you cannot put it to good use! EU-funded researchers have developed a circular value chain deriving income sustainably from wet straw, biogas digestate and similar residues, via products such as fertiliser, fuel pellets and mushroom substrate – and boosting energy generation in the process.

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Countries
Countries
  Algeria
  Argentina
  Australia
  Austria
  Bangladesh
  Belarus
  Belgium
  Benin
  Bolivia
  Bosnia and Herzegovina
  Brazil
  Bulgaria
  Burkina Faso
  Cambodia
  Cameroon
  Canada
  Cape Verde
  Chile
  China
  Colombia
  Costa Rica
  Croatia
  Cyprus
  Czechia
  Denmark
  Ecuador
  Egypt
  Estonia
  Ethiopia
  Faroe Islands
  Finland
  France
  French Polynesia
  Georgia


 

Published: 6 August 2020  
Related theme(s) and subtheme(s)
Agriculture & food
EnergyRenewable energy sources
EnvironmentClean technology and recycling
European Innovation Council (EIC) pilotEIC Accelerator Pilot
Green deal
Research policyHorizon 2020
Countries involved in the project described in the article
Denmark  |  Netherlands
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From value chain to value loop with biogas and mushrooms

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© gerasimov174 #262946677, source:stock.adobe.com 2020

The EU-funded circular economy project MUBIC focused on the transformation of low-value agricultural waste into high-value products – one of which is used to grow mushrooms, whose cultivation the partners set out to revolutionise.

More specifically, this product is a new type of mushroom substrate, the material on which the mushrooms are grown. ‘Along with other outputs, such as fuel pellets, fertiliser, and pre-treated feedstock for faster biogas production, the process shaped in MUBIC also delivers substantial sustainability gains,’ says project coordinator Peter Damgaard Nielsen of Danish SME Advanced Substrate Technologies (AST).

It notably increases the biogas yield from agricultural wastes like straw or horse bedding by about 30 %, through the prior cutting and grinding of this biomass. The ability to process wet straw, meadow grass and similar material is a particular plus point: the MUBIC process for these challenging types of feedstock also involves pretreatment with nitrogen to break down the lignin in the stalks, Nielsen explains.

Profitable, circular, green

‘Using this process, you get more biogas and you get it faster, because the bacteria in the biogas plant can also use the lignin as feed,’ says Nielsen. The nitrogen used for this pre-treatment is recovered from the biogas plant, through the treatment of the digestate – the residues of the feedstock.

The nitrogen is extracted from the digestate in facilities designed as annexes to the biogas plants themselves. As of July 2020, operations have begun at the first such add-on plant designed as a commercial facility, according to Nielsen.

In the MUBIC model, the digestate might, in fact, have started out as biomass supplied by the partners. ‘Our lorries take feedstock to the biogas plant and digestate back to the add-on plant, where we dry it,’ Nielsen continues.

The treated digestate is then converted into a variety of products. Along with the mushroom substrate, these outputs include fuel pellets that are significantly more sustainable than competing products because they are derived from a type of waste and because this waste is a residue of locally sourced biomass.

The MUBIC process delivers a pelletised substrate whose dry matter content, at 85 %, is much higher than that of conventional substrates, which typically average about 30 %. Thus, MUBIC substrate provides far more mushroom feed per cubic metre than competing products, Nielsen explains. Due to its high dry-matter content, it can be stored and does not require cooling during transport over longer distances – unlike conventional substrates, which might begin to rot.

MUBIC’s substrate complements another innovation developed in the project: a system by which mushrooms grown on trays move past pickers on a conveyor belt, as opposed to pickers having to move through the shelves in mushroom farms. This particular innovation was perfected by Dutch SME Panbo Systems, the second partner involved in the project, as a way to reduce harvesting costs.

Rooted in wet straw

MUBIC, which ended in January 2020, was funded via a Horizon 2020 programme specifically designed to help SMEs prepare their innovations for commercialisation. Without this support, the straw-to-substrate concept would have been shelved, says Nielsen, who emphasises that the funding enabled the partners to bring their idea to life.

AST had initially considered selling entire add-on plants, but eventually decided to focus on the products generated throughout the process instead: income is generated at several steps, from raw material that is largely available for free.

Spent substrate from mushroom production is one such residue, and a perfect example of the proposed circular approach. In MUBIC, it is recovered as feedstock for the production of biogas, and the digestate left over from this process is used to make fresh substrate.

Both the new mushroom cultivation system and the various products from MUBIC’s circular value chain have been met with interest, with new partnerships enabling the project partners to take these developments forward, Nielsen concludes.

Project details

  • Project acronym: MUBIC
  • Participants: Denmark (Coordinator), Netherlands, Denmark
  • Project N°: 778065
  • Total costs: € 5 466 532
  • EU contribution: € 2 499 999
  • Duration: August 2017 to January 2020

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